Bump start plugin to 0.15.0 (#1956)

Most important change is a fix for processes CPU usage calculation (see https://github.com/heim-rs/heim/issues/246)

.azure/azure-pipelines.yml

@@ -37,6 +37,8 @@ steps:
       fi
       if [ "$(uname)" == "Darwin" ]; then
         curl https://sh.rustup.rs -sSf | sh -s -- -y --no-modify-path --default-toolchain "stable"
+        echo "Installing clippy"
+        rustup component add clippy --toolchain stable-x86_64-apple-darwin
         export PATH=$HOME/.cargo/bin:$PATH
       fi
       rustup update
@@ -44,13 +46,13 @@ steps:
       echo "##vso[task.prependpath]$HOME/.cargo/bin"
       rustup component add rustfmt
     displayName: Install Rust
-  - bash: RUSTFLAGS="-D warnings" cargo test --all --features stable,test-bins
+  - bash: RUSTFLAGS="-D warnings" cargo test --all --features stable
     condition: eq(variables['style'], 'unflagged')
     displayName: Run tests
   - bash: RUSTFLAGS="-D warnings" cargo clippy --all --features=stable -- -D clippy::result_unwrap_used -D clippy::option_unwrap_used
     condition: eq(variables['style'], 'unflagged')
     displayName: Check clippy lints
-  - bash: NUSHELL_ENABLE_ALL_FLAGS=1 RUSTFLAGS="-D warnings" cargo test --all --features stable,test-bins
+  - bash: NUSHELL_ENABLE_ALL_FLAGS=1 RUSTFLAGS="-D warnings" cargo test --all --features stable
     condition: eq(variables['style'], 'canary')
     displayName: Run tests
   - bash: NUSHELL_ENABLE_ALL_FLAGS=1 RUSTFLAGS="-D warnings" cargo clippy --all --features=stable -- -D clippy::result_unwrap_used -D clippy::option_unwrap_used

.github/ISSUE_TEMPLATE/bug_report.md

@@ -23,8 +23,8 @@ A clear and concise description of what you expected to happen.
 If applicable, add screenshots to help explain your problem.
 
 **Configuration (please complete the following information):**
- - OS: [e.g. Windows]
- - Version [e.g. 0.4.0]
- - Optional features (if any)
+ - OS (e.g. Windows):
+ - Nu version (you can use the `version` command to find out): 
+ - Optional features (if any):
 
 Add any other context about the problem here.

.github/workflows/docker-publish.yml

@@ -13,7 +13,7 @@ jobs:
         - x86_64-unknown-linux-musl
         - x86_64-unknown-linux-gnu
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - name: Install rust-embedded/cross
       env: { VERSION: v0.1.16 }
       run: >-
@@ -62,7 +62,7 @@ jobs:
         - { tag: glibc,            base-image: scratch,                    arch: x86_64-unknown-linux-gnu,  plugin: false, use-patch: false}
         - { tag: musl,             base-image: scratch,                    arch: x86_64-unknown-linux-musl, plugin: false, use-patch: false}
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - uses: actions/download-artifact@master
       with: { name: '${{ matrix.arch }}', path: target/release }
     - name: Build and publish exact version

.gitignore

@@ -11,3 +11,12 @@ debian/debhelper-build-stamp
 debian/files
 debian/nu.substvars
 debian/nu/
+
+# macOS junk
+.DS_Store
+
+# JetBrains' IDE items
+.idea/*
+
+# VSCode's IDE items
+.vscode/*

.gitpod.Dockerfile

@@ -6,4 +6,9 @@ RUN sudo apt-get update && \
     sudo apt-get install -y \
         libssl-dev \
         libxcb-composite0-dev \
-        pkg-config
+        pkg-config \
+        libpython3.6 \
+        rust-lldb \
+    && sudo rm -rf /var/lib/apt/lists/*
+
+ENV RUST_LLDB=/usr/bin/lldb-8

.gitpod.yml

@@ -1,23 +1,19 @@
 image:
   file: .gitpod.Dockerfile
 tasks:
-  - init: cargo install --path . --force --features=stable
+  - name: Clippy
+    init: cargo clippy --all --features=stable -- -D clippy::result_unwrap_used -D clippy::option_unwrap_used
+  - name: Testing
+    init: cargo test --all --features=stable,test-bins
+  - name: Build
+    init: cargo build --features=stable
+  - name: Nu
+    init: cargo install --path . --features=stable
     command: nu
 github:
   prebuilds:
-    # enable for the master/default branch (defaults to true)
-    master: true
-    # enable for all branches in this repo (defaults to false)
     branches: true
-    # enable for pull requests coming from this repo (defaults to true)
-    pullRequests: true
-    # enable for pull requests coming from forks (defaults to false)
     pullRequestsFromForks: true
-    # add a "Review in Gitpod" button as a comment to pull requests (defaults to true)
-    addComment: true
-    # add a "Review in Gitpod" button to pull requests (defaults to false)
-    addBadge: false
-    # add a label once the prebuild is ready to pull requests (defaults to false)
     addLabel: prebuilt-in-gitpod
 vscode:
   extensions:
@@ -25,5 +21,5 @@ vscode:
     - Swellaby.vscode-rust-test-adapter@0.11.0:Xg+YeZZQiVpVUsIkH+uiiw==
     - serayuzgur.crates@0.4.7:HMkoguLcXp9M3ud7ac3eIw==
     - belfz.search-crates-io@1.2.1:kSLnyrOhXtYPjQpKnMr4eQ==
-    - vadimcn.vscode-lldb@1.4.5:lwHCNwtm0kmOBXeQUIPGMQ==
     - bungcip.better-toml@0.3.2:3QfgGxxYtGHfJKQU7H0nEw==
+    - webfreak.debug@0.24.0:1zVcRsAhewYEX3/A9xjMNw==

.theia/launch.json

@@ -0,0 +1,14 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+      {
+          "type": "gdb",
+          "request": "launch",
+          "name": "Debug Rust Code",
+          "preLaunchTask": "cargo",
+          "target": "${workspaceFolder}/target/debug/nu",
+          "cwd": "${workspaceFolder}",
+          "valuesFormatting": "parseText"
+      }
+  ]
+}

.theia/tasks.json

@@ -0,0 +1,12 @@
+{
+    "tasks": [
+        {
+            "command": "cargo",
+            "args": [
+                "build"
+            ],
+            "type": "process",
+            "label": "cargo",
+        }
+    ],
+}

CODE_OF_CONDUCT.md

@@ -55,7 +55,7 @@ a project may be further defined and clarified by project maintainers.
 ## Enforcement
 
 Instances of abusive, harassing, or otherwise unacceptable behavior may be
-reported by contacting the project team at wycats@gmail.com. All
+reported by contacting the project team at wycats@gmail.com via email or by reaching out to @jturner, @gedge, or @andras_io on discord. All
 complaints will be reviewed and investigated and will result in a response that
 is deemed necessary and appropriate to the circumstances. The project team is
 obligated to maintain confidentiality with regard to the reporter of an incident.

CONTRIBUTING.md

@@ -9,3 +9,50 @@ For speedy contributions open it in Gitpod, nu will be pre-installed with the la
 To get live support from the community see our [Discord](https://discordapp.com/invite/NtAbbGn), [Twitter](https://twitter.com/nu_shell) or file an issue or feature request here on [GitHub](https://github.com/nushell/nushell/issues/new/choose)!
 <!--WIP-->
 
+# Developing
+## Set up
+This is no different than other Rust projects.
+
+```shell
+git clone https://github.com/nushell/nushell
+cd nushell
+cargo build
+```
+
+## Useful Commands
+
+Build and run Nushell:
+
+```shell
+cargo build --release && cargo run --release
+```
+
+Run Clippy on Nushell:
+
+```shell
+cargo clippy --all --features=stable
+```
+
+Run all tests:
+
+```shell
+cargo test --all --features=stable
+```
+
+Run all tests for a specific command
+
+```shell
+cargo test --package nu-cli --test main -- commands::<command_name_here>
+```
+
+Check to see if there are code formatting issues
+
+```shell
+cargo fmt --all -- --check
+```
+
+Format the code in the project
+
+```shell
+cargo fmt --all
+```

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "nu"
-version = "0.13.0"
+version = "0.15.0"
 authors = ["The Nu Project Contributors"]
 description = "A new type of shell"
 license = "MIT"
@@ -18,31 +18,30 @@ members = ["crates/*/"]
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-nu-cli = { version = "0.13.0", path = "./crates/nu-cli" }
-nu-source = { version = "0.13.0", path = "./crates/nu-source" }
-nu-plugin = { version = "0.13.0", path = "./crates/nu-plugin" }
-nu-protocol = { version = "0.13.0", path = "./crates/nu-protocol" }
-nu-errors = { version = "0.13.0", path = "./crates/nu-errors" }
-nu-parser = { version = "0.13.0", path = "./crates/nu-parser" }
-nu-value-ext = { version = "0.13.0", path = "./crates/nu-value-ext" }
-nu_plugin_average = { version = "0.13.0", path = "./crates/nu_plugin_average", optional=true }
-nu_plugin_binaryview = { version = "0.13.0", path = "./crates/nu_plugin_binaryview", optional=true }
-nu_plugin_fetch = { version = "0.13.0", path = "./crates/nu_plugin_fetch", optional=true }
-nu_plugin_inc = { version = "0.13.0", path = "./crates/nu_plugin_inc", optional=true }
-nu_plugin_match = { version = "0.13.0", path = "./crates/nu_plugin_match", optional=true }
-nu_plugin_post = { version = "0.13.0", path = "./crates/nu_plugin_post", optional=true }
-nu_plugin_ps = { version = "0.13.0", path = "./crates/nu_plugin_ps", optional=true }
-nu_plugin_str = { version = "0.13.0", path = "./crates/nu_plugin_str", optional=true }
-nu_plugin_sys = { version = "0.13.0", path = "./crates/nu_plugin_sys", optional=true }
-nu_plugin_textview = { version = "0.13.0", path = "./crates/nu_plugin_textview", optional=true }
-nu_plugin_tree = { version = "0.13.0", path = "./crates/nu_plugin_tree", optional=true }
+nu-cli = { version = "0.15.0", path = "./crates/nu-cli" }
+nu-source = { version = "0.15.0", path = "./crates/nu-source" }
+nu-plugin = { version = "0.15.0", path = "./crates/nu-plugin" }
+nu-protocol = { version = "0.15.0", path = "./crates/nu-protocol" }
+nu-errors = { version = "0.15.0", path = "./crates/nu-errors" }
+nu-parser = { version = "0.15.0", path = "./crates/nu-parser" }
+nu-value-ext = { version = "0.15.0", path = "./crates/nu-value-ext" }
+nu_plugin_binaryview = { version = "0.15.0", path = "./crates/nu_plugin_binaryview", optional=true }
+nu_plugin_fetch = { version = "0.15.0", path = "./crates/nu_plugin_fetch", optional=true }
+nu_plugin_inc = { version = "0.15.0", path = "./crates/nu_plugin_inc", optional=true }
+nu_plugin_match = { version = "0.15.0", path = "./crates/nu_plugin_match", optional=true }
+nu_plugin_post = { version = "0.15.0", path = "./crates/nu_plugin_post", optional=true }
+nu_plugin_ps = { version = "0.15.0", path = "./crates/nu_plugin_ps", optional=true }
+nu_plugin_start = { version = "0.15.0", path = "./crates/nu_plugin_start", optional=true }
+nu_plugin_sys = { version = "0.15.0", path = "./crates/nu_plugin_sys", optional=true }
+nu_plugin_textview = { version = "0.15.0", path = "./crates/nu_plugin_textview", optional=true }
+nu_plugin_tree = { version = "0.15.0", path = "./crates/nu_plugin_tree", optional=true }
 
-crossterm = { version = "0.17.2", optional = true }
-semver = { version = "0.9.0", optional = true }
-syntect = { version = "4.1", default-features = false, features = ["default-fancy"], optional = true}
+crossterm = { version = "0.17.5", optional = true }
+semver = { version = "0.10.0", optional = true }
+syntect = { version = "4.2", default-features = false, features = ["default-fancy"], optional = true}
 url = { version = "2.1.1", optional = true }
 
-clap = "2.33.0"
+clap = "2.33.1"
 ctrlc = "3.1.4"
 dunce = "1.0.0"
 futures = { version = "0.3", features = ["compat", "io-compat"] }
@@ -50,65 +49,36 @@ log = "0.4.8"
 pretty_env_logger = "0.4.0"
 
 [dev-dependencies]
-nu-test-support = { version = "0.13.0", path = "./crates/nu-test-support" }
+nu-test-support = { version = "0.15.0", path = "./crates/nu-test-support" }
 
 [build-dependencies]
 toml = "0.5.6"
-serde = { version = "1.0.106", features = ["derive"] }
-nu-build = { version = "0.13.0", path = "./crates/nu-build" }
+serde = { version = "1.0.110", features = ["derive"] }
+nu-build = { version = "0.15.0", path = "./crates/nu-build" }
 
 [features]
-# Test executables
-test-bins = []
-
-default = ["sys", "ps", "textview", "inc", "str"]
-stable = ["default", "starship-prompt", "binaryview", "match", "tree", "average", "post", "fetch", "clipboard-cli", "trash-support"]
+default = ["sys", "ps", "textview", "inc"]
+stable = ["default", "starship-prompt", "binaryview", "match", "tree", "post", "fetch", "clipboard-cli", "trash-support", "start"]
 
 # Default
 textview = ["crossterm", "syntect", "url", "nu_plugin_textview"]
 sys = ["nu_plugin_sys"]
 ps = ["nu_plugin_ps"]
 inc = ["semver", "nu_plugin_inc"]
-str = ["nu_plugin_str"]
 
 # Stable
-average = ["nu_plugin_average"]
 binaryview = ["nu_plugin_binaryview"]
 fetch = ["nu_plugin_fetch"]
 match = ["nu_plugin_match"]
 post = ["nu_plugin_post"]
 trace = ["nu-parser/trace"]
 tree = ["nu_plugin_tree"]
+start = ["nu_plugin_start"]
 
 clipboard-cli = ["nu-cli/clipboard-cli"]
 starship-prompt = ["nu-cli/starship-prompt"]
 trash-support = ["nu-cli/trash-support"]
 
-[[bin]]
-name = "fail"
-path = "crates/nu-test-support/src/bins/fail.rs"
-required-features = ["test-bins"]
-
-[[bin]]
-name = "chop"
-path = "crates/nu-test-support/src/bins/chop.rs"
-required-features = ["test-bins"]
-
-[[bin]]
-name = "cococo"
-path = "crates/nu-test-support/src/bins/cococo.rs"
-required-features = ["test-bins"]
-
-[[bin]]
-name = "nonu"
-path = "crates/nu-test-support/src/bins/nonu.rs"
-required-features = ["test-bins"]
-
-[[bin]]
-name = "iecho"
-path = "crates/nu-test-support/src/bins/iecho.rs"
-required-features = ["test-bins"]
-
 # Core plugins that ship with `cargo install nu` by default
 # Currently, Cargo limits us to installing only one binary
 # unless we use [[bin]], so we use this as a workaround
@@ -127,22 +97,12 @@ name = "nu_plugin_core_ps"
 path = "src/plugins/nu_plugin_core_ps.rs"
 required-features = ["ps"]
 
-[[bin]]
-name = "nu_plugin_core_str"
-path = "src/plugins/nu_plugin_core_str.rs"
-required-features = ["str"]
-
 [[bin]]
 name = "nu_plugin_core_sys"
 path = "src/plugins/nu_plugin_core_sys.rs"
 required-features = ["sys"]
 
 # Stable plugins
-[[bin]]
-name = "nu_plugin_stable_average"
-path = "src/plugins/nu_plugin_stable_average.rs"
-required-features = ["average"]
-
 [[bin]]
 name = "nu_plugin_stable_fetch"
 path = "src/plugins/nu_plugin_stable_fetch.rs"
@@ -168,6 +128,11 @@ name = "nu_plugin_stable_tree"
 path = "src/plugins/nu_plugin_stable_tree.rs"
 required-features = ["tree"]
 
+[[bin]]
+name = "nu_plugin_stable_start"
+path = "src/plugins/nu_plugin_stable_start.rs"
+required-features = ["start"]
+
 # Main nu binary
 [[bin]]
 name = "nu"

README.md

@@ -44,7 +44,7 @@ Try it in Gitpod.
 
 Up-to-date installation instructions can be found in the [installation chapter of the book](https://www.nushell.sh/book/en/installation.html).  **Windows users**: please note that Nu works on Windows 10 and does not currently have Windows 7/8.1 support.
 
-To build Nu, you will need to use the **latest stable (1.39 or later)** version of the compiler.
+To build Nu, you will need to use the **latest stable (1.41 or later)** version of the compiler.
 
 Required dependencies:
 
@@ -144,19 +144,20 @@ Commands that work in the pipeline fit into one of three categories:
 Commands are separated by the pipe symbol (`|`) to denote a pipeline flowing left to right.
 
 ```
-/home/jonathan/Source/nushell(master)> ls | where type == "Directory" | autoview
-────┬───────────┬───────────┬──────────┬────────┬──────────────┬────────────────
- #  │ name      │ type      │ readonly │ size   │ accessed     │ modified
-────┼───────────┼───────────┼──────────┼────────┼──────────────┼────────────────
-  0 │ .azure    │ Directory │          │ 4.1 KB │ 2 months ago │ a day ago
-  1 │ target    │ Directory │          │ 4.1 KB │ 3 days ago   │ 3 days ago
-  2 │ images    │ Directory │          │ 4.1 KB │ 2 months ago │ 2 weeks ago
-  3 │ tests     │ Directory │          │ 4.1 KB │ 2 months ago │ 37 minutes ago
-  4 │ tmp       │ Directory │          │ 4.1 KB │ 2 weeks ago  │ 2 weeks ago
-  5 │ src       │ Directory │          │ 4.1 KB │ 2 months ago │ 37 minutes ago
-  6 │ assets    │ Directory │          │ 4.1 KB │ a month ago  │ a month ago
-  7 │ docs      │ Directory │          │ 4.1 KB │ 2 months ago │ 2 months ago
-────┴───────────┴───────────┴──────────┴────────┴──────────────┴────────────────
+/home/jonathan/Source/nushell(master)> ls | where type == "Dir" | autoview
+───┬────────┬──────┬────────┬──────────────
+ # │ name   │ type │ size   │ modified
+───┼────────┼──────┼────────┼──────────────
+ 0 │ assets │ Dir  │ 4.1 KB │ 1 week ago
+ 1 │ crates │ Dir  │ 4.1 KB │ 4 days ago
+ 2 │ debian │ Dir  │ 4.1 KB │ 1 week ago
+ 3 │ docker │ Dir  │ 4.1 KB │ 1 week ago
+ 4 │ docs   │ Dir  │ 4.1 KB │ 1 week ago
+ 5 │ images │ Dir  │ 4.1 KB │ 1 week ago
+ 6 │ src    │ Dir  │ 4.1 KB │ 1 week ago
+ 7 │ target │ Dir  │ 4.1 KB │ 23 hours ago
+ 8 │ tests  │ Dir  │ 4.1 KB │ 1 week ago
+───┴────────┴──────┴────────┴──────────────
 ```
 
 Because most of the time you'll want to see the output of a pipeline, `autoview` is assumed.
@@ -171,14 +172,15 @@ For example, we could use the built-in `ps` command as well to get a list of the
 
 ```text
 /home/jonathan/Source/nushell(master)> ps | where cpu > 0
-───┬───────┬─────────────────┬──────────┬──────────
- # │ pid   │ name            │ status   │ cpu
-───┼───────┼─────────────────┼──────────┼──────────
- 0 │   992 │ chrome          │ Sleeping │ 6.988768
- 1 │  4240 │ chrome          │ Sleeping │ 5.645982
- 2 │ 13973 │ qemu-system-x86 │ Sleeping │ 4.996551
- 3 │ 15746 │ nu              │ Sleeping │ 84.59905
-───┴───────┴─────────────────┴──────────┴──────────
+───┬────────┬───────────────────┬──────────┬─────────┬──────────┬──────────
+ # │ pid    │ name              │ status   │ cpu     │ mem      │ virtual
+───┼────────┼───────────────────┼──────────┼─────────┼──────────┼──────────
+ 0 │    435 │ irq/142-SYNA327   │ Sleeping │  7.5699 │      0 B │      0 B
+ 1 │   1609 │ pulseaudio        │ Sleeping │  6.5605 │  10.6 MB │   2.3 GB
+ 2 │   1625 │ gnome-shell       │ Sleeping │  6.5684 │ 639.6 MB │   7.3 GB
+ 3 │   2202 │ Web Content       │ Sleeping │  6.8157 │ 320.8 MB │   3.0 GB
+ 4 │ 328788 │ nu_plugin_core_ps │ Sleeping │ 92.5750 │   5.9 MB │ 633.2 MB
+───┴────────┴───────────────────┴──────────┴─────────┴──────────┴──────────
 ```
 
 ## Opening files
@@ -188,45 +190,49 @@ For example, you can load a .toml file as structured data and explore it:
 
 ```
 /home/jonathan/Source/nushell(master)> open Cargo.toml
-──────────────────┬────────────────┬──────────────────
- bin              │ dependencies   │ dev-dependencies
-──────────────────┼────────────────┼──────────────────
- [table: 12 rows] │ [table: 1 row] │ [table: 1 row]
-──────────────────┴────────────────┴──────────────────
+────────────────────┬───────────────────────────
+ bin                │ [table 18 rows]
+ build-dependencies │ [row nu-build serde toml]
+ dependencies       │ [row 29 columns]
+ dev-dependencies   │ [row nu-test-support]
+ features           │ [row 19 columns]
+ package            │ [row 12 columns]
+ workspace          │ [row members]
+────────────────────┴───────────────────────────
 ```
 
 We can pipeline this into a command that gets the contents of one of the columns:
 
 ```
 /home/jonathan/Source/nushell(master)> open Cargo.toml | get package
-─────────────────┬────────────────────────────┬─────────┬─────────┬──────┬─────────
- authors         │ description                │ edition │ license │ name │ version
-─────────────────┼────────────────────────────┼─────────┼─────────┼──────┼─────────
- [table: 3 rows] │ A shell for the GitHub era │ 2018    │ MIT     │ nu   │ 0.9.0
-─────────────────┴────────────────────────────┴─────────┴─────────┴──────┴─────────
+───────────────┬────────────────────────────────────
+ authors       │ [table 1 rows]
+ default-run   │ nu
+ description   │ A new type of shell
+ documentation │ https://www.nushell.sh/book/
+ edition       │ 2018
+ exclude       │ [table 1 rows]
+ homepage      │ https://www.nushell.sh
+ license       │ MIT
+ name          │ nu
+ readme        │ README.md
+ repository    │ https://github.com/nushell/nushell
+ version       │ 0.14.1
+───────────────┴────────────────────────────────────
 ```
 
 Finally, we can use commands outside of Nu once we have the data we want:
 
 ```
 /home/jonathan/Source/nushell(master)> open Cargo.toml | get package.version | echo $it
-0.9.0
+0.14.1
 ```
 
 Here we use the variable `$it` to refer to the value being piped to the external command.
 
 ## Configuration
 
-Nu has early support for configuring the shell. It currently supports the following settings:
-
-| Variable        | Type                 | Description                                                    |
-| --------------- | -------------------- | -------------------------------------------------------------- |
-| path            | table of strings     | PATH to use to find binaries                                   |
-| env             | row                  | the environment variables to pass to external commands         |
-| ctrlc_exit      | boolean              | whether or not to exit Nu after multiple ctrl-c presses        |
-| table_mode      | "light" or other     | enable lightweight or normal tables                            |
-| edit_mode       | "vi" or "emacs"      | changes line editing to "vi" or "emacs" mode                   |
-| completion_mode | "circular" or "list" | changes completion type to "circular" (default) or "list" mode |
+Nu has early support for configuring the shell. You can refer to the book for a list of [all supported variables](https://www.nushell.sh/book/en/configuration.html).
 
 To set one of these variables, you can use `config --set`. For example:
 
@@ -276,6 +282,31 @@ Nu adheres closely to a set of goals that make up its design philosophy. As feat
 
 You can find a list of Nu commands, complete with documentation, in [quick command references](https://www.nushell.sh/documentation.html#quick-command-references).
 
+# Progress
+
+Nu is in heavy development, and will naturally change as it matures and people use it.  The chart below isn't meant to be exhaustive, but rather helps give an idea for some of the areas of development and their relative completion:
+
+| Features | Not started | Prototype | MVP | Preview | Mature | Notes
+| -------- |:-----------:|:---------:|:---:|:-------:|:------:| -----
+| Aliases  |             |     X     |     |         |        | Initial implementation but lacks necessary features
+| Notebook |             |     X     |     |         |        | Initial jupyter support, but it loses state and lacks features
+| File ops |             |           |  X  |         |        | cp, mv, rm, mkdir have some support, but lacking others 
+| Environment |          |     X     |     |         |        | Temporary environment, but no session-wide env variables 
+| Shells   |             |     X     |     |         |        | Basic value and file shells, but no opt-in/opt-out for commands
+| Protocol |             |           |  X  |         |        | Streaming protocol is serviceable
+| Plugins  |             |     X     |     |         |        | Plugins work on one row at a time, lack batching and expression eval 
+| Errors   |             |           |  X  |         |        | Error reporting works, but could use usability polish
+| Documentation |        |     X     |     |         |        | Book and related are barebones and lack task-based lessons
+| Paging   |             |     X     |     |         |        | Textview has paging, but we'd like paging for tables
+| Functions|      X      |           |     |         |        | No functions, yet, only aliases
+| Variables|      X      |           |     |         |        | Nu doesn't yet support variables 
+| Completions |          |     X     |     |         |        | Completions are currently barebones, at best
+| Type-checking |        |     X     |     |         |        | Commands check basic types, but input/output isn't checked
+
+# Contributing
+
+See [Contributing](CONTRIBUTING.md) for details.
+
 # License
 
 The project is made available under the MIT license. See the `LICENSE` file for more information.

crates/nu-build/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "nu-build"
-version = "0.13.0"
+version = "0.15.0"
 authors = ["The Nu Project Contributors"]
 edition = "2018"
 description = "Core build system for nushell"
@@ -10,7 +10,7 @@ license = "MIT"
 doctest = false
 
 [dependencies]
-serde = { version = "1.0.106", features = ["derive"] }
+serde = { version = "1.0.110", features = ["derive"] }
 lazy_static = "1.4.0"
-serde_json = "1.0.51"
+serde_json = "1.0.53"
 toml = "0.5.6"

crates/nu-cli/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "nu-cli"
-version = "0.13.0"
+version = "0.15.0"
 authors = ["The Nu Project Contributors"]
 description = "CLI for nushell"
 edition = "2018"
@@ -10,37 +10,41 @@ license = "MIT"
 doctest = false
 
 [dependencies]
-nu-source = { version = "0.13.0", path = "../nu-source" }
-nu-plugin = { version = "0.13.0", path = "../nu-plugin" }
-nu-protocol = { version = "0.13.0", path = "../nu-protocol" }
-nu-errors = { version = "0.13.0", path = "../nu-errors" }
-nu-parser = { version = "0.13.0", path = "../nu-parser" }
-nu-value-ext = { version = "0.13.0", path = "../nu-value-ext" }
-nu-test-support = { version = "0.13.0", path = "../nu-test-support" }
+nu-source = { version = "0.15.0", path = "../nu-source" }
+nu-plugin = { version = "0.15.0", path = "../nu-plugin" }
+nu-protocol = { version = "0.15.0", path = "../nu-protocol" }
+nu-errors = { version = "0.15.0", path = "../nu-errors" }
+nu-parser = { version = "0.15.0", path = "../nu-parser" }
+nu-value-ext = { version = "0.15.0", path = "../nu-value-ext" }
+nu-test-support = { version = "0.15.0", path = "../nu-test-support" }
 
 ansi_term = "0.12.1"
 app_dirs = "1.2.1"
+async-recursion = "0.3.1"
+async-trait = "0.1.31"
+directories = "2.0.2"
 async-stream = "0.2"
-base64 = "0.12.0"
-bigdecimal = { version = "0.1.0", features = ["serde"] }
+base64 = "0.12.1"
+bigdecimal = { version = "0.1.2", features = ["serde"] }
 bson = { version = "0.14.1", features = ["decimal128"] }
-byte-unit = "3.0.3"
+byte-unit = "3.1.3"
 bytes = "0.5.4"
 calamine = "0.16"
 cfg-if = "0.1"
 chrono = { version = "0.4.11", features = ["serde"] }
-clap = "2.33.0"
+clap = "2.33.1"
 csv = "1.1"
 ctrlc = "3.1.4"
 derive-new = "0.5.8"
 dirs = "2.0.2"
 dunce = "1.0.0"
+eml-parser = "0.1.0"
 filesize = "0.2.0"
 futures = { version = "0.3", features = ["compat", "io-compat"] }
-futures-util = "0.3.4"
+futures-util = "0.3.5"
 futures_codec = "0.4"
-getset = "0.1.0"
-git2 = { version = "0.13.1", default_features = false }
+getset = "0.1.1"
+git2 = { version = "0.13.6", default_features = false }
 glob = "0.3.0"
 hex = "0.4"
 htmlescape = "0.3.1"
@@ -48,14 +52,14 @@ ical = "0.6.*"
 ichwh = "0.3.4"
 indexmap = { version = "1.3.2", features = ["serde-1"] }
 itertools = "0.9.0"
-language-reporting = "0.4.0"
+codespan-reporting = "0.9.4"
 log = "0.4.8"
 meval = "0.2"
 natural = "0.5.0"
 num-bigint = { version = "0.2.6", features = ["serde"] }
 num-traits = "0.2.11"
-parking_lot = "0.10.0"
-pin-utils = "0.1.0-alpha.4"
+parking_lot = "0.10.2"
+pin-utils = "0.1.0"
 pretty-hex = "0.1.1"
 pretty_env_logger = "0.4.0"
 prettytable-rs = "0.8.0"
@@ -63,13 +67,13 @@ ptree = {version = "0.2" }
 query_interface = "0.3.5"
 rand = "0.7"
 regex = "1"
-roxmltree = "0.10.1"
-rustyline = "6.1.1"
-serde = { version = "1.0.106", features = ["derive"] }
+roxmltree = "0.11.0"
+rustyline = "6.2.0"
+serde = { version = "1.0.110", features = ["derive"] }
 serde-hjson = "0.9.1"
-serde_bytes = "0.11.3"
+serde_bytes = "0.11.4"
 serde_ini = "0.2.0"
-serde_json = "1.0.51"
+serde_json = "1.0.53"
 serde_urlencoded = "0.6.1"
 serde_yaml = "0.8"
 shellexpand = "2.0.0"
@@ -80,22 +84,24 @@ termcolor = "1.1.0"
 textwrap = {version = "0.11.0", features = ["term_size"]}
 toml = "0.5.6"
 typetag = "0.1.4"
-umask = "0.1"
+umask = "1.0.0"
 unicode-xid = "0.2.0"
+which = "3"
 
-trash = { version = "1.0.0", optional = true }
+trash = { version = "1.0.1", optional = true }
 clipboard = { version = "0.5", optional = true }
-starship = { version = "0.39.0", optional = true }
+starship = { version = "0.41.3", optional = true }
+rayon = "1.3.0"
 
 [target.'cfg(unix)'.dependencies]
 users = "0.10.0"
 
 [dependencies.rusqlite]
-version = "0.22.0"
+version = "0.23.1"
 features = ["bundled", "blob"]
 
 [build-dependencies]
-nu-build = { version = "0.13.0", path = "../nu-build" }
+nu-build = { version = "0.15.0", path = "../nu-build" }
 
 [dev-dependencies]
 quickcheck = "0.9"

crates/nu-cli/src/cli.rs

@@ -6,12 +6,14 @@ use crate::commands::whole_stream_command;
 use crate::context::Context;
 #[cfg(not(feature = "starship-prompt"))]
 use crate::git::current_branch;
+use crate::path::canonicalize;
 use crate::prelude::*;
+use crate::EnvironmentSyncer;
 use futures_codec::FramedRead;
 
 use nu_errors::ShellError;
 use nu_protocol::hir::{ClassifiedCommand, Expression, InternalCommand, Literal, NamedArguments};
-use nu_protocol::{Primitive, ReturnSuccess, Scope, Signature, UntaggedValue, Value};
+use nu_protocol::{Primitive, ReturnSuccess, Signature, UntaggedValue, Value};
 
 use log::{debug, trace};
 use rustyline::error::ReadlineError;
@@ -22,9 +24,11 @@ use rustyline::{
 use std::error::Error;
 use std::io::{BufRead, BufReader, Write};
 use std::iter::Iterator;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::sync::atomic::Ordering;
 
+use rayon::prelude::*;
+
 fn load_plugin(path: &std::path::Path, context: &mut Context) -> Result<(), ShellError> {
     let mut child = std::process::Command::new(path)
         .stdin(std::process::Stdio::piped())
@@ -106,13 +110,19 @@ fn search_paths() -> Vec<std::path::PathBuf> {
         }
     }
 
-    #[cfg(not(debug_assertions))]
-    {
-        match env::var_os("PATH") {
-            Some(paths) => {
-                search_paths.extend(env::split_paths(&paths).collect::<Vec<_>>());
+    if let Ok(config) = crate::data::config::config(Tag::unknown()) {
+        if let Some(plugin_dirs) = config.get("plugin_dirs") {
+            if let Value {
+                value: UntaggedValue::Table(pipelines),
+                ..
+            } = plugin_dirs
+            {
+                for pipeline in pipelines {
+                    if let Ok(plugin_dir) = pipeline.as_string() {
+                        search_paths.push(PathBuf::from(plugin_dir));
+                    }
+                }
             }
-            None => println!("PATH is not defined in the environment."),
         }
     }
 
@@ -131,62 +141,60 @@ pub fn load_plugins(context: &mut Context) -> Result<(), ShellError> {
 
         pattern.push(std::path::Path::new("nu_plugin_[a-z0-9][a-z0-9]*"));
 
-        match glob::glob_with(&pattern.to_string_lossy(), opts) {
-            Err(_) => {}
-            Ok(binaries) => {
-                for bin in binaries.filter_map(Result::ok) {
-                    if !bin.is_file() {
-                        continue;
+        let plugs: Vec<_> = glob::glob_with(&pattern.to_string_lossy(), opts)?
+            .filter_map(|x| x.ok())
+            .collect();
+
+        let _failures: Vec<_> = plugs
+            .par_iter()
+            .map(|path| {
+                let bin_name = {
+                    if let Some(name) = path.file_name() {
+                        match name.to_str() {
+                            Some(raw) => raw,
+                            None => "",
+                        }
+                    } else {
+                        ""
+                    }
+                };
+
+                let is_valid_name = {
+                    #[cfg(windows)]
+                    {
+                        bin_name
+                            .chars()
+                            .all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '.')
                     }
 
-                    let bin_name = {
-                        if let Some(name) = bin.file_name() {
-                            match name.to_str() {
-                                Some(raw) => raw,
-                                None => continue,
-                            }
-                        } else {
-                            continue;
-                        }
-                    };
-
-                    let is_valid_name = {
-                        #[cfg(windows)]
-                        {
-                            bin_name
-                                .chars()
-                                .all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '.')
-                        }
-
-                        #[cfg(not(windows))]
-                        {
-                            bin_name
-                                .chars()
-                                .all(|c| c.is_ascii_alphanumeric() || c == '_')
-                        }
-                    };
-
-                    let is_executable = {
-                        #[cfg(windows)]
-                        {
-                            bin_name.ends_with(".exe") || bin_name.ends_with(".bat")
-                        }
-
-                        #[cfg(not(windows))]
-                        {
-                            true
-                        }
-                    };
-
-                    if is_valid_name && is_executable {
-                        trace!("Trying {:?}", bin.display());
-
-                        // we are ok if this plugin load fails
-                        let _ = load_plugin(&bin, context);
+                    #[cfg(not(windows))]
+                    {
+                        bin_name
+                            .chars()
+                            .all(|c| c.is_ascii_alphanumeric() || c == '_')
                     }
+                };
+
+                let is_executable = {
+                    #[cfg(windows)]
+                    {
+                        bin_name.ends_with(".exe") || bin_name.ends_with(".bat")
+                    }
+
+                    #[cfg(not(windows))]
+                    {
+                        true
+                    }
+                };
+
+                if is_valid_name && is_executable {
+                    trace!("Trying {:?}", path.display());
+
+                    // we are ok if this plugin load fails
+                    let _ = load_plugin(&path, &mut context.clone());
                 }
-            }
-        }
+            })
+            .collect();
     }
 
     Ok(())
@@ -223,7 +231,8 @@ fn create_default_starship_config() -> Option<toml::Value> {
 }
 
 pub fn create_default_context(
-    syncer: &mut crate::env::environment_syncer::EnvironmentSyncer,
+    syncer: &mut crate::EnvironmentSyncer,
+    interactive: bool,
 ) -> Result<Context, Box<dyn Error>> {
     syncer.load_environment();
 
@@ -237,28 +246,30 @@ pub fn create_default_context(
         context.add_commands(vec![
             // System/file operations
             whole_stream_command(Pwd),
-            per_item_command(Ls),
-            per_item_command(Du),
+            whole_stream_command(Ls),
+            whole_stream_command(Du),
             whole_stream_command(Cd),
-            per_item_command(Remove),
-            per_item_command(Open),
+            whole_stream_command(Remove),
+            whole_stream_command(Open),
             whole_stream_command(Config),
-            per_item_command(Help),
-            per_item_command(History),
+            whole_stream_command(Help),
+            whole_stream_command(History),
             whole_stream_command(Save),
-            per_item_command(Touch),
-            per_item_command(Cpy),
+            whole_stream_command(Touch),
+            whole_stream_command(Cpy),
             whole_stream_command(Date),
-            per_item_command(Calc),
-            per_item_command(Mkdir),
-            per_item_command(Move),
-            per_item_command(Kill),
+            whole_stream_command(Cal),
+            whole_stream_command(Calc),
+            whole_stream_command(Mkdir),
+            whole_stream_command(Move),
+            whole_stream_command(Kill),
             whole_stream_command(Version),
             whole_stream_command(Clear),
             whole_stream_command(What),
             whole_stream_command(Which),
             whole_stream_command(Debug),
-            per_item_command(Alias),
+            whole_stream_command(Alias),
+            whole_stream_command(WithEnv),
             // Statistics
             whole_stream_command(Size),
             whole_stream_command(Count),
@@ -268,24 +279,37 @@ pub fn create_default_context(
             whole_stream_command(Next),
             whole_stream_command(Previous),
             whole_stream_command(Shells),
-            per_item_command(Enter),
+            whole_stream_command(Enter),
             whole_stream_command(Exit),
             // Viewers
             whole_stream_command(Autoview),
             whole_stream_command(Table),
             // Text manipulation
+            whole_stream_command(Split),
             whole_stream_command(SplitColumn),
             whole_stream_command(SplitRow),
             whole_stream_command(Lines),
             whole_stream_command(Trim),
-            per_item_command(Echo),
-            per_item_command(Parse),
+            whole_stream_command(Echo),
+            whole_stream_command(Parse),
+            whole_stream_command(Str),
+            whole_stream_command(StrToDecimal),
+            whole_stream_command(StrToInteger),
+            whole_stream_command(StrDowncase),
+            whole_stream_command(StrUpcase),
+            whole_stream_command(StrCapitalize),
+            whole_stream_command(StrFindReplace),
+            whole_stream_command(StrSubstring),
+            whole_stream_command(StrSet),
+            whole_stream_command(StrToDatetime),
+            whole_stream_command(StrTrim),
+            whole_stream_command(BuildString),
             // Column manipulation
             whole_stream_command(Reject),
-            whole_stream_command(Pick),
+            whole_stream_command(Select),
             whole_stream_command(Get),
-            per_item_command(Edit),
-            per_item_command(Insert),
+            whole_stream_command(Update),
+            whole_stream_command(Insert),
             whole_stream_command(SplitBy),
             // Row manipulation
             whole_stream_command(Reverse),
@@ -293,28 +317,38 @@ pub fn create_default_context(
             whole_stream_command(Prepend),
             whole_stream_command(SortBy),
             whole_stream_command(GroupBy),
+            whole_stream_command(GroupByDate),
             whole_stream_command(First),
             whole_stream_command(Last),
-            whole_stream_command(Skip),
             whole_stream_command(Nth),
-            per_item_command(Format),
-            per_item_command(Where),
+            whole_stream_command(Drop),
+            whole_stream_command(Format),
+            whole_stream_command(Where),
             whole_stream_command(Compact),
             whole_stream_command(Default),
+            whole_stream_command(Skip),
+            whole_stream_command(SkipUntil),
             whole_stream_command(SkipWhile),
+            whole_stream_command(Keep),
+            whole_stream_command(KeepUntil),
+            whole_stream_command(KeepWhile),
             whole_stream_command(Range),
             whole_stream_command(Rename),
             whole_stream_command(Uniq),
-            per_item_command(Each),
+            whole_stream_command(Each),
+            whole_stream_command(IsEmpty),
             // Table manipulation
+            whole_stream_command(Merge),
             whole_stream_command(Shuffle),
             whole_stream_command(Wrap),
             whole_stream_command(Pivot),
             whole_stream_command(Headers),
             // Data processing
             whole_stream_command(Histogram),
+            whole_stream_command(Average),
             whole_stream_command(Sum),
             // File format output
+            whole_stream_command(To),
             whole_stream_command(ToBSON),
             whole_stream_command(ToCSV),
             whole_stream_command(ToHTML),
@@ -327,7 +361,9 @@ pub fn create_default_context(
             whole_stream_command(ToURL),
             whole_stream_command(ToYAML),
             // File format input
+            whole_stream_command(From),
             whole_stream_command(FromCSV),
+            whole_stream_command(FromEML),
             whole_stream_command(FromTSV),
             whole_stream_command(FromSSV),
             whole_stream_command(FromINI),
@@ -345,7 +381,7 @@ pub fn create_default_context(
             whole_stream_command(FromIcs),
             whole_stream_command(FromVcf),
             // "Private" commands (not intended to be accessed directly)
-            whole_stream_command(RunExternalCommand),
+            whole_stream_command(RunExternalCommand { interactive }),
         ]);
 
         cfg_if::cfg_if! {
@@ -361,9 +397,7 @@ pub fn create_default_context(
 
         #[cfg(feature = "clipboard")]
         {
-            context.add_commands(vec![whole_stream_command(
-                crate::commands::clip::clipboard::Clip,
-            )]);
+            context.add_commands(vec![whole_stream_command(crate::commands::clip::Clip)]);
         }
     }
 
@@ -375,7 +409,7 @@ pub async fn run_vec_of_pipelines(
     redirect_stdin: bool,
 ) -> Result<(), Box<dyn Error>> {
     let mut syncer = crate::EnvironmentSyncer::new();
-    let mut context = crate::create_default_context(&mut syncer)?;
+    let mut context = create_default_context(&mut syncer, false)?;
 
     let _ = crate::load_plugins(&mut context);
 
@@ -445,14 +479,14 @@ pub async fn run_pipeline_standalone(
             };
 
             context.maybe_print_errors(Text::from(line));
-            if error_code != 0 {
+            if error_code != 0 && exit_on_error {
                 std::process::exit(error_code);
             }
         }
 
         LineResult::Error(line, err) => {
-            context.with_host(|host| {
-                print_err(err, host, &Text::from(line.clone()));
+            context.with_host(|_host| {
+                print_err(err, &Text::from(line.clone()));
             });
 
             context.maybe_print_errors(Text::from(line));
@@ -468,9 +502,14 @@ pub async fn run_pipeline_standalone(
 }
 
 /// The entry point for the CLI. Will register all known internal commands, load experimental commands, load plugins, then prepare the prompt and line reader for input.
-pub async fn cli() -> Result<(), Box<dyn Error>> {
-    let mut syncer = crate::env::environment_syncer::EnvironmentSyncer::new();
-    let mut context = create_default_context(&mut syncer)?;
+pub async fn cli(
+    mut syncer: EnvironmentSyncer,
+    mut context: Context,
+) -> Result<(), Box<dyn Error>> {
+    #[cfg(windows)]
+    const DEFAULT_COMPLETION_MODE: CompletionType = CompletionType::Circular;
+    #[cfg(not(windows))]
+    const DEFAULT_COMPLETION_MODE: CompletionType = CompletionType::List;
 
     let _ = load_plugins(&mut context);
 
@@ -550,14 +589,28 @@ pub async fn cli() -> Result<(), Box<dyn Error>> {
 
         rl.set_edit_mode(edit_mode);
 
+        let max_history_size = config::config(Tag::unknown())?
+            .get("history_size")
+            .map(|i| i.value.expect_int())
+            .unwrap_or(100_000);
+
+        rl.set_max_history_size(max_history_size as usize);
+
+        let key_timeout = config::config(Tag::unknown())?
+            .get("key_timeout")
+            .map(|s| s.value.expect_int())
+            .unwrap_or(1);
+
+        rl.set_keyseq_timeout(key_timeout as i32);
+
         let completion_mode = config::config(Tag::unknown())?
             .get("completion_mode")
             .map(|s| match s.value.expect_string() {
                 "list" => CompletionType::List,
                 "circular" => CompletionType::Circular,
-                _ => CompletionType::Circular,
+                _ => DEFAULT_COMPLETION_MODE,
             })
-            .unwrap_or(CompletionType::Circular);
+            .unwrap_or(DEFAULT_COMPLETION_MODE);
 
         rl.set_completion_type(completion_mode);
 
@@ -565,6 +618,7 @@ pub async fn cli() -> Result<(), Box<dyn Error>> {
             #[cfg(feature = "starship-prompt")]
             {
                 std::env::set_var("STARSHIP_SHELL", "");
+                std::env::set_var("PWD", &cwd);
                 let mut starship_context =
                     starship::context::Context::new_with_dir(clap::ArgMatches::default(), cwd);
 
@@ -628,8 +682,8 @@ pub async fn cli() -> Result<(), Box<dyn Error>> {
                 rl.add_history_entry(line.clone());
                 let _ = rl.save_history(&History::path());
 
-                context.with_host(|host| {
-                    print_err(err, host, &Text::from(line.clone()));
+                context.with_host(|_host| {
+                    print_err(err, &Text::from(line.clone()));
                 });
 
                 context.maybe_print_errors(Text::from(line.clone()));
@@ -698,6 +752,7 @@ async fn process_line(
 
         Ok(line) => {
             let line = chomp_newline(line);
+            ctx.raw_input = line.to_string();
 
             let result = match nu_parser::lite_parse(&line, 0) {
                 Err(err) => {
@@ -710,7 +765,7 @@ async fn process_line(
             debug!("=== Parsed ===");
             debug!("{:#?}", result);
 
-            let classified_block = nu_parser::classify_block(&result, ctx.registry());
+            let mut classified_block = nu_parser::classify_block(&result, ctx.registry());
 
             debug!("{:#?}", classified_block);
             //println!("{:#?}", pipeline);
@@ -759,9 +814,9 @@ async fn process_line(
                             .as_ref()
                             .map(NamedArguments::is_empty)
                             .unwrap_or(true)
-                        && dunce::canonicalize(&name).is_ok()
-                        && PathBuf::from(&name).is_dir()
-                        && ichwh::which(&name).await.unwrap_or(None).is_none()
+                        && canonicalize(ctx.shell_manager.path(), name).is_ok()
+                        && Path::new(&name).is_dir()
+                        && which::which(&name).is_err()
                     {
                         // Here we work differently if we're in Windows because of the expected Windows behavior
                         #[cfg(windows)]
@@ -787,7 +842,8 @@ async fn process_line(
                                     ctx.shell_manager.set_path(val.to_string());
                                     return LineResult::Success(line.to_string());
                                 } else {
-                                    ctx.shell_manager.set_path(name.to_string());
+                                    ctx.shell_manager
+                                        .set_path(format!("{}\\", name.to_string()));
                                     return LineResult::Success(line.to_string());
                                 }
                             } else {
@@ -829,7 +885,20 @@ async fn process_line(
                 InputStream::empty()
             };
 
-            match run_block(&classified_block.block, ctx, input_stream, &Scope::empty()).await {
+            classified_block.block.expand_it_usage();
+
+            trace!("{:#?}", classified_block);
+            let env = ctx.get_env();
+            match run_block(
+                &classified_block.block,
+                ctx,
+                input_stream,
+                &Value::nothing(),
+                &IndexMap::new(),
+                &env,
+            )
+            .await
+            {
                 Ok(input) => {
                     // Running a pipeline gives us back a stream that we can then
                     // work through. At the top level, we just want to pull on the
@@ -841,11 +910,15 @@ async fn process_line(
                         shell_manager: ctx.shell_manager.clone(),
                         host: ctx.host.clone(),
                         ctrl_c: ctx.ctrl_c.clone(),
+                        current_errors: ctx.current_errors.clone(),
                         registry: ctx.registry.clone(),
                         name: Tag::unknown(),
+                        raw_input: line.to_string(),
                     };
 
-                    if let Ok(mut output_stream) = crate::commands::autoview::autoview(context) {
+                    if let Ok(mut output_stream) =
+                        crate::commands::autoview::autoview(context).await
+                    {
                         loop {
                             match output_stream.try_next().await {
                                 Ok(Some(ReturnSuccess::Value(Value {
@@ -877,26 +950,25 @@ async fn process_line(
     }
 }
 
-pub fn print_err(err: ShellError, host: &dyn Host, source: &Text) {
+pub fn print_err(err: ShellError, source: &Text) {
     if let Some(diag) = err.into_diagnostic() {
-        let writer = host.err_termcolor();
-        let mut source = source.to_string();
-        source.push_str(" ");
-        let files = nu_parser::Files::new(source);
+        let source = source.to_string();
+        let mut files = codespan_reporting::files::SimpleFiles::new();
+        files.add("shell", source);
+
+        let writer = codespan_reporting::term::termcolor::StandardStream::stderr(
+            codespan_reporting::term::termcolor::ColorChoice::Always,
+        );
+        let config = codespan_reporting::term::Config::default();
+
         let _ = std::panic::catch_unwind(move || {
-            let _ = language_reporting::emit(
-                &mut writer.lock(),
-                &files,
-                &diag,
-                &language_reporting::DefaultConfig,
-            );
+            let _ = codespan_reporting::term::emit(&mut writer.lock(), &config, &files, &diag);
         });
     }
 }
 
 #[cfg(test)]
 mod tests {
-
     #[quickcheck]
     fn quickcheck_parse(data: String) -> bool {
         if let Ok(lite_block) = nu_parser::lite_parse(&data, 0) {

crates/nu-cli/src/commands.rs

@@ -8,9 +8,13 @@ pub(crate) mod alias;
 pub(crate) mod append;
 pub(crate) mod args;
 pub(crate) mod autoview;
+pub(crate) mod average;
+pub(crate) mod build_string;
+pub(crate) mod cal;
 pub(crate) mod calc;
 pub(crate) mod cd;
 pub(crate) mod classified;
+#[cfg(feature = "clipboard")]
 pub(crate) mod clip;
 pub(crate) mod command;
 pub(crate) mod compact;
@@ -20,18 +24,20 @@ pub(crate) mod cp;
 pub(crate) mod date;
 pub(crate) mod debug;
 pub(crate) mod default;
+pub(crate) mod drop;
 pub(crate) mod du;
 pub(crate) mod each;
 pub(crate) mod echo;
-pub(crate) mod edit;
 pub(crate) mod enter;
 #[allow(unused)]
 pub(crate) mod evaluate_by;
 pub(crate) mod exit;
 pub(crate) mod first;
 pub(crate) mod format;
+pub(crate) mod from;
 pub(crate) mod from_bson;
 pub(crate) mod from_csv;
+pub(crate) mod from_eml;
 pub(crate) mod from_ics;
 pub(crate) mod from_ini;
 pub(crate) mod from_json;
@@ -47,23 +53,28 @@ pub(crate) mod from_xml;
 pub(crate) mod from_yaml;
 pub(crate) mod get;
 pub(crate) mod group_by;
+pub(crate) mod group_by_date;
 pub(crate) mod headers;
 pub(crate) mod help;
 pub(crate) mod histogram;
 pub(crate) mod history;
 pub(crate) mod insert;
+pub(crate) mod is_empty;
+pub(crate) mod keep;
+pub(crate) mod keep_until;
+pub(crate) mod keep_while;
 pub(crate) mod last;
 pub(crate) mod lines;
 pub(crate) mod ls;
 #[allow(unused)]
 pub(crate) mod map_max_by;
+pub(crate) mod merge;
 pub(crate) mod mkdir;
 pub(crate) mod mv;
 pub(crate) mod next;
 pub(crate) mod nth;
 pub(crate) mod open;
 pub(crate) mod parse;
-pub(crate) mod pick;
 pub(crate) mod pivot;
 pub(crate) mod plugin;
 pub(crate) mod prepend;
@@ -79,20 +90,23 @@ pub(crate) mod rm;
 pub(crate) mod run_alias;
 pub(crate) mod run_external;
 pub(crate) mod save;
+pub(crate) mod select;
 pub(crate) mod shells;
 pub(crate) mod shuffle;
 pub(crate) mod size;
 pub(crate) mod skip;
+pub(crate) mod skip_until;
 pub(crate) mod skip_while;
 pub(crate) mod sort_by;
+pub(crate) mod split;
 pub(crate) mod split_by;
-pub(crate) mod split_column;
-pub(crate) mod split_row;
+pub(crate) mod str_;
 pub(crate) mod sum;
 #[allow(unused)]
 pub(crate) mod t_sort_by;
 pub(crate) mod table;
 pub(crate) mod tags;
+pub(crate) mod to;
 pub(crate) mod to_bson;
 pub(crate) mod to_csv;
 pub(crate) mod to_html;
@@ -105,21 +119,25 @@ pub(crate) mod to_url;
 pub(crate) mod to_yaml;
 pub(crate) mod trim;
 pub(crate) mod uniq;
+pub(crate) mod update;
 pub(crate) mod version;
 pub(crate) mod what;
 pub(crate) mod where_;
 pub(crate) mod which_;
+pub(crate) mod with_env;
 pub(crate) mod wrap;
 
 pub(crate) use autoview::Autoview;
 pub(crate) use cd::Cd;
 pub(crate) use command::{
-    per_item_command, whole_stream_command, Command, PerItemCommand, UnevaluatedCallInfo,
-    WholeStreamCommand,
+    whole_stream_command, Command, Example, UnevaluatedCallInfo, WholeStreamCommand,
 };
 
 pub(crate) use alias::Alias;
 pub(crate) use append::Append;
+pub(crate) use average::Average;
+pub(crate) use build_string::BuildString;
+pub(crate) use cal::Cal;
 pub(crate) use calc::Calc;
 pub(crate) use compact::Compact;
 pub(crate) use config::Config;
@@ -128,10 +146,12 @@ pub(crate) use cp::Cpy;
 pub(crate) use date::Date;
 pub(crate) use debug::Debug;
 pub(crate) use default::Default;
+pub(crate) use drop::Drop;
 pub(crate) use du::Du;
 pub(crate) use each::Each;
 pub(crate) use echo::Echo;
-pub(crate) use edit::Edit;
+pub(crate) use is_empty::IsEmpty;
+pub(crate) use update::Update;
 pub(crate) mod kill;
 pub(crate) use kill::Kill;
 pub(crate) mod clear;
@@ -143,8 +163,10 @@ pub(crate) use evaluate_by::EvaluateBy;
 pub(crate) use exit::Exit;
 pub(crate) use first::First;
 pub(crate) use format::Format;
+pub(crate) use from::From;
 pub(crate) use from_bson::FromBSON;
 pub(crate) use from_csv::FromCSV;
+pub(crate) use from_eml::FromEML;
 pub(crate) use from_ics::FromIcs;
 pub(crate) use from_ini::FromINI;
 pub(crate) use from_json::FromJSON;
@@ -162,23 +184,27 @@ pub(crate) use from_yaml::FromYAML;
 pub(crate) use from_yaml::FromYML;
 pub(crate) use get::Get;
 pub(crate) use group_by::GroupBy;
+pub(crate) use group_by_date::GroupByDate;
 pub(crate) use headers::Headers;
 pub(crate) use help::Help;
 pub(crate) use histogram::Histogram;
 pub(crate) use history::History;
 pub(crate) use insert::Insert;
+pub(crate) use keep::Keep;
+pub(crate) use keep_until::KeepUntil;
+pub(crate) use keep_while::KeepWhile;
 pub(crate) use last::Last;
 pub(crate) use lines::Lines;
 pub(crate) use ls::Ls;
 #[allow(unused_imports)]
 pub(crate) use map_max_by::MapMaxBy;
+pub(crate) use merge::Merge;
 pub(crate) use mkdir::Mkdir;
 pub(crate) use mv::Move;
 pub(crate) use next::Next;
 pub(crate) use nth::Nth;
 pub(crate) use open::Open;
 pub(crate) use parse::Parse;
-pub(crate) use pick::Pick;
 pub(crate) use pivot::Pivot;
 pub(crate) use prepend::Prepend;
 pub(crate) use prev::Previous;
@@ -192,20 +218,28 @@ pub(crate) use reverse::Reverse;
 pub(crate) use rm::Remove;
 pub(crate) use run_external::RunExternalCommand;
 pub(crate) use save::Save;
+pub(crate) use select::Select;
 pub(crate) use shells::Shells;
 pub(crate) use shuffle::Shuffle;
 pub(crate) use size::Size;
 pub(crate) use skip::Skip;
+pub(crate) use skip_until::SkipUntil;
 pub(crate) use skip_while::SkipWhile;
 pub(crate) use sort_by::SortBy;
+pub(crate) use split::Split;
+pub(crate) use split::SplitColumn;
+pub(crate) use split::SplitRow;
 pub(crate) use split_by::SplitBy;
-pub(crate) use split_column::SplitColumn;
-pub(crate) use split_row::SplitRow;
+pub(crate) use str_::{
+    Str, StrCapitalize, StrDowncase, StrFindReplace, StrSet, StrSubstring, StrToDatetime,
+    StrToDecimal, StrToInteger, StrTrim, StrUpcase,
+};
 pub(crate) use sum::Sum;
 #[allow(unused_imports)]
 pub(crate) use t_sort_by::TSortBy;
 pub(crate) use table::Table;
 pub(crate) use tags::Tags;
+pub(crate) use to::To;
 pub(crate) use to_bson::ToBSON;
 pub(crate) use to_csv::ToCSV;
 pub(crate) use to_html::ToHTML;
@@ -224,4 +258,5 @@ pub(crate) use version::Version;
 pub(crate) use what::What;
 pub(crate) use where_::Where;
 pub(crate) use which_::Which;
+pub(crate) use with_env::WithEnv;
 pub(crate) use wrap::Wrap;

crates/nu-cli/src/commands/alias.rs

@@ -1,14 +1,25 @@
-use crate::commands::PerItemCommand;
+use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
+use crate::data::config;
 use crate::prelude::*;
 use nu_errors::ShellError;
 use nu_protocol::{
-    CallInfo, CommandAction, Primitive, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
+    hir::Block, CommandAction, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
 };
+use nu_source::Tagged;
 
 pub struct Alias;
 
-impl PerItemCommand for Alias {
+#[derive(Deserialize)]
+pub struct AliasArgs {
+    pub name: Tagged<String>,
+    pub args: Vec<Value>,
+    pub block: Block,
+    pub save: Option<bool>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Alias {
     fn name(&self) -> &str {
         "alias"
     }
@@ -17,49 +28,110 @@ impl PerItemCommand for Alias {
         Signature::build("alias")
             .required("name", SyntaxShape::String, "the name of the alias")
             .required("args", SyntaxShape::Table, "the arguments to the alias")
-            .required("block", SyntaxShape::Block, "the block to run on each row")
+            .required(
+                "block",
+                SyntaxShape::Block,
+                "the block to run as the body of the alias",
+            )
+            .switch("save", "save the alias to your config", Some('s'))
     }
 
     fn usage(&self) -> &str {
-        "Run a block on each row of the table."
+        "Define a shortcut for another command."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        _raw_args: &RawCommandArgs,
-        _input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        let call_info = call_info.clone();
-        let stream = async_stream! {
-            match (call_info.args.expect_nth(0)?, call_info.args.expect_nth(1)?, call_info.args.expect_nth(2)?) {
-                (Value {value: UntaggedValue::Primitive(Primitive::String(name)), .. },
-                Value { value: UntaggedValue::Table(list), .. },
-                Value {
-                    value: UntaggedValue::Block(block),
-                    tag
-                }) => {
-                    let mut args: Vec<String> = vec![];
-                    for item in list.iter() {
-                        if let Ok(string) = item.as_string() {
-                            args.push(format!("${}", string));
-                        } else {
-                            yield Err(ShellError::labeled_error("Expected a string", "expected a string", item.tag()));
-                        }
-                    }
-                    yield ReturnSuccess::action(CommandAction::AddAlias(name.to_string(), args, block.clone()))
-                }
-                _ => {
-                    yield Err(ShellError::labeled_error(
-                        "Expected `name [args] {block}",
-                        "needs a name, args, and a block",
-                        call_info.name_tag,
-                    ))
-                }
-            };
-        };
+        // args.process(registry, alias)?.run()
+        alias(args, registry)
+    }
 
-        Ok(stream.to_output_stream())
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "An alias without parameters",
+                example: "alias say-hi [] { echo 'Hello!' }",
+                result: None,
+            },
+            Example {
+                description: "An alias with a single parameter",
+                example: "alias l [x] { ls $x }",
+                result: None,
+            },
+        ]
+    }
+}
+
+// <<<<<<< HEAD
+// pub fn alias(alias_args: AliasArgs, ctx: RunnableContext) -> Result<OutputStream, ShellError> {
+// =======
+pub fn alias(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let mut raw_input = args.raw_input.clone();
+        let (AliasArgs { name, args: list, block, save}, ctx) = args.process(&registry).await?;
+        let mut processed_args: Vec<String> = vec![];
+
+        if let Some(true) = save {
+            let mut result = crate::data::config::read(name.clone().tag, &None)?;
+
+            // process the alias to remove the --save flag
+            let left_brace = raw_input.find('{').unwrap_or(0);
+            let right_brace = raw_input.rfind('}').unwrap_or(raw_input.len());
+            let mut left = raw_input[..left_brace].replace("--save", "").replace("-s", "");
+            let mut right = raw_input[right_brace..].replace("--save", "").replace("-s", "");
+            raw_input = format!("{}{}{}", left, &raw_input[left_brace..right_brace], right);
+
+            // create a value from raw_input alias
+            let alias: Value = raw_input.trim().to_string().into();
+            let alias_start = raw_input.find("[").unwrap_or(0); // used to check if the same alias already exists
+
+            // add to startup if alias doesn't exist and replce if it does
+            match result.get_mut("startup") {
+                Some(startup) => {
+                    if let UntaggedValue::Table(ref mut commands) = startup.value {
+                        if let Some(command) = commands.iter_mut().find(|command| {
+                            let cmd_str = command.as_string().unwrap_or_default();
+                            cmd_str.starts_with(&raw_input[..alias_start])
+                        }) {
+                            *command = alias;
+                        } else {
+                            commands.push(alias);
+                        }
+                    }
+                }
+                None => {
+                    let mut table = UntaggedValue::table(&[alias]);
+                    result.insert("startup".to_string(), table.into_value(Tag::default()));
+                }
+            }
+            config::write(&result, &None)?;
+        }
+
+        for item in list.iter() {
+            if let Ok(string) = item.as_string() {
+                processed_args.push(format!("${}", string));
+            } else {
+                yield Err(ShellError::labeled_error("Expected a string", "expected a string", item.tag()));
+            }
+        }
+        yield ReturnSuccess::action(CommandAction::AddAlias(name.to_string(), processed_args, block.clone()))
+    };
+
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Alias;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Alias {})
     }
 }

crates/nu-cli/src/commands/append.rs

@@ -2,7 +2,7 @@ use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{Signature, SyntaxShape, Value};
+use nu_protocol::{Signature, SyntaxShape, UntaggedValue, Value};
 
 #[derive(Deserialize)]
 struct AppendArgs {
@@ -11,6 +11,7 @@ struct AppendArgs {
 
 pub struct Append;
 
+#[async_trait]
 impl WholeStreamCommand for Append {
     fn name(&self) -> &str {
         "append"
@@ -28,22 +29,40 @@ impl WholeStreamCommand for Append {
         "Append the given row to the table"
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, append)?.run()
+        let (AppendArgs { row }, input) = args.process(registry).await?;
+
+        let eos = futures::stream::iter(vec![row]);
+
+        Ok(input.chain(eos).to_output_stream())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Add something to the end of a list or table",
+            example: "echo [1 2 3] | append 4",
+            result: Some(vec![
+                UntaggedValue::int(1).into(),
+                UntaggedValue::int(2).into(),
+                UntaggedValue::int(3).into(),
+                UntaggedValue::int(4).into(),
+            ]),
+        }]
     }
 }
 
-fn append(
-    AppendArgs { row }: AppendArgs,
-    RunnableContext { input, .. }: RunnableContext,
-) -> Result<OutputStream, ShellError> {
-    let mut after: VecDeque<Value> = VecDeque::new();
-    after.push_back(row);
-    let after = futures::stream::iter(after);
+#[cfg(test)]
+mod tests {
+    use super::Append;
 
-    Ok(OutputStream::from_input(input.chain(after)))
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Append {})
+    }
 }

crates/nu-cli/src/commands/autoview.rs

@@ -1,14 +1,20 @@
 use crate::commands::UnevaluatedCallInfo;
 use crate::commands::WholeStreamCommand;
+use crate::data::value::format_leaf;
 use crate::prelude::*;
 use nu_errors::ShellError;
 use nu_protocol::{hir, hir::Expression, hir::Literal, hir::SpannedExpression};
-use nu_protocol::{Primitive, ReturnSuccess, Scope, Signature, UntaggedValue, Value};
+use nu_protocol::{Primitive, Scope, Signature, UntaggedValue, Value};
+use parking_lot::Mutex;
+use prettytable::format::{FormatBuilder, LinePosition, LineSeparator};
+use prettytable::{color, Attr, Cell, Row, Table};
 use std::sync::atomic::AtomicBool;
 use std::sync::atomic::Ordering;
+use textwrap::fill;
 
 pub struct Autoview;
 
+#[async_trait]
 impl WholeStreamCommand for Autoview {
     fn name(&self) -> &str {
         "autoview"
@@ -22,7 +28,7 @@ impl WholeStreamCommand for Autoview {
         "View the contents of the pipeline as a table or list."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
@@ -33,14 +39,33 @@ impl WholeStreamCommand for Autoview {
             shell_manager: args.shell_manager,
             host: args.host,
             ctrl_c: args.ctrl_c,
+            current_errors: args.current_errors,
             name: args.call_info.name_tag,
+            raw_input: args.raw_input,
         })
+        .await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Automatically view the results",
+                example: "ls | autoview",
+                result: None,
+            },
+            Example {
+                description: "Autoview is also implied. The above can be written as",
+                example: "ls",
+                result: None,
+            },
+        ]
     }
 }
 
 pub struct RunnableContextWithoutInput {
     pub shell_manager: ShellManager,
     pub host: Arc<parking_lot::Mutex<Box<dyn Host>>>,
+    pub current_errors: Arc<Mutex<Vec<ShellError>>>,
     pub ctrl_c: Arc<AtomicBool>,
     pub registry: CommandRegistry,
     pub name: Tag,
@@ -52,6 +77,7 @@ impl RunnableContextWithoutInput {
             shell_manager: context.shell_manager,
             host: context.host,
             ctrl_c: context.ctrl_c,
+            current_errors: context.current_errors,
             registry: context.registry,
             name: context.name,
         };
@@ -59,221 +85,307 @@ impl RunnableContextWithoutInput {
     }
 }
 
-pub fn autoview(context: RunnableContext) -> Result<OutputStream, ShellError> {
+pub async fn autoview(context: RunnableContext) -> Result<OutputStream, ShellError> {
     let binary = context.get_command("binaryview");
     let text = context.get_command("textview");
     let table = context.get_command("table");
 
-    Ok(OutputStream::new(async_stream! {
-        let (mut input_stream, context) = RunnableContextWithoutInput::convert(context);
+    #[derive(PartialEq)]
+    enum AutoPivotMode {
+        Auto,
+        Always,
+        Never,
+    }
 
+    let pivot_mode = crate::data::config::config(Tag::unknown());
+    let pivot_mode = if let Some(v) = pivot_mode?.get("pivot_mode") {
+        match v.as_string() {
+            Ok(m) if m.to_lowercase() == "auto" => AutoPivotMode::Auto,
+            Ok(m) if m.to_lowercase() == "always" => AutoPivotMode::Always,
+            Ok(m) if m.to_lowercase() == "never" => AutoPivotMode::Never,
+            _ => AutoPivotMode::Always,
+        }
+    } else {
+        AutoPivotMode::Always
+    };
+
+    let (mut input_stream, context) = RunnableContextWithoutInput::convert(context);
+
+    if let Some(x) = input_stream.next().await {
         match input_stream.next().await {
-            Some(x) => {
-                match input_stream.next().await {
-                    Some(y) => {
-                        let ctrl_c = context.ctrl_c.clone();
-                        let stream = async_stream! {
-                            yield Ok(x);
-                            yield Ok(y);
+            Some(y) => {
+                let ctrl_c = context.ctrl_c.clone();
+                let stream = async_stream! {
+                    yield Ok(x);
+                    yield Ok(y);
 
-                            loop {
-                                match input_stream.next().await {
-                                    Some(z) => {
-                                        if ctrl_c.load(Ordering::SeqCst) {
-                                            break;
-                                        }
-                                        yield Ok(z);
-                                    }
-                                    _ => break,
+                    loop {
+                        match input_stream.next().await {
+                            Some(z) => {
+                                if ctrl_c.load(Ordering::SeqCst) {
+                                    break;
                                 }
+                                yield Ok(z);
                             }
-                        };
-                        let stream = stream.to_input_stream();
-
-                        if let Some(table) = table {
-                            let command_args = create_default_command_args(&context).with_input(stream);
-                            let result = table.run(command_args, &context.registry);
-                            result.collect::<Vec<_>>().await;
+                            _ => break,
                         }
                     }
-                    _ => {
-                        match x {
-                            Value {
-                                value: UntaggedValue::Primitive(Primitive::String(ref s)),
-                                tag: Tag { anchor, span },
-                            } if anchor.is_some() => {
-                                if let Some(text) = text {
-                                    let mut stream = VecDeque::new();
-                                    stream.push_back(UntaggedValue::string(s).into_value(Tag { anchor, span }));
-                                    let command_args = create_default_command_args(&context).with_input(stream);
-                                    let result = text.run(command_args, &context.registry);
-                                    result.collect::<Vec<_>>().await;
-                                } else {
-                                    out!("{}", s);
-                                }
+                };
+                let stream = stream.to_input_stream();
+
+                if let Some(table) = table {
+                    let command_args = create_default_command_args(&context).with_input(stream);
+                    let result = table.run(command_args, &context.registry).await;
+                    result.collect::<Vec<_>>().await;
+                }
+            }
+            _ => {
+                match x {
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::String(ref s)),
+                        tag: Tag { anchor, span },
+                    } if anchor.is_some() => {
+                        if let Some(text) = text {
+                            let mut stream = VecDeque::new();
+                            stream.push_back(
+                                UntaggedValue::string(s).into_value(Tag { anchor, span }),
+                            );
+                            let command_args =
+                                create_default_command_args(&context).with_input(stream);
+                            let result = text.run(command_args, &context.registry).await;
+                            result.collect::<Vec<_>>().await;
+                        } else {
+                            out!("{}", s);
+                        }
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::String(s)),
+                        ..
+                    } => {
+                        out!("{}", s);
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Line(ref s)),
+                        tag: Tag { anchor, span },
+                    } if anchor.is_some() => {
+                        if let Some(text) = text {
+                            let mut stream = VecDeque::new();
+                            stream.push_back(
+                                UntaggedValue::string(s).into_value(Tag { anchor, span }),
+                            );
+                            let command_args =
+                                create_default_command_args(&context).with_input(stream);
+                            let result = text.run(command_args, &context.registry).await;
+                            result.collect::<Vec<_>>().await;
+                        } else {
+                            out!("{}\n", s);
+                        }
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Line(s)),
+                        ..
+                    } => {
+                        out!("{}\n", s);
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Path(s)),
+                        ..
+                    } => {
+                        out!("{}", s.display());
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Int(n)),
+                        ..
+                    } => {
+                        out!("{}", n);
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Decimal(n)),
+                        ..
+                    } => {
+                        // TODO: normalize decimal to remove trailing zeros.
+                        // normalization will be available in next release of bigdecimal crate
+                        let mut output = n.to_string();
+                        if output.contains('.') {
+                            output = output.trim_end_matches('0').to_owned();
+                        }
+                        if output.ends_with('.') {
+                            output.push('0');
+                        }
+                        out!("{}", output);
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Boolean(b)),
+                        ..
+                    } => {
+                        out!("{}", b);
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Duration(_)),
+                        ..
+                    } => {
+                        let output = format_leaf(&x).plain_string(100_000);
+                        out!("{}", output);
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Date(d)),
+                        ..
+                    } => {
+                        out!("{}", d);
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Range(_)),
+                        ..
+                    } => {
+                        let output = format_leaf(&x).plain_string(100_000);
+                        out!("{}", output);
+                    }
+
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Binary(ref b)),
+                        ..
+                    } => {
+                        if let Some(binary) = binary {
+                            let mut stream = VecDeque::new();
+                            stream.push_back(x);
+                            let command_args =
+                                create_default_command_args(&context).with_input(stream);
+                            let result = binary.run(command_args, &context.registry).await;
+                            result.collect::<Vec<_>>().await;
+                        } else {
+                            use pretty_hex::*;
+                            out!("{:?}", b.hex_dump());
+                        }
+                    }
+
+                    Value {
+                        value: UntaggedValue::Error(e),
+                        ..
+                    } => {
+                        return Err(e);
+                    }
+
+                    Value {
+                        value: UntaggedValue::Row(row),
+                        ..
+                    } if pivot_mode == AutoPivotMode::Always
+                        || (pivot_mode == AutoPivotMode::Auto
+                            && (row
+                                .entries
+                                .iter()
+                                .map(|(_, v)| v.convert_to_string())
+                                .collect::<Vec<_>>()
+                                .iter()
+                                .fold(0usize, |acc, len| acc + len.len())
+                                + row.entries.iter().count() * 2)
+                                > textwrap::termwidth()) =>
+                    {
+                        let termwidth = std::cmp::max(textwrap::termwidth(), 20);
+
+                        enum TableMode {
+                            Light,
+                            Normal,
+                        }
+
+                        let mut table = Table::new();
+                        let table_mode = crate::data::config::config(Tag::unknown());
+
+                        let table_mode = if let Some(s) = table_mode?.get("table_mode") {
+                            match s.as_string() {
+                                Ok(typ) if typ == "light" => TableMode::Light,
+                                _ => TableMode::Normal,
                             }
-                            Value {
-                                value: UntaggedValue::Primitive(Primitive::String(s)),
-                                ..
-                            } => {
-                                out!("{}", s);
+                        } else {
+                            TableMode::Normal
+                        };
+
+                        match table_mode {
+                            TableMode::Light => {
+                                table.set_format(
+                                    FormatBuilder::new()
+                                        .separator(
+                                            LinePosition::Title,
+                                            LineSeparator::new('─', '─', ' ', ' '),
+                                        )
+                                        .separator(
+                                            LinePosition::Bottom,
+                                            LineSeparator::new(' ', ' ', ' ', ' '),
+                                        )
+                                        .padding(1, 1)
+                                        .build(),
+                                );
                             }
-                            Value {
-                                value: UntaggedValue::Primitive(Primitive::Line(ref s)),
-                                tag: Tag { anchor, span },
-                            } if anchor.is_some() => {
-                                if let Some(text) = text {
-                                    let mut stream = VecDeque::new();
-                                    stream.push_back(UntaggedValue::string(s).into_value(Tag { anchor, span }));
-                                    let command_args = create_default_command_args(&context).with_input(stream);
-                                    let result = text.run(command_args, &context.registry);
-                                    result.collect::<Vec<_>>().await;
-                                } else {
-                                    out!("{}\n", s);
-                                }
-                            }
-                            Value {
-                                value: UntaggedValue::Primitive(Primitive::Line(s)),
-                                ..
-                            } => {
-                                out!("{}\n", s);
-                            }
-                            Value {
-                                value: UntaggedValue::Primitive(Primitive::Path(s)),
-                                ..
-                            } => {
-                                out!("{}", s.display());
-                            }
-                            Value {
-                                value: UntaggedValue::Primitive(Primitive::Int(n)),
-                                ..
-                            } => {
-                                out!("{}", n);
-                            }
-                            Value {
-                                value: UntaggedValue::Primitive(Primitive::Decimal(n)),
-                                ..
-                            } => {
-                                out!("{}", n);
-                            }
-                            Value {
-                                value: UntaggedValue::Primitive(Primitive::Boolean(b)),
-                                ..
-                            } => {
-                                out!("{}", b);
+                            _ => {
+                                table.set_format(
+                                    FormatBuilder::new()
+                                        .column_separator('│')
+                                        .separator(
+                                            LinePosition::Top,
+                                            LineSeparator::new('─', '┬', ' ', ' '),
+                                        )
+                                        .separator(
+                                            LinePosition::Title,
+                                            LineSeparator::new('─', '┼', ' ', ' '),
+                                        )
+                                        .separator(
+                                            LinePosition::Bottom,
+                                            LineSeparator::new('─', '┴', ' ', ' '),
+                                        )
+                                        .padding(1, 1)
+                                        .build(),
+                                );
                             }
+                        }
 
-                            Value { value: UntaggedValue::Primitive(Primitive::Binary(ref b)), .. } => {
-                                if let Some(binary) = binary {
-                                    let mut stream = VecDeque::new();
-                                    stream.push_back(x);
-                                    let command_args = create_default_command_args(&context).with_input(stream);
-                                    let result = binary.run(command_args, &context.registry);
-                                    result.collect::<Vec<_>>().await;
-                                } else {
-                                    use pretty_hex::*;
-                                    out!("{:?}", b.hex_dump());
-                                }
-                            }
+                        let mut max_key_len = 0;
+                        for (key, _) in row.entries.iter() {
+                            max_key_len = std::cmp::max(max_key_len, key.chars().count());
+                        }
 
-                            Value { value: UntaggedValue::Error(e), .. } => {
-                                yield Err(e);
-                            }
+                        if max_key_len > (termwidth / 2 - 1) {
+                            max_key_len = termwidth / 2 - 1;
+                        }
 
-                            Value { value: UntaggedValue::Row(row), ..} => {
-                                use prettytable::format::{FormatBuilder, LinePosition, LineSeparator};
-                                use prettytable::{color, Attr, Cell, Row, Table};
-                                use crate::data::value::{format_leaf, style_leaf};
-                                use textwrap::fill;
+                        let max_val_len = termwidth - max_key_len - 5;
 
-                                let termwidth = std::cmp::max(textwrap::termwidth(), 20);
+                        for (key, value) in row.entries.iter() {
+                            table.add_row(Row::new(vec![
+                                Cell::new(&fill(&key, max_key_len))
+                                    .with_style(Attr::ForegroundColor(color::GREEN))
+                                    .with_style(Attr::Bold),
+                                Cell::new(&fill(
+                                    &format_leaf(value).plain_string(100_000),
+                                    max_val_len,
+                                )),
+                            ]));
+                        }
 
-                                enum TableMode {
-                                    Light,
-                                    Normal,
-                                }
+                        table.printstd();
 
-                                let mut table = Table::new();
-                                let table_mode = crate::data::config::config(Tag::unknown());
+                        // table.print_term(&mut *context.host.lock().out_terminal().ok_or_else(|| ShellError::untagged_runtime_error("Could not open terminal for output"))?)
+                        //     .map_err(|_| ShellError::untagged_runtime_error("Internal error: could not print to terminal (for unix systems check to make sure TERM is set)"))?;
+                    }
 
-                                let table_mode = if let Some(s) = table_mode?.get("table_mode") {
-                                    match s.as_string() {
-                                        Ok(typ) if typ == "light" => TableMode::Light,
-                                        _ => TableMode::Normal,
-                                    }
-                                } else {
-                                    TableMode::Normal
-                                };
-
-                                match table_mode {
-                                    TableMode::Light => {
-                                        table.set_format(
-                                            FormatBuilder::new()
-                                                .separator(LinePosition::Title, LineSeparator::new('─', '─', ' ', ' '))
-                                                .padding(1, 1)
-                                                .build(),
-                                        );
-                                    }
-                                    _ => {
-                                        table.set_format(
-                                            FormatBuilder::new()
-                                                .column_separator('│')
-                                                .separator(LinePosition::Top, LineSeparator::new('─', '┬', ' ', ' '))
-                                                .separator(LinePosition::Title, LineSeparator::new('─', '┼', ' ', ' '))
-                                                .separator(LinePosition::Bottom, LineSeparator::new('─', '┴', ' ', ' '))
-                                                .padding(1, 1)
-                                                .build(),
-                                        );
-                                    }
-                                }
-
-                                let mut max_key_len = 0;
-                                for (key, _) in row.entries.iter() {
-                                    max_key_len = std::cmp::max(max_key_len, key.chars().count());
-                                }
-
-                                if max_key_len > (termwidth/2 - 1) {
-                                    max_key_len = termwidth/2 - 1;
-                                }
-
-                                let max_val_len = termwidth - max_key_len - 5;
-
-                                for (key, value) in row.entries.iter() {
-                                    table.add_row(Row::new(vec![Cell::new(&fill(&key, max_key_len)).with_style(Attr::ForegroundColor(color::GREEN)).with_style(Attr::Bold),
-                                        Cell::new(&fill(&format_leaf(value).plain_string(100_000), max_val_len))]));
-                                }
-
-                                table.printstd();
-
-                                // table.print_term(&mut *context.host.lock().out_terminal().ok_or_else(|| ShellError::untagged_runtime_error("Could not open terminal for output"))?)
-                                //     .map_err(|_| ShellError::untagged_runtime_error("Internal error: could not print to terminal (for unix systems check to make sure TERM is set)"))?;
-                            }
-
-                            Value { value: ref item, .. } => {
-                                if let Some(table) = table {
-                                    let mut stream = VecDeque::new();
-                                    stream.push_back(x);
-                                    let command_args = create_default_command_args(&context).with_input(stream);
-                                    let result = table.run(command_args, &context.registry);
-                                    result.collect::<Vec<_>>().await;
-                                } else {
-                                    out!("{:?}", item);
-                                }
-                            }
+                    Value {
+                        value: ref item, ..
+                    } => {
+                        if let Some(table) = table {
+                            let mut stream = VecDeque::new();
+                            stream.push_back(x);
+                            let command_args =
+                                create_default_command_args(&context).with_input(stream);
+                            let result = table.run(command_args, &context.registry).await;
+                            result.collect::<Vec<_>>().await;
+                        } else {
+                            out!("{:?}", item);
                         }
                     }
                 }
             }
-            _ => {
-                //out!("<no results>");
-            }
         }
+    }
 
-        // Needed for async_stream to type check
-        if false {
-            yield ReturnSuccess::value(UntaggedValue::nothing().into_untagged_value());
-        }
-    }))
+    Ok(OutputStream::empty())
 }
 
 fn create_default_command_args(context: &RunnableContextWithoutInput) -> RawCommandArgs {
@@ -281,6 +393,7 @@ fn create_default_command_args(context: &RunnableContextWithoutInput) -> RawComm
     RawCommandArgs {
         host: context.host.clone(),
         ctrl_c: context.ctrl_c.clone(),
+        current_errors: context.current_errors.clone(),
         shell_manager: context.shell_manager.clone(),
         call_info: UnevaluatedCallInfo {
             args: hir::Call {
@@ -294,7 +407,19 @@ fn create_default_command_args(context: &RunnableContextWithoutInput) -> RawComm
                 is_last: true,
             },
             name_tag: context.name.clone(),
-            scope: Scope::empty(),
+            scope: Scope::new(),
         },
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Autoview;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Autoview {})
+    }
+}

crates/nu-cli/src/commands/average.rs

@@ -0,0 +1,173 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use crate::utils::data_processing::{reducer_for, Reduce};
+use bigdecimal::FromPrimitive;
+use nu_errors::ShellError;
+use nu_protocol::hir::{convert_number_to_u64, Number, Operator};
+use nu_protocol::{
+    Dictionary, Primitive, ReturnSuccess, ReturnValue, Signature, UntaggedValue, Value,
+};
+use num_traits::identities::Zero;
+
+use indexmap::map::IndexMap;
+
+pub struct Average;
+
+#[async_trait]
+impl WholeStreamCommand for Average {
+    fn name(&self) -> &str {
+        "average"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("average")
+    }
+
+    fn usage(&self) -> &str {
+        "Average the values."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        average(RunnableContext {
+            input: args.input,
+            registry: registry.clone(),
+            shell_manager: args.shell_manager,
+            host: args.host,
+            ctrl_c: args.ctrl_c,
+            current_errors: args.current_errors,
+            name: args.call_info.name_tag,
+            raw_input: args.raw_input,
+        })
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Average a list of numbers",
+            example: "echo [100 0 100 0] | average",
+            result: Some(vec![UntaggedValue::decimal(50).into()]),
+        }]
+    }
+}
+
+fn average(
+    RunnableContext {
+        mut input, name, ..
+    }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    let stream = async_stream! {
+        let mut values: Vec<Value> = input.drain_vec().await;
+        let action = reducer_for(Reduce::Sum);
+
+        if values.iter().all(|v| if let UntaggedValue::Primitive(_) = v.value {true} else {false}) {
+            match avg(&values, name) {
+                Ok(result) => yield ReturnSuccess::value(result),
+                Err(err) => yield Err(err),
+            }
+        } else {
+            let mut column_values = IndexMap::new();
+            for value in values {
+                match value.value {
+                    UntaggedValue::Row(row_dict) => {
+                        for (key, value) in row_dict.entries.iter() {
+                            column_values
+                                .entry(key.clone())
+                                .and_modify(|v: &mut Vec<Value>| v.push(value.clone()))
+                                .or_insert(vec![value.clone()]);
+                        }
+                    },
+                    table => {},
+                };
+            }
+
+            let mut column_totals = IndexMap::new();
+            for (col_name, col_vals) in column_values {
+                match avg(&col_vals, &name) {
+                    Ok(result) => {
+                        column_totals.insert(col_name, result);
+                    }
+                    Err(err) => yield Err(err),
+                }
+            }
+            yield ReturnSuccess::value(
+                UntaggedValue::Row(Dictionary {entries: column_totals}).into_untagged_value())
+        }
+    };
+
+    let stream: BoxStream<'static, ReturnValue> = stream.boxed();
+
+    Ok(stream.to_output_stream())
+}
+
+fn avg(values: &[Value], name: impl Into<Tag>) -> Result<Value, ShellError> {
+    let name = name.into();
+
+    let sum = reducer_for(Reduce::Sum);
+
+    let number = BigDecimal::from_usize(values.len()).expect("expected a usize-sized bigdecimal");
+
+    let total_rows = UntaggedValue::decimal(number);
+    let total = sum(Value::zero(), values.to_vec())?;
+
+    match total {
+        Value {
+            value: UntaggedValue::Primitive(Primitive::Bytes(num)),
+            ..
+        } => {
+            let left = UntaggedValue::from(Primitive::Int(num.into()));
+            let result = crate::data::value::compute_values(Operator::Divide, &left, &total_rows);
+
+            match result {
+                Ok(UntaggedValue::Primitive(Primitive::Decimal(result))) => {
+                    let number = Number::Decimal(result);
+                    let number = convert_number_to_u64(&number);
+                    Ok(UntaggedValue::bytes(number).into_value(name))
+                }
+                Ok(_) => Err(ShellError::labeled_error(
+                    "could not calculate average of non-integer or unrelated types",
+                    "source",
+                    name,
+                )),
+                Err((left_type, right_type)) => Err(ShellError::coerce_error(
+                    left_type.spanned(name.span),
+                    right_type.spanned(name.span),
+                )),
+            }
+        }
+        Value {
+            value: UntaggedValue::Primitive(other),
+            ..
+        } => {
+            let left = UntaggedValue::from(other);
+            let result = crate::data::value::compute_values(Operator::Divide, &left, &total_rows);
+
+            match result {
+                Ok(value) => Ok(value.into_value(name)),
+                Err((left_type, right_type)) => Err(ShellError::coerce_error(
+                    left_type.spanned(name.span),
+                    right_type.spanned(name.span),
+                )),
+            }
+        }
+        _ => Err(ShellError::labeled_error(
+            "could not calculate average of non-integer or unrelated types",
+            "source",
+            name,
+        )),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Average;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Average {})
+    }
+}

crates/nu-cli/src/commands/build_string.rs

@@ -0,0 +1,56 @@
+use crate::prelude::*;
+use nu_errors::ShellError;
+
+use crate::commands::WholeStreamCommand;
+use crate::data::value::format_leaf;
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
+
+#[derive(Deserialize)]
+pub struct BuildStringArgs {
+    rest: Vec<Value>,
+}
+
+pub struct BuildString;
+
+#[async_trait]
+impl WholeStreamCommand for BuildString {
+    fn name(&self) -> &str {
+        "build-string"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("build-string")
+            .rest(SyntaxShape::Any, "all values to form into the string")
+    }
+
+    fn usage(&self) -> &str {
+        "Builds a string from the arguments"
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        let tag = args.call_info.name_tag.clone();
+        let (BuildStringArgs { rest }, _) = args.process(&registry).await?;
+
+        let mut output_string = String::new();
+
+        for r in rest {
+            output_string.push_str(&format_leaf(&r).plain_string(100_000))
+        }
+
+        Ok(OutputStream::one(ReturnSuccess::value(
+            UntaggedValue::string(output_string).into_value(tag),
+        )))
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Builds a string from a string and a number, without spaces between them",
+            example: "build-string 'foo' 3",
+            result: None,
+        }]
+    }
+}

crates/nu-cli/src/commands/cal.rs

@@ -0,0 +1,357 @@
+use crate::commands::{command::EvaluatedWholeStreamCommandArgs, WholeStreamCommand};
+use crate::prelude::*;
+use chrono::{Datelike, Local, NaiveDate};
+use indexmap::IndexMap;
+use nu_errors::ShellError;
+use nu_protocol::{Dictionary, Signature, SyntaxShape, UntaggedValue, Value};
+
+pub struct Cal;
+
+#[async_trait]
+impl WholeStreamCommand for Cal {
+    fn name(&self) -> &str {
+        "cal"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("cal")
+            .switch("year", "Display the year column", Some('y'))
+            .switch("quarter", "Display the quarter column", Some('q'))
+            .switch("month", "Display the month column", Some('m'))
+            .named(
+                "full-year",
+                SyntaxShape::Int,
+                "Display a year-long calendar for the specified year",
+                None,
+            )
+            .switch(
+                "month-names",
+                "Display the month names instead of integers",
+                None,
+            )
+    }
+
+    fn usage(&self) -> &str {
+        "Display a calendar."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        cal(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "This month's calendar",
+                example: "cal",
+                result: None,
+            },
+            Example {
+                description: "The calendar for all of 2012",
+                example: "cal --full-year 2012",
+                result: None,
+            },
+        ]
+    }
+}
+
+pub async fn cal(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let args = args.evaluate_once(&registry).await?;
+    let mut calendar_vec_deque = VecDeque::new();
+    let tag = args.call_info.name_tag.clone();
+
+    let (current_year, current_month, current_day) = get_current_date();
+
+    let mut selected_year: i32 = current_year;
+    let mut current_day_option: Option<u32> = Some(current_day);
+
+    let month_range = if args.has("full-year") {
+        if let Some(full_year_value) = args.get("full-year") {
+            if let Ok(year_u64) = full_year_value.as_u64() {
+                selected_year = year_u64 as i32;
+
+                if selected_year != current_year {
+                    current_day_option = None
+                }
+            } else {
+                return Err(get_invalid_year_shell_error(&full_year_value.tag()));
+            }
+        }
+
+        (1, 12)
+    } else {
+        (current_month, current_month)
+    };
+
+    let add_months_of_year_to_table_result = add_months_of_year_to_table(
+        &args,
+        &mut calendar_vec_deque,
+        &tag,
+        selected_year,
+        month_range,
+        current_month,
+        current_day_option,
+    );
+
+    match add_months_of_year_to_table_result {
+        Ok(()) => Ok(futures::stream::iter(calendar_vec_deque).to_output_stream()),
+        Err(error) => Err(error),
+    }
+}
+
+fn get_invalid_year_shell_error(year_tag: &Tag) -> ShellError {
+    ShellError::labeled_error("The year is invalid", "invalid year", year_tag)
+}
+
+struct MonthHelper {
+    day_number_month_starts_on: u32,
+    number_of_days_in_month: u32,
+    selected_year: i32,
+    selected_month: u32,
+}
+
+impl MonthHelper {
+    pub fn new(selected_year: i32, selected_month: u32) -> Result<MonthHelper, ()> {
+        let mut month_helper = MonthHelper {
+            day_number_month_starts_on: 0,
+            number_of_days_in_month: 0,
+            selected_year,
+            selected_month,
+        };
+
+        let chosen_date_result_one = month_helper.update_day_number_month_starts_on();
+        let chosen_date_result_two = month_helper.update_number_of_days_in_month();
+
+        if chosen_date_result_one.is_ok() && chosen_date_result_two.is_ok() {
+            return Ok(month_helper);
+        }
+
+        Err(())
+    }
+
+    pub fn get_month_name(&self) -> String {
+        let month_name = match self.selected_month {
+            1 => "january",
+            2 => "february",
+            3 => "march",
+            4 => "april",
+            5 => "may",
+            6 => "june",
+            7 => "july",
+            8 => "august",
+            9 => "september",
+            10 => "october",
+            11 => "november",
+            _ => "december",
+        };
+
+        month_name.to_string()
+    }
+
+    fn update_day_number_month_starts_on(&mut self) -> Result<(), ()> {
+        let naive_date_result =
+            MonthHelper::get_naive_date(self.selected_year, self.selected_month);
+
+        match naive_date_result {
+            Ok(naive_date) => {
+                self.day_number_month_starts_on = naive_date.weekday().num_days_from_sunday();
+                Ok(())
+            }
+            _ => Err(()),
+        }
+    }
+
+    fn update_number_of_days_in_month(&mut self) -> Result<(), ()> {
+        // Chrono does not provide a method to output the amount of days in a month
+        // This is a workaround taken from the example code from the Chrono docs here:
+        // https://docs.rs/chrono/0.3.0/chrono/naive/date/struct.NaiveDate.html#example-30
+        let (adjusted_year, adjusted_month) = if self.selected_month == 12 {
+            (self.selected_year + 1, 1)
+        } else {
+            (self.selected_year, self.selected_month + 1)
+        };
+
+        let naive_date_result = MonthHelper::get_naive_date(adjusted_year, adjusted_month);
+
+        match naive_date_result {
+            Ok(naive_date) => {
+                self.number_of_days_in_month = naive_date.pred().day();
+                Ok(())
+            }
+            _ => Err(()),
+        }
+    }
+
+    fn get_naive_date(selected_year: i32, selected_month: u32) -> Result<NaiveDate, ()> {
+        if let Some(naive_date) = NaiveDate::from_ymd_opt(selected_year, selected_month, 1) {
+            return Ok(naive_date);
+        }
+
+        Err(())
+    }
+}
+
+fn get_current_date() -> (i32, u32, u32) {
+    let local_now_date = Local::now().date();
+
+    let current_year: i32 = local_now_date.year();
+    let current_month: u32 = local_now_date.month();
+    let current_day: u32 = local_now_date.day();
+
+    (current_year, current_month, current_day)
+}
+
+fn add_months_of_year_to_table(
+    args: &EvaluatedWholeStreamCommandArgs,
+    mut calendar_vec_deque: &mut VecDeque<Value>,
+    tag: &Tag,
+    selected_year: i32,
+    (start_month, end_month): (u32, u32),
+    current_month: u32,
+    current_day_option: Option<u32>,
+) -> Result<(), ShellError> {
+    for month_number in start_month..=end_month {
+        let mut new_current_day_option: Option<u32> = None;
+
+        if let Some(current_day) = current_day_option {
+            if month_number == current_month {
+                new_current_day_option = Some(current_day)
+            }
+        }
+
+        let add_month_to_table_result = add_month_to_table(
+            &args,
+            &mut calendar_vec_deque,
+            &tag,
+            selected_year,
+            month_number,
+            new_current_day_option,
+        );
+
+        add_month_to_table_result?
+    }
+
+    Ok(())
+}
+
+fn add_month_to_table(
+    args: &EvaluatedWholeStreamCommandArgs,
+    calendar_vec_deque: &mut VecDeque<Value>,
+    tag: &Tag,
+    selected_year: i32,
+    current_month: u32,
+    current_day_option: Option<u32>,
+) -> Result<(), ShellError> {
+    let month_helper_result = MonthHelper::new(selected_year, current_month);
+
+    let month_helper = match month_helper_result {
+        Ok(month_helper) => month_helper,
+        Err(()) => match args.get("full-year") {
+            Some(full_year_value) => {
+                return Err(get_invalid_year_shell_error(&full_year_value.tag()))
+            }
+            None => {
+                return Err(ShellError::labeled_error(
+                    "Issue parsing command",
+                    "invalid command",
+                    tag,
+                ))
+            }
+        },
+    };
+
+    let day_limit = month_helper.number_of_days_in_month + month_helper.day_number_month_starts_on;
+    let mut day_count: u32 = 1;
+
+    let days_of_the_week = [
+        "sunday",
+        "monday",
+        "tuesday",
+        "wednesday",
+        "thursday",
+        "friday",
+        "saturday",
+    ];
+
+    let should_show_year_column = args.has("year");
+    let should_show_month_column = args.has("month");
+    let should_show_quarter_column = args.has("quarter");
+    let should_show_month_names = args.has("month-names");
+
+    while day_count <= day_limit {
+        let mut indexmap = IndexMap::new();
+
+        if should_show_year_column {
+            indexmap.insert(
+                "year".to_string(),
+                UntaggedValue::int(month_helper.selected_year).into_value(tag),
+            );
+        }
+
+        if should_show_quarter_column {
+            indexmap.insert(
+                "quarter".to_string(),
+                UntaggedValue::int(((month_helper.selected_month - 1) / 3) + 1).into_value(tag),
+            );
+        }
+
+        if should_show_month_column {
+            let month_value = if should_show_month_names {
+                UntaggedValue::string(month_helper.get_month_name()).into_value(tag)
+            } else {
+                UntaggedValue::int(month_helper.selected_month).into_value(tag)
+            };
+
+            indexmap.insert("month".to_string(), month_value);
+        }
+
+        for day in &days_of_the_week {
+            let should_add_day_number_to_table =
+                (day_count <= day_limit) && (day_count > month_helper.day_number_month_starts_on);
+
+            let mut value = UntaggedValue::nothing().into_value(tag);
+
+            if should_add_day_number_to_table {
+                let day_count_with_offset = day_count - month_helper.day_number_month_starts_on;
+
+                value = UntaggedValue::int(day_count_with_offset).into_value(tag);
+
+                if let Some(current_day) = current_day_option {
+                    if current_day == day_count_with_offset {
+                        // TODO: Update the value here with a color when color support is added
+                        // This colors the current day
+                    }
+                }
+            }
+
+            indexmap.insert((*day).to_string(), value);
+
+            day_count += 1;
+        }
+
+        calendar_vec_deque
+            .push_back(UntaggedValue::Row(Dictionary::from(indexmap)).into_value(tag));
+    }
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Cal;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Cal {})
+    }
+}

crates/nu-cli/src/commands/calc.rs

@@ -1,11 +1,12 @@
-use crate::commands::PerItemCommand;
+use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, Primitive, ReturnSuccess, UntaggedValue, Value};
+use nu_protocol::{Primitive, ReturnSuccess, UntaggedValue, Value};
 
 pub struct Calc;
 
-impl PerItemCommand for Calc {
+#[async_trait]
+impl WholeStreamCommand for Calc {
     fn name(&self) -> &str {
         "calc"
     }
@@ -14,38 +15,50 @@ impl PerItemCommand for Calc {
         "Parse a math expression into a number"
     }
 
-    fn run(
+    async fn run(
         &self,
-        _call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        calc(input, raw_args)
+        calc(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Calculate math in the pipeline",
+            example: "echo '10 / 4' | calc",
+            result: Some(vec![UntaggedValue::decimal(2.5).into()]),
+        }]
     }
 }
 
-fn calc(input: Value, args: &RawCommandArgs) -> Result<OutputStream, ShellError> {
-    let name_span = &args.call_info.name_tag.span;
+pub async fn calc(
+    args: CommandArgs,
+    _registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let input = args.input;
+    let name = args.call_info.name_tag.span;
 
-    let output = if let Ok(string) = input.as_string() {
-        match parse(&string, &input.tag) {
-            Ok(value) => ReturnSuccess::value(value),
-            Err(err) => Err(ShellError::labeled_error(
-                "Calculation error",
-                err,
-                &input.tag.span,
-            )),
-        }
-    } else {
-        Err(ShellError::labeled_error(
-            "Expected a string from pipeline",
-            "requires string input",
-            name_span,
-        ))
-    };
-
-    Ok(vec![output].into())
+    Ok(input
+        .map(move |input| {
+            if let Ok(string) = input.as_string() {
+                match parse(&string, &input.tag) {
+                    Ok(value) => ReturnSuccess::value(value),
+                    Err(err) => Err(ShellError::labeled_error(
+                        "Calculation error",
+                        err,
+                        &input.tag.span,
+                    )),
+                }
+            } else {
+                Err(ShellError::labeled_error(
+                    "Expected a string from pipeline",
+                    "requires string input",
+                    name,
+                ))
+            }
+        })
+        .to_output_stream())
 }
 
 pub fn parse(math_expression: &str, tag: impl Into<Tag>) -> Result<Value, String> {
@@ -61,3 +74,15 @@ pub fn parse(math_expression: &str, tag: impl Into<Tag>) -> Result<Value, String
         Err(error) => Err(error.to_string()),
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Calc;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Calc {})
+    }
+}

crates/nu-cli/src/commands/cd.rs

@@ -1,10 +1,20 @@
 use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
+
+use std::path::PathBuf;
+
 use nu_errors::ShellError;
 use nu_protocol::{Signature, SyntaxShape};
+use nu_source::Tagged;
+
+#[derive(Deserialize)]
+pub struct CdArgs {
+    pub(crate) path: Option<Tagged<PathBuf>>,
+}
 
 pub struct Cd;
 
+#[async_trait]
 impl WholeStreamCommand for Cd {
     fn name(&self) -> &str {
         "cd"
@@ -22,17 +32,51 @@ impl WholeStreamCommand for Cd {
         "Change to a new path."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        cd(args, registry)
+        let name = args.call_info.name_tag.clone();
+        let shell_manager = args.shell_manager.clone();
+        let (args, _): (CdArgs, _) = args.process(&registry).await?;
+        shell_manager.cd(args, name)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Change to a new directory called 'dirname'",
+                example: "cd dirname",
+                result: None,
+            },
+            Example {
+                description: "Change to your home directory",
+                example: "cd",
+                result: None,
+            },
+            Example {
+                description: "Change to your home directory (alternate version)",
+                example: "cd ~",
+                result: None,
+            },
+            Example {
+                description: "Change to the previous directory",
+                example: "cd -",
+                result: None,
+            },
+        ]
     }
 }
 
-fn cd(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let shell_manager = args.shell_manager.clone();
-    let args = args.evaluate_once(registry)?;
-    shell_manager.cd(args)
+#[cfg(test)]
+mod tests {
+    use super::Cd;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Cd {})
+    }
 }

crates/nu-cli/src/commands/classified/block.rs

@@ -1,5 +1,4 @@
 use crate::commands::classified::expr::run_expression_block;
-//use crate::commands::classified::external::run_external_command;
 use crate::commands::classified::internal::run_internal_command;
 use crate::context::Context;
 use crate::prelude::*;
@@ -7,14 +6,16 @@ use crate::stream::InputStream;
 use futures::stream::TryStreamExt;
 use nu_errors::ShellError;
 use nu_protocol::hir::{Block, ClassifiedCommand, Commands};
-use nu_protocol::{ReturnSuccess, Scope, UntaggedValue, Value};
+use nu_protocol::{ReturnSuccess, UntaggedValue, Value};
 use std::sync::atomic::Ordering;
 
 pub(crate) async fn run_block(
     block: &Block,
     ctx: &mut Context,
     mut input: InputStream,
-    scope: &Scope,
+    it: &Value,
+    vars: &IndexMap<String, Value>,
+    env: &IndexMap<String, String>,
 ) -> Result<InputStream, ShellError> {
     let mut output: Result<InputStream, ShellError> = Ok(InputStream::empty());
     for pipeline in &block.block {
@@ -53,7 +54,7 @@ pub(crate) async fn run_block(
                 return Err(e);
             }
         }
-        output = run_pipeline(pipeline, ctx, input, scope).await;
+        output = run_pipeline(pipeline, ctx, input, it, vars, env).await;
 
         input = InputStream::empty();
     }
@@ -65,10 +66,11 @@ async fn run_pipeline(
     commands: &Commands,
     ctx: &mut Context,
     mut input: InputStream,
-    scope: &Scope,
+    it: &Value,
+    vars: &IndexMap<String, Value>,
+    env: &IndexMap<String, String>,
 ) -> Result<InputStream, ShellError> {
     let mut iter = commands.list.clone().into_iter().peekable();
-
     loop {
         let item: Option<ClassifiedCommand> = iter.next();
         let next: Option<&ClassifiedCommand> = iter.peek();
@@ -79,13 +81,13 @@ async fn run_pipeline(
             }
 
             (Some(ClassifiedCommand::Expr(expr)), _) => {
-                run_expression_block(*expr, ctx, input, scope)?
+                run_expression_block(*expr, ctx, it, vars, env).await?
             }
             (Some(ClassifiedCommand::Error(err)), _) => return Err(err.into()),
             (_, Some(ClassifiedCommand::Error(err))) => return Err(err.clone().into()),
 
             (Some(ClassifiedCommand::Internal(left)), _) => {
-                run_internal_command(left, ctx, input, scope)?
+                run_internal_command(left, ctx, input, it, vars, env).await?
             }
 
             (None, _) => break,

crates/nu-cli/src/commands/classified/expr.rs

@@ -3,27 +3,25 @@ use crate::prelude::*;
 
 use log::{log_enabled, trace};
 
+use futures::stream::once;
 use nu_errors::ShellError;
 use nu_protocol::hir::SpannedExpression;
-use nu_protocol::Scope;
+use nu_protocol::Value;
 
-pub(crate) fn run_expression_block(
+pub(crate) async fn run_expression_block(
     expr: SpannedExpression,
     context: &mut Context,
-    input: InputStream,
-    scope: &Scope,
+    it: &Value,
+    vars: &IndexMap<String, Value>,
+    env: &IndexMap<String, String>,
 ) -> Result<InputStream, ShellError> {
     if log_enabled!(log::Level::Trace) {
         trace!(target: "nu::run::expr", "->");
         trace!(target: "nu::run::expr", "{:?}", expr);
     }
 
-    let scope = scope.clone();
     let registry = context.registry().clone();
-    let stream = input.map(move |row| {
-        let scope = scope.clone().set_it(row);
-        evaluate_baseline_expr(&expr, &registry, &scope)
-    });
+    let output = evaluate_baseline_expr(&expr, &registry, it, vars, env).await?;
 
-    Ok(stream.to_input_stream())
+    Ok(once(async { Ok(output) }).to_input_stream())
 }

crates/nu-cli/src/commands/classified/external.rs

@@ -9,7 +9,7 @@ use std::sync::mpsc;
 
 use bytes::{BufMut, Bytes, BytesMut};
 use futures::executor::block_on_stream;
-use futures::stream::StreamExt;
+// use futures::stream::StreamExt;
 use futures_codec::FramedRead;
 use log::trace;
 
@@ -82,20 +82,6 @@ impl futures_codec::Decoder for MaybeTextCodec {
     }
 }
 
-pub fn nu_value_to_string(name_tag: &Tag, from: &Value) -> Result<String, ShellError> {
-    match &from.value {
-        UntaggedValue::Primitive(Primitive::Int(i)) => Ok(i.to_string()),
-        UntaggedValue::Primitive(Primitive::String(s))
-        | UntaggedValue::Primitive(Primitive::Line(s)) => Ok(s.clone()),
-        UntaggedValue::Primitive(Primitive::Path(p)) => Ok(p.to_string_lossy().to_string()),
-        unsupported => Err(ShellError::labeled_error(
-            format!("needs string data (given: {})", unsupported.type_name()),
-            "expected a string",
-            name_tag,
-        )),
-    }
-}
-
 pub(crate) async fn run_external_command(
     command: ExternalCommand,
     context: &mut Context,
@@ -113,88 +99,10 @@ pub(crate) async fn run_external_command(
         ));
     }
 
-    if command.has_it_argument() {
-        run_with_iterator_arg(command, context, input, scope, is_last)
-    } else {
-        run_with_stdin(command, context, input, scope, is_last)
-    }
+    run_with_stdin(command, context, input, scope, is_last).await
 }
 
-fn run_with_iterator_arg(
-    command: ExternalCommand,
-    context: &mut Context,
-    input: InputStream,
-    scope: &Scope,
-    is_last: bool,
-) -> Result<InputStream, ShellError> {
-    let path = context.shell_manager.path();
-
-    let mut inputs: InputStream =
-        trace_stream!(target: "nu::trace_stream::external::it", "input" = input);
-
-    let name_tag = command.name_tag.clone();
-    let scope = scope.clone();
-    let context = context.clone();
-
-    let stream = async_stream! {
-        while let Some(value) = inputs.next().await {
-            // Evaluate the expressions into values, and from values into strings for each iteration
-            let mut command_args = vec![];
-            let scope = scope.clone().set_it(value);
-            for arg in command.args.iter() {
-                let value = evaluate_baseline_expr(arg, &context.registry, &scope)?;
-                command_args.push(nu_value_to_string(&name_tag, &value)?);
-            }
-
-            let process_args = command_args
-            .iter()
-            .map(|arg| {
-                let arg = expand_tilde(arg.deref(), dirs::home_dir);
-
-                #[cfg(not(windows))]
-                {
-                    if argument_contains_whitespace(&arg) && argument_is_quoted(&arg) {
-                        if let Some(unquoted) = remove_quotes(&arg) {
-                            format!(r#""{}""#, unquoted)
-                        } else {
-                            arg.as_ref().to_string()
-                        }
-                    } else {
-                        arg.as_ref().to_string()
-                    }
-                }
-                #[cfg(windows)]
-                {
-                    if let Some(unquoted) = remove_quotes(&arg) {
-                        unquoted.to_string()
-                    } else {
-                        arg.as_ref().to_string()
-                    }
-                }
-            })
-            .collect::<Vec<String>>();
-
-            match spawn(&command, &path, &process_args[..], InputStream::empty(), is_last) {
-                Ok(mut res) => {
-                    while let Some(item) = res.next().await {
-                        yield Ok(item)
-                    }
-                }
-                Err(reason) => {
-                    yield Ok(Value {
-                        value: UntaggedValue::Error(reason),
-                        tag: name_tag
-                    });
-                    return;
-                }
-            }
-        }
-    };
-
-    Ok(stream.to_input_stream())
-}
-
-fn run_with_stdin(
+async fn run_with_stdin(
     command: ExternalCommand,
     context: &mut Context,
     input: InputStream,
@@ -207,8 +115,32 @@ fn run_with_stdin(
 
     let mut command_args = vec![];
     for arg in command.args.iter() {
-        let value = evaluate_baseline_expr(arg, &context.registry, scope)?;
-        command_args.push(value.as_string()?);
+        let value =
+            evaluate_baseline_expr(arg, &context.registry, &scope.it, &scope.vars, &scope.env)
+                .await?;
+        // Skip any arguments that don't really exist, treating them as optional
+        // FIXME: we may want to preserve the gap in the future, though it's hard to say
+        // what value we would put in its place.
+        if value.value.is_none() {
+            continue;
+        }
+        // Do the cleanup that we need to do on any argument going out:
+        let trimmed_value_string = value.as_string()?.trim_end_matches('\n').to_string();
+
+        let value_string;
+        #[cfg(not(windows))]
+        {
+            value_string = trimmed_value_string
+                .replace('$', "\\$")
+                .replace('"', "\\\"")
+                .to_string()
+        }
+        #[cfg(windows)]
+        {
+            value_string = trimmed_value_string
+        }
+
+        command_args.push(value_string);
     }
 
     let process_args = command_args
@@ -235,7 +167,7 @@ fn run_with_stdin(
         })
         .collect::<Vec<String>>();
 
-    spawn(&command, &path, &process_args[..], input, is_last)
+    spawn(&command, &path, &process_args[..], input, is_last, scope)
 }
 
 fn spawn(
@@ -244,6 +176,7 @@ fn spawn(
     args: &[String],
     input: InputStream,
     is_last: bool,
+    scope: &Scope,
 ) -> Result<InputStream, ShellError> {
     let command = command.clone();
 
@@ -273,6 +206,9 @@ fn spawn(
     process.current_dir(path);
     trace!(target: "nu::run::external", "cwd = {:?}", &path);
 
+    process.env_clear();
+    process.envs(scope.env.iter());
+
     // We want stdout regardless of what
     // we are doing ($it case or pipe stdin)
     if !is_last {
@@ -405,16 +341,27 @@ fn spawn(
                                 }
                             }
                         },
-                        Err(_) => {
-                            let _ = stdout_read_tx.send(Ok(Value {
-                                value: UntaggedValue::Error(ShellError::labeled_error(
-                                    "Unable to read from stdout.",
-                                    "unable to read from stdout",
-                                    &stdout_name_tag,
-                                )),
-                                tag: stdout_name_tag.clone(),
-                            }));
-                            break;
+                        Err(e) => {
+                            // If there's an exit status, it makes sense that we may error when
+                            // trying to read from its stdout pipe (likely been closed). In that
+                            // case, don't emit an error.
+                            let should_error = match child.wait() {
+                                Ok(exit_status) => !exit_status.success(),
+                                Err(_) => true,
+                            };
+
+                            if should_error {
+                                let _ = stdout_read_tx.send(Ok(Value {
+                                    value: UntaggedValue::Error(ShellError::labeled_error(
+                                        format!("Unable to read from stdout ({})", e),
+                                        "unable to read from stdout",
+                                        &stdout_name_tag,
+                                    )),
+                                    tag: stdout_name_tag.clone(),
+                                }));
+                            }
+
+                            return Ok(());
                         }
                     }
                 }
@@ -424,10 +371,7 @@ fn spawn(
             // than what other shells will do.
             let external_failed = match child.wait() {
                 Err(_) => true,
-                Ok(exit_status) => match exit_status.code() {
-                    Some(e) if e != 0 => true,
-                    _ => false,
-                },
+                Ok(exit_status) => !exit_status.success(),
             };
 
             if external_failed {
@@ -467,12 +411,12 @@ fn spawn(
 async fn did_find_command(name: &str) -> bool {
     #[cfg(not(windows))]
     {
-        ichwh::which(name).await.unwrap_or(None).is_some()
+        which::which(name).is_ok()
     }
 
     #[cfg(windows)]
     {
-        if ichwh::which(name).await.unwrap_or(None).is_some() {
+        if which::which(name).is_ok() {
             true
         } else {
             let cmd_builtins = [
@@ -514,6 +458,7 @@ fn add_quotes(argument: &str) -> String {
     format!("\"{}\"", argument)
 }
 
+#[allow(unused)]
 fn remove_quotes(argument: &str) -> Option<&str> {
     if !argument_is_quoted(argument) {
         return None;
@@ -566,7 +511,7 @@ mod tests {
         let mut ctx = Context::basic().expect("There was a problem creating a basic context.");
 
         assert!(
-            run_external_command(cmd, &mut ctx, input, &Scope::empty(), false)
+            run_external_command(cmd, &mut ctx, input, &Scope::new(), false)
                 .await
                 .is_err()
         );

crates/nu-cli/src/commands/classified/internal.rs

@@ -1,4 +1,4 @@
-use crate::commands::command::per_item_command;
+use crate::commands::command::whole_stream_command;
 use crate::commands::run_alias::AliasCommand;
 use crate::commands::UnevaluatedCallInfo;
 use crate::prelude::*;
@@ -7,32 +7,41 @@ use nu_errors::ShellError;
 use nu_protocol::hir::InternalCommand;
 use nu_protocol::{CommandAction, Primitive, ReturnSuccess, Scope, UntaggedValue, Value};
 
-pub(crate) fn run_internal_command(
+pub(crate) async fn run_internal_command(
     command: InternalCommand,
     context: &mut Context,
     input: InputStream,
-    scope: &Scope,
+    it: &Value,
+    vars: &IndexMap<String, Value>,
+    env: &IndexMap<String, String>,
 ) -> Result<InputStream, ShellError> {
     if log_enabled!(log::Level::Trace) {
         trace!(target: "nu::run::internal", "->");
         trace!(target: "nu::run::internal", "{}", command.name);
     }
 
+    let scope = Scope {
+        it: it.clone(),
+        vars: vars.clone(),
+        env: env.clone(),
+    };
     let objects: InputStream = trace_stream!(target: "nu::trace_stream::internal", "input" = input);
     let internal_command = context.expect_command(&command.name);
 
-    let result = {
-        context.run_command(
-            internal_command?,
-            Tag::unknown_anchor(command.name_span),
-            command.args.clone(),
-            scope,
-            objects,
-        )
+    let mut result = {
+        context
+            .run_command(
+                internal_command?,
+                Tag::unknown_anchor(command.name_span),
+                command.args.clone(),
+                &scope,
+                objects,
+            )
+            .await
     };
 
-    let mut result = trace_out_stream!(target: "nu::trace_stream::internal", "output" = result);
     let mut context = context.clone();
+    // let scope = scope.clone();
 
     let stream = async_stream! {
         let mut soft_errs: Vec<ShellError> = vec![];
@@ -51,12 +60,13 @@ pub(crate) fn run_internal_command(
                     }
                     CommandAction::AutoConvert(tagged_contents, extension) => {
                         let contents_tag = tagged_contents.tag.clone();
-                        let command_name = format!("from-{}", extension);
+                        let command_name = format!("from {}", extension);
                         let command = command.clone();
                         if let Some(converter) = context.registry.get_command(&command_name) {
                             let new_args = RawCommandArgs {
                                 host: context.host.clone(),
                                 ctrl_c: context.ctrl_c.clone(),
+                                current_errors: context.current_errors.clone(),
                                 shell_manager: context.shell_manager.clone(),
                                 call_info: UnevaluatedCallInfo {
                                     args: nu_protocol::hir::Call {
@@ -67,10 +77,10 @@ pub(crate) fn run_internal_command(
                                         is_last: false,
                                     },
                                     name_tag: Tag::unknown_anchor(command.name_span),
-                                    scope: Scope::empty(),
+                                    scope: scope.clone(),
                                 }
                             };
-                            let mut result = converter.run(new_args.with_input(vec![tagged_contents]), &context.registry);
+                            let mut result = converter.run(new_args.with_input(vec![tagged_contents]), &context.registry).await;
                             let result_vec: Vec<Result<ReturnSuccess, ShellError>> = result.drain_vec().await;
                             for res in result_vec {
                                 match res {
@@ -117,12 +127,12 @@ pub(crate) fn run_internal_command(
                     }
                     CommandAction::EnterShell(location) => {
                         context.shell_manager.insert_at_current(Box::new(
-                            FilesystemShell::with_location(location, context.registry().clone()),
+                            FilesystemShell::with_location(location, context.registry().clone())?,
                         ));
                     }
                     CommandAction::AddAlias(name, args, block) => {
                         context.add_commands(vec![
-                            per_item_command(AliasCommand::new(
+                            whole_stream_command(AliasCommand::new(
                                 name,
                                 args,
                                 block,

crates/nu-cli/src/commands/clear.rs

@@ -6,35 +6,52 @@ use std::process::Command;
 
 pub struct Clear;
 
+#[async_trait]
 impl WholeStreamCommand for Clear {
     fn name(&self) -> &str {
         "clear"
     }
+
     fn signature(&self) -> Signature {
         Signature::build("clear")
     }
+
     fn usage(&self) -> &str {
         "clears the terminal"
     }
-    fn run(
-        &self,
-        args: CommandArgs,
-        registry: &CommandRegistry,
-    ) -> Result<OutputStream, ShellError> {
-        clear(args, registry)
+
+    async fn run(&self, _: CommandArgs, _: &CommandRegistry) -> Result<OutputStream, ShellError> {
+        if cfg!(windows) {
+            Command::new("cmd")
+                .args(&["/C", "cls"])
+                .status()
+                .expect("failed to execute process");
+        } else if cfg!(unix) {
+            Command::new("/bin/sh")
+                .args(&["-c", "clear"])
+                .status()
+                .expect("failed to execute process");
+        }
+        Ok(OutputStream::empty())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Clear the screen",
+            example: "clear",
+            result: None,
+        }]
     }
 }
-fn clear(_args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    if cfg!(windows) {
-        Command::new("cmd")
-            .args(&["/C", "cls"])
-            .status()
-            .expect("failed to execute process");
-    } else if cfg!(unix) {
-        Command::new("/bin/sh")
-            .args(&["-c", "clear"])
-            .status()
-            .expect("failed to execute process");
+
+#[cfg(test)]
+mod tests {
+    use super::Clear;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Clear {})
     }
-    Ok(OutputStream::empty())
 }

crates/nu-cli/src/commands/clip.rs

@@ -1,106 +1,109 @@
-#[cfg(feature = "clipboard")]
-pub mod clipboard {
-    use crate::commands::WholeStreamCommand;
-    use crate::context::CommandRegistry;
-    use crate::prelude::*;
-    use futures::stream::StreamExt;
-    use nu_errors::ShellError;
-    use nu_protocol::{ReturnValue, Signature, Value};
+use crate::commands::WholeStreamCommand;
+use crate::context::CommandRegistry;
+use crate::prelude::*;
+use futures::stream::StreamExt;
+use nu_errors::ShellError;
+use nu_protocol::{Signature, Value};
 
-    use clipboard::{ClipboardContext, ClipboardProvider};
+use clipboard::{ClipboardContext, ClipboardProvider};
 
-    pub struct Clip;
+pub struct Clip;
 
-    #[derive(Deserialize)]
-    pub struct ClipArgs {}
-
-    impl WholeStreamCommand for Clip {
-        fn name(&self) -> &str {
-            "clip"
-        }
-
-        fn signature(&self) -> Signature {
-            Signature::build("clip")
-        }
-
-        fn usage(&self) -> &str {
-            "Copy the contents of the pipeline to the copy/paste buffer"
-        }
-
-        fn run(
-            &self,
-            args: CommandArgs,
-            registry: &CommandRegistry,
-        ) -> Result<OutputStream, ShellError> {
-            args.process(registry, clip)?.run()
-        }
+#[async_trait]
+impl WholeStreamCommand for Clip {
+    fn name(&self) -> &str {
+        "clip"
     }
 
-    pub fn clip(
-        ClipArgs {}: ClipArgs,
-        RunnableContext { input, name, .. }: RunnableContext,
+    fn signature(&self) -> Signature {
+        Signature::build("clip")
+    }
+
+    fn usage(&self) -> &str {
+        "Copy the contents of the pipeline to the copy/paste buffer"
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        let stream = async_stream! {
-            let values: Vec<Value> = input.collect().await;
-
-            let mut clip_stream = inner_clip(values, name).await;
-            while let Some(value) = clip_stream.next().await {
-                yield value;
-            }
-        };
-
-        let stream: BoxStream<'static, ReturnValue> = stream.boxed();
-
-        Ok(OutputStream::from(stream))
+        clip(args, registry).await
     }
 
-    async fn inner_clip(input: Vec<Value>, name: Tag) -> OutputStream {
-        if let Ok(clip_context) = ClipboardProvider::new() {
-            let mut clip_context: ClipboardContext = clip_context;
-            let mut new_copy_data = String::new();
-
-            if !input.is_empty() {
-                let mut first = true;
-                for i in input.iter() {
-                    if !first {
-                        new_copy_data.push_str("\n");
-                    } else {
-                        first = false;
-                    }
-
-                    let string: String = match i.as_string() {
-                        Ok(string) => string.to_string(),
-                        Err(_) => {
-                            return OutputStream::one(Err(ShellError::labeled_error(
-                                "Given non-string data",
-                                "expected strings from pipeline",
-                                name,
-                            )))
-                        }
-                    };
-
-                    new_copy_data.push_str(&string);
-                }
-            }
-
-            match clip_context.set_contents(new_copy_data) {
-                Ok(_) => {}
-                Err(_) => {
-                    return OutputStream::one(Err(ShellError::labeled_error(
-                        "Could not set contents of clipboard",
-                        "could not set contents of clipboard",
-                        name,
-                    )));
-                }
-            }
-
-            OutputStream::empty()
-        } else {
-            OutputStream::one(Err(ShellError::labeled_error(
-                "Could not open clipboard",
-                "could not open clipboard",
-                name,
-            )))
-        }
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Save text to the clipboard",
+            example: "echo 'secret value' | clip",
+            result: None,
+        }]
+    }
+}
+
+pub async fn clip(
+    args: CommandArgs,
+    _registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let input = args.input;
+    let name = args.call_info.name_tag.clone();
+    let values: Vec<Value> = input.collect().await;
+
+    if let Ok(clip_context) = ClipboardProvider::new() {
+        let mut clip_context: ClipboardContext = clip_context;
+        let mut new_copy_data = String::new();
+
+        if !values.is_empty() {
+            let mut first = true;
+            for i in values.iter() {
+                if !first {
+                    new_copy_data.push_str("\n");
+                } else {
+                    first = false;
+                }
+
+                let string: String = match i.as_string() {
+                    Ok(string) => string.to_string(),
+                    Err(_) => {
+                        return Err(ShellError::labeled_error(
+                            "Given non-string data",
+                            "expected strings from pipeline",
+                            name,
+                        ))
+                    }
+                };
+
+                new_copy_data.push_str(&string);
+            }
+        }
+
+        match clip_context.set_contents(new_copy_data) {
+            Ok(_) => {}
+            Err(_) => {
+                return Err(ShellError::labeled_error(
+                    "Could not set contents of clipboard",
+                    "could not set contents of clipboard",
+                    name,
+                ));
+            }
+        }
+    } else {
+        return Err(ShellError::labeled_error(
+            "Could not open clipboard",
+            "could not open clipboard",
+            name,
+        ));
+    }
+    Ok(OutputStream::empty())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Clip;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Clip {})
     }
 }

crates/nu-cli/src/commands/command.rs

@@ -7,7 +7,8 @@ use derive_new::new;
 use getset::Getters;
 use nu_errors::ShellError;
 use nu_protocol::hir;
-use nu_protocol::{CallInfo, EvaluatedArgs, ReturnValue, Scope, Signature, Value};
+use nu_protocol::{CallInfo, EvaluatedArgs, ReturnSuccess, Scope, Signature, UntaggedValue, Value};
+use parking_lot::Mutex;
 use serde::{Deserialize, Serialize};
 use std::ops::Deref;
 use std::sync::atomic::AtomicBool;
@@ -20,8 +21,8 @@ pub struct UnevaluatedCallInfo {
 }
 
 impl UnevaluatedCallInfo {
-    pub fn evaluate(self, registry: &CommandRegistry) -> Result<CallInfo, ShellError> {
-        let args = evaluate_args(&self.args, registry, &self.scope)?;
+    pub async fn evaluate(self, registry: &CommandRegistry) -> Result<CallInfo, ShellError> {
+        let args = evaluate_args(&self.args, registry, &self.scope).await?;
 
         Ok(CallInfo {
             args,
@@ -29,14 +30,14 @@ impl UnevaluatedCallInfo {
         })
     }
 
-    pub fn evaluate_with_new_it(
+    pub async fn evaluate_with_new_it(
         self,
         registry: &CommandRegistry,
         it: &Value,
     ) -> Result<CallInfo, ShellError> {
         let mut scope = self.scope.clone();
-        scope = scope.set_it(it.clone());
-        let args = evaluate_args(&self.args, registry, &scope)?;
+        scope.it = it.clone();
+        let args = evaluate_args(&self.args, registry, &scope).await?;
 
         Ok(CallInfo {
             args,
@@ -49,44 +50,16 @@ impl UnevaluatedCallInfo {
     }
 }
 
-pub trait CallInfoExt {
-    fn process<'de, T: Deserialize<'de>>(
-        &self,
-        shell_manager: &ShellManager,
-        ctrl_c: Arc<AtomicBool>,
-        callback: fn(T, &RunnablePerItemContext) -> Result<OutputStream, ShellError>,
-    ) -> Result<RunnablePerItemArgs<T>, ShellError>;
-}
-
-impl CallInfoExt for CallInfo {
-    fn process<'de, T: Deserialize<'de>>(
-        &self,
-        shell_manager: &ShellManager,
-        ctrl_c: Arc<AtomicBool>,
-        callback: fn(T, &RunnablePerItemContext) -> Result<OutputStream, ShellError>,
-    ) -> Result<RunnablePerItemArgs<T>, ShellError> {
-        let mut deserializer = ConfigDeserializer::from_call_info(self.clone());
-
-        Ok(RunnablePerItemArgs {
-            args: T::deserialize(&mut deserializer)?,
-            context: RunnablePerItemContext {
-                shell_manager: shell_manager.clone(),
-                name: self.name_tag.clone(),
-                ctrl_c,
-            },
-            callback,
-        })
-    }
-}
-
 #[derive(Getters)]
 #[get = "pub(crate)"]
 pub struct CommandArgs {
     pub host: Arc<parking_lot::Mutex<Box<dyn Host>>>,
     pub ctrl_c: Arc<AtomicBool>,
+    pub current_errors: Arc<Mutex<Vec<ShellError>>>,
     pub shell_manager: ShellManager,
     pub call_info: UnevaluatedCallInfo,
     pub input: InputStream,
+    pub raw_input: String,
 }
 
 #[derive(Getters, Clone)]
@@ -94,6 +67,7 @@ pub struct CommandArgs {
 pub struct RawCommandArgs {
     pub host: Arc<parking_lot::Mutex<Box<dyn Host>>>,
     pub ctrl_c: Arc<AtomicBool>,
+    pub current_errors: Arc<Mutex<Vec<ShellError>>>,
     pub shell_manager: ShellManager,
     pub call_info: UnevaluatedCallInfo,
 }
@@ -103,9 +77,11 @@ impl RawCommandArgs {
         CommandArgs {
             host: self.host,
             ctrl_c: self.ctrl_c,
+            current_errors: self.current_errors,
             shell_manager: self.shell_manager,
             call_info: self.call_info,
             input: input.into(),
+            raw_input: String::default(),
         }
     }
 }
@@ -117,7 +93,7 @@ impl std::fmt::Debug for CommandArgs {
 }
 
 impl CommandArgs {
-    pub fn evaluate_once(
+    pub async fn evaluate_once(
         self,
         registry: &CommandRegistry,
     ) -> Result<EvaluatedWholeStreamCommandArgs, ShellError> {
@@ -125,7 +101,7 @@ impl CommandArgs {
         let ctrl_c = self.ctrl_c.clone();
         let shell_manager = self.shell_manager.clone();
         let input = self.input;
-        let call_info = self.call_info.evaluate(registry)?;
+        let call_info = self.call_info.evaluate(registry).await?;
 
         Ok(EvaluatedWholeStreamCommandArgs::new(
             host,
@@ -136,7 +112,7 @@ impl CommandArgs {
         ))
     }
 
-    pub fn evaluate_once_with_scope(
+    pub async fn evaluate_once_with_scope(
         self,
         registry: &CommandRegistry,
         scope: &Scope,
@@ -150,7 +126,7 @@ impl CommandArgs {
             args: self.call_info.args,
             scope: scope.clone(),
         };
-        let call_info = call_info.evaluate(registry)?;
+        let call_info = call_info.evaluate(registry).await?;
 
         Ok(EvaluatedWholeStreamCommandArgs::new(
             host,
@@ -161,133 +137,36 @@ impl CommandArgs {
         ))
     }
 
-    pub fn process<'de, T: Deserialize<'de>, O: ToOutputStream>(
+    pub async fn process<'de, T: Deserialize<'de>>(
         self,
         registry: &CommandRegistry,
-        callback: fn(T, RunnableContext) -> Result<O, ShellError>,
-    ) -> Result<RunnableArgs<T, O>, ShellError> {
-        let shell_manager = self.shell_manager.clone();
-        let host = self.host.clone();
-        let ctrl_c = self.ctrl_c.clone();
-        let args = self.evaluate_once(registry)?;
-        let call_info = args.call_info.clone();
-        let (input, args) = args.split();
-        let name_tag = args.call_info.name_tag;
-        let mut deserializer = ConfigDeserializer::from_call_info(call_info);
-
-        Ok(RunnableArgs {
-            args: T::deserialize(&mut deserializer)?,
-            context: RunnableContext {
-                input,
-                registry: registry.clone(),
-                shell_manager,
-                name: name_tag,
-                host,
-                ctrl_c,
-            },
-            callback,
-        })
-    }
-
-    pub fn process_raw<'de, T: Deserialize<'de>>(
-        self,
-        registry: &CommandRegistry,
-        callback: fn(T, RunnableContext, RawCommandArgs) -> Result<OutputStream, ShellError>,
-    ) -> Result<RunnableRawArgs<T>, ShellError> {
-        let raw_args = RawCommandArgs {
-            host: self.host.clone(),
-            ctrl_c: self.ctrl_c.clone(),
-            shell_manager: self.shell_manager.clone(),
-            call_info: self.call_info.clone(),
-        };
-
-        let shell_manager = self.shell_manager.clone();
-        let host = self.host.clone();
-        let ctrl_c = self.ctrl_c.clone();
-        let args = self.evaluate_once(registry)?;
+    ) -> Result<(T, InputStream), ShellError> {
+        let args = self.evaluate_once(registry).await?;
         let call_info = args.call_info.clone();
 
-        let (input, args) = args.split();
-        let name_tag = args.call_info.name_tag;
         let mut deserializer = ConfigDeserializer::from_call_info(call_info);
 
-        Ok(RunnableRawArgs {
-            args: T::deserialize(&mut deserializer)?,
-            context: RunnableContext {
-                input,
-                registry: registry.clone(),
-                shell_manager,
-                name: name_tag,
-                host,
-                ctrl_c,
-            },
-            raw_args,
-            callback,
-        })
+        Ok((T::deserialize(&mut deserializer)?, args.input))
     }
 }
 
-pub struct RunnablePerItemContext {
-    pub shell_manager: ShellManager,
-    pub name: Tag,
-    pub ctrl_c: Arc<AtomicBool>,
-}
-
 pub struct RunnableContext {
     pub input: InputStream,
     pub shell_manager: ShellManager,
     pub host: Arc<parking_lot::Mutex<Box<dyn Host>>>,
     pub ctrl_c: Arc<AtomicBool>,
+    pub current_errors: Arc<Mutex<Vec<ShellError>>>,
     pub registry: CommandRegistry,
     pub name: Tag,
+    pub raw_input: String,
 }
 
 impl RunnableContext {
-    pub fn get_command(&self, name: &str) -> Option<Arc<Command>> {
+    pub fn get_command(&self, name: &str) -> Option<Command> {
         self.registry.get_command(name)
     }
 }
 
-pub struct RunnablePerItemArgs<T> {
-    args: T,
-    context: RunnablePerItemContext,
-    callback: fn(T, &RunnablePerItemContext) -> Result<OutputStream, ShellError>,
-}
-
-impl<T> RunnablePerItemArgs<T> {
-    pub fn run(self) -> Result<OutputStream, ShellError> {
-        (self.callback)(self.args, &self.context)
-    }
-}
-
-pub struct RunnableArgs<T, O: ToOutputStream> {
-    args: T,
-    context: RunnableContext,
-    callback: fn(T, RunnableContext) -> Result<O, ShellError>,
-}
-
-impl<T, O: ToOutputStream> RunnableArgs<T, O> {
-    pub fn run(self) -> Result<OutputStream, ShellError> {
-        (self.callback)(self.args, self.context).map(|v| v.to_output_stream())
-    }
-}
-
-pub struct RunnableRawArgs<T> {
-    args: T,
-    raw_args: RawCommandArgs,
-    context: RunnableContext,
-    callback: fn(T, RunnableContext, RawCommandArgs) -> Result<OutputStream, ShellError>,
-}
-
-impl<T> RunnableRawArgs<T> {
-    pub fn run(self) -> OutputStream {
-        match (self.callback)(self.args, self.context, self.raw_args) {
-            Ok(stream) => stream,
-            Err(err) => OutputStream::one(Err(err)),
-        }
-    }
-}
-
 pub struct EvaluatedWholeStreamCommandArgs {
     pub args: EvaluatedCommandArgs,
     pub input: InputStream,
@@ -398,6 +277,13 @@ impl EvaluatedCommandArgs {
     }
 }
 
+pub struct Example {
+    pub example: &'static str,
+    pub description: &'static str,
+    pub result: Option<Vec<Value>>,
+}
+
+#[async_trait]
 pub trait WholeStreamCommand: Send + Sync {
     fn name(&self) -> &str;
 
@@ -407,7 +293,7 @@ pub trait WholeStreamCommand: Send + Sync {
 
     fn usage(&self) -> &str;
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
@@ -416,152 +302,68 @@ pub trait WholeStreamCommand: Send + Sync {
     fn is_binary(&self) -> bool {
         false
     }
-}
 
-pub trait PerItemCommand: Send + Sync {
-    fn name(&self) -> &str;
-
-    fn signature(&self) -> Signature {
-        Signature::new(self.name()).desc(self.usage()).filter()
-    }
-
-    fn usage(&self) -> &str;
-
-    fn run(
-        &self,
-        call_info: &CallInfo,
-        registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        input: Value,
-    ) -> Result<OutputStream, ShellError>;
-
-    fn is_binary(&self) -> bool {
-        false
+    fn examples(&self) -> Vec<Example> {
+        Vec::new()
     }
 }
 
-pub enum Command {
-    WholeStream(Arc<dyn WholeStreamCommand>),
-    PerItem(Arc<dyn PerItemCommand>),
-}
+#[derive(Clone)]
+pub struct Command(Arc<dyn WholeStreamCommand>);
 
 impl PrettyDebugWithSource for Command {
     fn pretty_debug(&self, source: &str) -> DebugDocBuilder {
-        match self {
-            Command::WholeStream(command) => b::typed(
-                "whole stream command",
-                b::description(command.name())
-                    + b::space()
-                    + b::equals()
-                    + b::space()
-                    + command.signature().pretty_debug(source),
-            ),
-            Command::PerItem(command) => b::typed(
-                "per item command",
-                b::description(command.name())
-                    + b::space()
-                    + b::equals()
-                    + b::space()
-                    + command.signature().pretty_debug(source),
-            ),
-        }
+        b::typed(
+            "whole stream command",
+            b::description(self.name())
+                + b::space()
+                + b::equals()
+                + b::space()
+                + self.signature().pretty_debug(source),
+        )
     }
 }
 
 impl std::fmt::Debug for Command {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            Command::WholeStream(command) => write!(f, "WholeStream({})", command.name()),
-            Command::PerItem(command) => write!(f, "PerItem({})", command.name()),
-        }
+        write!(f, "Command({})", self.name())
     }
 }
 
 impl Command {
     pub fn name(&self) -> &str {
-        match self {
-            Command::WholeStream(command) => command.name(),
-            Command::PerItem(command) => command.name(),
-        }
+        self.0.name()
     }
 
     pub fn signature(&self) -> Signature {
-        match self {
-            Command::WholeStream(command) => command.signature(),
-            Command::PerItem(command) => command.signature(),
-        }
+        self.0.signature()
     }
 
     pub fn usage(&self) -> &str {
-        match self {
-            Command::WholeStream(command) => command.usage(),
-            Command::PerItem(command) => command.usage(),
-        }
+        self.0.usage()
     }
 
-    pub fn run(&self, args: CommandArgs, registry: &CommandRegistry) -> OutputStream {
+    pub async fn run(&self, args: CommandArgs, registry: &CommandRegistry) -> OutputStream {
         if args.call_info.switch_present("help") {
-            get_help(self.name(), self.usage(), self.signature()).into()
+            let cl = self.0.clone();
+            let registry = registry.clone();
+            OutputStream::one(Ok(ReturnSuccess::Value(
+                UntaggedValue::string(get_help(&*cl, &registry)).into_value(Tag::unknown()),
+            )))
         } else {
-            match self {
-                Command::WholeStream(command) => match command.run(args, registry) {
-                    Ok(stream) => stream,
-                    Err(err) => OutputStream::one(Err(err)),
-                },
-                Command::PerItem(command) => {
-                    self.run_helper(command.clone(), args, registry.clone())
-                }
+            match self.0.run(args, registry).await {
+                Ok(stream) => stream,
+                Err(err) => OutputStream::one(Err(err)),
             }
         }
     }
 
-    fn run_helper(
-        &self,
-        command: Arc<dyn PerItemCommand>,
-        args: CommandArgs,
-        registry: CommandRegistry,
-    ) -> OutputStream {
-        let raw_args = RawCommandArgs {
-            host: args.host,
-            ctrl_c: args.ctrl_c,
-            shell_manager: args.shell_manager,
-            call_info: args.call_info,
-        };
-
-        let out = args
-            .input
-            .map(move |x| {
-                let call_info = UnevaluatedCallInfo {
-                    args: raw_args.call_info.args.clone(),
-                    name_tag: raw_args.call_info.name_tag.clone(),
-                    scope: raw_args.call_info.scope.clone().set_it(x.clone()),
-                }
-                .evaluate(&registry);
-                // let call_info = raw_args
-                //     .clone()
-                //     .call_info
-                //     .evaluate(&registry, &Scope::it_value(x.clone()));
-
-                match call_info {
-                    Ok(call_info) => match command.run(&call_info, &registry, &raw_args, x) {
-                        Ok(o) => o,
-                        Err(e) => {
-                            futures::stream::iter(vec![ReturnValue::Err(e)]).to_output_stream()
-                        }
-                    },
-                    Err(e) => futures::stream::iter(vec![ReturnValue::Err(e)]).to_output_stream(),
-                }
-            })
-            .flatten();
-
-        out.to_output_stream()
+    pub fn is_binary(&self) -> bool {
+        self.0.is_binary()
     }
 
-    pub fn is_binary(&self) -> bool {
-        match self {
-            Command::WholeStream(command) => command.is_binary(),
-            Command::PerItem(command) => command.is_binary(),
-        }
+    pub fn stream_command(&self) -> &dyn WholeStreamCommand {
+        &*self.0
     }
 }
 
@@ -570,6 +372,7 @@ pub struct FnFilterCommand {
     func: fn(EvaluatedFilterCommandArgs) -> Result<OutputStream, ShellError>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for FnFilterCommand {
     fn name(&self) -> &str {
         &self.name
@@ -579,54 +382,52 @@ impl WholeStreamCommand for FnFilterCommand {
         "usage"
     }
 
-    fn run(
+    async fn run(
         &self,
-        args: CommandArgs,
-        registry: &CommandRegistry,
-    ) -> Result<OutputStream, ShellError> {
-        let CommandArgs {
+        CommandArgs {
             host,
             ctrl_c,
             shell_manager,
             call_info,
-            input,
-        } = args;
-
+            mut input,
+            ..
+        }: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
         let host: Arc<parking_lot::Mutex<dyn Host>> = host.clone();
         let registry: CommandRegistry = registry.clone();
         let func = self.func;
 
-        let result = input.map(move |it| {
-            let registry = registry.clone();
-            let call_info = match call_info.clone().evaluate_with_new_it(&registry, &it) {
-                Err(err) => return OutputStream::from(vec![Err(err)]).values,
-                Ok(args) => args,
-            };
+        let stream = async_stream! {
+            while let Some(it) = input.next().await {
+                let registry = registry.clone();
+                let call_info = match call_info.clone().evaluate_with_new_it(&registry, &it).await {
+                    Err(err) => { yield Err(err); return; },
+                    Ok(args) => args,
+                };
 
-            let args = EvaluatedFilterCommandArgs::new(
-                host.clone(),
-                ctrl_c.clone(),
-                shell_manager.clone(),
-                call_info,
-            );
+                let args = EvaluatedFilterCommandArgs::new(
+                    host.clone(),
+                    ctrl_c.clone(),
+                    shell_manager.clone(),
+                    call_info,
+                );
 
-            match func(args) {
-                Err(err) => OutputStream::from(vec![Err(err)]).values,
-                Ok(stream) => stream.values,
+                match func(args) {
+                    Err(err) => yield Err(err),
+                    Ok(mut stream) => {
+                        while let Some(value) = stream.values.next().await {
+                            yield value;
+                        }
+                    }
+                }
             }
-        });
+        };
 
-        let result = result.flatten();
-        let result: BoxStream<ReturnValue> = result.boxed();
-
-        Ok(result.into())
+        Ok(stream.to_output_stream())
     }
 }
 
-pub fn whole_stream_command(command: impl WholeStreamCommand + 'static) -> Arc<Command> {
-    Arc::new(Command::WholeStream(Arc::new(command)))
-}
-
-pub fn per_item_command(command: impl PerItemCommand + 'static) -> Arc<Command> {
-    Arc::new(Command::PerItem(Arc::new(command)))
+pub fn whole_stream_command(command: impl WholeStreamCommand + 'static) -> Command {
+    Command(Arc::new(command))
 }

crates/nu-cli/src/commands/compact.rs

@@ -1,9 +1,10 @@
 use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
+use futures::future;
 use futures::stream::StreamExt;
 use nu_errors::ShellError;
-use nu_protocol::{Signature, SyntaxShape, UntaggedValue, Value};
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
 use nu_source::Tagged;
 
 pub struct Compact;
@@ -13,6 +14,7 @@ pub struct CompactArgs {
     rest: Vec<Tagged<String>>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for Compact {
     fn name(&self) -> &str {
         "compact"
@@ -26,36 +28,78 @@ impl WholeStreamCommand for Compact {
         "Creates a table with non-empty rows"
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, compact)?.run()
+        compact(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Filter out all null entries in a list",
+                example: "echo [1 2 $null 3 $null $null] | compact target",
+                result: Some(vec![
+                    UntaggedValue::int(1).into(),
+                    UntaggedValue::int(2).into(),
+                    UntaggedValue::int(3).into(),
+                ]),
+            },
+            Example {
+                description: "Filter out all directory entries having no 'target'",
+                example: "ls -af | compact target",
+                result: None,
+            },
+        ]
     }
 }
 
-pub fn compact(
-    CompactArgs { rest: columns }: CompactArgs,
-    RunnableContext { input, .. }: RunnableContext,
+pub async fn compact(
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    let objects = input.filter(move |item| {
-        let keep = if columns.is_empty() {
-            item.is_some()
-        } else {
-            match item {
-                Value {
-                    value: UntaggedValue::Row(ref r),
-                    ..
-                } => columns
-                    .iter()
-                    .all(|field| r.get_data(field).borrow().is_some()),
-                _ => false,
-            }
-        };
-
-        futures::future::ready(keep)
-    });
-
-    Ok(objects.from_input_stream())
+    let registry = registry.clone();
+    let (CompactArgs { rest: columns }, input) = args.process(&registry).await?;
+    Ok(input
+        .filter_map(move |item| {
+            future::ready(if columns.is_empty() {
+                if !item.is_empty() {
+                    Some(ReturnSuccess::value(item))
+                } else {
+                    None
+                }
+            } else {
+                match item {
+                    Value {
+                        value: UntaggedValue::Row(ref r),
+                        ..
+                    } => {
+                        if columns
+                            .iter()
+                            .all(|field| r.get_data(field).borrow().is_some())
+                        {
+                            Some(ReturnSuccess::value(item))
+                        } else {
+                            None
+                        }
+                    }
+                    _ => None,
+                }
+            })
+        })
+        .to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Compact;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Compact {})
+    }
 }

crates/nu-cli/src/commands/config.rs

@@ -20,6 +20,7 @@ pub struct ConfigArgs {
     path: Tagged<bool>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for Config {
     fn name(&self) -> &str {
         "config"
@@ -30,7 +31,7 @@ impl WholeStreamCommand for Config {
             .named(
                 "load",
                 SyntaxShape::Path,
-                "load the config from the path give",
+                "load the config from the path given",
                 Some('l'),
             )
             .named(
@@ -65,124 +66,195 @@ impl WholeStreamCommand for Config {
         "Configuration management."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, config)?.run()
+        config(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "See all config values",
+                example: "config",
+                result: None,
+            },
+            Example {
+                description: "Set completion_mode to circular",
+                example: "config --set [completion_mode circular]",
+                result: None,
+            },
+            Example {
+                description: "Store the contents of the pipeline as a path",
+                example: "echo ['/usr/bin' '/bin'] | config --set_into path",
+                result: None,
+            },
+            Example {
+                description: "Get the current startup commands",
+                example: "config --get startup",
+                result: None,
+            },
+            Example {
+                description: "Remove the startup commands",
+                example: "config --remove startup",
+                result: None,
+            },
+            Example {
+                description: "Clear the config (be careful!)",
+                example: "config --clear",
+                result: None,
+            },
+            Example {
+                description: "Get the path to the current config file",
+                example: "config --path",
+                result: None,
+            },
+        ]
     }
 }
 
-pub fn config(
-    ConfigArgs {
-        load,
-        set,
-        set_into,
-        get,
-        clear,
-        remove,
-        path,
-    }: ConfigArgs,
-    RunnableContext { name, input, .. }: RunnableContext,
+pub async fn config(
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    let name_span = name.clone();
+    let name_span = args.call_info.name_tag.clone();
+    let name = args.call_info.name_tag.clone();
+    let registry = registry.clone();
 
-    let stream = async_stream! {
-        let configuration = if let Some(supplied) = load {
-            Some(supplied.item().clone())
-        } else {
-            None
-        };
+    let (
+        ConfigArgs {
+            load,
+            set,
+            set_into,
+            get,
+            clear,
+            remove,
+            path,
+        },
+        input,
+    ) = args.process(&registry).await?;
 
-        let mut result = crate::data::config::read(name_span, &configuration)?;
-
-        if let Some(v) = get {
-            let key = v.to_string();
-            let value = result
-                .get(&key)
-                .ok_or_else(|| ShellError::labeled_error("Missing key in config", "key", v.tag()))?;
-
-            match value {
-                Value {
-                    value: UntaggedValue::Table(list),
-                    ..
-                } => {
-                    for l in list {
-                        let value = l.clone();
-                        yield ReturnSuccess::value(l.clone());
-                    }
-                }
-                x => yield ReturnSuccess::value(x.clone()),
-            }
-        }
-        else if let Some((key, value)) = set {
-            result.insert(key.to_string(), value.clone());
-
-            config::write(&result, &configuration)?;
-
-            yield ReturnSuccess::value(UntaggedValue::Row(result.into()).into_value(&value.tag));
-        }
-        else if let Some(v) = set_into {
-            let rows: Vec<Value> = input.collect().await;
-            let key = v.to_string();
-
-            if rows.len() == 0 {
-                yield Err(ShellError::labeled_error("No values given for set_into", "needs value(s) from pipeline", v.tag()));
-            } else if rows.len() == 1 {
-                // A single value
-                let value = &rows[0];
-
-                result.insert(key.to_string(), value.clone());
-
-                config::write(&result, &configuration)?;
-
-                yield ReturnSuccess::value(UntaggedValue::Row(result.into()).into_value(name));
-            } else {
-                // Take in the pipeline as a table
-                let value = UntaggedValue::Table(rows).into_value(name.clone());
-
-                result.insert(key.to_string(), value.clone());
-
-                config::write(&result, &configuration)?;
-
-                yield ReturnSuccess::value(UntaggedValue::Row(result.into()).into_value(name));
-            }
-        }
-        else if let Tagged { item: true, tag } = clear {
-            result.clear();
-
-            config::write(&result, &configuration)?;
-
-            yield ReturnSuccess::value(UntaggedValue::Row(result.into()).into_value(tag));
-
-            return;
-        }
-        else if let Tagged { item: true, tag } = path {
-            let path = config::default_path_for(&configuration)?;
-
-            yield ReturnSuccess::value(UntaggedValue::Primitive(Primitive::Path(path)).into_value(tag));
-        }
-        else if let Some(v) = remove {
-            let key = v.to_string();
-
-            if result.contains_key(&key) {
-                result.swap_remove(&key);
-                config::write(&result, &configuration)?
-            } else {
-                yield Err(ShellError::labeled_error(
-                    "Key does not exist in config",
-                    "key",
-                    v.tag(),
-                ));
-            }
-
-            yield ReturnSuccess::value(UntaggedValue::Row(result.into()).into_value(v.tag()));
-        }
-        else {
-            yield ReturnSuccess::value(UntaggedValue::Row(result.into()).into_value(name));
-        }
+    let configuration = if let Some(supplied) = load {
+        Some(supplied.item().clone())
+    } else {
+        None
     };
 
-    Ok(stream.to_output_stream())
+    let mut result = crate::data::config::read(name_span, &configuration)?;
+
+    Ok(if let Some(v) = get {
+        let key = v.to_string();
+        let value = result
+            .get(&key)
+            .ok_or_else(|| ShellError::labeled_error("Missing key in config", "key", v.tag()))?;
+
+        match value {
+            Value {
+                value: UntaggedValue::Table(list),
+                ..
+            } => {
+                let list: Vec<_> = list
+                    .iter()
+                    .map(|x| ReturnSuccess::value(x.clone()))
+                    .collect();
+
+                futures::stream::iter(list).to_output_stream()
+            }
+            x => {
+                let x = x.clone();
+                OutputStream::one(ReturnSuccess::value(x))
+            }
+        }
+    } else if let Some((key, value)) = set {
+        result.insert(key.to_string(), value.clone());
+
+        config::write(&result, &configuration)?;
+
+        OutputStream::one(ReturnSuccess::value(
+            UntaggedValue::Row(result.into()).into_value(&value.tag),
+        ))
+    } else if let Some(v) = set_into {
+        let rows: Vec<Value> = input.collect().await;
+        let key = v.to_string();
+
+        if rows.is_empty() {
+            return Err(ShellError::labeled_error(
+                "No values given for set_into",
+                "needs value(s) from pipeline",
+                v.tag(),
+            ));
+        } else if rows.len() == 1 {
+            // A single value
+            let value = &rows[0];
+
+            result.insert(key, value.clone());
+
+            config::write(&result, &configuration)?;
+
+            OutputStream::one(ReturnSuccess::value(
+                UntaggedValue::Row(result.into()).into_value(name),
+            ))
+        } else {
+            // Take in the pipeline as a table
+            let value = UntaggedValue::Table(rows).into_value(name.clone());
+
+            result.insert(key, value);
+
+            config::write(&result, &configuration)?;
+
+            OutputStream::one(ReturnSuccess::value(
+                UntaggedValue::Row(result.into()).into_value(name),
+            ))
+        }
+    } else if let Tagged { item: true, tag } = clear {
+        result.clear();
+
+        config::write(&result, &configuration)?;
+
+        OutputStream::one(ReturnSuccess::value(
+            UntaggedValue::Row(result.into()).into_value(tag),
+        ))
+    } else if let Tagged { item: true, tag } = path {
+        let path = config::default_path_for(&configuration)?;
+
+        OutputStream::one(ReturnSuccess::value(
+            UntaggedValue::Primitive(Primitive::Path(path)).into_value(tag),
+        ))
+    } else if let Some(v) = remove {
+        let key = v.to_string();
+
+        if result.contains_key(&key) {
+            result.swap_remove(&key);
+            config::write(&result, &configuration)?;
+            futures::stream::iter(vec![ReturnSuccess::value(
+                UntaggedValue::Row(result.into()).into_value(v.tag()),
+            )])
+            .to_output_stream()
+        } else {
+            return Err(ShellError::labeled_error(
+                "Key does not exist in config",
+                "key",
+                v.tag(),
+            ));
+        }
+    } else {
+        futures::stream::iter(vec![ReturnSuccess::value(
+            UntaggedValue::Row(result.into()).into_value(name),
+        )])
+        .to_output_stream()
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Config;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Config {})
+    }
 }

crates/nu-cli/src/commands/count.rs

@@ -3,13 +3,11 @@ use crate::context::CommandRegistry;
 use crate::prelude::*;
 use futures::stream::StreamExt;
 use nu_errors::ShellError;
-use nu_protocol::{ReturnSuccess, Signature, UntaggedValue, Value};
+use nu_protocol::{Signature, UntaggedValue, Value};
 
 pub struct Count;
 
-#[derive(Deserialize)]
-pub struct CountArgs {}
-
+#[async_trait]
 impl WholeStreamCommand for Count {
     fn name(&self) -> &str {
         "count"
@@ -20,27 +18,39 @@ impl WholeStreamCommand for Count {
     }
 
     fn usage(&self) -> &str {
-        "Show the total number of rows."
+        "Show the total number of rows or items."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
-        registry: &CommandRegistry,
+        _registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, count)?.run()
+        let name = args.call_info.name_tag.clone();
+        let rows: Vec<Value> = args.input.collect().await;
+
+        Ok(OutputStream::one(
+            UntaggedValue::int(rows.len()).into_value(name),
+        ))
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Count the number of entries in a list",
+            example: "echo [1 2 3 4 5] | count",
+            result: Some(vec![UntaggedValue::int(5).into()]),
+        }]
     }
 }
 
-pub fn count(
-    CountArgs {}: CountArgs,
-    RunnableContext { input, name, .. }: RunnableContext,
-) -> Result<OutputStream, ShellError> {
-    let stream = async_stream! {
-        let rows: Vec<Value> = input.collect().await;
+#[cfg(test)]
+mod tests {
+    use super::Count;
 
-        yield ReturnSuccess::value(UntaggedValue::int(rows.len()).into_value(name))
-    };
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
 
-    Ok(stream.to_output_stream())
+        test_examples(Count {})
+    }
 }

crates/nu-cli/src/commands/cp.rs

@@ -1,8 +1,8 @@
-use crate::commands::command::RunnablePerItemContext;
+use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, Signature, SyntaxShape, Value};
+use nu_protocol::{Signature, SyntaxShape};
 use nu_source::Tagged;
 use std::path::PathBuf;
 
@@ -15,7 +15,8 @@ pub struct CopyArgs {
     pub recursive: Tagged<bool>,
 }
 
-impl PerItemCommand for Cpy {
+#[async_trait]
+impl WholeStreamCommand for Cpy {
     fn name(&self) -> &str {
         "cp"
     }
@@ -35,20 +36,41 @@ impl PerItemCommand for Cpy {
         "Copy files."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        _input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        call_info
-            .process(&raw_args.shell_manager, raw_args.ctrl_c.clone(), cp)?
-            .run()
+        let shell_manager = args.shell_manager.clone();
+        let name = args.call_info.name_tag.clone();
+        let (args, _) = args.process(&registry).await?;
+        shell_manager.cp(args, name)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Copy myfile to dir_b",
+                example: "cp myfile dir_b",
+                result: None,
+            },
+            Example {
+                description: "Recursively copy dir_a to dir_b",
+                example: "cp -r dir_a dir_b",
+                result: None,
+            },
+        ]
     }
 }
 
-fn cp(args: CopyArgs, context: &RunnablePerItemContext) -> Result<OutputStream, ShellError> {
-    let shell_manager = context.shell_manager.clone();
-    shell_manager.cp(args, context)
+#[cfg(test)]
+mod tests {
+    use super::Cpy;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Cpy {})
+    }
 }

crates/nu-cli/src/commands/date.rs

@@ -11,6 +11,7 @@ use nu_protocol::{Signature, UntaggedValue};
 
 pub struct Date;
 
+#[async_trait]
 impl WholeStreamCommand for Date {
     fn name(&self) -> &str {
         "date"
@@ -26,12 +27,27 @@ impl WholeStreamCommand for Date {
         "Get the current datetime."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        date(args, registry)
+        date(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Get the current local time and date",
+                example: "date",
+                result: None,
+            },
+            Example {
+                description: "Get the current UTC time and date",
+                example: "date --utc",
+                result: None,
+            },
+        ]
     }
 }
 
@@ -75,10 +91,13 @@ where
     UntaggedValue::Row(Dictionary::from(indexmap)).into_value(&tag)
 }
 
-pub fn date(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
+pub async fn date(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let args = args.evaluate_once(&registry).await?;
 
-    let mut date_out = VecDeque::new();
     let tag = args.call_info.name_tag.clone();
 
     let value = if args.has("utc") {
@@ -89,7 +108,17 @@ pub fn date(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStrea
         date_to_value(local, tag)
     };
 
-    date_out.push_back(value);
-
-    Ok(futures::stream::iter(date_out).to_output_stream())
+    Ok(OutputStream::one(value))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Date;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Date {})
+    }
 }

crates/nu-cli/src/commands/debug.rs

@@ -10,6 +10,7 @@ pub struct DebugArgs {
     raw: bool,
 }
 
+#[async_trait]
 impl WholeStreamCommand for Debug {
     fn name(&self) -> &str {
         "debug"
@@ -23,19 +24,21 @@ impl WholeStreamCommand for Debug {
         "Print the Rust debug representation of the values"
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, debug_value)?.run()
+        debug_value(args, registry).await
     }
 }
 
-fn debug_value(
-    DebugArgs { raw }: DebugArgs,
-    RunnableContext { input, .. }: RunnableContext,
-) -> Result<impl ToOutputStream, ShellError> {
+async fn debug_value(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let (DebugArgs { raw }, input) = args.process(&registry).await?;
     Ok(input
         .map(move |v| {
             if raw {
@@ -48,3 +51,15 @@ fn debug_value(
         })
         .to_output_stream())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Debug;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Debug {})
+    }
+}

crates/nu-cli/src/commands/default.rs

@@ -14,6 +14,7 @@ struct DefaultArgs {
 
 pub struct Default;
 
+#[async_trait]
 impl WholeStreamCommand for Default {
     fn name(&self) -> &str {
         "default"
@@ -33,23 +34,32 @@ impl WholeStreamCommand for Default {
         "Sets a default row's column if missing."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, default)?.run()
+        default(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Give a default 'target' to all file entries",
+            example: "ls -af | default target 'nothing'",
+            result: None,
+        }]
     }
 }
 
-fn default(
-    DefaultArgs { column, value }: DefaultArgs,
-    RunnableContext { input, .. }: RunnableContext,
+async fn default(
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    let stream = input
-        .map(move |item| {
-            let mut result = VecDeque::new();
+    let registry = registry.clone();
+    let (DefaultArgs { column, value }, input) = args.process(&registry).await?;
 
+    Ok(input
+        .map(move |item| {
             let should_add = match item {
                 Value {
                     value: UntaggedValue::Row(ref r),
@@ -60,16 +70,24 @@ fn default(
 
             if should_add {
                 match item.insert_data_at_path(&column.item, value.clone()) {
-                    Some(new_value) => result.push_back(ReturnSuccess::value(new_value)),
-                    None => result.push_back(ReturnSuccess::value(item)),
+                    Some(new_value) => ReturnSuccess::value(new_value),
+                    None => ReturnSuccess::value(item),
                 }
             } else {
-                result.push_back(ReturnSuccess::value(item));
+                ReturnSuccess::value(item)
             }
-
-            futures::stream::iter(result)
         })
-        .flatten();
-
-    Ok(stream.to_output_stream())
+        .to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Default;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Default {})
+    }
 }

crates/nu-cli/src/commands/drop.rs

@@ -0,0 +1,83 @@
+use crate::commands::WholeStreamCommand;
+use crate::context::CommandRegistry;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{Signature, SyntaxShape, UntaggedValue};
+use nu_source::Tagged;
+
+pub struct Drop;
+
+#[derive(Deserialize)]
+pub struct DropArgs {
+    rows: Option<Tagged<u64>>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Drop {
+    fn name(&self) -> &str {
+        "drop"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("drop").optional(
+            "rows",
+            SyntaxShape::Number,
+            "starting from the back, the number of rows to drop",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Drop the last number of rows."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        let (DropArgs { rows }, input) = args.process(&registry).await?;
+        let mut v: Vec<_> = input.into_vec().await;
+
+        let rows_to_drop = if let Some(quantity) = rows {
+            *quantity as usize
+        } else {
+            1
+        };
+
+        for _ in 0..rows_to_drop {
+            v.pop();
+        }
+
+        Ok(futures::stream::iter(v).to_output_stream())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Remove the last item of a list/table",
+                example: "echo [1 2 3] | drop",
+                result: Some(vec![
+                    UntaggedValue::int(1).into(),
+                    UntaggedValue::int(2).into(),
+                ]),
+            },
+            Example {
+                description: "Remove the last 2 items of a list/table",
+                example: "echo [1 2 3] | drop 2",
+                result: Some(vec![UntaggedValue::int(1).into()]),
+            },
+        ]
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Drop;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Drop {})
+    }
+}

crates/nu-cli/src/commands/du.rs

@@ -1,14 +1,13 @@
-extern crate filesize;
-
-use crate::commands::command::RunnablePerItemContext;
+use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
 use filesize::file_real_size_fast;
 use glob::*;
 use indexmap::map::IndexMap;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
 use nu_source::Tagged;
 use std::path::PathBuf;
+use std::sync::atomic::Ordering;
 
 const NAME: &str = "du";
 const GLOB_PARAMS: MatchOptions = MatchOptions {
@@ -31,7 +30,8 @@ pub struct DuArgs {
     min_size: Option<Tagged<u64>>,
 }
 
-impl PerItemCommand for Du {
+#[async_trait]
+impl WholeStreamCommand for Du {
     fn name(&self) -> &str {
         NAME
     }
@@ -73,22 +73,30 @@ impl PerItemCommand for Du {
         "Find disk usage sizes of specified items"
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        _input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        call_info
-            .process(&raw_args.shell_manager, raw_args.ctrl_c.clone(), du)?
-            .run()
+        du(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Disk usage of the current directory",
+            example: "du",
+            result: None,
+        }]
     }
 }
 
-fn du(args: DuArgs, ctx: &RunnablePerItemContext) -> Result<OutputStream, ShellError> {
-    let tag = ctx.name.clone();
+async fn du(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let tag = args.call_info.name_tag.clone();
+    let ctrl_c = args.ctrl_c.clone();
+    let ctrl_c_copy = ctrl_c.clone();
 
+    let (args, _): (DuArgs, _) = args.process(&registry).await?;
     let exclude = args.exclude.map_or(Ok(None), move |x| {
         Pattern::new(&x.item)
             .map(Option::Some)
@@ -117,7 +125,6 @@ fn du(args: DuArgs, ctx: &RunnablePerItemContext) -> Result<OutputStream, ShellE
     })
     .map(|v| v.map_err(glob_err_into));
 
-    let ctrl_c = ctx.ctrl_c.clone();
     let all = args.all;
     let deref = args.deref;
     let max_depth = args.max_depth.map(|f| f.item);
@@ -131,25 +138,30 @@ fn du(args: DuArgs, ctx: &RunnablePerItemContext) -> Result<OutputStream, ShellE
         all,
     };
 
-    let stream = futures::stream::iter(paths)
-        .interruptible(ctrl_c)
-        .map(move |path| match path {
-            Ok(p) => {
-                if p.is_dir() {
-                    Ok(ReturnSuccess::Value(
-                        DirInfo::new(p, &params, max_depth).into(),
-                    ))
-                } else {
-                    FileInfo::new(p, deref, tag.clone()).map(|v| ReturnSuccess::Value(v.into()))
-                }
-            }
-            Err(e) => Err(e),
-        });
+    let inp = futures::stream::iter(paths);
 
-    Ok(stream.to_output_stream())
+    Ok(inp
+        .flat_map(move |path| match path {
+            Ok(p) => {
+                let mut output = vec![];
+                if p.is_dir() {
+                    output.push(Ok(ReturnSuccess::Value(
+                        DirInfo::new(p, &params, max_depth, ctrl_c.clone()).into(),
+                    )));
+                } else {
+                    for v in FileInfo::new(p, deref, tag.clone()).into_iter() {
+                        output.push(Ok(ReturnSuccess::Value(v.into())));
+                    }
+                }
+                futures::stream::iter(output)
+            }
+            Err(e) => futures::stream::iter(vec![Err(e)]),
+        })
+        .interruptible(ctrl_c_copy)
+        .to_output_stream())
 }
 
-struct DirBuilder {
+pub struct DirBuilder {
     tag: Tag,
     min: Option<u64>,
     deref: bool,
@@ -157,7 +169,25 @@ struct DirBuilder {
     all: bool,
 }
 
-struct DirInfo {
+impl DirBuilder {
+    pub fn new(
+        tag: Tag,
+        min: Option<u64>,
+        deref: bool,
+        exclude: Option<Pattern>,
+        all: bool,
+    ) -> DirBuilder {
+        DirBuilder {
+            tag,
+            min,
+            deref,
+            exclude,
+            all,
+        }
+    }
+}
+
+pub struct DirInfo {
     dirs: Vec<DirInfo>,
     files: Vec<FileInfo>,
     errors: Vec<ShellError>,
@@ -200,7 +230,12 @@ impl FileInfo {
 }
 
 impl DirInfo {
-    fn new(path: impl Into<PathBuf>, params: &DirBuilder, depth: Option<u64>) -> Self {
+    pub fn new(
+        path: impl Into<PathBuf>,
+        params: &DirBuilder,
+        depth: Option<u64>,
+        ctrl_c: Arc<AtomicBool>,
+    ) -> Self {
         let path = path.into();
 
         let mut s = Self {
@@ -216,9 +251,15 @@ impl DirInfo {
         match std::fs::read_dir(&s.path) {
             Ok(d) => {
                 for f in d {
+                    if ctrl_c.load(Ordering::SeqCst) {
+                        break;
+                    }
+
                     match f {
                         Ok(i) => match i.file_type() {
-                            Ok(t) if t.is_dir() => s = s.add_dir(i.path(), depth, &params),
+                            Ok(t) if t.is_dir() => {
+                                s = s.add_dir(i.path(), depth, &params, ctrl_c.clone())
+                            }
                             Ok(_t) => s = s.add_file(i.path(), &params),
                             Err(e) => s = s.add_error(e.into()),
                         },
@@ -236,6 +277,7 @@ impl DirInfo {
         path: impl Into<PathBuf>,
         mut depth: Option<u64>,
         params: &DirBuilder,
+        ctrl_c: Arc<AtomicBool>,
     ) -> Self {
         if let Some(current) = depth {
             if let Some(new) = current.checked_sub(1) {
@@ -245,7 +287,7 @@ impl DirInfo {
             }
         }
 
-        let d = DirInfo::new(path, &params, depth);
+        let d = DirInfo::new(path, &params, depth, ctrl_c);
         self.size += d.size;
         self.blocks += d.blocks;
         self.dirs.push(d);
@@ -280,6 +322,10 @@ impl DirInfo {
         self.errors.push(e);
         self
     }
+
+    pub fn get_size(&self) -> u64 {
+        self.size
+    }
 }
 
 fn glob_err_into(e: GlobError) -> ShellError {
@@ -374,3 +420,15 @@ impl From<FileInfo> for Value {
         UntaggedValue::row(r).retag(&f.tag)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Du;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Du {})
+    }
+}

crates/nu-cli/src/commands/each.rs

@@ -1,16 +1,24 @@
 use crate::commands::classified::block::run_block;
-use crate::commands::PerItemCommand;
+use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 
 use futures::stream::once;
-
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, ReturnSuccess, Scope, Signature, SyntaxShape, UntaggedValue, Value};
+use nu_protocol::{
+    hir::Block, hir::Expression, hir::SpannedExpression, hir::Synthetic, Scope, Signature,
+    SyntaxShape, UntaggedValue, Value,
+};
 
 pub struct Each;
 
-impl PerItemCommand for Each {
+#[derive(Deserialize)]
+pub struct EachArgs {
+    block: Block,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Each {
     fn name(&self) -> &str {
         "each"
     }
@@ -27,60 +35,107 @@ impl PerItemCommand for Each {
         "Run a block on each row of the table."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
+        args: CommandArgs,
         registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        input: Value,
     ) -> Result<OutputStream, ShellError> {
-        let call_info = call_info.clone();
-        let registry = registry.clone();
-        let raw_args = raw_args.clone();
-        let stream = async_stream! {
-            match call_info.args.expect_nth(0)? {
-                Value {
-                    value: UntaggedValue::Block(block),
-                    tag
-                } => {
-                    let mut context = Context::from_raw(&raw_args, &registry);
-                    let input_clone = input.clone();
-                    let input_stream = once(async { Ok(input) }).to_input_stream();
+        each(args, registry).await
+    }
 
-                    let result = run_block(
-                        block,
-                        &mut context,
-                        input_stream,
-                        &Scope::new(input_clone),
-                    ).await;
-
-                    match result {
-                        Ok(mut stream) => {
-                            let errors = context.get_errors();
-                            if let Some(error) = errors.first() {
-                                yield Err(error.clone());
-                                return;
-                            }
-
-                            while let Some(result) = stream.next().await {
-                                yield Ok(ReturnSuccess::Value(result));
-                            }
-                        }
-                        Err(e) => {
-                            yield Err(e);
-                        }
-                    }
-                }
-                Value { tag, .. } => {
-                    yield Err(ShellError::labeled_error(
-                        "Expected a block",
-                        "each needs a block",
-                        tag,
-                    ))
-                }
-            };
-        };
-
-        Ok(stream.to_output_stream())
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Echo the square of each integer",
+                example: "echo [1 2 3] | each { echo $(= $it * $it) }",
+                result: Some(vec![
+                    UntaggedValue::int(1).into(),
+                    UntaggedValue::int(4).into(),
+                    UntaggedValue::int(9).into(),
+                ]),
+            },
+            Example {
+                description: "Echo the sum of each row",
+                example: "echo [[1 2] [3 4]] | each { echo $it | sum }",
+                result: Some(vec![
+                    UntaggedValue::int(3).into(),
+                    UntaggedValue::int(7).into(),
+                ]),
+            },
+        ]
+    }
+}
+
+fn is_expanded_it_usage(head: &SpannedExpression) -> bool {
+    match &*head {
+        SpannedExpression {
+            expr: Expression::Synthetic(Synthetic::String(s)),
+            ..
+        } if s == "expanded-each" => true,
+        _ => false,
+    }
+}
+
+async fn process_row(
+    block: Arc<Block>,
+    scope: Arc<Scope>,
+    head: Arc<Box<SpannedExpression>>,
+    mut context: Arc<Context>,
+    input: Value,
+) -> Result<OutputStream, ShellError> {
+    let input_clone = input.clone();
+    let input_stream = if is_expanded_it_usage(&head) {
+        InputStream::empty()
+    } else {
+        once(async { Ok(input_clone) }).to_input_stream()
+    };
+    Ok(run_block(
+        &block,
+        Arc::make_mut(&mut context),
+        input_stream,
+        &input,
+        &scope.vars,
+        &scope.env,
+    )
+    .await?
+    .to_output_stream())
+}
+
+async fn each(
+    raw_args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let head = Arc::new(raw_args.call_info.args.head.clone());
+    let scope = Arc::new(raw_args.call_info.scope.clone());
+    let context = Arc::new(Context::from_raw(&raw_args, &registry));
+    let (each_args, input): (EachArgs, _) = raw_args.process(&registry).await?;
+    let block = Arc::new(each_args.block);
+    Ok(input
+        .then(move |input| {
+            let block = block.clone();
+            let scope = scope.clone();
+            let head = head.clone();
+            let context = context.clone();
+            async {
+                match process_row(block, scope, head, context, input).await {
+                    Ok(s) => s,
+                    Err(e) => OutputStream::one(Err(e)),
+                }
+            }
+        })
+        .flatten()
+        .to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Each;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Each {})
     }
 }

crates/nu-cli/src/commands/echo.rs

@@ -1,10 +1,20 @@
+use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
+use nu_protocol::hir::Operator;
+use nu_protocol::{
+    Primitive, RangeInclusion, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
+};
 
 pub struct Echo;
 
-impl PerItemCommand for Echo {
+#[derive(Deserialize)]
+pub struct EchoArgs {
+    pub rest: Vec<Value>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Echo {
     fn name(&self) -> &str {
         "echo"
     }
@@ -17,31 +27,41 @@ impl PerItemCommand for Echo {
         "Echo the arguments back to the user."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
+        args: CommandArgs,
         registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        _input: Value,
     ) -> Result<OutputStream, ShellError> {
-        run(call_info, registry, raw_args)
+        echo(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Put a hello message in the pipeline",
+                example: "echo 'hello'",
+                result: Some(vec![Value::from("hello")]),
+            },
+            Example {
+                description: "Print the value of the special '$nu' variable",
+                example: "echo $nu",
+                result: None,
+            },
+        ]
     }
 }
 
-fn run(
-    call_info: &CallInfo,
-    _registry: &CommandRegistry,
-    _raw_args: &RawCommandArgs,
-) -> Result<OutputStream, ShellError> {
-    let mut output = vec![];
+fn echo(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let (args, _): (EchoArgs, _) = args.process(&registry).await?;
 
-    if let Some(ref positional) = call_info.args.positional {
-        for i in positional {
+        for i in args.rest {
             match i.as_string() {
                 Ok(s) => {
-                    output.push(Ok(ReturnSuccess::Value(
+                    yield Ok(ReturnSuccess::Value(
                         UntaggedValue::string(s).into_value(i.tag.clone()),
-                    )));
+                    ));
                 }
                 _ => match i {
                     Value {
@@ -49,19 +69,59 @@ fn run(
                         ..
                     } => {
                         for value in table {
-                            output.push(Ok(ReturnSuccess::Value(value.clone())));
+                            yield Ok(ReturnSuccess::Value(value.clone()));
+                        }
+                    }
+                    Value {
+                        value: UntaggedValue::Primitive(Primitive::Range(range)),
+                        tag
+                    } => {
+                        let mut current = range.from.0.item;
+                        while current != range.to.0.item {
+                            yield Ok(ReturnSuccess::Value(UntaggedValue::Primitive(current.clone()).into_value(&tag)));
+                            current = match crate::data::value::compute_values(Operator::Plus, &UntaggedValue::Primitive(current), &UntaggedValue::int(1)) {
+                                Ok(result) => match result {
+                                    UntaggedValue::Primitive(p) => p,
+                                    _ => {
+                                        yield Err(ShellError::unimplemented("Internal error: expected a primitive result from increment"));
+                                        return;
+                                    }
+                                },
+                                Err((left_type, right_type)) => {
+                                    yield Err(ShellError::coerce_error(
+                                        left_type.spanned(tag.span),
+                                        right_type.spanned(tag.span),
+                                    ));
+                                    return;
+                                }
+                            }
+                        }
+                        match range.to.1 {
+                            RangeInclusion::Inclusive => {
+                                yield Ok(ReturnSuccess::Value(UntaggedValue::Primitive(current.clone()).into_value(&tag)));
+                            }
+                            _ => {}
                         }
                     }
                     _ => {
-                        output.push(Ok(ReturnSuccess::Value(i.clone())));
+                        yield Ok(ReturnSuccess::Value(i.clone()));
                     }
                 },
             }
         }
-    }
-
-    // TODO: This whole block can probably be replaced with `.map()`
-    let stream = futures::stream::iter(output);
+    };
 
     Ok(stream.to_output_stream())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Echo;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Echo {})
+    }
+}

crates/nu-cli/src/commands/edit.rs

@@ -1,72 +0,0 @@
-use crate::commands::PerItemCommand;
-use crate::context::CommandRegistry;
-use crate::prelude::*;
-use nu_errors::ShellError;
-use nu_protocol::{CallInfo, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
-use nu_value_ext::ValueExt;
-
-pub struct Edit;
-
-impl PerItemCommand for Edit {
-    fn name(&self) -> &str {
-        "edit"
-    }
-
-    fn signature(&self) -> Signature {
-        Signature::build("edit")
-            .required(
-                "Field",
-                SyntaxShape::ColumnPath,
-                "the name of the column to edit",
-            )
-            .required(
-                "Value",
-                SyntaxShape::String,
-                "the new value to give the cell(s)",
-            )
-    }
-
-    fn usage(&self) -> &str {
-        "Edit an existing column to have a new value."
-    }
-
-    fn run(
-        &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        _raw_args: &RawCommandArgs,
-        value: Value,
-    ) -> Result<OutputStream, ShellError> {
-        let value_tag = value.tag();
-        let field = call_info.args.expect_nth(0)?.as_column_path()?;
-        let replacement = call_info.args.expect_nth(1)?.tagged_unknown();
-
-        let stream = match value {
-            obj
-            @
-            Value {
-                value: UntaggedValue::Row(_),
-                ..
-            } => match obj.replace_data_at_column_path(&field, replacement.item.clone()) {
-                Some(v) => futures::stream::iter(vec![Ok(ReturnSuccess::Value(v))]),
-                None => {
-                    return Err(ShellError::labeled_error(
-                        "edit could not find place to insert column",
-                        "column name",
-                        &field.tag,
-                    ))
-                }
-            },
-
-            _ => {
-                return Err(ShellError::labeled_error(
-                    "Unrecognized type in stream",
-                    "original value",
-                    value_tag,
-                ))
-            }
-        };
-
-        Ok(stream.to_output_stream())
-    }
-}

crates/nu-cli/src/commands/enter.rs

@@ -1,15 +1,23 @@
-use crate::commands::PerItemCommand;
 use crate::commands::UnevaluatedCallInfo;
+use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
 use nu_protocol::{
-    CallInfo, CommandAction, Primitive, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
+    CommandAction, Primitive, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
 };
+use nu_source::Tagged;
+use std::path::PathBuf;
 
 pub struct Enter;
 
-impl PerItemCommand for Enter {
+#[derive(Deserialize)]
+pub struct EnterArgs {
+    location: Tagged<PathBuf>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Enter {
     fn name(&self) -> &str {
         "enter"
     }
@@ -26,132 +34,151 @@ impl PerItemCommand for Enter {
         "Create a new shell and begin at this path."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
+        args: CommandArgs,
         registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        _input: Value,
     ) -> Result<OutputStream, ShellError> {
-        let registry = registry.clone();
-        let raw_args = raw_args.clone();
-        match call_info.args.expect_nth(0)? {
-            Value {
-                value: UntaggedValue::Primitive(Primitive::Path(location)),
-                tag,
-                ..
-            } => {
-                let location_string = location.display().to_string();
-                let location_clone = location_string.clone();
-                let tag_clone = tag.clone();
+        enter(args, registry)
+    }
 
-                if location_string.starts_with("help") {
-                    let spec = location_string.split(':').collect::<Vec<&str>>();
-
-                    if spec.len() == 2 {
-                        let (_, command) = (spec[0], spec[1]);
-
-                        if registry.has(command) {
-                            return Ok(vec![Ok(ReturnSuccess::Action(
-                                CommandAction::EnterHelpShell(
-                                    UntaggedValue::string(command).into_value(Tag::unknown()),
-                                ),
-                            ))]
-                            .into());
-                        }
-                    }
-                    Ok(vec![Ok(ReturnSuccess::Action(CommandAction::EnterHelpShell(
-                        UntaggedValue::nothing().into_value(Tag::unknown()),
-                    )))]
-                    .into())
-                } else if location.is_dir() {
-                    Ok(vec![Ok(ReturnSuccess::Action(CommandAction::EnterShell(
-                        location_clone,
-                    )))]
-                    .into())
-                } else {
-                    let stream = async_stream! {
-                        // If it's a file, attempt to open the file as a value and enter it
-                        let cwd = raw_args.shell_manager.path();
-
-                        let full_path = std::path::PathBuf::from(cwd);
-
-                        let (file_extension, contents, contents_tag) =
-                            crate::commands::open::fetch(
-                                &full_path,
-                                &location_clone,
-                                tag_clone.span,
-                            ).await?;
-
-                        match contents {
-                            UntaggedValue::Primitive(Primitive::String(_)) => {
-                                let tagged_contents = contents.into_value(&contents_tag);
-
-                                if let Some(extension) = file_extension {
-                                    let command_name = format!("from-{}", extension);
-                                    if let Some(converter) =
-                                        registry.get_command(&command_name)
-                                    {
-                                        let new_args = RawCommandArgs {
-                                            host: raw_args.host,
-                                            ctrl_c: raw_args.ctrl_c,
-                                            shell_manager: raw_args.shell_manager,
-                                            call_info: UnevaluatedCallInfo {
-                                                args: nu_protocol::hir::Call {
-                                                    head: raw_args.call_info.args.head,
-                                                    positional: None,
-                                                    named: None,
-                                                    span: Span::unknown(),
-                                                    is_last: false,
-                                                },
-                                                name_tag: raw_args.call_info.name_tag,
-                                                scope: raw_args.call_info.scope.clone()
-                                            },
-                                        };
-                                        let mut result = converter.run(
-                                            new_args.with_input(vec![tagged_contents]),
-                                            &registry,
-                                        );
-                                        let result_vec: Vec<Result<ReturnSuccess, ShellError>> =
-                                            result.drain_vec().await;
-                                        for res in result_vec {
-                                            match res {
-                                                Ok(ReturnSuccess::Value(Value {
-                                                    value,
-                                                    ..
-                                                })) => {
-                                                    yield Ok(ReturnSuccess::Action(CommandAction::EnterValueShell(
-                                                        Value {
-                                                            value,
-                                                            tag: contents_tag.clone(),
-                                                        })));
-                                                }
-                                                x => yield x,
-                                            }
-                                        }
-                                    } else {
-                                        yield Ok(ReturnSuccess::Action(CommandAction::EnterValueShell(tagged_contents)));
-                                    }
-                                } else {
-                                    yield Ok(ReturnSuccess::Action(CommandAction::EnterValueShell(tagged_contents)));
-                                }
-                            }
-                            _ => {
-                                let tagged_contents = contents.into_value(contents_tag);
-
-                                yield Ok(ReturnSuccess::Action(CommandAction::EnterValueShell(tagged_contents)));
-                            }
-                        }
-                    };
-                    Ok(stream.to_output_stream())
-                }
-            }
-            x => Ok(
-                vec![Ok(ReturnSuccess::Action(CommandAction::EnterValueShell(
-                    x.clone(),
-                )))]
-                .into(),
-            ),
-        }
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Enter a path as a new shell",
+                example: "enter ../projectB",
+                result: None,
+            },
+            Example {
+                description: "Enter a file as a new shell",
+                example: "enter package.json",
+                result: None,
+            },
+        ]
+    }
+}
+
+fn enter(raw_args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let scope = raw_args.call_info.scope.clone();
+        let shell_manager = raw_args.shell_manager.clone();
+        let head = raw_args.call_info.args.head.clone();
+        let ctrl_c = raw_args.ctrl_c.clone();
+        let current_errors = raw_args.current_errors.clone();
+        let host = raw_args.host.clone();
+        let tag = raw_args.call_info.name_tag.clone();
+        let (EnterArgs { location }, _) = raw_args.process(&registry).await?;
+        let location_string = location.display().to_string();
+        let location_clone = location_string.clone();
+
+        if location_string.starts_with("help") {
+            let spec = location_string.split(':').collect::<Vec<&str>>();
+
+            if spec.len() == 2 {
+                let (_, command) = (spec[0], spec[1]);
+
+                if registry.has(command) {
+                    yield Ok(ReturnSuccess::Action(CommandAction::EnterHelpShell(
+                        UntaggedValue::string(command).into_value(Tag::unknown()),
+                    )));
+                    return;
+                }
+            }
+            yield Ok(ReturnSuccess::Action(CommandAction::EnterHelpShell(
+                UntaggedValue::nothing().into_value(Tag::unknown()),
+            )));
+        } else if location.is_dir() {
+            yield Ok(ReturnSuccess::Action(CommandAction::EnterShell(
+                location_clone,
+            )));
+        } else {
+            // If it's a file, attempt to open the file as a value and enter it
+            let cwd = shell_manager.path();
+
+            let full_path = std::path::PathBuf::from(cwd);
+
+            let (file_extension, contents, contents_tag) =
+                crate::commands::open::fetch(
+                    &full_path,
+                    &PathBuf::from(location_clone),
+                    tag.span,
+                ).await?;
+
+            match contents {
+                UntaggedValue::Primitive(Primitive::String(_)) => {
+                    let tagged_contents = contents.into_value(&contents_tag);
+
+                    if let Some(extension) = file_extension {
+                        let command_name = format!("from {}", extension);
+                        if let Some(converter) =
+                            registry.get_command(&command_name)
+                        {
+                            let new_args = RawCommandArgs {
+                                host,
+                                ctrl_c,
+                                current_errors,
+                                shell_manager,
+                                call_info: UnevaluatedCallInfo {
+                                    args: nu_protocol::hir::Call {
+                                        head,
+                                        positional: None,
+                                        named: None,
+                                        span: Span::unknown(),
+                                        is_last: false,
+                                    },
+                                    name_tag: tag.clone(),
+                                    scope: scope.clone()
+                                },
+                            };
+                            let mut result = converter.run(
+                                new_args.with_input(vec![tagged_contents]),
+                                &registry,
+                            ).await;
+                            let result_vec: Vec<Result<ReturnSuccess, ShellError>> =
+                                result.drain_vec().await;
+                            for res in result_vec {
+                                match res {
+                                    Ok(ReturnSuccess::Value(Value {
+                                        value,
+                                        ..
+                                    })) => {
+                                        yield Ok(ReturnSuccess::Action(CommandAction::EnterValueShell(
+                                            Value {
+                                                value,
+                                                tag: contents_tag.clone(),
+                                            })));
+                                    }
+                                    x => yield x,
+                                }
+                            }
+                        } else {
+                            yield Ok(ReturnSuccess::Action(CommandAction::EnterValueShell(tagged_contents)));
+                        }
+                    } else {
+                        yield Ok(ReturnSuccess::Action(CommandAction::EnterValueShell(tagged_contents)));
+                    }
+                }
+                _ => {
+                    let tagged_contents = contents.into_value(contents_tag);
+
+                    yield Ok(ReturnSuccess::Action(CommandAction::EnterValueShell(tagged_contents)));
+                }
+            }
+        }
+    };
+
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Enter;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Enter {})
     }
 }

crates/nu-cli/src/commands/evaluate_by.rs

@@ -13,6 +13,7 @@ pub struct EvaluateByArgs {
     evaluate_with: Option<Tagged<String>>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for EvaluateBy {
     fn name(&self) -> &str {
         "evaluate-by"
@@ -31,42 +32,52 @@ impl WholeStreamCommand for EvaluateBy {
         "Creates a new table with the data from the tables rows evaluated by the column given."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, evaluate_by)?.run()
+        evaluate_by(args, registry).await
     }
 }
 
-pub fn evaluate_by(
-    EvaluateByArgs { evaluate_with }: EvaluateByArgs,
-    RunnableContext { input, name, .. }: RunnableContext,
+pub async fn evaluate_by(
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    let stream = async_stream! {
-        let values: Vec<Value> = input.collect().await;
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
+    let (EvaluateByArgs { evaluate_with }, mut input) = args.process(&registry).await?;
+    let values: Vec<Value> = input.collect().await;
 
-        if values.is_empty() {
-            yield Err(ShellError::labeled_error(
-                    "Expected table from pipeline",
-                    "requires a table input",
-                    name
-                ))
+    if values.is_empty() {
+        Err(ShellError::labeled_error(
+            "Expected table from pipeline",
+            "requires a table input",
+            name,
+        ))
+    } else {
+        let evaluate_with = if let Some(evaluator) = evaluate_with {
+            Some(evaluator.item().clone())
         } else {
+            None
+        };
 
-            let evaluate_with = if let Some(evaluator) = evaluate_with {
-                Some(evaluator.item().clone())
-            } else {
-                None
-            };
-
-            match evaluate(&values[0], evaluate_with, name) {
-                Ok(evaluated) => yield ReturnSuccess::value(evaluated),
-                Err(err) => yield Err(err)
-            }
+        match evaluate(&values[0], evaluate_with, name) {
+            Ok(evaluated) => Ok(OutputStream::one(ReturnSuccess::value(evaluated))),
+            Err(err) => Err(err),
         }
-    };
-
-    Ok(stream.to_output_stream())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::EvaluateBy;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(EvaluateBy {})
+    }
 }

crates/nu-cli/src/commands/exit.rs

@@ -6,6 +6,7 @@ use nu_protocol::{CommandAction, ReturnSuccess, Signature};
 
 pub struct Exit;
 
+#[async_trait]
 impl WholeStreamCommand for Exit {
     fn name(&self) -> &str {
         "exit"
@@ -19,21 +20,54 @@ impl WholeStreamCommand for Exit {
         "Exit the current shell (or all shells)"
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        exit(args, registry)
+        exit(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Exit the current shell",
+                example: "exit",
+                result: None,
+            },
+            Example {
+                description: "Exit all shells (exiting Nu)",
+                example: "exit --now",
+                result: None,
+            },
+        ]
     }
 }
 
-pub fn exit(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
+pub async fn exit(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let args = args.evaluate_once(&registry).await?;
 
-    if args.call_info.args.has("now") {
-        Ok(vec![Ok(ReturnSuccess::Action(CommandAction::Exit))].into())
+    let command_action = if args.call_info.args.has("now") {
+        CommandAction::Exit
     } else {
-        Ok(vec![Ok(ReturnSuccess::Action(CommandAction::LeaveShell))].into())
+        CommandAction::LeaveShell
+    };
+
+    Ok(OutputStream::one(ReturnSuccess::action(command_action)))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Exit;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Exit {})
     }
 }

crates/nu-cli/src/commands/first.rs

@@ -2,7 +2,7 @@ use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{Signature, SyntaxShape};
+use nu_protocol::{Signature, SyntaxShape, UntaggedValue};
 use nu_source::Tagged;
 
 pub struct First;
@@ -12,6 +12,7 @@ pub struct FirstArgs {
     rows: Option<Tagged<usize>>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for First {
     fn name(&self) -> &str {
         "first"
@@ -29,24 +30,53 @@ impl WholeStreamCommand for First {
         "Show only the first number of rows."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, first)?.run()
+        first(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Return the first item of a list/table",
+                example: "echo [1 2 3] | first",
+                result: Some(vec![UntaggedValue::int(1).into()]),
+            },
+            Example {
+                description: "Return the first 2 items of a list/table",
+                example: "echo [1 2 3] | first 2",
+                result: Some(vec![
+                    UntaggedValue::int(1).into(),
+                    UntaggedValue::int(2).into(),
+                ]),
+            },
+        ]
     }
 }
 
-fn first(
-    FirstArgs { rows }: FirstArgs,
-    context: RunnableContext,
-) -> Result<OutputStream, ShellError> {
+async fn first(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let (FirstArgs { rows }, input) = args.process(&registry).await?;
     let rows_desired = if let Some(quantity) = rows {
         *quantity
     } else {
         1
     };
 
-    Ok(OutputStream::from_input(context.input.take(rows_desired)))
+    Ok(input.take(rows_desired).to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::First;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(First {})
+    }
 }

crates/nu-cli/src/commands/format.rs

@@ -1,17 +1,21 @@
-use crate::commands::PerItemCommand;
+use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
+use crate::evaluate::evaluate_baseline_expr;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{
-    CallInfo, ColumnPath, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
-};
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue};
 use nu_source::Tagged;
-use nu_value_ext::{as_column_path, get_data_by_column_path};
 use std::borrow::Borrow;
 
 pub struct Format;
 
-impl PerItemCommand for Format {
+#[derive(Deserialize)]
+pub struct FormatArgs {
+    pattern: Tagged<String>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Format {
     fn name(&self) -> &str {
         "format"
     }
@@ -19,7 +23,7 @@ impl PerItemCommand for Format {
     fn signature(&self) -> Signature {
         Signature::build("format").required(
             "pattern",
-            SyntaxShape::Any,
+            SyntaxShape::String,
             "the pattern to output. Eg) \"{foo}: {bar}\"",
         )
     }
@@ -28,63 +32,66 @@ impl PerItemCommand for Format {
         "Format columns into a string using a simple pattern."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        _raw_args: &RawCommandArgs,
-        value: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        //let value_tag = value.tag();
-        let pattern = call_info.args.expect_nth(0)?;
+        format_command(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Print filenames with their sizes",
+            example: "ls | format '{name}: {size}'",
+            result: None,
+        }]
+    }
+}
+
+fn format_command(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let scope = args.call_info.scope.clone();
+        let (FormatArgs { pattern }, mut input) = args.process(&registry).await?;
         let pattern_tag = pattern.tag.clone();
-        let pattern = pattern.as_string()?;
 
         let format_pattern = format(&pattern);
         let commands = format_pattern;
 
-        let output = match value {
-            value
-            @
-            Value {
-                value: UntaggedValue::Row(_),
-                ..
-            } => {
-                let mut output = String::new();
+        while let Some(value) = input.next().await {
+            let mut output = String::new();
 
-                for command in &commands {
-                    match command {
-                        FormatCommand::Text(s) => {
-                            output.push_str(&s);
-                        }
-                        FormatCommand::Column(c) => {
-                            let key = to_column_path(&c, &pattern_tag)?;
+            for command in &commands {
+                match command {
+                    FormatCommand::Text(s) => {
+                        output.push_str(&s);
+                    }
+                    FormatCommand::Column(c) => {
+                        // FIXME: use the correct spans
+                        let full_column_path = nu_parser::parse_full_column_path(&(c.to_string()).spanned(Span::unknown()), &registry);
 
-                            let fetcher = get_data_by_column_path(
-                                &value,
-                                &key,
-                                Box::new(move |(_, _, error)| error),
-                            );
+                        let result = evaluate_baseline_expr(&full_column_path.0, &registry, &value, &scope.vars, &scope.env).await;
 
-                            if let Ok(c) = fetcher {
-                                output
-                                    .push_str(&value::format_leaf(c.borrow()).plain_string(100_000))
-                            }
+                        if let Ok(c) = result {
+                            output
+                                .push_str(&value::format_leaf(c.borrow()).plain_string(100_000))
+                        } else {
                             // That column doesn't match, so don't emit anything
                         }
                     }
                 }
-
-                output
             }
-            _ => String::new(),
-        };
 
-        Ok(futures::stream::iter(vec![ReturnSuccess::value(
-            UntaggedValue::string(output).into_untagged_value(),
-        )])
-        .to_output_stream())
-    }
+            yield ReturnSuccess::value(
+                UntaggedValue::string(output).into_untagged_value())
+        }
+    };
+
+    Ok(stream.to_output_stream())
 }
 
 #[derive(Debug)]
@@ -132,26 +139,14 @@ fn format(input: &str) -> Vec<FormatCommand> {
     output
 }
 
-fn to_column_path(
-    path_members: &str,
-    tag: impl Into<Tag>,
-) -> Result<Tagged<ColumnPath>, ShellError> {
-    let tag = tag.into();
+#[cfg(test)]
+mod tests {
+    use super::Format;
 
-    as_column_path(
-        &UntaggedValue::Table(
-            path_members
-                .split('.')
-                .map(|x| {
-                    let member = match x.parse::<u64>() {
-                        Ok(v) => UntaggedValue::int(v),
-                        Err(_) => UntaggedValue::string(x),
-                    };
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
 
-                    member.into_value(&tag)
-                })
-                .collect(),
-        )
-        .into_value(&tag),
-    )
+        test_examples(Format {})
+    }
 }

crates/nu-cli/src/commands/from.rs

@@ -0,0 +1,49 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{ReturnSuccess, Signature, UntaggedValue};
+
+pub struct From;
+
+#[async_trait]
+impl WholeStreamCommand for From {
+    fn name(&self) -> &str {
+        "from"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("from")
+    }
+
+    fn usage(&self) -> &str {
+        "Parse content (string or binary) as a table (input format based on subcommand, like csv, ini, json, toml)"
+    }
+
+    async fn run(
+        &self,
+        _args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        let registry = registry.clone();
+        let stream = async_stream! {
+            yield Ok(ReturnSuccess::Value(
+                UntaggedValue::string(crate::commands::help::get_help(&From, &registry))
+                    .into_value(Tag::unknown()),
+            ));
+        };
+
+        Ok(stream.to_output_stream())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::From;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(From {})
+    }
+}

crates/nu-cli/src/commands/from_bson.rs

@@ -8,25 +8,34 @@ use std::str::FromStr;
 
 pub struct FromBSON;
 
+#[async_trait]
 impl WholeStreamCommand for FromBSON {
     fn name(&self) -> &str {
-        "from-bson"
+        "from bson"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-bson")
+        Signature::build("from bson")
     }
 
     fn usage(&self) -> &str {
-        "Parse text as .bson and create table."
+        "Parse binary as .bson and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        from_bson(args, registry)
+        from_bson(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Convert bson data to a table",
+            example: "open file.bin | from bson",
+            result: None,
+        }]
     }
 }
 
@@ -199,27 +208,37 @@ pub fn from_bson_bytes_to_value(bytes: Vec<u8>, tag: impl Into<Tag>) -> Result<V
     convert_bson_value_to_nu_value(&Bson::Array(docs), tag)
 }
 
-fn from_bson(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
+async fn from_bson(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let args = args.evaluate_once(&registry).await?;
     let tag = args.name_tag();
     let input = args.input;
 
-    let stream = async_stream! {
-        let bytes = input.collect_binary(tag.clone()).await?;
+    let bytes = input.collect_binary(tag.clone()).await?;
 
-        match from_bson_bytes_to_value(bytes.item, tag.clone()) {
-            Ok(x) => yield ReturnSuccess::value(x),
-            Err(_) => {
-                yield Err(ShellError::labeled_error_with_secondary(
-                    "Could not parse as BSON",
-                    "input cannot be parsed as BSON",
-                    tag.clone(),
-                    "value originates from here",
-                    bytes.tag,
-                ))
-            }
-        }
-    };
-
-    Ok(stream.to_output_stream())
+    match from_bson_bytes_to_value(bytes.item, tag.clone()) {
+        Ok(x) => Ok(OutputStream::one(ReturnSuccess::value(x))),
+        Err(_) => Err(ShellError::labeled_error_with_secondary(
+            "Could not parse as BSON",
+            "input cannot be parsed as BSON",
+            tag.clone(),
+            "value originates from here",
+            bytes.tag,
+        )),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::FromBSON;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromBSON {})
+    }
 }

crates/nu-cli/src/commands/from_csv.rs

@@ -12,13 +12,14 @@ pub struct FromCSVArgs {
     separator: Option<Value>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for FromCSV {
     fn name(&self) -> &str {
-        "from-csv"
+        "from csv"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-csv")
+        Signature::build("from csv")
             .named(
                 "separator",
                 SyntaxShape::String,
@@ -36,22 +37,49 @@ impl WholeStreamCommand for FromCSV {
         "Parse text as .csv and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, from_csv)?.run()
+        from_csv(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Convert comma-separated data to a table",
+                example: "open data.txt | from csv",
+                result: None,
+            },
+            Example {
+                description: "Convert comma-separated data to a table, ignoring headers",
+                example: "open data.txt | from csv --headerless",
+                result: None,
+            },
+            Example {
+                description: "Convert semicolon-separated data to a table",
+                example: "open data.txt | from csv --separator ';'",
+                result: None,
+            },
+        ]
     }
 }
 
-fn from_csv(
-    FromCSVArgs {
-        headerless,
-        separator,
-    }: FromCSVArgs,
-    runnable_context: RunnableContext,
+async fn from_csv(
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
+
+    let (
+        FromCSVArgs {
+            headerless,
+            separator,
+        },
+        input,
+    ) = args.process(&registry).await?;
     let sep = match separator {
         Some(Value {
             value: UntaggedValue::Primitive(Primitive::String(s)),
@@ -75,5 +103,17 @@ fn from_csv(
         _ => ',',
     };
 
-    from_delimited_data(headerless, sep, "CSV", runnable_context)
+    from_delimited_data(headerless, sep, "CSV", input, name).await
+}
+
+#[cfg(test)]
+mod tests {
+    use super::FromCSV;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromCSV {})
+    }
 }

crates/nu-cli/src/commands/from_delimited_data.rs

@@ -1,7 +1,7 @@
 use crate::prelude::*;
 use csv::{ErrorKind, ReaderBuilder};
 use nu_errors::ShellError;
-use nu_protocol::{ReturnSuccess, TaggedDictBuilder, UntaggedValue, Value};
+use nu_protocol::{TaggedDictBuilder, UntaggedValue, Value};
 
 fn from_delimited_string_to_value(
     s: String,
@@ -41,44 +41,40 @@ fn from_delimited_string_to_value(
     Ok(UntaggedValue::Table(rows).into_value(&tag))
 }
 
-pub fn from_delimited_data(
+pub async fn from_delimited_data(
     headerless: bool,
     sep: char,
     format_name: &'static str,
-    RunnableContext { input, name, .. }: RunnableContext,
+    input: InputStream,
+    name: Tag,
 ) -> Result<OutputStream, ShellError> {
     let name_tag = name;
+    let concat_string = input.collect_string(name_tag.clone()).await?;
 
-    let stream = async_stream! {
-        let concat_string = input.collect_string(name_tag.clone()).await?;
+    match from_delimited_string_to_value(concat_string.item, headerless, sep, name_tag.clone()) {
+        Ok(x) => match x {
+            Value {
+                value: UntaggedValue::Table(list),
+                ..
+            } => Ok(futures::stream::iter(list).to_output_stream()),
+            x => Ok(OutputStream::one(x)),
+        },
+        Err(err) => {
+            let line_one = match pretty_csv_error(err) {
+                Some(pretty) => format!("Could not parse as {} ({})", format_name, pretty),
+                None => format!("Could not parse as {}", format_name),
+            };
+            let line_two = format!("input cannot be parsed as {}", format_name);
 
-        match from_delimited_string_to_value(concat_string.item, headerless, sep, name_tag.clone()) {
-            Ok(x) => match x {
-                Value { value: UntaggedValue::Table(list), .. } => {
-                    for l in list {
-                        yield ReturnSuccess::value(l);
-                    }
-                }
-                x => yield ReturnSuccess::value(x),
-            },
-            Err(err) => {
-                let line_one = match pretty_csv_error(err) {
-                    Some(pretty) => format!("Could not parse as {} ({})", format_name,pretty),
-                    None => format!("Could not parse as {}", format_name),
-                };
-                let line_two = format!("input cannot be parsed as {}", format_name);
-                yield Err(ShellError::labeled_error_with_secondary(
-                    line_one,
-                    line_two,
-                    name_tag.clone(),
-                    "value originates from here",
-                    concat_string.tag,
-                ))
-            } ,
+            Err(ShellError::labeled_error_with_secondary(
+                line_one,
+                line_two,
+                name_tag.clone(),
+                "value originates from here",
+                concat_string.tag,
+            ))
         }
-    };
-
-    Ok(stream.to_output_stream())
+    }
 }
 
 fn pretty_csv_error(err: csv::Error) -> Option<String> {

crates/nu-cli/src/commands/from_eml.rs

@@ -0,0 +1,140 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use ::eml_parser::eml::*;
+use ::eml_parser::EmlParser;
+use nu_errors::ShellError;
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, TaggedDictBuilder, UntaggedValue};
+use nu_source::Tagged;
+
+pub struct FromEML;
+
+const DEFAULT_BODY_PREVIEW: usize = 50;
+
+#[derive(Deserialize, Clone)]
+pub struct FromEMLArgs {
+    #[serde(rename(deserialize = "preview-body"))]
+    preview_body: Option<Tagged<usize>>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for FromEML {
+    fn name(&self) -> &str {
+        "from eml"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("from eml").named(
+            "preview-body",
+            SyntaxShape::Int,
+            "How many bytes of the body to preview",
+            Some('b'),
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Parse text as .eml and create table."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        from_eml(args, registry).await
+    }
+}
+
+fn emailaddress_to_value(tag: &Tag, email_address: &EmailAddress) -> TaggedDictBuilder {
+    let mut dict = TaggedDictBuilder::with_capacity(tag, 2);
+    let (n, a) = match email_address {
+        EmailAddress::AddressOnly { address } => {
+            (UntaggedValue::nothing(), UntaggedValue::string(address))
+        }
+        EmailAddress::NameAndEmailAddress { name, address } => {
+            (UntaggedValue::string(name), UntaggedValue::string(address))
+        }
+    };
+
+    dict.insert_untagged("Name", n);
+    dict.insert_untagged("Address", a);
+
+    dict
+}
+
+fn headerfieldvalue_to_value(tag: &Tag, value: &HeaderFieldValue) -> UntaggedValue {
+    use HeaderFieldValue::*;
+
+    match value {
+        SingleEmailAddress(address) => emailaddress_to_value(tag, address).into_untagged_value(),
+        MultipleEmailAddresses(addresses) => UntaggedValue::Table(
+            addresses
+                .iter()
+                .map(|a| emailaddress_to_value(tag, a).into_value())
+                .collect(),
+        ),
+        Unstructured(s) => UntaggedValue::string(s),
+        Empty => UntaggedValue::nothing(),
+    }
+}
+
+async fn from_eml(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let registry = registry.clone();
+    let (eml_args, input): (FromEMLArgs, _) = args.process(&registry).await?;
+    let value = input.collect_string(tag.clone()).await?;
+
+    let body_preview = eml_args
+        .preview_body
+        .map(|b| b.item)
+        .unwrap_or(DEFAULT_BODY_PREVIEW);
+
+    let eml = EmlParser::from_string(value.item)
+        .with_body_preview(body_preview)
+        .parse()
+        .map_err(|_| {
+            ShellError::labeled_error(
+                "Could not parse .eml file",
+                "could not parse .eml file",
+                &tag,
+            )
+        })?;
+
+    let mut dict = TaggedDictBuilder::new(&tag);
+
+    if let Some(subj) = eml.subject {
+        dict.insert_untagged("Subject", UntaggedValue::string(subj));
+    }
+
+    if let Some(from) = eml.from {
+        dict.insert_untagged("From", headerfieldvalue_to_value(&tag, &from));
+    }
+
+    if let Some(to) = eml.to {
+        dict.insert_untagged("To", headerfieldvalue_to_value(&tag, &to));
+    }
+
+    for HeaderField { name, value } in eml.headers.iter() {
+        dict.insert_untagged(name, headerfieldvalue_to_value(&tag, &value));
+    }
+
+    if let Some(body) = eml.body {
+        dict.insert_untagged("Body", UntaggedValue::string(body));
+    }
+
+    Ok(OutputStream::one(ReturnSuccess::value(dict.into_value())))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::FromEML;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromEML {})
+    }
+}

crates/nu-cli/src/commands/from_ics.rs

@@ -9,20 +9,21 @@ use std::io::BufReader;
 
 pub struct FromIcs;
 
+#[async_trait]
 impl WholeStreamCommand for FromIcs {
     fn name(&self) -> &str {
-        "from-ics"
+        "from ics"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-ics")
+        Signature::build("from ics")
     }
 
     fn usage(&self) -> &str {
         "Parse text as .ics and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
@@ -32,11 +33,12 @@ impl WholeStreamCommand for FromIcs {
 }
 
 fn from_ics(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
-    let tag = args.name_tag();
-    let input = args.input;
-
+    let registry = registry.clone();
     let stream = async_stream! {
+        let args = args.evaluate_once(&registry).await?;
+        let tag = args.name_tag();
+        let input = args.input;
+
         let input_string = input.collect_string(tag.clone()).await?.item;
         let input_bytes = input_string.as_bytes();
         let buf_reader = BufReader::new(input_bytes);
@@ -238,3 +240,15 @@ fn params_to_value(params: Vec<(String, Vec<String>)>, tag: Tag) -> Value {
 
     row.into_value()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::FromIcs;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromIcs {})
+    }
+}

crates/nu-cli/src/commands/from_ini.rs

@@ -1,30 +1,31 @@
 use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{Primitive, ReturnSuccess, Signature, TaggedDictBuilder, UntaggedValue, Value};
+use nu_protocol::{Primitive, Signature, TaggedDictBuilder, UntaggedValue, Value};
 use std::collections::HashMap;
 
 pub struct FromINI;
 
+#[async_trait]
 impl WholeStreamCommand for FromINI {
     fn name(&self) -> &str {
-        "from-ini"
+        "from ini"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-ini")
+        Signature::build("from ini")
     }
 
     fn usage(&self) -> &str {
         "Parse text as .ini and create table"
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        from_ini(args, registry)
+        from_ini(args, registry).await
     }
 }
 
@@ -63,34 +64,42 @@ pub fn from_ini_string_to_value(
     Ok(convert_ini_top_to_nu_value(&v, tag))
 }
 
-fn from_ini(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
+async fn from_ini(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let args = args.evaluate_once(&registry).await?;
     let tag = args.name_tag();
     let input = args.input;
+    let concat_string = input.collect_string(tag.clone()).await?;
 
-    let stream = async_stream! {
-        let concat_string = input.collect_string(tag.clone()).await?;
-
-        match from_ini_string_to_value(concat_string.item, tag.clone()) {
-            Ok(x) => match x {
-                Value { value: UntaggedValue::Table(list), .. } => {
-                    for l in list {
-                        yield ReturnSuccess::value(l);
-                    }
-                }
-                x => yield ReturnSuccess::value(x),
-            },
-            Err(_) => {
-                yield Err(ShellError::labeled_error_with_secondary(
-                    "Could not parse as INI",
-                    "input cannot be parsed as INI",
-                    &tag,
-                    "value originates from here",
-                    concat_string.tag,
-                ))
-            }
-        }
-    };
-
-    Ok(stream.to_output_stream())
+    match from_ini_string_to_value(concat_string.item, tag.clone()) {
+        Ok(x) => match x {
+            Value {
+                value: UntaggedValue::Table(list),
+                ..
+            } => Ok(futures::stream::iter(list).to_output_stream()),
+            x => Ok(OutputStream::one(x)),
+        },
+        Err(_) => Err(ShellError::labeled_error_with_secondary(
+            "Could not parse as INI",
+            "input cannot be parsed as INI",
+            &tag,
+            "value originates from here",
+            concat_string.tag,
+        )),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::FromINI;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromINI {})
+    }
 }

crates/nu-cli/src/commands/from_json.rs

@@ -10,13 +10,14 @@ pub struct FromJSONArgs {
     objects: bool,
 }
 
+#[async_trait]
 impl WholeStreamCommand for FromJSON {
     fn name(&self) -> &str {
-        "from-json"
+        "from json"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-json").switch(
+        Signature::build("from json").switch(
             "objects",
             "treat each line as a separate value",
             Some('o'),
@@ -27,12 +28,12 @@ impl WholeStreamCommand for FromJSON {
         "Parse text as .json and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, from_json)?.run()
+        from_json(args, registry)
     }
 }
 
@@ -70,13 +71,12 @@ pub fn from_json_string_to_value(s: String, tag: impl Into<Tag>) -> serde_hjson:
     Ok(convert_json_value_to_nu_value(&v, tag))
 }
 
-fn from_json(
-    FromJSONArgs { objects }: FromJSONArgs,
-    RunnableContext { input, name, .. }: RunnableContext,
-) -> Result<OutputStream, ShellError> {
-    let name_tag = name;
+fn from_json(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let name_tag = args.call_info.name_tag.clone();
+    let registry = registry.clone();
 
     let stream = async_stream! {
+        let (FromJSONArgs { objects }, mut input) = args.process(&registry).await?;
         let concat_string = input.collect_string(name_tag.clone()).await?;
 
         if objects {
@@ -131,3 +131,15 @@ fn from_json(
 
     Ok(stream.to_output_stream())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::FromJSON;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromJSON {})
+    }
+}

crates/nu-cli/src/commands/from_ods.rs

@@ -13,13 +13,14 @@ pub struct FromODSArgs {
     headerless: bool,
 }
 
+#[async_trait]
 impl WholeStreamCommand for FromODS {
     fn name(&self) -> &str {
-        "from-ods"
+        "from ods"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-ods").switch(
+        Signature::build("from ods").switch(
             "headerless",
             "don't treat the first row as column names",
             None,
@@ -30,25 +31,21 @@ impl WholeStreamCommand for FromODS {
         "Parse OpenDocument Spreadsheet(.ods) data and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, from_ods)?.run()
+        from_ods(args, registry)
     }
 }
 
-fn from_ods(
-    FromODSArgs {
-        headerless: _headerless,
-    }: FromODSArgs,
-    runnable_context: RunnableContext,
-) -> Result<OutputStream, ShellError> {
-    let input = runnable_context.input;
-    let tag = runnable_context.name;
+fn from_ods(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let registry = registry.clone();
 
     let stream = async_stream! {
+        let (FromODSArgs { headerless: _headerless }, mut input) = args.process(&registry).await?;
         let bytes = input.collect_binary(tag.clone()).await?;
         let mut buf: Cursor<Vec<u8>> = Cursor::new(bytes.item);
         let mut ods = Ods::<_>::new(buf).map_err(|_| ShellError::labeled_error(
@@ -96,3 +93,15 @@ fn from_ods(
 
     Ok(stream.to_output_stream())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::FromODS;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromODS {})
+    }
+}

crates/nu-cli/src/commands/from_sqlite.rs

@@ -1,56 +1,58 @@
 use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{Primitive, ReturnSuccess, Signature, TaggedDictBuilder, UntaggedValue, Value};
+use nu_protocol::{Primitive, Signature, TaggedDictBuilder, UntaggedValue, Value};
 use rusqlite::{types::ValueRef, Connection, Row, NO_PARAMS};
 use std::io::Write;
 use std::path::Path;
 
 pub struct FromSQLite;
 
+#[async_trait]
 impl WholeStreamCommand for FromSQLite {
     fn name(&self) -> &str {
-        "from-sqlite"
+        "from sqlite"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-sqlite")
+        Signature::build("from sqlite")
     }
 
     fn usage(&self) -> &str {
         "Parse binary data as sqlite .db and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        from_sqlite(args, registry)
+        from_sqlite(args, registry).await
     }
 }
 
 pub struct FromDB;
 
+#[async_trait]
 impl WholeStreamCommand for FromDB {
     fn name(&self) -> &str {
-        "from-db"
+        "from db"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-db")
+        Signature::build("from db")
     }
 
     fn usage(&self) -> &str {
         "Parse binary data as db and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        from_sqlite(args, registry)
+        from_sqlite(args, registry).await
     }
 }
 
@@ -63,6 +65,7 @@ pub fn convert_sqlite_file_to_nu_value(
     let mut meta_out = Vec::new();
     let mut meta_stmt = conn.prepare("select name from sqlite_master where type='table'")?;
     let mut meta_rows = meta_stmt.query(NO_PARAMS)?;
+
     while let Some(meta_row) = meta_rows.next()? {
         let table_name: String = meta_row.get(0)?;
         let mut meta_dict = TaggedDictBuilder::new(tag.clone());
@@ -132,34 +135,47 @@ pub fn from_sqlite_bytes_to_value(
     }
 }
 
-fn from_sqlite(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
+async fn from_sqlite(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let args = args.evaluate_once(&registry).await?;
     let tag = args.name_tag();
     let input = args.input;
 
-    let stream = async_stream! {
-        let bytes = input.collect_binary(tag.clone()).await?;
-        match from_sqlite_bytes_to_value(bytes.item, tag.clone()) {
-            Ok(x) => match x {
-                Value { value: UntaggedValue::Table(list), .. } => {
-                    for l in list {
-                        yield ReturnSuccess::value(l);
-                    }
-                }
-                _ => yield ReturnSuccess::value(x),
-            }
-            Err(err) => {
-                println!("{:?}", err);
-                yield Err(ShellError::labeled_error_with_secondary(
-                    "Could not parse as SQLite",
-                    "input cannot be parsed as SQLite",
-                    &tag,
-                    "value originates from here",
-                    bytes.tag,
-                ))
-            }
-        }
-    };
+    let bytes = input.collect_binary(tag.clone()).await?;
 
-    Ok(stream.to_output_stream())
+    match from_sqlite_bytes_to_value(bytes.item, tag.clone()) {
+        Ok(x) => match x {
+            Value {
+                value: UntaggedValue::Table(list),
+                ..
+            } => Ok(futures::stream::iter(list).to_output_stream()),
+            _ => Ok(OutputStream::one(x)),
+        },
+        Err(err) => {
+            println!("{:?}", err);
+
+            Err(ShellError::labeled_error_with_secondary(
+                "Could not parse as SQLite",
+                "input cannot be parsed as SQLite",
+                &tag,
+                "value originates from here",
+                bytes.tag,
+            ))
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::FromSQLite;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromSQLite {})
+    }
 }

crates/nu-cli/src/commands/from_ssv.rs

@@ -17,9 +17,10 @@ pub struct FromSSVArgs {
     minimum_spaces: Option<Tagged<usize>>,
 }
 
-const STRING_REPRESENTATION: &str = "from-ssv";
+const STRING_REPRESENTATION: &str = "from ssv";
 const DEFAULT_MINIMUM_SPACES: usize = 2;
 
+#[async_trait]
 impl WholeStreamCommand for FromSSV {
     fn name(&self) -> &str {
         STRING_REPRESENTATION
@@ -45,12 +46,12 @@ impl WholeStreamCommand for FromSSV {
         "Parse text as space-separated values and create a table. The default minimum number of spaces counted as a separator is 2."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, from_ssv)?.run()
+        from_ssv(args, registry)
     }
 }
 
@@ -250,15 +251,11 @@ fn from_ssv_string_to_value(
     Some(UntaggedValue::Table(rows).into_value(&tag))
 }
 
-fn from_ssv(
-    FromSSVArgs {
-        headerless,
-        aligned_columns,
-        minimum_spaces,
-    }: FromSSVArgs,
-    RunnableContext { input, name, .. }: RunnableContext,
-) -> Result<OutputStream, ShellError> {
+fn from_ssv(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let name = args.call_info.name_tag.clone();
+    let registry = registry.clone();
     let stream = async_stream! {
+        let (FromSSVArgs { headerless, aligned_columns, minimum_spaces }, mut input) = args.process(&registry).await?;
         let concat_string = input.collect_string(name.clone()).await?;
         let split_at = match minimum_spaces {
             Some(number) => number.item,
@@ -489,4 +486,12 @@ mod tests {
         assert_eq!(aligned_columns_headerless, separator_headerless);
         assert_eq!(aligned_columns_with_headers, separator_with_headers);
     }
+
+    #[test]
+    fn examples_work_as_expected() {
+        use super::FromSSV;
+        use crate::examples::test as test_examples;
+
+        test_examples(FromSSV {})
+    }
 }

crates/nu-cli/src/commands/from_toml.rs

@@ -5,20 +5,21 @@ use nu_protocol::{Primitive, ReturnSuccess, Signature, TaggedDictBuilder, Untagg
 
 pub struct FromTOML;
 
+#[async_trait]
 impl WholeStreamCommand for FromTOML {
     fn name(&self) -> &str {
-        "from-toml"
+        "from toml"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-toml")
+        Signature::build("from toml")
     }
 
     fn usage(&self) -> &str {
         "Parse text as .toml and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
@@ -67,11 +68,12 @@ pub fn from_toml(
     args: CommandArgs,
     registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
-    let tag = args.name_tag();
-    let input = args.input;
-
+    let registry = registry.clone();
     let stream = async_stream! {
+        let args = args.evaluate_once(&registry).await?;
+        let tag = args.name_tag();
+        let input = args.input;
+
         let concat_string = input.collect_string(tag.clone()).await?;
         match from_toml_string_to_value(concat_string.item, tag.clone()) {
             Ok(x) => match x {
@@ -96,3 +98,15 @@ pub fn from_toml(
 
     Ok(stream.to_output_stream())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::FromTOML;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromTOML {})
+    }
+}

crates/nu-cli/src/commands/from_tsv.rs

@@ -11,13 +11,14 @@ pub struct FromTSVArgs {
     headerless: bool,
 }
 
+#[async_trait]
 impl WholeStreamCommand for FromTSV {
     fn name(&self) -> &str {
-        "from-tsv"
+        "from tsv"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-tsv").switch(
+        Signature::build("from tsv").switch(
             "headerless",
             "don't treat the first row as column names",
             None,
@@ -28,18 +29,34 @@ impl WholeStreamCommand for FromTSV {
         "Parse text as .tsv and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, from_tsv)?.run()
+        from_tsv(args, registry).await
     }
 }
 
-fn from_tsv(
-    FromTSVArgs { headerless }: FromTSVArgs,
-    runnable_context: RunnableContext,
+async fn from_tsv(
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    from_delimited_data(headerless, '\t', "TSV", runnable_context)
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
+    let (FromTSVArgs { headerless }, input) = args.process(&registry).await?;
+
+    from_delimited_data(headerless, '\t', "TSV", input, name).await
+}
+
+#[cfg(test)]
+mod tests {
+    use super::FromTSV;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromTSV {})
+    }
 }

crates/nu-cli/src/commands/from_url.rs

@@ -5,59 +5,70 @@ use nu_protocol::{ReturnSuccess, Signature, TaggedDictBuilder, UntaggedValue};
 
 pub struct FromURL;
 
+#[async_trait]
 impl WholeStreamCommand for FromURL {
     fn name(&self) -> &str {
-        "from-url"
+        "from url"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-url")
+        Signature::build("from url")
     }
 
     fn usage(&self) -> &str {
         "Parse url-encoded string as a table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        from_url(args, registry)
+        from_url(args, registry).await
     }
 }
 
-fn from_url(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
+async fn from_url(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let args = args.evaluate_once(&registry).await?;
     let tag = args.name_tag();
     let input = args.input;
 
-    let stream = async_stream! {
-        let concat_string = input.collect_string(tag.clone()).await?;
+    let concat_string = input.collect_string(tag.clone()).await?;
 
-        let result = serde_urlencoded::from_str::<Vec<(String, String)>>(&concat_string.item);
+    let result = serde_urlencoded::from_str::<Vec<(String, String)>>(&concat_string.item);
 
-        match result {
-            Ok(result) => {
-                let mut row = TaggedDictBuilder::new(tag);
+    match result {
+        Ok(result) => {
+            let mut row = TaggedDictBuilder::new(tag);
 
-                for (k,v) in result {
-                    row.insert_untagged(k, UntaggedValue::string(v));
-                }
-
-                yield ReturnSuccess::value(row.into_value());
-            }
-            _ => {
-                yield Err(ShellError::labeled_error_with_secondary(
-                    "String not compatible with url-encoding",
-                    "input not url-encoded",
-                    tag,
-                    "value originates from here",
-                    concat_string.tag,
-                ));
+            for (k, v) in result {
+                row.insert_untagged(k, UntaggedValue::string(v));
             }
+
+            Ok(OutputStream::one(ReturnSuccess::value(row.into_value())))
         }
-    };
-
-    Ok(stream.to_output_stream())
+        _ => Err(ShellError::labeled_error_with_secondary(
+            "String not compatible with url-encoding",
+            "input not url-encoded",
+            tag,
+            "value originates from here",
+            concat_string.tag,
+        )),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::FromURL;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromURL {})
+    }
 }

crates/nu-cli/src/commands/from_vcf.rs

@@ -9,52 +9,61 @@ use std::io::BufReader;
 
 pub struct FromVcf;
 
+#[async_trait]
 impl WholeStreamCommand for FromVcf {
     fn name(&self) -> &str {
-        "from-vcf"
+        "from vcf"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-vcf")
+        Signature::build("from vcf")
     }
 
     fn usage(&self) -> &str {
         "Parse text as .vcf and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        from_vcf(args, registry)
+        from_vcf(args, registry).await
     }
 }
 
-fn from_vcf(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
+async fn from_vcf(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let args = args.evaluate_once(&registry).await?;
     let tag = args.name_tag();
     let input = args.input;
 
-    let stream = async_stream! {
-        let input_string = input.collect_string(tag.clone()).await?.item;
-        let input_bytes = input_string.as_bytes();
-        let buf_reader = BufReader::new(input_bytes);
-        let parser = ical::VcardParser::new(buf_reader);
+    let input_string = input.collect_string(tag.clone()).await?.item;
+    let input_bytes = input_string.as_bytes();
+    let buf_reader = BufReader::new(input_bytes);
+    let parser = ical::VcardParser::new(buf_reader);
 
-        for contact in parser {
-            match contact {
-                Ok(c) => yield ReturnSuccess::value(contact_to_value(c, tag.clone())),
-                Err(_) => yield Err(ShellError::labeled_error(
+    let mut values_vec_deque = VecDeque::new();
+
+    for contact in parser {
+        match contact {
+            Ok(c) => {
+                values_vec_deque.push_back(ReturnSuccess::value(contact_to_value(c, tag.clone())))
+            }
+            Err(_) => {
+                return Err(ShellError::labeled_error(
                     "Could not parse as .vcf",
                     "input cannot be parsed as .vcf",
-                    tag.clone()
-                )),
+                    tag.clone(),
+                ))
             }
         }
-    };
+    }
 
-    Ok(stream.to_output_stream())
+    Ok(futures::stream::iter(values_vec_deque).to_output_stream())
 }
 
 fn contact_to_value(contact: VcardContact, tag: Tag) -> Value {
@@ -100,3 +109,15 @@ fn params_to_value(params: Vec<(String, Vec<String>)>, tag: Tag) -> Value {
 
     row.into_value()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::FromVcf;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromVcf {})
+    }
+}

crates/nu-cli/src/commands/from_xlsx.rs

@@ -13,13 +13,14 @@ pub struct FromXLSXArgs {
     headerless: bool,
 }
 
+#[async_trait]
 impl WholeStreamCommand for FromXLSX {
     fn name(&self) -> &str {
-        "from-xlsx"
+        "from xlsx"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-xlsx").switch(
+        Signature::build("from xlsx").switch(
             "headerless",
             "don't treat the first row as column names",
             None,
@@ -30,25 +31,20 @@ impl WholeStreamCommand for FromXLSX {
         "Parse binary Excel(.xlsx) data and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, from_xlsx)?.run()
+        from_xlsx(args, registry)
     }
 }
 
-fn from_xlsx(
-    FromXLSXArgs {
-        headerless: _headerless,
-    }: FromXLSXArgs,
-    runnable_context: RunnableContext,
-) -> Result<OutputStream, ShellError> {
-    let input = runnable_context.input;
-    let tag = runnable_context.name;
-
+fn from_xlsx(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let registry = registry.clone();
     let stream = async_stream! {
+        let (FromXLSXArgs { headerless: _headerless }, mut input) = args.process(&registry).await?;
         let value = input.collect_binary(tag.clone()).await?;
 
         let mut buf: Cursor<Vec<u8>> = Cursor::new(value.item);
@@ -97,3 +93,15 @@ fn from_xlsx(
 
     Ok(stream.to_output_stream())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::FromXLSX;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromXLSX {})
+    }
+}

crates/nu-cli/src/commands/from_xml.rs

@@ -5,20 +5,21 @@ use nu_protocol::{Primitive, ReturnSuccess, Signature, TaggedDictBuilder, Untagg
 
 pub struct FromXML;
 
+#[async_trait]
 impl WholeStreamCommand for FromXML {
     fn name(&self) -> &str {
-        "from-xml"
+        "from xml"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-xml")
+        Signature::build("from xml")
     }
 
     fn usage(&self) -> &str {
         "Parse text as .xml and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
@@ -99,11 +100,12 @@ pub fn from_xml_string_to_value(s: String, tag: impl Into<Tag>) -> Result<Value,
 }
 
 fn from_xml(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
-    let tag = args.name_tag();
-    let input = args.input;
-
+    let registry = registry.clone();
     let stream = async_stream! {
+        let args = args.evaluate_once(&registry).await?;
+        let tag = args.name_tag();
+        let input = args.input;
+
         let concat_string = input.collect_string(tag.clone()).await?;
 
         match from_xml_string_to_value(concat_string.item, tag.clone()) {
@@ -300,4 +302,12 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn examples_work_as_expected() {
+        use super::FromXML;
+        use crate::examples::test as test_examples;
+
+        test_examples(FromXML {})
+    }
 }

crates/nu-cli/src/commands/from_yaml.rs

@@ -1,53 +1,55 @@
 use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{Primitive, ReturnSuccess, Signature, TaggedDictBuilder, UntaggedValue, Value};
+use nu_protocol::{Primitive, Signature, TaggedDictBuilder, UntaggedValue, Value};
 
 pub struct FromYAML;
 
+#[async_trait]
 impl WholeStreamCommand for FromYAML {
     fn name(&self) -> &str {
-        "from-yaml"
+        "from yaml"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-yaml")
+        Signature::build("from yaml")
     }
 
     fn usage(&self) -> &str {
         "Parse text as .yaml/.yml and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        from_yaml(args, registry)
+        from_yaml(args, registry).await
     }
 }
 
 pub struct FromYML;
 
+#[async_trait]
 impl WholeStreamCommand for FromYML {
     fn name(&self) -> &str {
-        "from-yml"
+        "from yml"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("from-yml")
+        Signature::build("from yml")
     }
 
     fn usage(&self) -> &str {
         "Parse text as .yaml/.yml and create table."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        from_yaml(args, registry)
+        from_yaml(args, registry).await
     }
 }
 
@@ -118,34 +120,43 @@ pub fn from_yaml_string_to_value(s: String, tag: impl Into<Tag>) -> Result<Value
     Ok(convert_yaml_value_to_nu_value(&v, tag)?)
 }
 
-fn from_yaml(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
+async fn from_yaml(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let args = args.evaluate_once(&registry).await?;
     let tag = args.name_tag();
     let input = args.input;
 
-    let stream = async_stream! {
-        let concat_string = input.collect_string(tag.clone()).await?;
+    let concat_string = input.collect_string(tag.clone()).await?;
 
-        match from_yaml_string_to_value(concat_string.item, tag.clone()) {
-            Ok(x) => match x {
-                Value { value: UntaggedValue::Table(list), .. } => {
-                    for l in list {
-                        yield ReturnSuccess::value(l);
-                    }
-                }
-                x => yield ReturnSuccess::value(x),
-            },
-            Err(_) => {
-                yield Err(ShellError::labeled_error_with_secondary(
-                    "Could not parse as YAML",
-                    "input cannot be parsed as YAML",
-                    &tag,
-                    "value originates from here",
-                    &concat_string.tag,
-                ))
-            }
-        }
-    };
-
-    Ok(stream.to_output_stream())
+    match from_yaml_string_to_value(concat_string.item, tag.clone()) {
+        Ok(x) => match x {
+            Value {
+                value: UntaggedValue::Table(list),
+                ..
+            } => Ok(futures::stream::iter(list).to_output_stream()),
+            x => Ok(OutputStream::one(x)),
+        },
+        Err(_) => Err(ShellError::labeled_error_with_secondary(
+            "Could not parse as YAML",
+            "input cannot be parsed as YAML",
+            &tag,
+            "value originates from here",
+            &concat_string.tag,
+        )),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::FromYAML;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(FromYAML {})
+    }
 }

crates/nu-cli/src/commands/get.rs

@@ -4,8 +4,8 @@ use indexmap::set::IndexSet;
 use log::trace;
 use nu_errors::ShellError;
 use nu_protocol::{
-    did_you_mean, ColumnPath, PathMember, Primitive, ReturnSuccess, ReturnValue, Signature,
-    SyntaxShape, UnspannedPathMember, UntaggedValue, Value,
+    did_you_mean, ColumnPath, PathMember, Primitive, ReturnSuccess, Signature, SyntaxShape,
+    UnspannedPathMember, UntaggedValue, Value,
 };
 use nu_source::span_for_spanned_list;
 use nu_value_ext::get_data_by_column_path;
@@ -17,6 +17,7 @@ pub struct GetArgs {
     rest: Vec<ColumnPath>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for Get {
     fn name(&self) -> &str {
         "get"
@@ -33,12 +34,27 @@ impl WholeStreamCommand for Get {
         "Open given cells as text."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, get)?.run()
+        get(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Extract the name of files as a list",
+                example: "ls | get name",
+                result: None,
+            },
+            Example {
+                description: "Extract the cpu list from the sys information",
+                example: "sys | get cpu",
+                result: None,
+            },
+        ]
     }
 }
 
@@ -176,30 +192,21 @@ pub fn get_column_path(path: &ColumnPath, obj: &Value) -> Result<Value, ShellErr
     )
 }
 
-pub fn get(
-    GetArgs { rest: mut fields }: GetArgs,
-    RunnableContext { mut input, .. }: RunnableContext,
-) -> Result<OutputStream, ShellError> {
-    if fields.is_empty() {
-        let stream = async_stream! {
+pub fn get(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let (GetArgs { rest: mut fields }, mut input) = args.process(&registry).await?;
+        if fields.is_empty() {
             let mut vec = input.drain_vec().await;
 
             let descs = nu_protocol::merge_descriptors(&vec);
             for desc in descs {
                 yield ReturnSuccess::value(desc);
             }
-        };
-
-        let stream: BoxStream<'static, ReturnValue> = stream.boxed();
-
-        Ok(stream.to_output_stream())
-    } else {
-        let member = fields.remove(0);
-        trace!("get {:?} {:?}", member, fields);
-        let stream = input
-            .map(move |item| {
-                let mut result = VecDeque::new();
-
+        } else {
+            let member = fields.remove(0);
+            trace!("get {:?} {:?}", member, fields);
+            while let Some(item) = input.next().await {
                 let member = vec![member.clone()];
 
                 let column_paths = vec![&member, &fields]
@@ -217,25 +224,34 @@ pub fn get(
                                 ..
                             } => {
                                 for item in rows {
-                                    result.push_back(ReturnSuccess::value(item.clone()));
+                                    yield ReturnSuccess::value(item.clone());
                                 }
                             }
                             Value {
                                 value: UntaggedValue::Primitive(Primitive::Nothing),
                                 ..
                             } => {}
-                            other => result.push_back(ReturnSuccess::value(other.clone())),
+                            other => yield ReturnSuccess::value(other.clone()),
                         },
-                        Err(reason) => result.push_back(ReturnSuccess::value(
+                        Err(reason) => yield ReturnSuccess::value(
                             UntaggedValue::Error(reason).into_untagged_value(),
-                        )),
+                        ),
                     }
                 }
+            }
+        }
+    };
+    Ok(stream.to_output_stream())
+}
 
-                futures::stream::iter(result)
-            })
-            .flatten();
+#[cfg(test)]
+mod tests {
+    use super::Get;
 
-        Ok(stream.to_output_stream())
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Get {})
     }
 }

crates/nu-cli/src/commands/group_by.rs

@@ -1,24 +1,25 @@
 use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
+use indexmap::indexmap;
 use nu_errors::ShellError;
-use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, TaggedDictBuilder, UntaggedValue, Value};
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
 use nu_source::Tagged;
-use nu_value_ext::get_data_by_key;
 
 pub struct GroupBy;
 
 #[derive(Deserialize)]
 pub struct GroupByArgs {
-    column_name: Tagged<String>,
+    column_name: Option<Tagged<String>>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for GroupBy {
     fn name(&self) -> &str {
         "group-by"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("group-by").required(
+        Signature::build("group-by").optional(
             "column_name",
             SyntaxShape::String,
             "the name of the column to group by",
@@ -29,37 +30,68 @@ impl WholeStreamCommand for GroupBy {
         "Creates a new table with the data from the table rows grouped by the column given."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, group_by)?.run()
+        group_by(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Group items by type",
+                example: r#"ls | group-by type"#,
+                result: None,
+            },
+            Example {
+                description: "Group items by their value",
+                example: "echo [1 3 1 3 2 1 1] | group-by",
+                result: Some(vec![UntaggedValue::row(indexmap! {
+                    "1".to_string() => UntaggedValue::Table(vec![
+                        UntaggedValue::int(1).into(),
+                        UntaggedValue::int(1).into(),
+                        UntaggedValue::int(1).into(),
+                        UntaggedValue::int(1).into(),
+                    ]).into(),
+
+                    "3".to_string() => UntaggedValue::Table(vec![
+                        UntaggedValue::int(3).into(),
+                        UntaggedValue::int(3).into(),
+                    ]).into(),
+
+                    "2".to_string() => UntaggedValue::Table(vec![
+                        UntaggedValue::int(2).into(),
+                    ]).into(),
+                })
+                .into()]),
+            },
+        ]
     }
 }
 
-pub fn group_by(
-    GroupByArgs { column_name }: GroupByArgs,
-    RunnableContext { input, name, .. }: RunnableContext,
+pub async fn group_by(
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    let stream = async_stream! {
-        let values: Vec<Value> = input.collect().await;
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
+    let (GroupByArgs { column_name }, input) = args.process(&registry).await?;
+    let values: Vec<Value> = input.collect().await;
 
-        if values.is_empty() {
-            yield Err(ShellError::labeled_error(
-                    "Expected table from pipeline",
-                    "requires a table input",
-                    column_name.span()
-                ))
-        } else {
-            match group(&column_name, values, name) {
-                Ok(grouped) => yield ReturnSuccess::value(grouped),
-                Err(err) => yield Err(err)
-            }
+    if values.is_empty() {
+        Err(ShellError::labeled_error(
+            "Expected table from pipeline",
+            "requires a table input",
+            name,
+        ))
+    } else {
+        match crate::utils::data::group(column_name, &values, None, &name) {
+            Ok(grouped) => Ok(OutputStream::one(ReturnSuccess::value(grouped))),
+            Err(err) => Err(err),
         }
-    };
-
-    Ok(stream.to_output_stream())
+    }
 }
 
 pub fn group(
@@ -67,50 +99,7 @@ pub fn group(
     values: Vec<Value>,
     tag: impl Into<Tag>,
 ) -> Result<Value, ShellError> {
-    let tag = tag.into();
-
-    let mut groups: indexmap::IndexMap<String, Vec<Value>> = indexmap::IndexMap::new();
-
-    for value in values {
-        let group_key = get_data_by_key(&value, column_name.borrow_spanned());
-
-        if let Some(group_key) = group_key {
-            let group_key = group_key.as_string()?.to_string();
-            let group = groups.entry(group_key).or_insert(vec![]);
-            group.push(value);
-        } else {
-            let possibilities = value.data_descriptors();
-
-            let mut possible_matches: Vec<_> = possibilities
-                .iter()
-                .map(|x| (natural::distance::levenshtein_distance(x, column_name), x))
-                .collect();
-
-            possible_matches.sort();
-
-            if !possible_matches.is_empty() {
-                return Err(ShellError::labeled_error(
-                    "Unknown column",
-                    format!("did you mean '{}'?", possible_matches[0].1),
-                    column_name.tag(),
-                ));
-            } else {
-                return Err(ShellError::labeled_error(
-                    "Unknown column",
-                    "row does not contain this column",
-                    column_name.tag(),
-                ));
-            }
-        }
-    }
-
-    let mut out = TaggedDictBuilder::new(&tag);
-
-    for (k, v) in groups.iter() {
-        out.insert_untagged(k, UntaggedValue::table(v));
-    }
-
-    Ok(out.into_value())
+    crate::utils::data::group(Some(column_name.clone()), &values, None, tag)
 }
 
 #[cfg(test)]
@@ -220,4 +209,12 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn examples_work_as_expected() {
+        use super::GroupBy;
+        use crate::examples::test as test_examples;
+
+        test_examples(GroupBy {})
+    }
 }

crates/nu-cli/src/commands/group_by_date.rs

@@ -0,0 +1,126 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, Value};
+use nu_source::Tagged;
+
+pub struct GroupByDate;
+
+#[derive(Deserialize)]
+pub struct GroupByDateArgs {
+    column_name: Option<Tagged<String>>,
+    format: Option<Tagged<String>>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for GroupByDate {
+    fn name(&self) -> &str {
+        "group-by date"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("group-by date")
+            .optional(
+                "column_name",
+                SyntaxShape::String,
+                "the name of the column to group by",
+            )
+            .named(
+                "format",
+                SyntaxShape::String,
+                "Specify date and time formatting",
+                Some('f'),
+            )
+    }
+
+    fn usage(&self) -> &str {
+        "Creates a new table with the data from the table rows grouped by the column given."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        group_by_date(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Group files by type",
+            example: "ls | group-by date --format '%d/%m/%Y'",
+            result: None,
+        }]
+    }
+}
+
+enum Grouper {
+    ByDate(Option<String>),
+}
+
+pub async fn group_by_date(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
+    let (
+        GroupByDateArgs {
+            column_name,
+            format,
+        },
+        input,
+    ) = args.process(&registry).await?;
+    let values: Vec<Value> = input.collect().await;
+
+    if values.is_empty() {
+        Err(ShellError::labeled_error(
+            "Expected table from pipeline",
+            "requires a table input",
+            name,
+        ))
+    } else {
+        let grouper = if let Some(Tagged { item: fmt, tag: _ }) = format {
+            Grouper::ByDate(Some(fmt))
+        } else {
+            Grouper::ByDate(None)
+        };
+
+        match grouper {
+            Grouper::ByDate(None) => {
+                match crate::utils::data::group(
+                    column_name,
+                    &values,
+                    Some(Box::new(|row: &Value| row.format("%Y-%b-%d"))),
+                    &name,
+                ) {
+                    Ok(grouped) => Ok(OutputStream::one(ReturnSuccess::value(grouped))),
+                    Err(err) => Err(err),
+                }
+            }
+            Grouper::ByDate(Some(fmt)) => {
+                match crate::utils::data::group(
+                    column_name,
+                    &values,
+                    Some(Box::new(move |row: &Value| row.format(&fmt))),
+                    &name,
+                ) {
+                    Ok(grouped) => Ok(OutputStream::one(ReturnSuccess::value(grouped))),
+                    Err(err) => Err(err),
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::GroupByDate;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(GroupByDate {})
+    }
+}

crates/nu-cli/src/commands/headers.rs

@@ -8,33 +8,41 @@ use nu_protocol::Dictionary;
 use nu_protocol::{ReturnSuccess, Signature, UntaggedValue, Value};
 
 pub struct Headers;
-#[derive(Deserialize)]
-pub struct HeadersArgs {}
 
+#[async_trait]
 impl WholeStreamCommand for Headers {
     fn name(&self) -> &str {
         "headers"
     }
+
     fn signature(&self) -> Signature {
         Signature::build("headers")
     }
+
     fn usage(&self) -> &str {
         "Use the first row of the table as column names"
     }
-    fn run(
+
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, headers)?.run()
+        headers(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Create headers for a raw string",
+            example: r#"echo "a b c|1 2 3" | split row "|" | split column " " | headers"#,
+            result: None,
+        }]
     }
 }
 
-pub fn headers(
-    HeadersArgs {}: HeadersArgs,
-    RunnableContext { input, .. }: RunnableContext,
-) -> Result<OutputStream, ShellError> {
+pub fn headers(args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
     let stream = async_stream! {
+        let mut input = args.input;
         let rows: Vec<Value> = input.collect().await;
 
         if rows.len() < 1 {
@@ -78,3 +86,15 @@ pub fn headers(
 
     Ok(stream.to_output_stream())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Headers;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Headers {})
+    }
+}

crates/nu-cli/src/commands/help.rs

@@ -1,93 +1,105 @@
-use crate::commands::PerItemCommand;
+use crate::commands::WholeStreamCommand;
 use crate::data::command_dict;
 
 use crate::prelude::*;
 use nu_errors::ShellError;
 use nu_protocol::{
-    CallInfo, NamedType, PositionalType, Primitive, ReturnSuccess, Signature, SyntaxShape,
-    TaggedDictBuilder, UntaggedValue, Value,
+    NamedType, PositionalType, ReturnSuccess, Signature, SyntaxShape, TaggedDictBuilder,
+    UntaggedValue,
 };
-use nu_source::SpannedItem;
+use nu_source::{SpannedItem, Tagged};
 use nu_value_ext::get_data_by_key;
 
 pub struct Help;
 
-impl PerItemCommand for Help {
+#[derive(Deserialize)]
+pub struct HelpArgs {
+    rest: Vec<Tagged<String>>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Help {
     fn name(&self) -> &str {
         "help"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("help").rest(SyntaxShape::Any, "the name of command(s) to get help on")
+        Signature::build("help").rest(SyntaxShape::String, "the name of command to get help on")
     }
 
     fn usage(&self) -> &str {
         "Display help information about commands."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
+        args: CommandArgs,
         registry: &CommandRegistry,
-        _raw_args: &RawCommandArgs,
-        _input: Value,
     ) -> Result<OutputStream, ShellError> {
-        let tag = &call_info.name_tag;
+        help(args, registry)
+    }
+}
 
-        match call_info.args.nth(0) {
-            Some(Value {
-                value: UntaggedValue::Primitive(Primitive::String(document)),
-                tag,
-            }) => {
-                let mut help = VecDeque::new();
-                if document == "commands" {
-                    let mut sorted_names = registry.names();
-                    sorted_names.sort();
-                    for cmd in sorted_names {
-                        let mut short_desc = TaggedDictBuilder::new(tag.clone());
-                        let value = command_dict(
-                            registry.get_command(&cmd).ok_or_else(|| {
-                                ShellError::labeled_error(
-                                    format!("Could not load {}", cmd),
-                                    "could not load command",
-                                    tag,
-                                )
-                            })?,
-                            tag.clone(),
-                        );
-
-                        short_desc.insert_untagged("name", cmd);
-                        short_desc.insert_untagged(
-                            "description",
-                            get_data_by_key(&value, "usage".spanned_unknown())
-                                .ok_or_else(|| {
-                                    ShellError::labeled_error(
-                                        "Expected a usage key",
-                                        "expected a 'usage' key",
-                                        &value.tag,
-                                    )
-                                })?
-                                .as_string()?,
-                        );
-
-                        help.push_back(ReturnSuccess::value(short_desc.into_value()));
+fn help(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
+    let stream = async_stream! {
+        let (HelpArgs { rest }, mut input) = args.process(&registry).await?;
+        if let Some(document) = rest.get(0) {
+            if document.item == "commands" {
+                let mut sorted_names = registry.names();
+                sorted_names.sort();
+                for cmd in sorted_names {
+                    // If it's a subcommand, don't list it during the commands list
+                    if cmd.contains(' ') {
+                        continue;
                     }
-                } else if let Some(command) = registry.get_command(document) {
-                    return Ok(
-                        get_help(&command.name(), &command.usage(), command.signature()).into(),
+                    let mut short_desc = TaggedDictBuilder::new(name.clone());
+                    let document_tag = document.tag.clone();
+                    let value = command_dict(
+                        registry.get_command(&cmd).ok_or_else(|| {
+                            ShellError::labeled_error(
+                                format!("Could not load {}", cmd),
+                                "could not load command",
+                                document_tag,
+                            )
+                        })?,
+                        name.clone(),
                     );
-                } else {
-                    return Err(ShellError::labeled_error(
-                        "Can't find command (use 'help commands' for full list)",
-                        "can't find command",
-                        tag,
-                    ));
+
+                    short_desc.insert_untagged("name", cmd);
+                    short_desc.insert_untagged(
+                        "description",
+                        get_data_by_key(&value, "usage".spanned_unknown())
+                            .ok_or_else(|| {
+                                ShellError::labeled_error(
+                                    "Expected a usage key",
+                                    "expected a 'usage' key",
+                                    &value.tag,
+                                )
+                            })?
+                            .as_string()?,
+                    );
+
+                    yield ReturnSuccess::value(short_desc.into_value());
                 }
-                let help = futures::stream::iter(help);
-                Ok(help.to_output_stream())
+            } else if rest.len() == 2 {
+                // Check for a subcommand
+                let command_name = format!("{} {}", rest[0].item, rest[1].item);
+                if let Some(command) = registry.get_command(&command_name) {
+                    yield Ok(ReturnSuccess::Value(UntaggedValue::string(get_help(command.stream_command(), &registry)).into_value(Tag::unknown())));
+                }
+            } else if let Some(command) = registry.get_command(&document.item) {
+                yield Ok(ReturnSuccess::Value(UntaggedValue::string(get_help(command.stream_command(), &registry)).into_value(Tag::unknown())));
+            } else {
+                yield Err(ShellError::labeled_error(
+                    "Can't find command (use 'help commands' for full list)",
+                    "can't find command",
+                    document.tag.span,
+                ));
             }
-            _ => {
-                let msg = r#"Welcome to Nushell.
+        } else {
+            let msg = r#"Welcome to Nushell.
 
 Here are some tips to help you get started.
   * help commands - list all available commands
@@ -109,28 +121,30 @@ Get the processes on your system actively using CPU:
 
 You can also learn more at https://www.nushell.sh/book/"#;
 
-                let output_stream = futures::stream::iter(vec![ReturnSuccess::value(
-                    UntaggedValue::string(msg).into_value(tag),
-                )]);
-
-                Ok(output_stream.to_output_stream())
-            }
+            yield Ok(ReturnSuccess::Value(UntaggedValue::string(msg).into_value(Tag::unknown())));
         }
-    }
+    };
+
+    Ok(stream.to_output_stream())
 }
 
-pub(crate) fn get_help(
-    cmd_name: &str,
-    cmd_usage: &str,
-    cmd_sig: Signature,
-) -> impl Into<OutputStream> {
-    let mut help = VecDeque::new();
+#[allow(clippy::cognitive_complexity)]
+pub fn get_help(cmd: &dyn WholeStreamCommand, registry: &CommandRegistry) -> String {
+    let cmd_name = cmd.name();
+    let signature = cmd.signature();
     let mut long_desc = String::new();
 
-    long_desc.push_str(&cmd_usage);
+    long_desc.push_str(&cmd.usage());
     long_desc.push_str("\n");
 
-    let signature = cmd_sig;
+    let mut subcommands = String::new();
+    for name in registry.names() {
+        if name.starts_with(&format!("{} ", cmd_name)) {
+            let subcommand = registry.get_command(&name).expect("This shouldn't happen");
+
+            subcommands.push_str(&format!("  {} - {}\n", name, subcommand.usage()));
+        }
+    }
 
     let mut one_liner = String::new();
     one_liner.push_str(&signature.name);
@@ -151,16 +165,25 @@ pub(crate) fn get_help(
         one_liner.push_str(" ...args");
     }
 
+    if !subcommands.is_empty() {
+        one_liner.push_str("<subcommand> ");
+    }
+
     if !signature.named.is_empty() {
         one_liner.push_str("{flags} ");
     }
 
     long_desc.push_str(&format!("\nUsage:\n  > {}\n", one_liner));
 
+    if !subcommands.is_empty() {
+        long_desc.push_str("\nSubcommands:\n");
+        long_desc.push_str(&subcommands);
+    }
+
     if !signature.positional.is_empty() || signature.rest_positional.is_some() {
-        long_desc.push_str("\nparameters:\n");
-        for positional in signature.positional {
-            match positional.0 {
+        long_desc.push_str("\nParameters:\n");
+        for positional in &signature.positional {
+            match &positional.0 {
                 PositionalType::Mandatory(name, _m) => {
                     long_desc.push_str(&format!("  <{}> {}\n", name, positional.1));
                 }
@@ -170,79 +193,110 @@ pub(crate) fn get_help(
             }
         }
 
-        if let Some(rest_positional) = signature.rest_positional {
+        if let Some(rest_positional) = &signature.rest_positional {
             long_desc.push_str(&format!("  ...args: {}\n", rest_positional.1));
         }
     }
     if !signature.named.is_empty() {
-        long_desc.push_str("\nflags:\n");
-        for (flag, ty) in signature.named {
-            let msg = match ty.0 {
-                NamedType::Switch(s) => {
-                    if let Some(c) = s {
-                        format!(
-                            "  -{}, --{}{} {}\n",
-                            c,
-                            flag,
-                            if !ty.1.is_empty() { ":" } else { "" },
-                            ty.1
-                        )
-                    } else {
-                        format!(
-                            "  --{}{} {}\n",
-                            flag,
-                            if !ty.1.is_empty() { ":" } else { "" },
-                            ty.1
-                        )
-                    }
-                }
-                NamedType::Mandatory(s, m) => {
-                    if let Some(c) = s {
-                        format!(
-                            "  -{}, --{} <{}> (required parameter){} {}\n",
-                            c,
-                            flag,
-                            m.display(),
-                            if !ty.1.is_empty() { ":" } else { "" },
-                            ty.1
-                        )
-                    } else {
-                        format!(
-                            "  --{} <{}> (required parameter){} {}\n",
-                            flag,
-                            m.display(),
-                            if !ty.1.is_empty() { ":" } else { "" },
-                            ty.1
-                        )
-                    }
-                }
-                NamedType::Optional(s, o) => {
-                    if let Some(c) = s {
-                        format!(
-                            "  -{}, --{} <{}>{} {}\n",
-                            c,
-                            flag,
-                            o.display(),
-                            if !ty.1.is_empty() { ":" } else { "" },
-                            ty.1
-                        )
-                    } else {
-                        format!(
-                            "  --{} <{}>{} {}\n",
-                            flag,
-                            o.display(),
-                            if !ty.1.is_empty() { ":" } else { "" },
-                            ty.1
-                        )
-                    }
-                }
-            };
-            long_desc.push_str(&msg);
-        }
+        long_desc.push_str(&get_flags_section(&signature))
     }
 
-    help.push_back(ReturnSuccess::value(
-        UntaggedValue::string(long_desc).into_value(Tag::from((0, cmd_name.len(), None))),
-    ));
-    help
+    let palette = crate::shell::palette::DefaultPalette {};
+    let examples = cmd.examples();
+    if !examples.is_empty() {
+        long_desc.push_str("\nExamples:");
+    }
+    for example in examples {
+        long_desc.push_str("\n");
+        long_desc.push_str("  ");
+        long_desc.push_str(example.description);
+        let colored_example =
+            crate::shell::helper::Painter::paint_string(example.example, registry, &palette);
+        long_desc.push_str(&format!("\n  > {}\n", colored_example));
+    }
+
+    long_desc.push_str("\n");
+
+    long_desc
+}
+
+fn get_flags_section(signature: &Signature) -> String {
+    let mut long_desc = String::new();
+    long_desc.push_str("\nFlags:\n");
+    for (flag, ty) in &signature.named {
+        let msg = match ty.0 {
+            NamedType::Switch(s) => {
+                if let Some(c) = s {
+                    format!(
+                        "  -{}, --{}{} {}\n",
+                        c,
+                        flag,
+                        if !ty.1.is_empty() { ":" } else { "" },
+                        ty.1
+                    )
+                } else {
+                    format!(
+                        "  --{}{} {}\n",
+                        flag,
+                        if !ty.1.is_empty() { ":" } else { "" },
+                        ty.1
+                    )
+                }
+            }
+            NamedType::Mandatory(s, m) => {
+                if let Some(c) = s {
+                    format!(
+                        "  -{}, --{} <{}> (required parameter){} {}\n",
+                        c,
+                        flag,
+                        m.display(),
+                        if !ty.1.is_empty() { ":" } else { "" },
+                        ty.1
+                    )
+                } else {
+                    format!(
+                        "  --{} <{}> (required parameter){} {}\n",
+                        flag,
+                        m.display(),
+                        if !ty.1.is_empty() { ":" } else { "" },
+                        ty.1
+                    )
+                }
+            }
+            NamedType::Optional(s, o) => {
+                if let Some(c) = s {
+                    format!(
+                        "  -{}, --{} <{}>{} {}\n",
+                        c,
+                        flag,
+                        o.display(),
+                        if !ty.1.is_empty() { ":" } else { "" },
+                        ty.1
+                    )
+                } else {
+                    format!(
+                        "  --{} <{}>{} {}\n",
+                        flag,
+                        o.display(),
+                        if !ty.1.is_empty() { ":" } else { "" },
+                        ty.1
+                    )
+                }
+            }
+        };
+        long_desc.push_str(&msg);
+    }
+    long_desc
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Help;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Help {})
+    }
 }

crates/nu-cli/src/commands/histogram.rs

@@ -17,6 +17,7 @@ pub struct HistogramArgs {
     rest: Vec<Tagged<String>>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for Histogram {
     fn name(&self) -> &str {
         "histogram"
@@ -39,20 +40,44 @@ impl WholeStreamCommand for Histogram {
         "Creates a new table with a histogram based on the column name passed in."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, histogram)?.run()
+        histogram(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Get a histogram for the types of files",
+                example: "ls | histogram type",
+                result: None,
+            },
+            Example {
+                description:
+                    "Get a histogram for the types of files, with frequency column named count",
+                example: "ls | histogram type count",
+                result: None,
+            },
+            Example {
+                description: "Get a histogram for a list of numbers",
+                example: "echo [1 2 3 1 1 1 2 2 1 1] | histogram",
+                result: None,
+            },
+        ]
     }
 }
 
 pub fn histogram(
-    HistogramArgs { column_name, rest }: HistogramArgs,
-    RunnableContext { input, name, .. }: RunnableContext,
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
     let stream = async_stream! {
+        let (HistogramArgs { column_name, rest}, mut input) = args.process(&registry).await?;
         let values: Vec<Value> = input.collect().await;
 
         let Tagged { item: group_by, .. } = column_name.clone();
@@ -83,6 +108,32 @@ pub fn histogram(
 
                 let column = (*column_name).clone();
 
+                let count_column_name = "count".to_string();
+                let count_shell_error = ShellError::labeled_error("Unable to load group count", "unabled to load group count", &name);
+                let mut count_values: Vec<u64> = Vec::new();
+
+                for table_entry in reduced.table_entries() {
+                    match table_entry {
+                        Value {
+                            value: UntaggedValue::Table(list),
+                            ..
+                        } => {
+                            for i in list {
+                                if let Ok(count) = i.value.clone().into_value(&name).as_u64() {
+                                    count_values.push(count);
+                                } else {
+                                    yield Err(count_shell_error);
+                                    return;
+                                }
+                            }
+                        }
+                        _ => {
+                            yield Err(count_shell_error);
+                            return;
+                        }
+                    }
+                }
+
                 if let Value { value: UntaggedValue::Table(start), .. } = datasets.get(0).ok_or_else(|| ShellError::labeled_error("Unable to load dataset", "unabled to load dataset", &name))? {
                     for percentage in start.iter() {
 
@@ -90,6 +141,8 @@ pub fn histogram(
                         let value: Tagged<String> = group_labels.get(idx).ok_or_else(|| ShellError::labeled_error("Unable to load group labels", "unabled to load group labels", &name))?.clone();
                         fact.insert_value(&column, UntaggedValue::string(value.item).into_value(value.tag));
 
+                        fact.insert_untagged(&count_column_name, UntaggedValue::int(count_values[idx]));
+
                         if let Value { value: UntaggedValue::Primitive(Primitive::Int(ref num)), ref tag } = percentage.clone() {
                             let string = std::iter::repeat("*").take(num.to_i32().ok_or_else(|| ShellError::labeled_error("Expected a number", "expected a number", tag))? as usize).collect::<String>();
                             fact.insert_untagged(&frequency_column_name, UntaggedValue::string(string));
@@ -158,3 +211,15 @@ fn percentages(values: &Value, max: Value, tag: impl Into<Tag>) -> Result<Value,
 
     Ok(results)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Histogram;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Histogram {})
+    }
+}

crates/nu-cli/src/commands/history.rs

@@ -1,14 +1,15 @@
 use crate::cli::History as HistoryFile;
-use crate::commands::PerItemCommand;
+use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, ReturnSuccess, Signature, UntaggedValue, Value};
+use nu_protocol::{ReturnSuccess, Signature, UntaggedValue};
 use std::fs::File;
 use std::io::{BufRead, BufReader};
 
 pub struct History;
 
-impl PerItemCommand for History {
+#[async_trait]
+impl WholeStreamCommand for History {
     fn name(&self) -> &str {
         "history"
     }
@@ -21,29 +22,42 @@ impl PerItemCommand for History {
         "Display command history."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        _raw_args: &RawCommandArgs,
-        _input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        let tag = call_info.name_tag.clone();
-
-        let stream = async_stream! {
-            let history_path = HistoryFile::path();
-            let file = File::open(history_path);
-            if let Ok(file) = file {
-                let reader = BufReader::new(file);
-                for line in reader.lines() {
-                    if let Ok(line) = line {
-                        yield ReturnSuccess::value(UntaggedValue::string(line).into_value(tag.clone()));
-                    }
-                }
-            } else {
-                yield Err(ShellError::labeled_error("Could not open history", "history file could not be opened", tag.clone()));
-            }
-        };
-        Ok(stream.to_output_stream())
+        history(args, registry)
+    }
+}
+
+fn history(args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag;
+    let stream = async_stream! {
+        let history_path = HistoryFile::path();
+        let file = File::open(history_path);
+        if let Ok(file) = file {
+            let reader = BufReader::new(file);
+            for line in reader.lines() {
+                if let Ok(line) = line {
+                    yield ReturnSuccess::value(UntaggedValue::string(line).into_value(tag.clone()));
+                }
+            }
+        } else {
+            yield Err(ShellError::labeled_error("Could not open history", "history file could not be opened", tag.clone()));
+        }
+    };
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::History;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(History {})
     }
 }

crates/nu-cli/src/commands/insert.rs

@@ -1,13 +1,20 @@
-use crate::commands::PerItemCommand;
+use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
+use nu_protocol::{ColumnPath, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
 use nu_value_ext::ValueExt;
 
 pub struct Insert;
 
-impl PerItemCommand for Insert {
+#[derive(Deserialize)]
+pub struct InsertArgs {
+    column: ColumnPath,
+    value: Value,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Insert {
     fn name(&self) -> &str {
         "insert"
     }
@@ -27,40 +34,56 @@ impl PerItemCommand for Insert {
     }
 
     fn usage(&self) -> &str {
-        "Edit an existing column to have a new value."
+        "Insert a new column with a given value."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        _raw_args: &RawCommandArgs,
-        value: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        let value_tag = value.tag();
-        let field = call_info.args.expect_nth(0)?.as_column_path()?;
-        let replacement = call_info.args.expect_nth(1)?.tagged_unknown();
+        insert(args, registry)
+    }
+}
 
-        let stream = match value {
-            obj
-            @
-            Value {
-                value: UntaggedValue::Row(_),
-                ..
-            } => match obj.insert_data_at_column_path(&field, replacement.item.clone()) {
-                Ok(v) => futures::stream::iter(vec![Ok(ReturnSuccess::Value(v))]),
-                Err(err) => return Err(err),
-            },
+fn insert(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+
+    let stream = async_stream! {
+        let (InsertArgs { column, value }, mut input) = args.process(&registry).await?;
+        while let Some(row) = input.next().await {
+            match row {
+                Value {
+                    value: UntaggedValue::Row(_),
+                    ..
+                } => match row.insert_data_at_column_path(&column, value.clone()) {
+                    Ok(v) => yield Ok(ReturnSuccess::Value(v)),
+                    Err(err) => yield Err(err),
+                },
+
+                Value { tag, ..} => {
+                    yield Err(ShellError::labeled_error(
+                        "Unrecognized type in stream",
+                        "original value",
+                        tag,
+                    ));
+                }
 
-            _ => {
-                return Err(ShellError::labeled_error(
-                    "Unrecognized type in stream",
-                    "original value",
-                    value_tag,
-                ))
             }
         };
 
-        Ok(stream.to_output_stream())
+    };
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Insert;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Insert {})
     }
 }

crates/nu-cli/src/commands/is_empty.rs

@@ -0,0 +1,211 @@
+use crate::commands::WholeStreamCommand;
+use crate::context::CommandRegistry;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{ColumnPath, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
+use nu_source::Tagged;
+use nu_value_ext::ValueExt;
+
+enum IsEmptyFor {
+    Value,
+    RowWithFieldsAndFallback(Vec<Tagged<ColumnPath>>, Value),
+    RowWithField(Tagged<ColumnPath>),
+    RowWithFieldAndFallback(Box<Tagged<ColumnPath>>, Value),
+}
+
+pub struct IsEmpty;
+
+#[derive(Deserialize)]
+pub struct IsEmptyArgs {
+    rest: Vec<Value>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for IsEmpty {
+    fn name(&self) -> &str {
+        "empty?"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("empty?").rest(
+            SyntaxShape::Any,
+            "the names of the columns to check emptiness followed by the replacement value.",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Checks emptiness. The last value is the replacement value for any empty column(s) given to check against the table."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        is_empty(args, registry)
+    }
+}
+
+fn is_empty(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let (IsEmptyArgs { rest }, mut input) = args.process(&registry).await?;
+        while let Some(value) = input.next().await {
+            let value_tag = value.tag();
+
+            let action = if rest.len() <= 2 {
+                let field = rest.get(0);
+                let replacement_if_true = rest.get(1);
+
+                match (field, replacement_if_true) {
+                    (Some(field), Some(replacement_if_true)) => {
+                        IsEmptyFor::RowWithFieldAndFallback(
+                            Box::new(field.as_column_path()?),
+                            replacement_if_true.clone(),
+                        )
+                    }
+                    (Some(field), None) => IsEmptyFor::RowWithField(field.as_column_path()?),
+                    (_, _) => IsEmptyFor::Value,
+                }
+            } else {
+                // let no_args = vec![];
+                let mut arguments = rest.iter().rev();
+                let replacement_if_true = match arguments.next() {
+                    Some(arg) => arg.clone(),
+                    None => UntaggedValue::boolean(value.is_empty()).into_value(&value_tag),
+                };
+
+                IsEmptyFor::RowWithFieldsAndFallback(
+                    arguments
+                        .map(|a| a.as_column_path())
+                        .filter_map(Result::ok)
+                        .collect(),
+                    replacement_if_true,
+                )
+            };
+
+            match action {
+                IsEmptyFor::Value => yield Ok(ReturnSuccess::Value(
+                    UntaggedValue::boolean(value.is_empty()).into_value(value_tag),
+                )),
+                IsEmptyFor::RowWithFieldsAndFallback(fields, default) => {
+                    let mut out = value;
+
+                    for field in fields.iter() {
+                        let val =
+                            crate::commands::get::get_column_path(&field, &out)?;
+
+                        let emptiness_value = match out {
+                            obj
+                            @
+                            Value {
+                                value: UntaggedValue::Row(_),
+                                ..
+                            } => {
+                                if val.is_empty() {
+                                    match obj.replace_data_at_column_path(&field, default.clone()) {
+                                        Some(v) => Ok(v),
+                                        None => Err(ShellError::labeled_error(
+                                            "empty? could not find place to check emptiness",
+                                            "column name",
+                                            &field.tag,
+                                        )),
+                                    }
+                                } else {
+                                    Ok(obj)
+                                }
+                            }
+                            _ => Err(ShellError::labeled_error(
+                                "Unrecognized type in stream",
+                                "original value",
+                                &value_tag,
+                            )),
+                        };
+
+                        out = emptiness_value?;
+                    }
+
+                    yield Ok(ReturnSuccess::Value(out))
+                }
+                IsEmptyFor::RowWithField(field) => {
+                    let val =
+                        crate::commands::get::get_column_path(&field, &value)?;
+
+                    match &value {
+                        obj
+                        @
+                        Value {
+                            value: UntaggedValue::Row(_),
+                            ..
+                        } => {
+                            if val.is_empty() {
+                                match obj.replace_data_at_column_path(
+                                    &field,
+                                    UntaggedValue::boolean(true).into_value(&value_tag),
+                                ) {
+                                    Some(v) => yield Ok(ReturnSuccess::Value(v)),
+                                    None => yield Err(ShellError::labeled_error(
+                                        "empty? could not find place to check emptiness",
+                                        "column name",
+                                        &field.tag,
+                                    )),
+                                }
+                            } else {
+                                yield Ok(ReturnSuccess::Value(value))
+                            }
+                        }
+                        _ => yield Err(ShellError::labeled_error(
+                            "Unrecognized type in stream",
+                            "original value",
+                            &value_tag,
+                        )),
+                    }
+                }
+                IsEmptyFor::RowWithFieldAndFallback(field, default) => {
+                    let val =
+                        crate::commands::get::get_column_path(&field, &value)?;
+
+                    match &value {
+                        obj
+                        @
+                        Value {
+                            value: UntaggedValue::Row(_),
+                            ..
+                        } => {
+                            if val.is_empty() {
+                                match obj.replace_data_at_column_path(&field, default) {
+                                    Some(v) => yield Ok(ReturnSuccess::Value(v)),
+                                    None => yield Err(ShellError::labeled_error(
+                                        "empty? could not find place to check emptiness",
+                                        "column name",
+                                        &field.tag,
+                                    )),
+                                }
+                            } else {
+                                yield Ok(ReturnSuccess::Value(value))
+                            }
+                        }
+                        _ => yield Err(ShellError::labeled_error(
+                            "Unrecognized type in stream",
+                            "original value",
+                            &value_tag,
+                        )),
+                    }
+                }
+            }
+        }
+    };
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::IsEmpty;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(IsEmpty {})
+    }
+}

crates/nu-cli/src/commands/keep.rs

@@ -0,0 +1,95 @@
+use crate::commands::WholeStreamCommand;
+use crate::context::CommandRegistry;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue};
+use nu_source::Tagged;
+
+pub struct Keep;
+
+#[derive(Deserialize)]
+pub struct KeepArgs {
+    rows: Option<Tagged<usize>>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Keep {
+    fn name(&self) -> &str {
+        "keep"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("keep").optional(
+            "rows",
+            SyntaxShape::Int,
+            "starting from the front, the number of rows to keep",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Keep the number of rows only"
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        keep(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Keep the first row",
+                example: "echo [1 2 3] | keep",
+                result: Some(vec![UntaggedValue::int(1).into()]),
+            },
+            Example {
+                description: "Keep the first four rows",
+                example: "echo [1 2 3 4 5] | keep 4",
+                result: Some(vec![
+                    UntaggedValue::int(1).into(),
+                    UntaggedValue::int(2).into(),
+                    UntaggedValue::int(3).into(),
+                    UntaggedValue::int(4).into(),
+                ]),
+            },
+        ]
+    }
+}
+
+fn keep(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let (KeepArgs { rows }, mut input) = args.process(&registry).await?;
+        let mut rows_desired = if let Some(quantity) = rows {
+            *quantity
+        } else {
+            1
+        };
+
+        while let Some(input) = input.next().await {
+            if rows_desired > 0 {
+                yield ReturnSuccess::value(input);
+                rows_desired -= 1;
+            } else {
+                break;
+            }
+        }
+    };
+
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Keep;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Keep {})
+    }
+}

crates/nu-cli/src/commands/keep_until.rs

@@ -0,0 +1,124 @@
+use crate::commands::WholeStreamCommand;
+use crate::evaluate::evaluate_baseline_expr;
+use crate::prelude::*;
+use log::trace;
+use nu_errors::ShellError;
+use nu_protocol::{
+    hir::ClassifiedCommand, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
+};
+
+pub struct KeepUntil;
+
+#[async_trait]
+impl WholeStreamCommand for KeepUntil {
+    fn name(&self) -> &str {
+        "keep-until"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("keep-until")
+            .required(
+                "condition",
+                SyntaxShape::Math,
+                "the condition that must be met to stop keeping rows",
+            )
+            .filter()
+    }
+
+    fn usage(&self) -> &str {
+        "Keeps rows until the condition matches."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        let registry = registry.clone();
+        let scope = args.call_info.scope.clone();
+        let stream = async_stream! {
+            let mut call_info = args.evaluate_once(&registry).await?;
+
+            let block = call_info.args.expect_nth(0)?.clone();
+
+            let condition = match block {
+                Value {
+                    value: UntaggedValue::Block(block),
+                    tag,
+                } => {
+                    if block.block.len() != 1 {
+                        yield Err(ShellError::labeled_error(
+                            "Expected a condition",
+                            "expected a condition",
+                            tag,
+                        ));
+                        return;
+                    }
+                    match block.block[0].list.get(0) {
+                        Some(item) => match item {
+                            ClassifiedCommand::Expr(expr) => expr.clone(),
+                            _ => {
+                                yield Err(ShellError::labeled_error(
+                                    "Expected a condition",
+                                    "expected a condition",
+                                    tag,
+                                ));
+                                return;
+                            }
+                        },
+                        None => {
+                            yield Err(ShellError::labeled_error(
+                                "Expected a condition",
+                                "expected a condition",
+                                tag,
+                            ));
+                            return;
+                        }
+                    }
+                }
+                Value { tag, .. } => {
+                    yield Err(ShellError::labeled_error(
+                        "Expected a condition",
+                        "expected a condition",
+                        tag,
+                    ));
+                    return;
+                }
+            };
+
+            while let Some(item) = call_info.input.next().await {
+                let condition = condition.clone();
+                trace!("ITEM = {:?}", item);
+                let result =
+                    evaluate_baseline_expr(&*condition, &registry, &item, &scope.vars, &scope.env)
+                        .await;
+                trace!("RESULT = {:?}", result);
+
+                let return_value = match result {
+                    Ok(ref v) if v.is_true() => false,
+                    _ => true,
+                };
+
+                if return_value {
+                    yield ReturnSuccess::value(item);
+                } else {
+                    break;
+                }
+            }
+        };
+
+        Ok(stream.to_output_stream())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::KeepUntil;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(KeepUntil {})
+    }
+}

crates/nu-cli/src/commands/keep_while.rs

@@ -0,0 +1,124 @@
+use crate::commands::WholeStreamCommand;
+use crate::evaluate::evaluate_baseline_expr;
+use crate::prelude::*;
+use log::trace;
+use nu_errors::ShellError;
+use nu_protocol::{
+    hir::ClassifiedCommand, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
+};
+
+pub struct KeepWhile;
+
+#[async_trait]
+impl WholeStreamCommand for KeepWhile {
+    fn name(&self) -> &str {
+        "keep-while"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("keep-while")
+            .required(
+                "condition",
+                SyntaxShape::Math,
+                "the condition that must be met to keep rows",
+            )
+            .filter()
+    }
+
+    fn usage(&self) -> &str {
+        "Keeps rows while the condition matches."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        let registry = registry.clone();
+        let scope = args.call_info.scope.clone();
+        let stream = async_stream! {
+            let mut call_info = args.evaluate_once(&registry).await?;
+
+            let block = call_info.args.expect_nth(0)?.clone();
+
+            let condition = match block {
+                Value {
+                    value: UntaggedValue::Block(block),
+                    tag,
+                } => {
+                    if block.block.len() != 1 {
+                        yield Err(ShellError::labeled_error(
+                            "Expected a condition",
+                            "expected a condition",
+                            tag,
+                        ));
+                        return;
+                    }
+                    match block.block[0].list.get(0) {
+                        Some(item) => match item {
+                            ClassifiedCommand::Expr(expr) => expr.clone(),
+                            _ => {
+                                yield Err(ShellError::labeled_error(
+                                    "Expected a condition",
+                                    "expected a condition",
+                                    tag,
+                                ));
+                                return;
+                            }
+                        },
+                        None => {
+                            yield Err(ShellError::labeled_error(
+                                "Expected a condition",
+                                "expected a condition",
+                                tag,
+                            ));
+                            return;
+                        }
+                    }
+                }
+                Value { tag, .. } => {
+                    yield Err(ShellError::labeled_error(
+                        "Expected a condition",
+                        "expected a condition",
+                        tag,
+                    ));
+                    return;
+                }
+            };
+
+            while let Some(item) = call_info.input.next().await {
+                let condition = condition.clone();
+                trace!("ITEM = {:?}", item);
+                let result =
+                    evaluate_baseline_expr(&*condition, &registry, &item, &scope.vars, &scope.env)
+                        .await;
+                trace!("RESULT = {:?}", result);
+
+                let return_value = match result {
+                    Ok(ref v) if v.is_true() => true,
+                    _ => false,
+                };
+
+                if return_value {
+                    yield ReturnSuccess::value(item);
+                } else {
+                    break;
+                }
+            }
+        };
+
+        Ok(stream.to_output_stream())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::KeepWhile;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(KeepWhile {})
+    }
+}

crates/nu-cli/src/commands/kill.rs

@@ -1,8 +1,8 @@
-use crate::commands::command::RunnablePerItemContext;
+use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, Signature, SyntaxShape, Value};
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue};
 use nu_source::Tagged;
 use std::process::{Command, Stdio};
 
@@ -16,7 +16,8 @@ pub struct KillArgs {
     pub quiet: Tagged<bool>,
 }
 
-impl PerItemCommand for Kill {
+#[async_trait]
+impl WholeStreamCommand for Kill {
     fn name(&self) -> &str {
         "kill"
     }
@@ -37,68 +38,97 @@ impl PerItemCommand for Kill {
         "Kill a process using the process id."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        _input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        call_info
-            .process(&raw_args.shell_manager, raw_args.ctrl_c.clone(), kill)?
-            .run()
+        kill(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Kill the pid using the most memory",
+                example: "ps | sort-by mem | last | kill $it.pid",
+                result: None,
+            },
+            Example {
+                description: "Force kill a given pid",
+                example: "kill --force 12345",
+                result: None,
+            },
+        ]
     }
 }
 
-fn kill(
-    KillArgs {
-        pid,
-        rest,
-        force,
-        quiet,
-    }: KillArgs,
-    _context: &RunnablePerItemContext,
-) -> Result<OutputStream, ShellError> {
-    let mut cmd = if cfg!(windows) {
-        let mut cmd = Command::new("taskkill");
+fn kill(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
 
-        if *force {
-            cmd.arg("/F");
-        }
+    let stream = async_stream! {
+        let (KillArgs {
+            pid,
+            rest,
+            force,
+            quiet,
+        }, mut input) = args.process(&registry).await?;
+        let mut cmd = if cfg!(windows) {
+            let mut cmd = Command::new("taskkill");
 
-        cmd.arg("/PID");
-        cmd.arg(pid.item().to_string());
+            if *force {
+                cmd.arg("/F");
+            }
 
-        // each pid must written as `/PID 0` otherwise
-        // taskkill will act as `killall` unix command
-        for id in &rest {
             cmd.arg("/PID");
-            cmd.arg(id.item().to_string());
+            cmd.arg(pid.item().to_string());
+
+            // each pid must written as `/PID 0` otherwise
+            // taskkill will act as `killall` unix command
+            for id in &rest {
+                cmd.arg("/PID");
+                cmd.arg(id.item().to_string());
+            }
+
+            cmd
+        } else {
+            let mut cmd = Command::new("kill");
+
+            if *force {
+                cmd.arg("-9");
+            }
+
+            cmd.arg(pid.item().to_string());
+
+            cmd.args(rest.iter().map(move |id| id.item().to_string()));
+
+            cmd
+        };
+
+        // pipe everything to null
+        if *quiet {
+            cmd.stdin(Stdio::null())
+                .stdout(Stdio::null())
+                .stderr(Stdio::null());
         }
 
-        cmd
-    } else {
-        let mut cmd = Command::new("kill");
+        cmd.status().expect("failed to execute shell command");
 
-        if *force {
-            cmd.arg("-9");
+        if false {
+            yield ReturnSuccess::value(UntaggedValue::nothing().into_value(Tag::unknown()));
         }
-
-        cmd.arg(pid.item().to_string());
-
-        cmd.args(rest.iter().map(move |id| id.item().to_string()));
-
-        cmd
     };
 
-    // pipe everything to null
-    if *quiet {
-        cmd.stdin(Stdio::null())
-            .stdout(Stdio::null())
-            .stderr(Stdio::null());
-    }
-
-    cmd.status().expect("failed to execute shell command");
-
-    Ok(OutputStream::empty())
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Kill;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Kill {})
+    }
 }

crates/nu-cli/src/commands/last.rs

@@ -2,7 +2,7 @@ use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, Value};
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
 use nu_source::Tagged;
 
 pub struct Last;
@@ -12,6 +12,7 @@ pub struct LastArgs {
     rows: Option<Tagged<u64>>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for Last {
     fn name(&self) -> &str {
         "last"
@@ -29,33 +30,68 @@ impl WholeStreamCommand for Last {
         "Show only the last number of rows."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, last)?.run()
+        last(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Get the last row",
+                example: "echo [1 2 3] | last",
+                result: Some(vec![Value::from(UntaggedValue::from(BigInt::from(3)))]),
+            },
+            Example {
+                description: "Get the last three rows",
+                example: "echo [1 2 3 4 5] | last 3",
+                result: Some(vec![
+                    UntaggedValue::int(3).into(),
+                    UntaggedValue::int(4).into(),
+                    UntaggedValue::int(5).into(),
+                ]),
+            },
+        ]
     }
 }
 
-fn last(LastArgs { rows }: LastArgs, context: RunnableContext) -> Result<OutputStream, ShellError> {
-    let stream = async_stream! {
-        let v: Vec<_> = context.input.into_vec().await;
+async fn last(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let (LastArgs { rows }, input) = args.process(&registry).await?;
+    let v: Vec<_> = input.into_vec().await;
 
-        let rows_desired = if let Some(quantity) = rows {
-            *quantity
-        } else {
-         1
-        };
-
-        let count = (rows_desired as usize);
-        if count < v.len() {
-            let k = v.len() - count;
-            for x in v[k..].iter() {
-                let y: Value = x.clone();
-                yield ReturnSuccess::value(y)
-            }
-        }
+    let rows_desired = if let Some(quantity) = rows {
+        *quantity
+    } else {
+        1
     };
-    Ok(stream.to_output_stream())
+
+    let mut values_vec_deque = VecDeque::new();
+
+    let count = rows_desired as usize;
+
+    if count < v.len() {
+        let k = v.len() - count;
+
+        for x in v[k..].iter() {
+            values_vec_deque.push_back(ReturnSuccess::value(x.clone()));
+        }
+    }
+
+    Ok(futures::stream::iter(values_vec_deque).to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Last;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Last {})
+    }
 }

crates/nu-cli/src/commands/lines.rs

@@ -5,6 +5,7 @@ use nu_protocol::{Primitive, ReturnSuccess, Signature, UntaggedValue, Value};
 
 pub struct Lines;
 
+#[async_trait]
 impl WholeStreamCommand for Lines {
     fn name(&self) -> &str {
         "lines"
@@ -18,13 +19,21 @@ impl WholeStreamCommand for Lines {
         "Split single string into rows, one per line."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
         lines(args, registry)
     }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Split multi-line string into lines",
+            example: r#"^echo "two\nlines" | lines"#,
+            result: None,
+        }]
+    }
 }
 
 fn ends_with_line_ending(st: &str) -> bool {
@@ -38,14 +47,14 @@ fn ends_with_line_ending(st: &str) -> bool {
 }
 
 fn lines(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
-    let tag = args.name_tag();
-    let name_span = tag.span;
-    let mut input = args.input;
-
     let mut leftover = vec![];
     let mut leftover_string = String::new();
+    let registry = registry.clone();
     let stream = async_stream! {
+        let args = args.evaluate_once(&registry).await.unwrap();
+        let tag = args.name_tag();
+        let name_span = tag.span;
+        let mut input = args.input;
         loop {
             match input.next().await {
                 Some(Value { value: UntaggedValue::Primitive(Primitive::String(st)), ..}) => {
@@ -65,6 +74,7 @@ fn lines(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream,
                     }
 
                     let success_lines: Vec<_> = lines.iter().map(|x| ReturnSuccess::value(UntaggedValue::line(x).into_untagged_value())).collect();
+
                     yield futures::stream::iter(success_lines)
                 }
                 Some(Value { value: UntaggedValue::Primitive(Primitive::Line(st)), ..}) => {
@@ -111,6 +121,17 @@ fn lines(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream,
         }
     }
     .flatten();
-
     Ok(stream.to_output_stream())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Lines;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Lines {})
+    }
+}

crates/nu-cli/src/commands/ls.rs

@@ -1,7 +1,7 @@
-use crate::commands::command::RunnablePerItemContext;
+use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, Signature, SyntaxShape, Value};
+use nu_protocol::{Signature, SyntaxShape};
 use nu_source::Tagged;
 use std::path::PathBuf;
 
@@ -16,9 +16,12 @@ pub struct LsArgs {
     pub short_names: bool,
     #[serde(rename = "with-symlink-targets")]
     pub with_symlink_targets: bool,
+    #[serde(rename = "du")]
+    pub du: bool,
 }
 
-impl PerItemCommand for Ls {
+#[async_trait]
+impl WholeStreamCommand for Ls {
     fn name(&self) -> &str {
         "ls"
     }
@@ -46,25 +49,58 @@ impl PerItemCommand for Ls {
                 "display the paths to the target files that symlinks point to",
                 Some('w'),
             )
+            .switch(
+                "du",
+                "display the apparent directory size in place of the directory metadata size",
+                Some('d'),
+            )
     }
 
     fn usage(&self) -> &str {
         "View the contents of the current or given path."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        _input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        call_info
-            .process(&raw_args.shell_manager, raw_args.ctrl_c.clone(), ls)?
-            .run()
+        let name = args.call_info.name_tag.clone();
+        let ctrl_c = args.ctrl_c.clone();
+        let shell_manager = args.shell_manager.clone();
+        let (args, _) = args.process(&registry).await?;
+        shell_manager.ls(args, name, ctrl_c)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "List all files in the current directory",
+                example: "ls",
+                result: None,
+            },
+            Example {
+                description: "List all files in a subdirectory",
+                example: "ls subdir",
+                result: None,
+            },
+            Example {
+                description: "List all rust files",
+                example: "ls *.rs",
+                result: None,
+            },
+        ]
     }
 }
 
-fn ls(args: LsArgs, context: &RunnablePerItemContext) -> Result<OutputStream, ShellError> {
-    context.shell_manager.ls(args, context)
+#[cfg(test)]
+mod tests {
+    use super::Ls;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Ls {})
+    }
 }

crates/nu-cli/src/commands/map_max_by.rs

@@ -14,6 +14,7 @@ pub struct MapMaxByArgs {
     column_name: Option<Tagged<String>>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for MapMaxBy {
     fn name(&self) -> &str {
         "map-max-by"
@@ -32,43 +33,52 @@ impl WholeStreamCommand for MapMaxBy {
         "Creates a new table with the data from the tables rows maxed by the column given."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, map_max_by)?.run()
+        map_max_by(args, registry).await
     }
 }
 
-pub fn map_max_by(
-    MapMaxByArgs { column_name }: MapMaxByArgs,
-    RunnableContext { input, name, .. }: RunnableContext,
+pub async fn map_max_by(
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    let stream = async_stream! {
-        let values: Vec<Value> = input.collect().await;
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
+    let (MapMaxByArgs { column_name }, mut input) = args.process(&registry).await?;
+    let values: Vec<Value> = input.collect().await;
 
-
-        if values.is_empty() {
-            yield Err(ShellError::labeled_error(
-                    "Expected table from pipeline",
-                    "requires a table input",
-                    name
-                ))
+    if values.is_empty() {
+        Err(ShellError::labeled_error(
+            "Expected table from pipeline",
+            "requires a table input",
+            name,
+        ))
+    } else {
+        let map_by_column = if let Some(column_to_map) = column_name {
+            Some(column_to_map.item().clone())
         } else {
+            None
+        };
 
-            let map_by_column = if let Some(column_to_map) = column_name {
-                Some(column_to_map.item().clone())
-            } else {
-                None
-            };
-
-            match map_max(&values[0], map_by_column, name) {
-                Ok(table_maxed) => yield ReturnSuccess::value(table_maxed),
-                Err(err) => yield Err(err)
-            }
+        match map_max(&values[0], map_by_column, name) {
+            Ok(table_maxed) => Ok(OutputStream::one(ReturnSuccess::value(table_maxed))),
+            Err(err) => Err(err),
         }
-    };
-
-    Ok(stream.to_output_stream())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::MapMaxBy;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(MapMaxBy {})
+    }
 }

crates/nu-cli/src/commands/merge.rs

@@ -0,0 +1,115 @@
+use crate::commands::classified::block::run_block;
+use crate::commands::WholeStreamCommand;
+use crate::context::CommandRegistry;
+use crate::data::value::merge_values;
+use crate::prelude::*;
+
+use indexmap::IndexMap;
+use nu_errors::ShellError;
+use nu_protocol::{hir::Block, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
+pub struct Merge;
+
+#[derive(Deserialize)]
+pub struct MergeArgs {
+    block: Block,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Merge {
+    fn name(&self) -> &str {
+        "merge"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("merge").required(
+            "block",
+            SyntaxShape::Block,
+            "the block to run and merge into the table",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Merge a table."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        merge(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Merge a 1-based index column with some ls output",
+            example: "ls | select name | keep 3 | merge { echo [1 2 3] | wrap index }",
+            result: None,
+        }]
+    }
+}
+
+fn merge(raw_args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let scope = raw_args.call_info.scope.clone();
+    let stream = async_stream! {
+        let mut context = Context::from_raw(&raw_args, &registry);
+        let name_tag = raw_args.call_info.name_tag.clone();
+        let (merge_args, mut input): (MergeArgs, _) = raw_args.process(&registry).await?;
+        let block = merge_args.block;
+
+        let table: Option<Vec<Value>> = match run_block(&block,
+                &mut context,
+                InputStream::empty(),
+                &scope.it,
+                &scope.vars,
+                &scope.env).await {
+            Ok(mut stream) => Some(stream.drain_vec().await),
+            Err(err) => {
+                yield Err(err);
+                return;
+            }
+        };
+
+
+        let table = table.unwrap_or_else(|| vec![Value {
+            value: UntaggedValue::row(IndexMap::default()),
+            tag: name_tag,
+        }]);
+
+        let mut idx = 0;
+
+        while let Some(value) = input.next().await {
+            let other = table.get(idx);
+
+            match other {
+                Some(replacement) => {
+                    match merge_values(&value.value, &replacement.value) {
+                        Ok(merged_value) => yield ReturnSuccess::value(merged_value.into_value(&value.tag)),
+                        Err(err) => {
+                            let message = format!("The row at {:?} types mismatch", idx);
+                            yield Err(ShellError::labeled_error("Could not merge", &message, &value.tag));
+                        }
+                    }
+                }
+                None => yield ReturnSuccess::value(value),
+            }
+
+            idx += 1;
+        }
+    };
+
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Merge;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Merge {})
+    }
+}

crates/nu-cli/src/commands/mkdir.rs

@@ -1,8 +1,8 @@
-use crate::commands::command::RunnablePerItemContext;
+use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, Signature, SyntaxShape, Value};
+use nu_protocol::{Signature, SyntaxShape};
 use nu_source::Tagged;
 use std::path::PathBuf;
 
@@ -11,35 +11,60 @@ pub struct Mkdir;
 #[derive(Deserialize)]
 pub struct MkdirArgs {
     pub rest: Vec<Tagged<PathBuf>>,
+    #[serde(rename = "show-created-paths")]
+    pub show_created_paths: bool,
 }
 
-impl PerItemCommand for Mkdir {
+#[async_trait]
+impl WholeStreamCommand for Mkdir {
     fn name(&self) -> &str {
         "mkdir"
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("mkdir").rest(SyntaxShape::Path, "the name(s) of the path(s) to create")
+        Signature::build("mkdir")
+            .rest(SyntaxShape::Path, "the name(s) of the path(s) to create")
+            .switch("show-created-paths", "show the path(s) created.", Some('s'))
     }
 
     fn usage(&self) -> &str {
         "Make directories, creates intermediary directories as required."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        _input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        call_info
-            .process(&raw_args.shell_manager, raw_args.ctrl_c.clone(), mkdir)?
-            .run()
+        mkdir(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Make a directory named foo",
+            example: "mkdir foo",
+            result: None,
+        }]
     }
 }
 
-fn mkdir(args: MkdirArgs, context: &RunnablePerItemContext) -> Result<OutputStream, ShellError> {
-    let shell_manager = context.shell_manager.clone();
-    shell_manager.mkdir(args, context)
+async fn mkdir(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
+    let shell_manager = args.shell_manager.clone();
+    let (args, _) = args.process(&registry).await?;
+
+    shell_manager.mkdir(args, name)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Mkdir;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Mkdir {})
+    }
 }

crates/nu-cli/src/commands/mv.rs

@@ -1,8 +1,8 @@
-use crate::commands::command::RunnablePerItemContext;
+use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{CallInfo, Signature, SyntaxShape, Value};
+use nu_protocol::{Signature, SyntaxShape};
 use nu_source::Tagged;
 use std::path::PathBuf;
 
@@ -14,7 +14,8 @@ pub struct MoveArgs {
     pub dst: Tagged<PathBuf>,
 }
 
-impl PerItemCommand for Move {
+#[async_trait]
+impl WholeStreamCommand for Move {
     fn name(&self) -> &str {
         "mv"
     }
@@ -37,20 +38,59 @@ impl PerItemCommand for Move {
         "Move files or directories."
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        _input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        call_info
-            .process(&raw_args.shell_manager, raw_args.ctrl_c.clone(), mv)?
-            .run()
+        mv(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Rename a file",
+                example: "mv before.txt after.txt",
+                result: None,
+            },
+            Example {
+                description: "Move a file into a directory",
+                example: "mv test.txt my/subdirectory",
+                result: None,
+            },
+            Example {
+                description: "Move many files into a directory",
+                example: "mv *.txt my/subdirectory",
+                result: None,
+            },
+        ]
     }
 }
 
-fn mv(args: MoveArgs, context: &RunnablePerItemContext) -> Result<OutputStream, ShellError> {
-    let shell_manager = context.shell_manager.clone();
-    shell_manager.mv(args, context)
+fn mv(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let name = args.call_info.name_tag.clone();
+        let shell_manager = args.shell_manager.clone();
+        let (args, _) = args.process(&registry).await?;
+        let mut result = shell_manager.mv(args, name)?;
+
+        while let Some(item) = result.next().await {
+            yield item;
+        }
+    };
+
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Move;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Move {})
+    }
 }

crates/nu-cli/src/commands/next.rs

@@ -5,6 +5,7 @@ use nu_protocol::{CommandAction, ReturnSuccess, Signature};
 
 pub struct Next;
 
+#[async_trait]
 impl WholeStreamCommand for Next {
     fn name(&self) -> &str {
         "n"
@@ -18,7 +19,7 @@ impl WholeStreamCommand for Next {
         "Go to next shell."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
@@ -30,3 +31,15 @@ impl WholeStreamCommand for Next {
 fn next(_args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
     Ok(vec![Ok(ReturnSuccess::Action(CommandAction::NextShell))].into())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Next;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Next {})
+    }
+}

crates/nu-cli/src/commands/nth.rs

@@ -2,7 +2,7 @@ use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{ReturnSuccess, Signature, SyntaxShape};
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, Value};
 use nu_source::Tagged;
 
 #[derive(Deserialize)]
@@ -13,6 +13,7 @@ struct NthArgs {
 
 pub struct Nth;
 
+#[async_trait]
 impl WholeStreamCommand for Nth {
     fn name(&self) -> &str {
         "nth"
@@ -32,25 +33,37 @@ impl WholeStreamCommand for Nth {
         "Return only the selected rows"
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, nth)?.run()
+        nth(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Get the second row",
+                example: "echo [first second third] | nth 1",
+                result: Some(vec![Value::from("second")]),
+            },
+            Example {
+                description: "Get the first and third rows",
+                example: "echo [first second third] | nth 0 2",
+                result: Some(vec![Value::from("first"), Value::from("third")]),
+            },
+        ]
     }
 }
 
-fn nth(
-    NthArgs {
-        row_number,
-        rest: and_rows,
-    }: NthArgs,
-    RunnableContext { input, .. }: RunnableContext,
-) -> Result<OutputStream, ShellError> {
-    let stream = input
-        .enumerate()
-        .map(move |(idx, item)| {
+fn nth(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let (NthArgs { row_number, rest: and_rows}, input) = args.process(&registry).await?;
+
+        let mut inp = input.enumerate();
+        while let Some((idx, item)) = inp.next().await {
             let row_number = vec![row_number.clone()];
 
             let row_numbers = vec![&row_number, &and_rows]
@@ -58,18 +71,26 @@ fn nth(
                 .flatten()
                 .collect::<Vec<&Tagged<u64>>>();
 
-            let mut result = VecDeque::new();
-
             if row_numbers
                 .iter()
                 .any(|requested| requested.item == idx as u64)
             {
-                result.push_back(ReturnSuccess::value(item));
+                yield ReturnSuccess::value(item);
             }
-
-            futures::stream::iter(result)
-        })
-        .flatten();
+        }
+    };
 
     Ok(stream.to_output_stream())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Nth;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Nth {})
+    }
+}

crates/nu-cli/src/commands/open.rs

@@ -1,14 +1,20 @@
+use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{
-    CallInfo, CommandAction, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
-};
-use nu_source::{AnchorLocation, Span};
+use nu_protocol::{CommandAction, ReturnSuccess, Signature, SyntaxShape, UntaggedValue};
+use nu_source::{AnchorLocation, Span, Tagged};
 use std::path::{Path, PathBuf};
 
 pub struct Open;
 
-impl PerItemCommand for Open {
+#[derive(Deserialize)]
+pub struct OpenArgs {
+    path: Tagged<PathBuf>,
+    raw: Tagged<bool>,
+}
+
+#[async_trait]
+impl WholeStreamCommand for Open {
     fn name(&self) -> &str {
         "open"
     }
@@ -31,68 +37,55 @@ impl PerItemCommand for Open {
         "Load a file into a cell, convert to table if possible (avoid by appending '--raw')"
     }
 
-    fn run(
+    async fn run(
         &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        raw_args: &RawCommandArgs,
-        _input: Value,
+        args: CommandArgs,
+        registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        run(call_info, raw_args)
+        open(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Opens \"users.csv\" and creates a table from the data",
+            example: "open users.csv",
+            result: None,
+        }]
     }
 }
 
-fn run(call_info: &CallInfo, raw_args: &RawCommandArgs) -> Result<OutputStream, ShellError> {
-    let shell_manager = &raw_args.shell_manager;
-    let cwd = PathBuf::from(shell_manager.path());
+async fn open(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let cwd = PathBuf::from(args.shell_manager.path());
     let full_path = cwd;
+    let registry = registry.clone();
 
-    let path = call_info.args.nth(0).ok_or_else(|| {
-        ShellError::labeled_error(
-            "No file or directory specified",
-            "for command",
-            &call_info.name_tag,
-        )
-    })?;
+    let (OpenArgs { path, raw }, _) = args.process(&registry).await?;
+    let result = fetch(&full_path, &path.item, path.tag.span).await;
 
-    let path_buf = path.as_path()?;
-    let path_str = path_buf.display().to_string();
-    let path_span = path.tag.span;
-    let has_raw = call_info.args.has("raw");
+    let (file_extension, contents, contents_tag) = result?;
 
-    let stream = async_stream! {
-
-        let result = fetch(&full_path, &path_str, path_span).await;
-
-        if let Err(e) = result {
-            yield Err(e);
-            return;
-        }
-        let (file_extension, contents, contents_tag) = result?;
-
-        let file_extension = if has_raw {
-            None
-        } else {
-            // If the extension could not be determined via mimetype, try to use the path
-            // extension. Some file types do not declare their mimetypes (such as bson files).
-            file_extension.or(path_str.split('.').last().map(String::from))
-        };
-
-        let tagged_contents = contents.into_value(&contents_tag);
-
-        if let Some(extension) = file_extension {
-            yield Ok(ReturnSuccess::Action(CommandAction::AutoConvert(tagged_contents, extension)))
-        } else {
-            yield ReturnSuccess::value(tagged_contents);
-        }
+    let file_extension = if raw.item {
+        None
+    } else {
+        // If the extension could not be determined via mimetype, try to use the path
+        // extension. Some file types do not declare their mimetypes (such as bson files).
+        file_extension.or_else(|| path.extension().map(|x| x.to_string_lossy().to_string()))
     };
 
-    Ok(stream.to_output_stream())
+    let tagged_contents = contents.into_value(&contents_tag);
+
+    if let Some(extension) = file_extension {
+        Ok(OutputStream::one(ReturnSuccess::action(
+            CommandAction::AutoConvert(tagged_contents, extension),
+        )))
+    } else {
+        Ok(OutputStream::one(ReturnSuccess::value(tagged_contents)))
+    }
 }
 
 pub async fn fetch(
     cwd: &PathBuf,
-    location: &str,
+    location: &PathBuf,
     span: Span,
 ) -> Result<(Option<String>, UntaggedValue, Tag), ShellError> {
     let mut cwd = cwd.clone();
@@ -252,3 +245,15 @@ fn read_be_u16(input: &[u8]) -> Option<Vec<u16>> {
         Some(result)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Open;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Open {})
+    }
+}

crates/nu-cli/src/commands/parse.rs

@@ -1,143 +0,0 @@
-use crate::commands::PerItemCommand;
-use crate::context::CommandRegistry;
-use crate::prelude::*;
-use nu_errors::ShellError;
-use nu_protocol::{
-    CallInfo, ReturnSuccess, Signature, SyntaxShape, TaggedDictBuilder, UntaggedValue, Value,
-};
-
-use regex::Regex;
-
-#[derive(Debug)]
-enum ParseCommand {
-    Text(String),
-    Column(String),
-}
-
-fn parse(input: &str) -> Vec<ParseCommand> {
-    let mut output = vec![];
-
-    //let mut loop_input = input;
-    let mut loop_input = input.chars();
-    loop {
-        let mut before = String::new();
-
-        while let Some(c) = loop_input.next() {
-            if c == '{' {
-                break;
-            }
-            before.push(c);
-        }
-
-        if !before.is_empty() {
-            output.push(ParseCommand::Text(before.to_string()));
-        }
-        // Look for column as we're now at one
-        let mut column = String::new();
-
-        while let Some(c) = loop_input.next() {
-            if c == '}' {
-                break;
-            }
-            column.push(c);
-        }
-
-        if !column.is_empty() {
-            output.push(ParseCommand::Column(column.to_string()));
-        }
-
-        if before.is_empty() && column.is_empty() {
-            break;
-        }
-    }
-
-    output
-}
-
-fn column_names(commands: &[ParseCommand]) -> Vec<String> {
-    let mut output = vec![];
-
-    for command in commands {
-        if let ParseCommand::Column(c) = command {
-            output.push(c.clone());
-        }
-    }
-
-    output
-}
-
-fn build_regex(commands: &[ParseCommand]) -> String {
-    let mut output = String::new();
-
-    for command in commands {
-        match command {
-            ParseCommand::Text(s) => {
-                output.push_str(&s.replace("(", "\\("));
-            }
-            ParseCommand::Column(_) => {
-                output.push_str("(.*)");
-            }
-        }
-    }
-
-    output
-}
-pub struct Parse;
-
-impl PerItemCommand for Parse {
-    fn name(&self) -> &str {
-        "parse"
-    }
-
-    fn signature(&self) -> Signature {
-        Signature::build("parse").required(
-            "pattern",
-            SyntaxShape::Any,
-            "the pattern to match. Eg) \"{foo}: {bar}\"",
-        )
-    }
-
-    fn usage(&self) -> &str {
-        "Parse columns from string data using a simple pattern."
-    }
-
-    fn run(
-        &self,
-        call_info: &CallInfo,
-        _registry: &CommandRegistry,
-        _raw_args: &RawCommandArgs,
-        value: Value,
-    ) -> Result<OutputStream, ShellError> {
-        //let value_tag = value.tag();
-        let pattern = call_info.args.expect_nth(0)?.as_string()?;
-
-        let parse_pattern = parse(&pattern);
-        let parse_regex = build_regex(&parse_pattern);
-
-        let column_names = column_names(&parse_pattern);
-        let regex = Regex::new(&parse_regex).map_err(|_| {
-            ShellError::labeled_error("Could not parse regex", "could not parse regex", &value.tag)
-        })?;
-
-        let output = if let Ok(s) = value.as_string() {
-            let mut results = vec![];
-            for cap in regex.captures_iter(&s) {
-                let mut dict = TaggedDictBuilder::new(value.tag());
-
-                for (idx, column_name) in column_names.iter().enumerate() {
-                    dict.insert_untagged(
-                        column_name,
-                        UntaggedValue::string(&cap[idx + 1].to_string()),
-                    );
-                }
-
-                results.push(ReturnSuccess::value(dict.into_value()));
-            }
-
-            VecDeque::from(results)
-        } else {
-            VecDeque::new()
-        };
-        Ok(output.into())
-    }
-}

crates/nu-cli/src/commands/parse/command.rs

@@ -0,0 +1,175 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{Signature, SyntaxShape, TaggedDictBuilder, UntaggedValue, Value};
+use nu_source::Tagged;
+
+use regex::Regex;
+
+#[derive(Deserialize)]
+struct Arguments {
+    pattern: Tagged<String>,
+    regex: Tagged<bool>,
+}
+
+pub struct Command;
+
+#[async_trait]
+impl WholeStreamCommand for Command {
+    fn name(&self) -> &str {
+        "parse"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("parse")
+            .required(
+                "pattern",
+                SyntaxShape::String,
+                "the pattern to match. Eg) \"{foo}: {bar}\"",
+            )
+            .switch("regex", "use full regex syntax for patterns", Some('r'))
+    }
+
+    fn usage(&self) -> &str {
+        "Parse columns from string data using a simple pattern."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        operate(args, registry).await
+    }
+}
+
+pub async fn operate(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let name_tag = args.call_info.name_tag.clone();
+    let (Arguments { regex, pattern }, mut input) = args.process(&registry).await?;
+
+    let regex_pattern = if let Tagged { item: true, tag } = regex {
+        Regex::new(&pattern.item)
+            .map_err(|_| ShellError::labeled_error("Invalid regex", "invalid regex", tag.span))?
+    } else {
+        let parse_regex = build_regex(&pattern.item, name_tag.clone())?;
+
+        Regex::new(&parse_regex).map_err(|_| {
+            ShellError::labeled_error("Invalid pattern", "invalid pattern", name_tag.span)
+        })?
+    };
+
+    let columns = column_names(&regex_pattern);
+    let mut parsed: VecDeque<Value> = VecDeque::new();
+
+    while let Some(v) = input.next().await {
+        match v.as_string() {
+            Ok(s) => {
+                let results = regex_pattern.captures_iter(&s);
+
+                for c in results {
+                    let mut dict = TaggedDictBuilder::new(&v.tag);
+
+                    for (column_name, cap) in columns.iter().zip(c.iter().skip(1)) {
+                        let cap_string = cap.map(|v| v.as_str()).unwrap_or("").to_string();
+                        dict.insert_untagged(column_name, UntaggedValue::string(cap_string));
+                    }
+
+                    parsed.push_back(dict.into_value());
+                }
+            }
+            Err(_) => {
+                return Err(ShellError::labeled_error_with_secondary(
+                    "Expected string input",
+                    "expected string input",
+                    &name_tag,
+                    "value originated here",
+                    v.tag,
+                ))
+            }
+        }
+    }
+
+    Ok(futures::stream::iter(parsed).to_output_stream())
+}
+
+fn build_regex(input: &str, tag: Tag) -> Result<String, ShellError> {
+    let mut output = "(?s)\\A".to_string();
+
+    //let mut loop_input = input;
+    let mut loop_input = input.chars().peekable();
+    loop {
+        let mut before = String::new();
+        while let Some(c) = loop_input.next() {
+            if c == '{' {
+                // If '{{', still creating a plaintext parse command, but just for a single '{' char
+                if loop_input.peek() == Some(&'{') {
+                    let _ = loop_input.next();
+                } else {
+                    break;
+                }
+            }
+            before.push(c);
+        }
+
+        if !before.is_empty() {
+            output.push_str(&regex::escape(&before));
+        }
+
+        // Look for column as we're now at one
+        let mut column = String::new();
+        while let Some(c) = loop_input.next() {
+            if c == '}' {
+                break;
+            }
+            column.push(c);
+
+            if loop_input.peek().is_none() {
+                return Err(ShellError::labeled_error(
+                    "Found opening `{` without an associated closing `}`",
+                    "invalid parse pattern",
+                    tag,
+                ));
+            }
+        }
+
+        if !column.is_empty() {
+            output.push_str("(?P<");
+            output.push_str(&column);
+            output.push_str(">.*?)");
+        }
+
+        if before.is_empty() && column.is_empty() {
+            break;
+        }
+    }
+
+    output.push_str("\\z");
+    Ok(output)
+}
+
+fn column_names(regex: &Regex) -> Vec<String> {
+    regex
+        .capture_names()
+        .enumerate()
+        .skip(1)
+        .map(|(i, name)| {
+            name.map(String::from)
+                .unwrap_or_else(|| format!("Capture{}", i))
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Command;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Command {})
+    }
+}

crates/nu-cli/src/commands/parse/mod.rs

@@ -0,0 +1,3 @@
+mod command;
+
+pub use command::Command as Parse;

crates/nu-cli/src/commands/pivot.rs

@@ -18,6 +18,7 @@ pub struct PivotArgs {
     ignore_titles: bool,
 }
 
+#[async_trait]
 impl WholeStreamCommand for Pivot {
     fn name(&self) -> &str {
         "pivot"
@@ -45,25 +46,28 @@ impl WholeStreamCommand for Pivot {
         "Pivots the table contents so rows become columns and columns become rows."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, pivot)?.run()
+        pivot(args, registry)
     }
 }
 
-pub fn pivot(args: PivotArgs, context: RunnableContext) -> Result<OutputStream, ShellError> {
+pub fn pivot(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
     let stream = async_stream! {
-        let input = context.input.into_vec().await;
+        let (args, mut input): (PivotArgs, _) = args.process(&registry).await?;
+        let input = input.into_vec().await;
 
         let descs = merge_descriptors(&input);
 
         let mut headers: Vec<String> = vec![];
 
         if args.rest.len() > 0 && args.header_row {
-            yield Err(ShellError::labeled_error("Can not provide header names and use header row", "using header row", context.name));
+            yield Err(ShellError::labeled_error("Can not provide header names and use header row", "using header row", name));
             return;
         }
 
@@ -75,17 +79,17 @@ pub fn pivot(args: PivotArgs, context: RunnableContext) -> Result<OutputStream,
                             if let Ok(s) = x.as_string() {
                                 headers.push(s.to_string());
                             } else {
-                                yield Err(ShellError::labeled_error("Header row needs string headers", "used non-string headers", context.name));
+                                yield Err(ShellError::labeled_error("Header row needs string headers", "used non-string headers", name));
                                 return;
                             }
                         }
                         _ => {
-                            yield Err(ShellError::labeled_error("Header row is incomplete and can't be used", "using incomplete header row", context.name));
+                            yield Err(ShellError::labeled_error("Header row is incomplete and can't be used", "using incomplete header row", name));
                             return;
                         }
                     }
                 } else {
-                    yield Err(ShellError::labeled_error("Header row is incomplete and can't be used", "using incomplete header row", context.name));
+                    yield Err(ShellError::labeled_error("Header row is incomplete and can't be used", "using incomplete header row", name));
                     return;
                 }
             }
@@ -107,7 +111,7 @@ pub fn pivot(args: PivotArgs, context: RunnableContext) -> Result<OutputStream,
 
         for desc in descs {
             let mut column_num: usize = 0;
-            let mut dict = TaggedDictBuilder::new(&context.name);
+            let mut dict = TaggedDictBuilder::new(&name);
 
             if !args.ignore_titles && !args.header_row {
                 dict.insert_untagged(headers[column_num].clone(), UntaggedValue::string(desc.clone()));
@@ -134,3 +138,15 @@ pub fn pivot(args: PivotArgs, context: RunnableContext) -> Result<OutputStream,
 
     Ok(OutputStream::new(stream))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Pivot;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Pivot {})
+    }
+}

crates/nu-cli/src/commands/plugin.rs

@@ -3,7 +3,7 @@ use crate::prelude::*;
 use derive_new::new;
 use log::trace;
 use nu_errors::ShellError;
-use nu_protocol::{Primitive, ReturnSuccess, ReturnValue, Signature, UntaggedValue, Value};
+use nu_protocol::{ReturnSuccess, ReturnValue, Signature, UntaggedValue, Value};
 use serde::{self, Deserialize, Serialize};
 use std::io::prelude::*;
 use std::io::BufReader;
@@ -42,6 +42,7 @@ pub struct PluginCommand {
     config: Signature,
 }
 
+#[async_trait]
 impl WholeStreamCommand for PluginCommand {
     fn name(&self) -> &str {
         &self.name
@@ -55,7 +56,7 @@ impl WholeStreamCommand for PluginCommand {
         &self.config.usage
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
@@ -70,180 +71,80 @@ pub fn filter_plugin(
     registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
     trace!("filter_plugin :: {}", path);
+    let registry = registry.clone();
 
-    let scope = &args
-        .call_info
-        .scope
-        .clone()
-        .set_it(UntaggedValue::string("$it").into_untagged_value());
+    let scope = args.call_info.scope.clone();
 
-    let args = args.evaluate_once_with_scope(registry, &scope)?;
+    let stream = async_stream! {
+        let mut args = args.evaluate_once_with_scope(&registry, &scope).await?;
 
-    let mut child = std::process::Command::new(path)
-        .stdin(std::process::Stdio::piped())
-        .stdout(std::process::Stdio::piped())
-        .spawn()
-        .expect("Failed to spawn child process");
+        let mut child = std::process::Command::new(path)
+            .stdin(std::process::Stdio::piped())
+            .stdout(std::process::Stdio::piped())
+            .spawn()
+            .expect("Failed to spawn child process");
 
-    let mut bos: VecDeque<Value> = VecDeque::new();
-    bos.push_back(UntaggedValue::Primitive(Primitive::BeginningOfStream).into_untagged_value());
-    let bos = futures::stream::iter(bos);
+        let call_info = args.call_info.clone();
 
-    let mut eos: VecDeque<Value> = VecDeque::new();
-    eos.push_back(UntaggedValue::Primitive(Primitive::EndOfStream).into_untagged_value());
-    let eos = futures::stream::iter(eos);
+        trace!("filtering :: {:?}", call_info);
 
-    let call_info = args.call_info.clone();
+        // Beginning of the stream
+        {
+            let stdin = child.stdin.as_mut().expect("Failed to open stdin");
+            let stdout = child.stdout.as_mut().expect("Failed to open stdout");
 
-    trace!("filtering :: {:?}", call_info);
+            let mut reader = BufReader::new(stdout);
 
-    let stream = bos
-        .chain(args.input)
-        .chain(eos)
-        .map(move |v| match v {
-            Value {
-                value: UntaggedValue::Primitive(Primitive::BeginningOfStream),
-                ..
-            } => {
-                let stdin = child.stdin.as_mut().expect("Failed to open stdin");
-                let stdout = child.stdout.as_mut().expect("Failed to open stdout");
+            let request = JsonRpc::new("begin_filter", call_info.clone());
+            let request_raw = serde_json::to_string(&request);
 
-                let mut reader = BufReader::new(stdout);
-
-                let request = JsonRpc::new("begin_filter", call_info.clone());
-                let request_raw = serde_json::to_string(&request);
-
-                match request_raw {
-                    Err(_) => {
-                        let mut result = VecDeque::new();
-                        result.push_back(Err(ShellError::labeled_error(
-                            "Could not load json from plugin",
-                            "could not load json from plugin",
-                            &call_info.name_tag,
-                        )));
-                        return result;
-                    }
-                    Ok(request_raw) => match stdin.write(format!("{}\n", request_raw).as_bytes()) {
-                        Ok(_) => {}
-                        Err(err) => {
-                            let mut result = VecDeque::new();
-                            result.push_back(Err(ShellError::unexpected(format!("{}", err))));
-                            return result;
-                        }
-                    },
+            match request_raw {
+                Err(_) => {
+                    yield Err(ShellError::labeled_error(
+                        "Could not load json from plugin",
+                        "could not load json from plugin",
+                        &call_info.name_tag,
+                    ));
                 }
-
-                let mut input = String::new();
-                match reader.read_line(&mut input) {
-                    Ok(_) => {
-                        let response = serde_json::from_str::<NuResult>(&input);
-                        match response {
-                            Ok(NuResult::response { params }) => match params {
-                                Ok(params) => params,
-                                Err(e) => {
-                                    let mut result = VecDeque::new();
-                                    result.push_back(ReturnValue::Err(e));
-                                    result
-                                }
-                            },
-                            Err(e) => {
-                                let mut result = VecDeque::new();
-                                result.push_back(Err(ShellError::untagged_runtime_error(format!(
-                                    "Error while processing begin_filter response: {:?} {}",
-                                    e, input
-                                ))));
-                                result
-                            }
-                        }
-                    }
-                    Err(e) => {
-                        let mut result = VecDeque::new();
-                        result.push_back(Err(ShellError::untagged_runtime_error(format!(
-                            "Error while reading begin_filter response: {:?}",
-                            e
-                        ))));
-                        result
-                    }
-                }
-            }
-            Value {
-                value: UntaggedValue::Primitive(Primitive::EndOfStream),
-                ..
-            } => {
-                let stdin = child.stdin.as_mut().expect("Failed to open stdin");
-                let stdout = child.stdout.as_mut().expect("Failed to open stdout");
-
-                let mut reader = BufReader::new(stdout);
-
-                let request: JsonRpc<std::vec::Vec<Value>> = JsonRpc::new("end_filter", vec![]);
-                let request_raw = match serde_json::to_string(&request) {
-                    Ok(req) => req,
+                Ok(request_raw) => match stdin.write(format!("{}\n", request_raw).as_bytes()) {
+                    Ok(_) => {}
                     Err(err) => {
-                        let mut result = VecDeque::new();
-                        result.push_back(Err(ShellError::unexpected(format!("{}", err))));
-                        return result;
+                        yield Err(ShellError::unexpected(format!("{}", err)));
                     }
-                };
+                },
+            }
 
-                let _ = stdin.write(format!("{}\n", request_raw).as_bytes()); // TODO: Handle error
-
-                let mut input = String::new();
-                let result = match reader.read_line(&mut input) {
-                    Ok(_) => {
-                        let response = serde_json::from_str::<NuResult>(&input);
-                        match response {
-                            Ok(NuResult::response { params }) => match params {
-                                Ok(params) => {
-                                    let request: JsonRpc<std::vec::Vec<Value>> =
-                                        JsonRpc::new("quit", vec![]);
-                                    let request_raw = serde_json::to_string(&request);
-                                    match request_raw {
-                                        Ok(request_raw) => {
-                                            let _ = stdin.write(format!("{}\n", request_raw).as_bytes()); // TODO: Handle error
-                                        }
-                                        Err(e) => {
-                                            let mut result = VecDeque::new();
-                                            result.push_back(Err(ShellError::untagged_runtime_error(format!(
-                                                "Error while processing begin_filter response: {:?} {}",
-                                                e, input
-                                            ))));
-                                            return result;
-                                        }
-                                    }
-
-                                    params
-                                }
-                                Err(e) => {
-                                    let mut result = VecDeque::new();
-                                    result.push_back(ReturnValue::Err(e));
-                                    result
-                                }
-                            },
+            let mut input = String::new();
+            match reader.read_line(&mut input) {
+                Ok(_) => {
+                    let response = serde_json::from_str::<NuResult>(&input);
+                    match response {
+                        Ok(NuResult::response { params }) => match params {
+                            Ok(params) => for param in params { yield param },
                             Err(e) => {
-                                let mut result = VecDeque::new();
-                                result.push_back(Err(ShellError::untagged_runtime_error(format!(
-                                    "Error while processing end_filter response: {:?} {}",
-                                    e, input
-                                ))));
-                                result
+                                yield ReturnValue::Err(e);
                             }
+                        },
+                        Err(e) => {
+                            yield Err(ShellError::untagged_runtime_error(format!(
+                                "Error while processing begin_filter response: {:?} {}",
+                                e, input
+                            )));
                         }
                     }
-                    Err(e) => {
-                        let mut result = VecDeque::new();
-                        result.push_back(Err(ShellError::untagged_runtime_error(format!(
-                            "Error while reading end_filter: {:?}",
-                            e
-                        ))));
-                        result
-                    }
-                };
-
-                let _ = child.wait();
-
-                result
+                }
+                Err(e) => {
+                    yield Err(ShellError::untagged_runtime_error(format!(
+                        "Error while reading begin_filter response: {:?}",
+                        e
+                    )));
+                }
             }
-            _ => {
+        }
+
+        // Stream contents
+        {
+            while let Some(v) = args.input.next().await {
                 let stdin = child.stdin.as_mut().expect("Failed to open stdin");
                 let stdout = child.stdout.as_mut().expect("Failed to open stdout");
 
@@ -256,12 +157,10 @@ pub fn filter_plugin(
                         let _ = stdin.write(format!("{}\n", request_raw).as_bytes()); // TODO: Handle error
                     }
                     Err(e) => {
-                        let mut result = VecDeque::new();
-                        result.push_back(Err(ShellError::untagged_runtime_error(format!(
+                        yield Err(ShellError::untagged_runtime_error(format!(
                             "Error while processing filter response: {:?}",
                             e
-                        ))));
-                        return result;
+                        )));
                     }
                 }
 
@@ -271,36 +170,110 @@ pub fn filter_plugin(
                         let response = serde_json::from_str::<NuResult>(&input);
                         match response {
                             Ok(NuResult::response { params }) => match params {
-                                Ok(params) => params,
+                                Ok(params) => for param in params { yield param },
                                 Err(e) => {
-                                    let mut result = VecDeque::new();
-                                    result.push_back(ReturnValue::Err(e));
-                                    result
+                                    yield ReturnValue::Err(e);
                                 }
                             },
                             Err(e) => {
-                                let mut result = VecDeque::new();
-                                result.push_back(Err(ShellError::untagged_runtime_error(format!(
+                                yield Err(ShellError::untagged_runtime_error(format!(
                                     "Error while processing filter response: {:?}\n== input ==\n{}",
                                     e, input
-                                ))));
-                                result
+                                )));
                             }
                         }
                     }
                     Err(e) => {
-                        let mut result = VecDeque::new();
-                        result.push_back(Err(ShellError::untagged_runtime_error(format!(
+                        yield Err(ShellError::untagged_runtime_error(format!(
                             "Error while reading filter response: {:?}",
                             e
-                        ))));
-                        result
+                        )));
                     }
                 }
+
             }
-        })
-        .map(futures::stream::iter) // convert to a stream
-        .flatten();
+        }
+
+        // post stream contents
+        {
+            let stdin = child.stdin.as_mut().expect("Failed to open stdin");
+            let stdout = child.stdout.as_mut().expect("Failed to open stdout");
+
+            let mut reader = BufReader::new(stdout);
+
+            let request: JsonRpc<std::vec::Vec<Value>> = JsonRpc::new("end_filter", vec![]);
+            let request_raw = serde_json::to_string(&request);
+
+            match request_raw {
+                Err(_) => {
+                    yield Err(ShellError::labeled_error(
+                        "Could not load json from plugin",
+                        "could not load json from plugin",
+                        &call_info.name_tag,
+                    ));
+                }
+                Ok(request_raw) => match stdin.write(format!("{}\n", request_raw).as_bytes()) {
+                    Ok(_) => {}
+                    Err(err) => {
+                        yield Err(ShellError::unexpected(format!("{}", err)));
+                    }
+                },
+            }
+
+            let mut input = String::new();
+            match reader.read_line(&mut input) {
+                Ok(_) => {
+                    let response = serde_json::from_str::<NuResult>(&input);
+                    match response {
+                        Ok(NuResult::response { params }) => match params {
+                            Ok(params) => for param in params { yield param },
+                            Err(e) => {
+                                yield ReturnValue::Err(e);
+                            }
+                        },
+                        Err(e) => {
+                            yield Err(ShellError::untagged_runtime_error(format!(
+                                "Error while processing end_filter response: {:?} {}",
+                                e, input
+                            )));
+                        }
+                    }
+                }
+                Err(e) => {
+                    yield Err(ShellError::untagged_runtime_error(format!(
+                        "Error while reading end_filter response: {:?}",
+                        e
+                    )));
+                }
+            }
+        }
+
+        // End of the stream
+        {
+            let stdin = child.stdin.as_mut().expect("Failed to open stdin");
+            let stdout = child.stdout.as_mut().expect("Failed to open stdout");
+
+            let mut reader = BufReader::new(stdout);
+
+            let request: JsonRpc<std::vec::Vec<Value>> = JsonRpc::new("quit", vec![]);
+            let request_raw = serde_json::to_string(&request);
+
+            match request_raw {
+                Ok(request_raw) => {
+                    let _ = stdin.write(format!("{}\n", request_raw).as_bytes()); // TODO: Handle error
+                }
+                Err(e) => {
+                    yield Err(ShellError::untagged_runtime_error(format!(
+                        "Error while processing quit response: {:?}",
+                        e
+                    )));
+                    return;
+                }
+            }
+        }
+
+        let _ = child.wait();
+    };
 
     Ok(stream.to_output_stream())
 }
@@ -312,6 +285,7 @@ pub struct PluginSink {
     config: Signature,
 }
 
+#[async_trait]
 impl WholeStreamCommand for PluginSink {
     fn name(&self) -> &str {
         &self.name
@@ -325,7 +299,7 @@ impl WholeStreamCommand for PluginSink {
         &self.config.usage
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
@@ -339,10 +313,11 @@ pub fn sink_plugin(
     args: CommandArgs,
     registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
-    let call_info = args.call_info.clone();
-
+    let registry = registry.clone();
     let stream = async_stream! {
+        let args = args.evaluate_once(&registry).await?;
+        let call_info = args.call_info.clone();
+
         let input: Vec<Value> = args.input.collect().await;
 
         let request = JsonRpc::new("sink", (call_info.clone(), input));

crates/nu-cli/src/commands/prepend.rs

@@ -2,7 +2,7 @@ use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{Signature, SyntaxShape, Value};
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
 
 #[derive(Deserialize)]
 struct PrependArgs {
@@ -11,6 +11,7 @@ struct PrependArgs {
 
 pub struct Prepend;
 
+#[async_trait]
 impl WholeStreamCommand for Prepend {
     fn name(&self) -> &str {
         "prepend"
@@ -28,20 +29,51 @@ impl WholeStreamCommand for Prepend {
         "Prepend the given row to the front of the table"
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, prepend)?.run()
+        prepend(args, registry)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Add something to the beginning of a list or table",
+            example: "echo [2 3 4] | prepend 1",
+            result: Some(vec![
+                UntaggedValue::int(1).into(),
+                UntaggedValue::int(2).into(),
+                UntaggedValue::int(3).into(),
+                UntaggedValue::int(4).into(),
+            ]),
+        }]
     }
 }
 
-fn prepend(
-    PrependArgs { row }: PrependArgs,
-    RunnableContext { input, .. }: RunnableContext,
-) -> Result<OutputStream, ShellError> {
-    let prepend = futures::stream::iter(vec![row]);
+fn prepend(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
 
-    Ok(prepend.chain(input).to_output_stream())
+    let stream = async_stream! {
+        let (PrependArgs { row }, mut input) = args.process(&registry).await?;
+
+        yield ReturnSuccess::value(row);
+        while let Some(item) = input.next().await {
+            yield ReturnSuccess::value(item);
+        }
+    };
+
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Prepend;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Prepend {})
+    }
 }

crates/nu-cli/src/commands/prev.rs

@@ -6,6 +6,7 @@ use crate::commands::WholeStreamCommand;
 
 pub struct Previous;
 
+#[async_trait]
 impl WholeStreamCommand for Previous {
     fn name(&self) -> &str {
         "p"
@@ -19,7 +20,7 @@ impl WholeStreamCommand for Previous {
         "Go to previous shell."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
@@ -31,3 +32,15 @@ impl WholeStreamCommand for Previous {
 fn previous(_args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
     Ok(vec![Ok(ReturnSuccess::Action(CommandAction::PreviousShell))].into())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Previous;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Previous {})
+    }
+}

crates/nu-cli/src/commands/pwd.rs

@@ -5,6 +5,7 @@ use nu_protocol::Signature;
 
 pub struct Pwd;
 
+#[async_trait]
 impl WholeStreamCommand for Pwd {
     fn name(&self) -> &str {
         "pwd"
@@ -18,17 +19,42 @@ impl WholeStreamCommand for Pwd {
         "Output the current working directory."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        pwd(args, registry)
+        pwd(args, registry).await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Print the current working directory",
+            example: "pwd",
+            result: None,
+        }]
     }
 }
 
-pub fn pwd(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+pub async fn pwd(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
     let shell_manager = args.shell_manager.clone();
-    let args = args.evaluate_once(registry)?;
+    let args = args.evaluate_once(&registry).await?;
+
     shell_manager.pwd(args)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Pwd;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Pwd {})
+    }
+}

crates/nu-cli/src/commands/range.rs

@@ -3,7 +3,7 @@ use crate::context::CommandRegistry;
 use crate::deserializer::NumericRange;
 use crate::prelude::*;
 use nu_errors::ShellError;
-use nu_protocol::{Signature, SyntaxShape};
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape};
 use nu_source::Tagged;
 
 #[derive(Deserialize)]
@@ -13,6 +13,7 @@ struct RangeArgs {
 
 pub struct Range;
 
+#[async_trait]
 impl WholeStreamCommand for Range {
     fn name(&self) -> &str {
         "range"
@@ -30,25 +31,43 @@ impl WholeStreamCommand for Range {
         "Return only the selected rows"
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, range)?.run()
+        range(args, registry)
     }
 }
 
-fn range(
-    RangeArgs { area }: RangeArgs,
-    RunnableContext { input, .. }: RunnableContext,
-) -> Result<OutputStream, ShellError> {
-    let range = area.item;
-    let (from, _) = range.from;
-    let (to, _) = range.to;
+fn range(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let registry = registry.clone();
+    let stream = async_stream! {
+        let (RangeArgs { area }, mut input) = args.process(&registry).await?;
+        let range = area.item;
+        let (from, _) = range.from;
+        let (to, _) = range.to;
 
-    let from = *from as usize;
-    let to = *to as usize;
+        let from = *from as usize;
+        let to = *to as usize;
 
-    Ok(input.skip(from).take(to - from + 1).to_output_stream())
+        let mut inp = input.skip(from).take(to - from + 1);
+        while let Some(item) = inp.next().await {
+            yield ReturnSuccess::value(item);
+        }
+    };
+
+    Ok(stream.to_output_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Range;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Range {})
+    }
 }

crates/nu-cli/src/commands/reduce_by.rs

@@ -13,6 +13,7 @@ pub struct ReduceByArgs {
     reduce_with: Option<Tagged<String>>,
 }
 
+#[async_trait]
 impl WholeStreamCommand for ReduceBy {
     fn name(&self) -> &str {
         "reduce-by"
@@ -31,42 +32,52 @@ impl WholeStreamCommand for ReduceBy {
         "Creates a new table with the data from the tables rows reduced by the command given."
     }
 
-    fn run(
+    async fn run(
         &self,
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        args.process(registry, reduce_by)?.run()
+        reduce_by(args, registry).await
     }
 }
 
-pub fn reduce_by(
-    ReduceByArgs { reduce_with }: ReduceByArgs,
-    RunnableContext { input, name, .. }: RunnableContext,
+pub async fn reduce_by(
+    args: CommandArgs,
+    registry: &CommandRegistry,
 ) -> Result<OutputStream, ShellError> {
-    let stream = async_stream! {
-        let values: Vec<Value> = input.collect().await;
+    let registry = registry.clone();
+    let name = args.call_info.name_tag.clone();
+    let (ReduceByArgs { reduce_with }, mut input) = args.process(&registry).await?;
+    let values: Vec<Value> = input.collect().await;
 
-        if values.is_empty() {
-            yield Err(ShellError::labeled_error(
-                    "Expected table from pipeline",
-                    "requires a table input",
-                    name
-                ))
-        } else {
+    if values.is_empty() {
+        return Err(ShellError::labeled_error(
+            "Expected table from pipeline",
+            "requires a table input",
+            name,
+        ));
+    }
 
-            let reduce_with = if let Some(reducer) = reduce_with {
-                Some(reducer.item().clone())
-            } else {
-                None
-            };
-
-            match reduce(&values[0], reduce_with, name) {
-                Ok(reduced) => yield ReturnSuccess::value(reduced),
-                Err(err) => yield Err(err)
-            }
-        }
+    let reduce_with = if let Some(reducer) = reduce_with {
+        Some(reducer.item().clone())
+    } else {
+        None
     };
 
-    Ok(stream.to_output_stream())
+    match reduce(&values[0], reduce_with, name) {
+        Ok(reduced) => Ok(OutputStream::one(ReturnSuccess::value(reduced))),
+        Err(err) => Err(err),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::ReduceBy;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(ReduceBy {})
+    }
 }