2f18b9c856
# Description After this pr, nushell is able to raise errors with a backtrace, which should make users easier to debug. To enable the feature, users need to set env variable via `$env.NU_BACKTRACE = 1`. But yeah it might not work perfectly, there are some corner cases which might not be handled. I think it should close #13379 in another way. ### About the change The implementation mostly contained with 2 parts: 1. introduce a new `ChainedError` struct as well as a new `ShellError::ChainedError` variant. If `eval_instruction` returned an error, it converts the error to `ShellError::ChainedError`. `ChainedError` struct is responsable to display errors properly. It needs to handle the following 2 cases: - if we run a function which runs `error make` internally, it needs to display the error itself along with caller span. - if we run a `error make` directly, or some commands directly returns an error, we just want nushell raise an error about `error make`. 2. Attach caller spans to `ListStream` and `ByteStream`, because they are lazy streams, and *only* contains the span that runs it directly(like `^false`, for example), so nushell needs to add all caller spans to the stream. For example: in `def a [] { ^false }; def b [] { a; 33 }; b`, when we run `b`, which runs `a`, which runs `^false`, the `ByteStream` only contains the span of `^false`, we need to make it contains the span of `a`, so nushell is able to get all spans if something bad happened. This behavior is happened after running `Instruction::Call`, if it returns a `ByteStream` and `ListStream`, it will call `push_caller_span` method to attach call spans. # User-Facing Changes It's better to demostrate how it works by examples, given the following definition: ```nushell > $env.NU_BACKTRACE = 1 > def a [x] { if $x == 3 { error make {msg: 'a custom error'}}} > def a_2 [x] { if $x == 3 { ^false } else { $x } } > def a_3 [x] { if $x == 3 { [1 2 3] | each {error make {msg: 'a custom error inside list stream'} } } } > def b [--list-stream --external] { if $external == true { # error with non-zero exit code, which is generated from external command. a_2 1; a_2 3; a_2 2 } else if $list_stream == true { # error generated by list-stream a_3 1; a_3 3; a_3 2 } else { # error generated by command directly a 1; a 2; a 3 } } ``` Run `b` directly shows the following error: <details> ```nushell Error: chained_error × oops ╭─[entry #27:1:1] 1 │ b · ┬ · ╰── error happened when running this ╰──── Error: chained_error × oops ╭─[entry #26:10:19] 9 │ # error generated by command directly 10 │ a 1; a 2; a 3 · ┬ · ╰── error happened when running this 11 │ } ╰──── Error: × a custom error ╭─[entry #6:1:26] 1 │ def a [x] { if $x == 3 { error make {msg: 'a custom error'}}} · ─────┬──── · ╰── originates from here ╰──── ``` </details> Run `b --list-stream` shows the following error <details> ```nushell Error: chained_error × oops ╭─[entry #28:1:1] 1 │ b --list-stream · ┬ · ╰── error happened when running this ╰──── Error: nu:🐚:eval_block_with_input × Eval block failed with pipeline input ╭─[entry #26:7:16] 6 │ # error generated by list-stream 7 │ a_3 1; a_3 3; a_3 2 · ─┬─ · ╰── source value 8 │ } else { ╰──── Error: nu:🐚:eval_block_with_input × Eval block failed with pipeline input ╭─[entry #23:1:29] 1 │ def a_3 [x] { if $x == 3 { [1 2 3] | each {error make {msg: 'a custom error inside list stream'} } } } · ┬ · ╰── source value ╰──── Error: × a custom error inside list stream ╭─[entry #23:1:44] 1 │ def a_3 [x] { if $x == 3 { [1 2 3] | each {error make {msg: 'a custom error inside list stream'} } } } · ─────┬──── · ╰── originates from here ╰──── ``` </details> Run `b --external` shows the following error: <details> ```nushell Error: chained_error × oops ╭─[entry #29:1:1] 1 │ b --external · ┬ · ╰── error happened when running this ╰──── Error: nu:🐚:eval_block_with_input × Eval block failed with pipeline input ╭─[entry #26:4:16] 3 │ # error with non-zero exit code, which is generated from external command. 4 │ a_2 1; a_2 3; a_2 2 · ─┬─ · ╰── source value 5 │ } else if $list_stream == true { ╰──── Error: nu:🐚:non_zero_exit_code × External command had a non-zero exit code ╭─[entry #7:1:29] 1 │ def a_2 [x] { if $x == 3 { ^false } else { $x } } · ──┬── · ╰── exited with code 1 ╰──── ``` </details> It also added a message to guide the usage of NU_BACKTRACE, see the last line in the following example: ```shell ls asdfasd Error: nu:🐚:io::not_found × I/O error ╰─▶ × Entity not found ╭─[entry #17:1:4] 1 │ ls asdfasd · ───┬─── · ╰── Entity not found ╰──── help: The error occurred at '/home/windsoilder/projects/nushell/asdfasd' set the `NU_BACKTRACE=1` environment variable to display a backtrace. ``` # Tests + Formatting Added some tests for the behavior. # After Submitting |
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|---|---|---|
| .cargo | ||
| .githooks | ||
| .github | ||
| assets | ||
| benches | ||
| clippy/wasm | ||
| crates | ||
| devdocs | ||
| docker | ||
| scripts | ||
| src | ||
| tests | ||
| wix | ||
| .gitattributes | ||
| .gitignore | ||
| Cargo.lock | ||
| Cargo.toml | ||
| CITATION.cff | ||
| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| Cross.toml | ||
| LICENSE | ||
| README.md | ||
| rust-toolchain.toml | ||
| SECURITY.md | ||
| toolkit.nu | ||
| typos.toml | ||
Nushell
A new type of shell.
Table of Contents
- Status
- Learning About Nu
- Installation
- Configuration
- Philosophy
- Goals
- Officially Supported By
- Contributing
- License
Status
This project has reached a minimum-viable-product level of quality. Many people use it as their daily driver, but it may be unstable for some commands. Nu's design is subject to change as it matures.
Learning About Nu
The Nushell book is the primary source of Nushell documentation. You can find a full list of Nu commands in the book, and we have many examples of using Nu in our cookbook.
We're also active on Discord; come and chat with us!
Installation
To quickly install Nu:
# Linux and macOS
brew install nushell
# Windows
winget install nushell
To use Nu in GitHub Action, check setup-nu for more detail.
Detailed installation instructions can be found in the installation chapter of the book. Nu is available via many package managers:
For details about which platforms the Nushell team actively supports, see our platform support policy.
Configuration
The default configurations can be found at sample_config which are the configuration files one gets when they startup Nushell for the first time.
It sets all of the default configuration to run Nushell. From here one can then customize this file for their specific needs.
To see where config.nu is located on your system simply type this command.
$nu.config-path
Please see our book for all of the Nushell documentation.
Philosophy
Nu draws inspiration from projects like PowerShell, functional programming languages, and modern CLI tools. Rather than thinking of files and data as raw streams of text, Nu looks at each input as something with structure. For example, when you list the contents of a directory what you get back is a table of rows, where each row represents an item in that directory. These values can be piped through a series of steps, in a series of commands called a 'pipeline'.
Pipelines
In Unix, it's common to pipe between commands to split up a sophisticated command over multiple steps. Nu takes this a step further and builds heavily on the idea of pipelines. As in the Unix philosophy, Nu allows commands to output to stdout and read from stdin. Additionally, commands can output structured data (you can think of this as a third kind of stream). Commands that work in the pipeline fit into one of three categories:
- Commands that produce a stream (e.g.,
ls) - Commands that filter a stream (e.g.,
where type == "dir") - Commands that consume the output of the pipeline (e.g.,
table)
Commands are separated by the pipe symbol (|) to denote a pipeline flowing left to right.
ls | where type == "dir" | table
# => ╭────┬──────────┬──────┬─────────┬───────────────╮
# => │ # │ name │ type │ size │ modified │
# => ├────┼──────────┼──────┼─────────┼───────────────┤
# => │ 0 │ .cargo │ dir │ 0 B │ 9 minutes ago │
# => │ 1 │ assets │ dir │ 0 B │ 2 weeks ago │
# => │ 2 │ crates │ dir │ 4.0 KiB │ 2 weeks ago │
# => │ 3 │ docker │ dir │ 0 B │ 2 weeks ago │
# => │ 4 │ docs │ dir │ 0 B │ 2 weeks ago │
# => │ 5 │ images │ dir │ 0 B │ 2 weeks ago │
# => │ 6 │ pkg_mgrs │ dir │ 0 B │ 2 weeks ago │
# => │ 7 │ samples │ dir │ 0 B │ 2 weeks ago │
# => │ 8 │ src │ dir │ 4.0 KiB │ 2 weeks ago │
# => │ 9 │ target │ dir │ 0 B │ a day ago │
# => │ 10 │ tests │ dir │ 4.0 KiB │ 2 weeks ago │
# => │ 11 │ wix │ dir │ 0 B │ 2 weeks ago │
# => ╰────┴──────────┴──────┴─────────┴───────────────╯
Because most of the time you'll want to see the output of a pipeline, table is assumed.
We could have also written the above:
ls | where type == "dir"
Being able to use the same commands and compose them differently is an important philosophy in Nu.
For example, we could use the built-in ps command to get a list of the running processes, using the same where as above.
ps | where cpu > 0
# => ╭───┬───────┬───────────┬───────┬───────────┬───────────╮
# => │ # │ pid │ name │ cpu │ mem │ virtual │
# => ├───┼───────┼───────────┼───────┼───────────┼───────────┤
# => │ 0 │ 2240 │ Slack.exe │ 16.40 │ 178.3 MiB │ 232.6 MiB │
# => │ 1 │ 16948 │ Slack.exe │ 16.32 │ 205.0 MiB │ 197.9 MiB │
# => │ 2 │ 17700 │ nu.exe │ 3.77 │ 26.1 MiB │ 8.8 MiB │
# => ╰───┴───────┴───────────┴───────┴───────────┴───────────╯
Opening files
Nu can load file and URL contents as raw text or structured data (if it recognizes the format). For example, you can load a .toml file as structured data and explore it:
open Cargo.toml
# => ╭──────────────────┬────────────────────╮
# => │ bin │ [table 1 row] │
# => │ dependencies │ {record 25 fields} │
# => │ dev-dependencies │ {record 8 fields} │
# => │ features │ {record 10 fields} │
# => │ package │ {record 13 fields} │
# => │ patch │ {record 1 field} │
# => │ profile │ {record 3 fields} │
# => │ target │ {record 3 fields} │
# => │ workspace │ {record 1 field} │
# => ╰──────────────────┴────────────────────╯
We can pipe this into a command that gets the contents of one of the columns:
open Cargo.toml | get package
# => ╭───────────────┬────────────────────────────────────╮
# => │ authors │ [list 1 item] │
# => │ default-run │ nu │
# => │ description │ A new type of shell │
# => │ documentation │ https://www.nushell.sh/book/ │
# => │ edition │ 2018 │
# => │ exclude │ [list 1 item] │
# => │ homepage │ https://www.nushell.sh │
# => │ license │ MIT │
# => │ metadata │ {record 1 field} │
# => │ name │ nu │
# => │ repository │ https://github.com/nushell/nushell │
# => │ rust-version │ 1.60 │
# => │ version │ 0.72.0 │
# => ╰───────────────┴────────────────────────────────────╯
And if needed we can drill down further:
open Cargo.toml | get package.version
# => 0.72.0
Plugins
Nu supports plugins that offer additional functionality to the shell and follow the same structured data model that built-in commands use. There are a few examples in the crates/nu_plugins_* directories.
Plugins are binaries that are available in your path and follow a nu_plugin_* naming convention.
These binaries interact with nu via a simple JSON-RPC protocol where the command identifies itself and passes along its configuration, making it available for use.
If the plugin is a filter, data streams to it one element at a time, and it can stream data back in return via stdin/stdout.
If the plugin is a sink, it is given the full vector of final data and is given free reign over stdin/stdout to use as it pleases.
The awesome-nu repo lists a variety of nu-plugins while the showcase repo shows off informative blog posts that have been written about Nushell along with videos that highlight technical topics that have been presented.
Goals
Nu adheres closely to a set of goals that make up its design philosophy. As features are added, they are checked against these goals.
-
First and foremost, Nu is cross-platform. Commands and techniques should work across platforms and Nu has first-class support for Windows, macOS, and Linux.
-
Nu ensures compatibility with existing platform-specific executables.
-
Nu's workflow and tools should have the usability expected of modern software in 2022 (and beyond).
-
Nu views data as either structured or unstructured. It is a structured shell like PowerShell.
-
Finally, Nu views data functionally. Rather than using mutation, pipelines act as a means to load, change, and save data without mutable state.
Officially Supported By
Please submit an issue or PR to be added to this list.
Contributing
See Contributing for details. Thanks to all the people who already contributed!
License
The project is made available under the MIT license. See the LICENSE file for more information.