nushell/crates
Jakub Žádník a3f817d71b
Re-implement aliases (#8123)
# Description

This PR adds an alternative alias implementation. Old aliases still work
but you need to use `old-alias` instead of `alias`.

Instead of replacing spans in the original code and re-parsing, which
proved to be extremely error-prone and a constant source of panics, the
new implementation creates a new command that references the old
command. Consider the new alias defined as `alias ll = ls -l`. The
parser creates a new command called `ll` and remembers that it is
actually a `ls` command called with the `-l` flag. Then, when the parser
sees the `ll` command, it will translate it to `ls -l` and passes to it
any parameters that were passed to the call to `ll`. It works quite
similar to how known externals defined with `extern` are implemented.

The new alias implementation should work the same way as the old
aliases, including exporting from modules, referencing both known and
unknown externals. It seems to preserve custom completions and pipeline
metadata. It is quite robust in most cases but there are some rough
edges (see later).

Fixes https://github.com/nushell/nushell/issues/7648,
https://github.com/nushell/nushell/issues/8026,
https://github.com/nushell/nushell/issues/7512,
https://github.com/nushell/nushell/issues/5780,
https://github.com/nushell/nushell/issues/7754

No effect: https://github.com/nushell/nushell/issues/8122 (we might
revisit the completions code after this PR)

Should use custom command instead:
https://github.com/nushell/nushell/issues/6048

# User-Facing Changes

Since aliases are now basically commands, it has some new implications:

1. `alias spam = "spam"` (requires command call)
	* **workaround**: use `alias spam = echo "spam"`
2. `def foo [] { 'foo' }; alias foo = ls -l` (foo defined more than
once)
* **workaround**: use different name (commands also have this
limitation)
4. `alias ls = (ls | sort-by type name -i)`
* **workaround**: Use custom command. _The common issue with this is
that it is currently not easy to pass flags through custom commands and
command referencing itself will lead to stack overflow. Both of these
issues are meant to be addressed._
5. TODO: Help messages, `which` command, `$nu.scope.aliases`, etc.
* Should we treat the aliases as commands or should they be separated
from regular commands?
6. Needs better error message and syntax highlight for recursed alias
(`alias f = f`)
7. Can't create alias with the same name as existing command (`alias ls
= ls -a`)
	* Might be possible to add support for it (not 100% sure)
8. Standalone `alias` doesn't list aliases anymore
9. Can't alias parser keywords (e.g., stuff like `alias ou = overlay
use` won't work)
	* TODO: Needs a better error message when attempting to do so

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.
2023-02-27 20:44:05 +13:00
..
nu_plugin_custom_values Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu_plugin_example Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu_plugin_formats Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu_plugin_gstat Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu_plugin_inc Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu_plugin_python update nu_plugin_python due to signature changes (#8107) 2023-02-18 13:27:24 +00:00
nu_plugin_query Added examples to query web plugin (#8171) 2023-02-22 19:01:15 +00:00
nu-cli Add Remove welcome message tutorial (#8217) 2023-02-27 19:49:50 +13:00
nu-cmd-lang Re-implement aliases (#8123) 2023-02-27 20:44:05 +13:00
nu-color-config Display empty records and lists (#7925) 2023-02-22 16:18:33 +00:00
nu-command Re-implement aliases (#8123) 2023-02-27 20:44:05 +13:00
nu-engine FEATURE: print example command results in the help (#8189) 2023-02-26 21:05:11 +01:00
nu-explore Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu-glob Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu-json Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu-parser Re-implement aliases (#8123) 2023-02-27 20:44:05 +13:00
nu-path Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu-plugin Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu-pretty-hex Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu-protocol Re-implement aliases (#8123) 2023-02-27 20:44:05 +13:00
nu-system Bump errno from 0.2.8 to 0.3.0 (#8131) 2023-02-22 12:56:31 +00:00
nu-table table --collapse dont do truncation return message instead (#8172) 2023-02-22 18:35:45 +00:00
nu-term-grid Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu-test-support Update to 0.76.1 version for development (#8161) 2023-02-21 23:21:39 +00:00
nu-utils Compress $HOME into ~ in prompt (#8173) 2023-02-22 16:36:26 -06:00
README.md Remove old nushell/merge engine-q 2022-02-07 14:54:06 -05:00

Nushell core libraries and plugins

These sub-crates form both the foundation for Nu and a set of plugins which extend Nu with additional functionality.

Foundational libraries are split into two kinds of crates:

  • Core crates - those crates that work together to build the Nushell language engine
  • Support crates - a set of crates that support the engine with additional features like JSON support, ANSI support, and more.

Plugins are likewise also split into two types:

  • Core plugins - plugins that provide part of the default experience of Nu, including access to the system properties, processes, and web-connectivity features.
  • Extra plugins - these plugins run a wide range of different capabilities like working with different file types, charting, viewing binary data, and more.