This is partially "feng-shui programming" of moving things to new
separate places.
The later commits include "`git blame` tollbooths" by moving out chunks
of code into new files, which requires an extra step to track things
with `git blame`. We can negiotiate if you want to keep particular
things in their original place.
If egregious I tried to add a bit of documentation. If I see something
that is unused/unnecessarily `pub` I will try to remove that.
- Move `nu_protocol::Exportable` to `nu-parser`
- Guess doccomment for `Exportable`
- Move `Unit` enum from `value` to `AST`
- Move engine state `Variable` def into its folder
- Move error-related files in `nu-protocol` subdir
- Move `pipeline_data` module into its own folder
- Move `stream.rs` over into the `pipeline_data` mod
- Move `PipelineMetadata` into its own file
- Doccomment `PipelineMetadata`
- Remove unused `is_leap_year` in `value/mod`
- Note about criminal `type_compatible` helper
- Move duration fmting into new `value/duration.rs`
- Move filesize fmting logic to new `value/filesize`
- Split reexports from standard imports in `value/mod`
- Doccomment trait `CustomValue`
- Polish doccomments and intradoc links
# Description
This adds `match` and basic pattern matching.
An example:
```
match $x {
1..10 => { print "Value is between 1 and 10" }
{ foo: $bar } => { print $"Value has a 'foo' field with value ($bar)" }
[$a, $b] => { print $"Value is a list with two items: ($a) and ($b)" }
_ => { print "Value is none of the above" }
}
```
Like the recent changes to `if` to allow it to be used as an expression,
`match` can also be used as an expression. This allows you to assign the
result to a variable, eg) `let xyz = match ...`
I've also included a short-hand pattern for matching records, as I think
it might help when doing a lot of record patterns: `{$foo}` which is
equivalent to `{foo: $foo}`.
There are still missing components, so consider this the first step in
full pattern matching support. Currently missing:
* Patterns for strings
* Or-patterns (like the `|` in Rust)
* Patterns for tables (unclear how we want to match a table, so it'll
need some design)
* Patterns for binary values
* And much more
# User-Facing Changes
[see above]
# 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
> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```
# 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.
