Commit Graph

19 Commits

Author SHA1 Message Date
Micha Reiser 7dfde3b929
Update Rust toolchain to 1.89 (#19807) 2025-08-07 18:21:50 +02:00
Dhruv Manilawala 56258bb3b7
[ty] Add documentation for server traits (#19137)
This PR adds some basic documentation for the traits in the server
implementation.
2025-07-07 14:26:09 +00:00
Micha Reiser 015222900f
Support cancellation requests (#18627) 2025-06-12 22:08:42 +02:00
Micha Reiser 9ae698fe30
Switch to Rust 2024 edition (#18129) 2025-05-16 13:25:28 +02:00
Micha Reiser fa628018b2
Use `#[expect(lint)]` over `#[allow(lint)]` where possible (#17822) 2025-05-03 21:20:31 +02:00
Micha Reiser cb7f56fb20
[red-knot] Don't use latency-sensitive for handlers (#17227)
## Summary

The priority latency-sensitive is reserved for actions that need to run
immediately because they would otherwise block the user's action. An
example of this is a format request. VS code blocks the editor until the
save action is complete. That's why formatting a document is very
sensitive to delays and it's important that we always have a worker
thread available to run a format request *immediately*. Another example
are code completions, where it's important that they appear immediately
when the user types.

On the other hand, showing diagnostics, hover, or inlay hints has high
priority but users are used that the editor takes a few ms to compute
the overlay.
Computing this information can also be expensive (e.g. find all
references), blocking the worker for quiet some time (a few 100ms).
That's why it's important
that those requests don't clog the sensitive worker threads.
2025-04-08 08:33:30 +02:00
Dhruv Manilawala 1447553bc2
Improve logging system using `logLevel`, avoid trace value (#15232)
## Summary

Refer to the VS Code PR
(https://github.com/astral-sh/ruff-vscode/pull/659) for details on the
change.

This PR changes the following:

1. Add tracing span for both request (request id and method name) and
notification (method name) handler
2. Remove the `RUFF_TRACE` environment variable. This was being used to
turn on / off logging for the server
3. Similarly, remove reading the `trace` value from the initialization
options
4. Remove handling the `$/setTrace` notification
5. Remove the specialized `TraceLogWriter` used for Zed and VS Code
(https://github.com/astral-sh/ruff/pull/12564)

Regarding the (5) for the Zed editor, the reason that was implemented
was because there was no way of looking at the stderr messages in the
editor which has been changed. Now, it captures the stderr as part of
the "Server Logs".
(82492d74a8/crates/language_tools/src/lsp_log.rs (L548-L552))

### Question

Regarding (1), I think having just a simple trace level message should
be good for now as the spans are not hierarchical. This could be tackled
with #12744. The difference between the two:

<details><summary>Using <code>tracing::trace</code></summary>
<p>

```
   0.019243416s DEBUG ThreadId(08) ruff_server::session::index::ruff_settings: Ignored path via `exclude`: /Users/dhruv/playground/ruff/.vscode
   0.026398750s  INFO main ruff_server::session::index: Registering workspace: /Users/dhruv/playground/ruff
   0.026802125s TRACE ruff:main ruff_server::server::api: Received notification "textDocument/didOpen"
   0.026930666s TRACE ruff:main ruff_server::server::api: Received notification "textDocument/didOpen"
   0.026962333s TRACE ruff:main ruff_server::server::api: Received request "textDocument/diagnostic" (1)
   0.027042875s TRACE ruff:main ruff_server::server::api: Received request "textDocument/diagnostic" (2)
   0.027097500s TRACE ruff:main ruff_server::server::api: Received request "textDocument/codeAction" (3)
   0.027107458s DEBUG ruff:worker:0 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
   0.027123541s DEBUG ruff:worker:3 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/organize_imports.py
   0.027514875s  INFO     ruff:main ruff_server::server: Configuration file watcher successfully registered
   0.285689833s TRACE     ruff:main ruff_server::server::api: Received request "textDocument/codeAction" (4)
  45.741101666s TRACE     ruff:main ruff_server::server::api: Received notification "textDocument/didClose"
  47.108745500s TRACE     ruff:main ruff_server::server::api: Received notification "textDocument/didOpen"
  47.109802041s TRACE     ruff:main ruff_server::server::api: Received request "textDocument/diagnostic" (5)
  47.109926958s TRACE     ruff:main ruff_server::server::api: Received request "textDocument/codeAction" (6)
  47.110027791s DEBUG ruff:worker:6 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
  51.863679125s TRACE     ruff:main ruff_server::server::api: Received request "textDocument/hover" (7)
```

</p>
</details> 

<details><summary>Using <code>tracing::trace_span</code></summary>
<p>

Only logging the enter event:

```
   0.018638750s DEBUG ThreadId(11) ruff_server::session::index::ruff_settings: Ignored path via `exclude`: /Users/dhruv/playground/ruff/.vscode
   0.025895791s  INFO main ruff_server::session::index: Registering workspace: /Users/dhruv/playground/ruff
   0.026378791s TRACE ruff:main notification{method="textDocument/didOpen"}: ruff_server::server::api: enter
   0.026531208s TRACE ruff:main notification{method="textDocument/didOpen"}: ruff_server::server::api: enter
   0.026567583s TRACE ruff:main request{id=1 method="textDocument/diagnostic"}: ruff_server::server::api: enter
   0.026652541s TRACE ruff:main request{id=2 method="textDocument/diagnostic"}: ruff_server::server::api: enter
   0.026711041s DEBUG ruff:worker:2 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/organize_imports.py
   0.026729166s DEBUG ruff:worker:1 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
   0.027023083s  INFO     ruff:main ruff_server::server: Configuration file watcher successfully registered
   5.197554750s TRACE     ruff:main notification{method="textDocument/didClose"}: ruff_server::server::api: enter
   6.534458000s TRACE     ruff:main notification{method="textDocument/didOpen"}: ruff_server::server::api: enter
   6.535027958s TRACE     ruff:main request{id=3 method="textDocument/diagnostic"}: ruff_server::server::api: enter
   6.535271166s DEBUG ruff:worker:3 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/organize_imports.py
   6.544240583s TRACE     ruff:main request{id=4 method="textDocument/codeAction"}: ruff_server::server::api: enter
   7.049692458s TRACE     ruff:main request{id=5 method="textDocument/codeAction"}: ruff_server::server::api: enter
   7.508142541s TRACE     ruff:main request{id=6 method="textDocument/hover"}: ruff_server::server::api: enter
   7.872421958s TRACE     ruff:main request{id=7 method="textDocument/hover"}: ruff_server::server::api: enter
   8.024498583s TRACE     ruff:main request{id=8 method="textDocument/codeAction"}: ruff_server::server::api: enter
  13.895063666s TRACE     ruff:main request{id=9 method="textDocument/codeAction"}: ruff_server::server::api: enter
  14.774706083s TRACE     ruff:main request{id=10 method="textDocument/hover"}: ruff_server::server::api: enter
  16.058918958s TRACE     ruff:main notification{method="textDocument/didChange"}: ruff_server::server::api: enter
  16.060562208s TRACE     ruff:main request{id=11 method="textDocument/diagnostic"}: ruff_server::server::api: enter
  16.061109083s DEBUG ruff:worker:8 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
  21.561742875s TRACE     ruff:main notification{method="textDocument/didChange"}: ruff_server::server::api: enter
  21.563573791s TRACE     ruff:main request{id=12 method="textDocument/diagnostic"}: ruff_server::server::api: enter
  21.564206750s DEBUG ruff:worker:4 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
  21.826691375s TRACE     ruff:main request{id=13 method="textDocument/codeAction"}: ruff_server::server::api: enter
  22.091080125s TRACE     ruff:main request{id=14 method="textDocument/codeAction"}: ruff_server::server::api: enter
```

</p>
</details> 


**Todo**

- [x] Update documentation (I'll be adding a troubleshooting section
under "Editors" as a follow-up which is for all editors)
- [x] Check for backwards compatibility. I don't think this should break
backwards compatibility as it's mainly targeted towards improving the
debugging experience.

~**Before I go on to updating the documentation, I'd appreciate initial
review on the chosen approach.**~

resolves: #14959 

## Test Plan

Refer to the test plan in
https://github.com/astral-sh/ruff-vscode/pull/659.

Example logs at `debug` level:

```
   0.010770083s DEBUG ThreadId(15) ruff_server::session::index::ruff_settings: Ignored path via `exclude`: /Users/dhruv/playground/ruff/.vscode
   0.018101916s  INFO main ruff_server::session::index: Registering workspace: /Users/dhruv/playground/ruff
   0.018559916s DEBUG ruff:worker:4 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
   0.018992375s  INFO     ruff:main ruff_server::server: Configuration file watcher successfully registered
  23.408802375s DEBUG ruff:worker:11 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
  24.329127416s DEBUG  ruff:worker:6 ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
```

Example logs at `trace` level:

```
   0.010296375s DEBUG ThreadId(13) ruff_server::session::index::ruff_settings: Ignored path via `exclude`: /Users/dhruv/playground/ruff/.vscode
   0.017422583s  INFO main ruff_server::session::index: Registering workspace: /Users/dhruv/playground/ruff
   0.018034458s TRACE ruff:main notification{method="textDocument/didOpen"}: ruff_server::server::api: enter
   0.018199708s TRACE ruff:worker:0 request{id=1 method="textDocument/diagnostic"}: ruff_server::server::api: enter
   0.018251167s DEBUG ruff:worker:0 request{id=1 method="textDocument/diagnostic"}: ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
   0.018528708s  INFO     ruff:main ruff_server::server: Configuration file watcher successfully registered
   1.611798417s TRACE ruff:worker:1 request{id=2 method="textDocument/codeAction"}: ruff_server::server::api: enter
   1.861757542s TRACE ruff:worker:4 request{id=3 method="textDocument/codeAction"}: ruff_server::server::api: enter
   7.027361792s TRACE ruff:worker:2 request{id=4 method="textDocument/codeAction"}: ruff_server::server::api: enter
   7.851361500s TRACE ruff:worker:5 request{id=5 method="textDocument/codeAction"}: ruff_server::server::api: enter
   7.901690875s TRACE     ruff:main notification{method="textDocument/didChange"}: ruff_server::server::api: enter
   7.903063167s TRACE ruff:worker:10 request{id=6 method="textDocument/diagnostic"}: ruff_server::server::api: enter
   7.903183500s DEBUG ruff:worker:10 request{id=6 method="textDocument/diagnostic"}: ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
   8.702385292s TRACE      ruff:main notification{method="textDocument/didChange"}: ruff_server::server::api: enter
   8.704106625s TRACE  ruff:worker:3 request{id=7 method="textDocument/diagnostic"}: ruff_server::server::api: enter
   8.704304875s DEBUG  ruff:worker:3 request{id=7 method="textDocument/diagnostic"}: ruff_server::resolve: Included path via `include`: /Users/dhruv/playground/ruff/lsp/play.py
   8.966853458s TRACE  ruff:worker:9 request{id=8 method="textDocument/codeAction"}: ruff_server::server::api: enter
   9.229622792s TRACE  ruff:worker:6 request{id=9 method="textDocument/codeAction"}: ruff_server::server::api: enter
  10.513111583s TRACE  ruff:worker:7 request{id=10 method="textDocument/codeAction"}: ruff_server::server::api: enter
```
2025-01-08 18:18:00 +05:30
Jane Lewis 507f5c1137
`ruff server`: Tracing system now respects log level and trace level, with options to log to a file (#11747)
## Summary

Fixes #10968.
Fixes #11545.

The server's tracing system has been rewritten from the ground up. The
server now has trace level and log level settings which restrict the
tracing events and spans that get logged.

* A `logLevel` setting has been added, which lets a user set the log
level. By default, it is set to `"info"`.
* A `logFile` setting has also been added, which lets the user supply an
optional file to send tracing output (it does not have to exist as a
file yet). By default, if this is unset, tracing output will be sent to
`stderr`.
* A `$/setTrace` handler has also been added, and we also set the trace
level from the initialization options. For editors without direct
support for tracing, the environment variable `RUFF_TRACE` can override
the trace level.
* Small changes have been made to how we display tracing output. We no
longer use `tracing-tree`, and instead use
`tracing_subscriber::fmt::Layer` to format output. Thread names are now
included in traces, and I've made some adjustment to thread worker names
to be more useful.

## Test Plan

In VS Code, with `ruff.trace.server` set to its default value, no logs
from Ruff should appear.

After changing `ruff.trace.server` to either `messages` or `verbose`,
you should see log messages at `info` level or higher appear in Ruff's
output:
<img width="1005" alt="Screenshot 2024-06-10 at 10 35 04 AM"
src="https://github.com/astral-sh/ruff/assets/19577865/6050d107-9815-4bd2-96d0-e86f096a57f5">

In Helix, by default, no logs from Ruff should appear.

To set the trace level in Helix, you'll need to modify your language
configuration as follows:
```toml
[language-server.ruff]
command = "/Users/jane/astral/ruff/target/debug/ruff"
args = ["server", "--preview"]
environment = { "RUFF_TRACE" = "messages" }
```

After doing this, logs of `info` level or higher should be visible in
Helix:
<img width="1216" alt="Screenshot 2024-06-10 at 10 39 26 AM"
src="https://github.com/astral-sh/ruff/assets/19577865/8ff88692-d3f7-4fd1-941e-86fb338fcdcc">

You can use `:log-open` to quickly open the Helix log file.

In Neovim, by default, no logs from Ruff should appear.

To set the trace level in Neovim, you'll need to modify your
configuration as follows:
```lua
require('lspconfig').ruff.setup {
  cmd = {"/path/to/debug/executable", "server", "--preview"},
  cmd_env = { RUFF_TRACE = "messages" }
}
```

You should see logs appear in `:LspLog` that look like the following:
<img width="1490" alt="Screenshot 2024-06-11 at 11 24 01 AM"
src="https://github.com/astral-sh/ruff/assets/19577865/576cd5fa-03cf-477a-b879-b29a9a1200ff">

You can adjust `logLevel` and `logFile` in `settings`:
```lua
require('lspconfig').ruff.setup {
  cmd = {"/path/to/debug/executable", "server", "--preview"},
  cmd_env = { RUFF_TRACE = "messages" },
  settings = {
    logLevel = "debug",
    logFile = "your/log/file/path/log.txt"
  }
}
```

The `logLevel` and `logFile` can also be set in Helix like so:
```toml
[language-server.ruff.config.settings]
logLevel = "debug"
logFile = "your/log/file/path/log.txt"
```

Even if this log file does not exist, it should now be created and
written to after running the server:

<img width="1148" alt="Screenshot 2024-06-10 at 10 43 44 AM"
src="https://github.com/astral-sh/ruff/assets/19577865/ab533cf7-d5ac-4178-97f1-e56da17450dd">
2024-06-11 11:29:47 -07:00
T-256 5b500fc4dc
`ruff server`: Add support for documents not exist on disk (#11588)
Co-authored-by: T-256 <Tester@test.com>
Co-authored-by: Micha Reiser <micha@reiser.io>
2024-05-31 08:34:10 +02:00
Jane Lewis b0731ef9cb
`ruff server`: Support Jupyter Notebook (`*.ipynb`) files (#11206)
## Summary

Closes https://github.com/astral-sh/ruff/issues/10858.

`ruff server` now supports `*.ipynb` (aka Jupyter Notebook) files.
Extensive internal changes have been made to facilitate this, which I've
done some work to contextualize with documentation and an pre-review
that highlights notable sections of the code.

`*.ipynb` cells should behave similarly to `*.py` documents, with one
major exception. The format command `ruff.applyFormat` will only apply
to the currently selected notebook cell - if you want to format an
entire notebook document, use `Format Notebook` from the VS Code context
menu.

## Test Plan

The VS Code extension does not yet have Jupyter Notebook support
enabled, so you'll first need to enable it manually. To do this,
checkout the `pre-release` branch and modify `src/common/server.ts` as
follows:

Before:
![Screenshot 2024-05-13 at 10 59
06 PM](https://github.com/astral-sh/ruff/assets/19577865/c6a3c604-c405-4968-b8a2-5d670de89172)

After:
![Screenshot 2024-05-13 at 10 58
24 PM](https://github.com/astral-sh/ruff/assets/19577865/94ab2e3d-0609-448d-9c8c-cd07c69a513b)

I recommend testing this PR with large, complicated notebook files. I
used notebook files from [this popular
repository](https://github.com/jakevdp/PythonDataScienceHandbook/tree/master/notebooks)
in my preliminary testing.

The main thing to test is ensuring that notebook cells behave the same
as Python documents, besides the aforementioned issue with
`ruff.applyFormat`. You should also test adding and deleting cells (in
particular, deleting all the code cells and ensure that doesn't break
anything), changing the kind of a cell (i.e. from markup -> code or vice
versa), and creating a new notebook file from scratch. Finally, you
should also test that source actions work as expected (and across the
entire notebook).

Note: `ruff.applyAutofix` and `ruff.applyOrganizeImports` are currently
broken for notebook files, and I suspect it has something to do with
https://github.com/astral-sh/ruff/issues/11248. Once this is fixed, I
will update the test plan accordingly.

---------

Co-authored-by: nolan <nolan.king90@gmail.com>
2024-05-21 22:29:30 +00:00
Nolan 7c8c1c71a3
Implement hover menu support for ruff-server; Issue #10595 (#11096)
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## Summary

Add support for hover menu to ruff_server, as requested in
[10595](https://github.com/astral-sh/ruff/issues/10595).
Majority of new code is in hover.rs.
I reused the regex from ruff-lsp's implementation. Also reused the
format_rule_text function from ruff/src/commands/rule.rs
Added capability registration in server.rs, and added the handler to
api.rs.

## Test Plan

Tested in NVIM v0.10.0-dev-2582+g2a8cef6bd, configured with lspconfig
using the default options (other than cmd pointing to my test build,
with options "server" and "--preview"). OS: Ubuntu 24.04, kernel
6.8.0-22.

---------

Co-authored-by: Jane Lewis <me@jane.engineering>
2024-04-23 20:16:02 +00:00
Jane Lewis 62478c3070
`ruff server`: Support publish diagnostics as a fallback when pull diagnostics aren't supported (#11092)
## Summary

Fixes #11059 

Several major editors don't support [pull
diagnostics](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_pullDiagnostics),
a method of sending diagnostics to the client that was introduced in
version `0.3.17` of the specification. Until now, `ruff server` has only
used pull diagnostics, which resulted in diagnostics not being available
on Neovim and Helix, which don't support pull diagnostics yet (though
Neovim `10.0` will have support for this).

`ruff server` will now utilize the older method of sending diagnostics,
known as 'publish diagnostics', when pull diagnostics aren't supported
by the client. This involves re-linting a document every time it is
opened or modified, and then sending the diagnostics generated from that
lint to the client via the `textDocument/publishDiagnostics`
notification.

## Test Plan

The easiest way to test that this PR works is to check if diagnostics
show up on Neovim `<=0.9`.
2024-04-22 21:06:35 -07:00
Jane Lewis 0a6327418d
`ruff server` refreshes diagnostics for open files when file configuration is changed (#10988)
## Summary

The server now requests a [workspace diagnostic
refresh](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#diagnostic_refresh)
when a configuration file gets changed. This means that diagnostics for
all open files will be automatically re-requested by the client on a
config change.

## Test Plan

You can test this by opening several files in VS Code, setting `select`
in your file configuration to `[]`, and observing that the diagnostics
go away once the file is saved (besides any `Pylance` diagnostics).
Restore it to what it was before, and you should see the diagnostics
automatically return once a save happens.
2024-04-17 09:14:45 -07:00
Jane Lewis 2882604451
`ruff server`: Important errors are now shown as popups (#10951)
## Summary

Fixes #10866.

Introduces the `show_err_msg!` macro which will send a message to be
shown as a popup to the client via the `window/showMessage` LSP method.

## Test Plan

Insert various `show_err_msg!` calls in common code paths (for example,
at the beginning of `event_loop`) and confirm that these messages appear
in your editor.

To test that panicking works correctly, add this to the top of the `fn
run` definition in
`crates/ruff_server/src/server/api/requests/execute_command.rs`:

```rust
panic!("This should appear");
```

Then, try running a command like `Ruff: Format document` from the
command palette (`Ctrl/Cmd+Shift+P`). You should see the following
messages appear:


![Screenshot 2024-04-16 at 11 20
57 AM](https://github.com/astral-sh/ruff/assets/19577865/ae430da6-82c3-4841-a419-664ff34034e8)
2024-04-16 18:32:53 +00:00
Jane Lewis c11e6d709c
`ruff server` now supports commands for auto-fixing, organizing imports, and formatting (#10654)
## Summary

This builds off of the work in
https://github.com/astral-sh/ruff/pull/10652 to implement a command
executor, backwards compatible with the commands from the previous LSP
(`ruff.applyAutofix`, `ruff.applyFormat` and
`ruff.applyOrganizeImports`).

This involved a lot of refactoring and tweaks to the code action
resolution code - the most notable change is that workspace edits are
specified in a slightly different way, using the more general `changes`
field instead of the `document_changes` field (which isn't supported on
all LSP clients). Additionally, the API for synchronous request handlers
has been updated to include access to the `Requester`, which we use to
send a `workspace/applyEdit` request to the client.

## Test Plan



https://github.com/astral-sh/ruff/assets/19577865/7932e30f-d944-4e35-b828-1d81aa56c087
2024-04-05 23:27:35 +00:00
Jane Lewis 257964a8bc
`ruff server` now supports `source.fixAll` source action (#10597)
## Summary

`ruff server` now has source action `source.fixAll` as an available code
action.

This also fixes https://github.com/astral-sh/ruff/issues/10593 in the
process of revising the code for quick fix code actions.

## Test Plan




https://github.com/astral-sh/ruff/assets/19577865/f4c07425-e68a-445f-a4ed-949c9197a6be
2024-04-03 16:22:17 +00:00
Jane Lewis 4f06d59ff6
Automatic configuration reloading for `ruff server` (#10404)
## Summary

Fixes #10366.

`ruff server` now registers a file watcher on the client side using the
LSP protocol, and listen for events on configuration files. On such an
event, it reloads the configuration in the 'nearest' workspace to the
file that was changed.

## Test Plan

N/A
2024-03-21 20:17:07 +00:00
Auguste Lalande 3ed707f245
Spellcheck & grammar (#10375)
## Summary

I used `codespell` and `gramma` to identify mispellings and grammar
errors throughout the codebase and fixed them. I tried not to make any
controversial changes, but feel free to revert as you see fit.
2024-03-13 02:34:23 +00:00
Jane Lewis 0c84fbb6db
`ruff server` - A new built-in LSP for Ruff, written in Rust (#10158)
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## Summary

This PR introduces the `ruff_server` crate and a new `ruff server`
command. `ruff_server` is a re-implementation of
[`ruff-lsp`](https://github.com/astral-sh/ruff-lsp), written entirely in
Rust. It brings significant performance improvements, much tighter
integration with Ruff, a foundation for supporting entirely new language
server features, and more!

This PR is an early version of `ruff_lsp` that we're calling the
**pre-release** version. Anyone is more than welcome to use it and
submit bug reports for any issues they encounter - we'll have some
documentation on how to set it up with a few common editors, and we'll
also provide a pre-release VSCode extension for those interested.

This pre-release version supports:
- **Diagnostics for `.py` files**
- **Quick fixes**
- **Full-file formatting**
- **Range formatting**
- **Multiple workspace folders**
- **Automatic linter/formatter configuration** - taken from any
`pyproject.toml` files in the workspace.

Many thanks to @MichaReiser for his [proof-of-concept
work](https://github.com/astral-sh/ruff/pull/7262), which was important
groundwork for making this PR possible.

## Architectural Decisions

I've made an executive choice to go with `lsp-server` as a base
framework for the LSP, in favor of `tower-lsp`. There were several
reasons for this:

1. I would like to avoid `async` in our implementation. LSPs are mostly
computationally bound rather than I/O bound, and `async` adds a lot of
complexity to the API, while also making harder to reason about
execution order. This leads into the second reason, which is...
2. Any handlers that mutate state should be blocking and run in the
event loop, and the state should be lock-free. This is the approach that
`rust-analyzer` uses (also with the `lsp-server`/`lsp-types` crates as a
framework), and it gives us assurances about data mutation and execution
order. `tower-lsp` doesn't support this, which has caused some
[issues](https://github.com/ebkalderon/tower-lsp/issues/284) around data
races and out-of-order handler execution.
3. In general, I think it makes sense to have tight control over
scheduling and the specifics of our implementation, in exchange for a
slightly higher up-front cost of writing it ourselves. We'll be able to
fine-tune it to our needs and support future LSP features without
depending on an upstream maintainer.

## Test Plan

The pre-release of `ruff_server` will have snapshot tests for common
document editing scenarios. An expanded test suite is on the roadmap for
future version of `ruff_server`.
2024-03-08 20:57:23 -08:00