## 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">
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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`.
