ruff server - A new built-in LSP for Ruff, written in Rust

Cargo.toml

@@ -32,6 +32,7 @@ console_error_panic_hook = { version = "0.1.7" }
 console_log = { version = "1.0.0" }
 countme = { version = "3.0.1" }
 criterion = { version = "0.5.1", default-features = false }
+crossbeam = { version = "0.8.4" }
 dirs = { version = "5.0.0" }
 drop_bomb = { version = "0.1.5" }
 env_logger = { version = "0.10.1" }
@@ -52,10 +53,14 @@ is-macro = { version = "0.3.5" }
 is-wsl = { version = "0.4.0" }
 itertools = { version = "0.12.1" }
 js-sys = { version = "0.3.67" }
+jod-thread = { version = "0.1.2" }
 lalrpop-util = { version = "0.20.0", default-features = false }
 lexical-parse-float = { version = "0.8.0", features = ["format"] }
+libc = { version = "0.2.153" }
 libcst = { version = "1.1.0", default-features = false }
 log = { version = "0.4.17" }
+lsp-server = { version = "0.7.6" }
+lsp-types = { version = "0.95.0", features = ["proposed"] }
 memchr = { version = "2.7.1" }
 mimalloc = { version = "0.1.39" }
 natord = { version = "1.0.9" }
@@ -97,6 +102,7 @@ toml = { version = "0.8.9" }
 tracing = { version = "0.1.40" }
 tracing-indicatif = { version = "0.3.6" }
 tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }
+tracing-tree = { version = "0.2.4" }
 typed-arena = { version = "2.0.2" }
 unic-ucd-category = { version = "0.9" }
 unicode-ident = { version = "1.0.12" }

crates/ruff/Cargo.toml

@@ -20,6 +20,7 @@ ruff_macros = { path = "../ruff_macros" }
 ruff_notebook = { path = "../ruff_notebook" }
 ruff_python_ast = { path = "../ruff_python_ast" }
 ruff_python_formatter = { path = "../ruff_python_formatter" }
+ruff_server = { path = "../ruff_server" }
 ruff_source_file = { path = "../ruff_source_file" }
 ruff_text_size = { path = "../ruff_text_size" }
 ruff_workspace = { path = "../ruff_workspace" }
@@ -52,6 +53,8 @@ tempfile = { workspace = true }
 thiserror = { workspace = true }
 toml = { workspace = true }
 tracing = { workspace = true, features = ["log"] }
+tracing-subscriber = { workspace = true, features = ["registry"]}
+tracing-tree = { workspace = true }
 walkdir = { workspace = true }
 wild = { workspace = true }
 

crates/ruff/src/args.rs

@@ -126,6 +126,8 @@ pub enum Command {
     GenerateShellCompletion { shell: clap_complete_command::Shell },
     /// Run the Ruff formatter on the given files or directories.
     Format(FormatCommand),
+    /// Run the language server.
+    Server(ServerCommand),
     /// Display Ruff's version
     Version {
         #[arg(long, value_enum, default_value = "text")]
@@ -494,6 +496,9 @@ pub struct FormatCommand {
     pub range: Option<FormatRange>,
 }
 
+#[derive(Clone, Debug, clap::Parser)]
+pub struct ServerCommand;
+
 #[derive(Debug, Clone, Copy, clap::ValueEnum)]
 pub enum HelpFormat {
     Text,

crates/ruff/src/commands/mod.rs

@@ -7,6 +7,7 @@ pub(crate) mod format;
 pub(crate) mod format_stdin;
 pub(crate) mod linter;
 pub(crate) mod rule;
+pub(crate) mod server;
 pub(crate) mod show_files;
 pub(crate) mod show_settings;
 pub(crate) mod version;

crates/ruff/src/commands/server.rs

@@ -0,0 +1,69 @@
+use crate::ExitStatus;
+use anyhow::Result;
+use ruff_linter::logging::LogLevel;
+use ruff_server::Server;
+use tracing::{level_filters::LevelFilter, metadata::Level, subscriber::Interest, Metadata};
+use tracing_subscriber::{
+    layer::{Context, Filter, SubscriberExt},
+    Layer, Registry,
+};
+use tracing_tree::time::Uptime;
+
+pub(crate) fn run_server(log_level: LogLevel) -> Result<ExitStatus> {
+    let trace_level = if log_level == LogLevel::Verbose {
+        Level::TRACE
+    } else {
+        Level::DEBUG
+    };
+
+    let subscriber = Registry::default().with(
+        tracing_tree::HierarchicalLayer::default()
+            .with_indent_lines(true)
+            .with_indent_amount(2)
+            .with_bracketed_fields(true)
+            .with_targets(true)
+            .with_writer(|| Box::new(std::io::stderr()))
+            .with_timer(Uptime::default())
+            .with_filter(LoggingFilter { trace_level }),
+    );
+
+    tracing::subscriber::set_global_default(subscriber)?;
+
+    let server = Server::new()?;
+
+    server.run().map(|()| ExitStatus::Success)
+}
+
+struct LoggingFilter {
+    trace_level: Level,
+}
+
+impl LoggingFilter {
+    fn is_enabled(&self, meta: &Metadata<'_>) -> bool {
+        let filter = if meta.target().starts_with("ruff") {
+            self.trace_level
+        } else {
+            Level::INFO
+        };
+
+        meta.level() <= &filter
+    }
+}
+
+impl<S> Filter<S> for LoggingFilter {
+    fn enabled(&self, meta: &Metadata<'_>, _cx: &Context<'_, S>) -> bool {
+        self.is_enabled(meta)
+    }
+
+    fn callsite_enabled(&self, meta: &'static Metadata<'static>) -> Interest {
+        if self.is_enabled(meta) {
+            Interest::always()
+        } else {
+            Interest::never()
+        }
+    }
+
+    fn max_level_hint(&self) -> Option<LevelFilter> {
+        Some(LevelFilter::from_level(self.trace_level))
+    }
+}

crates/ruff/src/lib.rs

@@ -7,7 +7,7 @@ use std::process::ExitCode;
 use std::sync::mpsc::channel;
 
 use anyhow::Result;
-use args::GlobalConfigArgs;
+use args::{GlobalConfigArgs, ServerCommand};
 use clap::CommandFactory;
 use colored::Colorize;
 use log::warn;
@@ -190,6 +190,7 @@ pub fn run(
         }
         Command::Check(args) => check(args, global_options),
         Command::Format(args) => format(args, global_options),
+        Command::Server(args) => server(args, global_options.log_level()),
     }
 }
 
@@ -203,6 +204,12 @@ fn format(args: FormatCommand, global_options: GlobalConfigArgs) -> Result<ExitS
     }
 }
 
+#[allow(clippy::needless_pass_by_value)] // TODO: remove once we start taking arguments from here
+fn server(args: ServerCommand, log_level: LogLevel) -> Result<ExitStatus> {
+    let ServerCommand {} = args;
+    commands::server::run_server(log_level)
+}
+
 pub fn check(args: CheckCommand, global_options: GlobalConfigArgs) -> Result<ExitStatus> {
     let (cli, config_arguments) = args.partition(global_options)?;
 

crates/ruff_formatter/src/lib.rs

@@ -545,6 +545,10 @@ impl PrintedRange {
         &self.code
     }
 
+    pub fn into_code(self) -> String {
+        self.code
+    }
+
     /// The range the formatted code corresponds to in the source document.
     pub fn source_range(&self) -> TextRange {
         self.source_range