See if this helps with red knot

## Summary

When following the step-by-step instructions to run the benchmarks in
`CONTRIBUTING.md`, I encountered two errors:

**Error 1:**
`bash: hyperfine: command not found`
    
**Solution**: I updated the instructions to include the step of
installing the benchmark tool.

**Error 2:**
```shell
$ ./target/release/ruff ./crates/ruff_linter/resources/test/cpython/ 
error: `ruff <path>` has been removed. Use `ruff check <path>` instead.
```
**Solution**: I added `check`.

## Test Plan

I tested it by running the benchmark-related commands in a new workspace
within GitHub Codespaces.

.pre-commit-config.yaml

@@ -6,6 +6,8 @@ exclude: |
     crates/red_knot_workspace/resources/.*|
     crates/ruff_linter/resources/.*|
     crates/ruff_linter/src/rules/.*/snapshots/.*|
+    crates/ruff_notebook/resources/.*|
+    crates/ruff_server/resources/.*|
     crates/ruff/resources/.*|
     crates/ruff_python_formatter/resources/.*|
     crates/ruff_python_formatter/tests/snapshots/.*|
@@ -15,7 +17,7 @@ exclude: |
 
 repos:
   - repo: https://github.com/abravalheri/validate-pyproject
-    rev: v0.18
+    rev: v0.19
     hooks:
       - id: validate-pyproject
 
@@ -57,7 +59,7 @@ repos:
         pass_filenames: false # This makes it a lot faster
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.5.7
+    rev: v0.6.1
     hooks:
       - id: ruff-format
       - id: ruff

CONTRIBUTING.md

@@ -2,35 +2,6 @@
 
 Welcome! We're happy to have you here. Thank you in advance for your contribution to Ruff.
 
-- [The Basics](#the-basics)
-    - [Prerequisites](#prerequisites)
-    - [Development](#development)
-    - [Project Structure](#project-structure)
-    - [Example: Adding a new lint rule](#example-adding-a-new-lint-rule)
-        - [Rule naming convention](#rule-naming-convention)
-        - [Rule testing: fixtures and snapshots](#rule-testing-fixtures-and-snapshots)
-    - [Example: Adding a new configuration option](#example-adding-a-new-configuration-option)
-- [MkDocs](#mkdocs)
-- [Release Process](#release-process)
-    - [Creating a new release](#creating-a-new-release)
-- [Ecosystem CI](#ecosystem-ci)
-- [Benchmarking and Profiling](#benchmarking-and-profiling)
-    - [CPython Benchmark](#cpython-benchmark)
-    - [Microbenchmarks](#microbenchmarks)
-        - [Benchmark-driven Development](#benchmark-driven-development)
-        - [PR Summary](#pr-summary)
-        - [Tips](#tips)
-    - [Profiling Projects](#profiling-projects)
-        - [Linux](#linux)
-        - [Mac](#mac)
-- [`cargo dev`](#cargo-dev)
-- [Subsystems](#subsystems)
-    - [Compilation Pipeline](#compilation-pipeline)
-    - [Import Categorization](#import-categorization)
-        - [Project root](#project-root)
-        - [Package root](#package-root)
-        - [Import categorization](#import-categorization-1)
-
 ## The Basics
 
 Ruff welcomes contributions in the form of pull requests.
@@ -333,22 +304,34 @@ even patch releases may contain [non-backwards-compatible changes](https://semve
 ### Creating a new release
 
 1. Install `uv`: `curl -LsSf https://astral.sh/uv/install.sh | sh`
+
 1. Run `./scripts/release.sh`; this command will:
+
     - Generate a temporary virtual environment with `rooster`
     - Generate a changelog entry in `CHANGELOG.md`
     - Update versions in `pyproject.toml` and `Cargo.toml`
     - Update references to versions in the `README.md` and documentation
     - Display contributors for the release
+
 1. The changelog should then be editorialized for consistency
+
     - Often labels will be missing from pull requests they will need to be manually organized into the proper section
     - Changes should be edited to be user-facing descriptions, avoiding internal details
+
 1. Highlight any breaking changes in `BREAKING_CHANGES.md`
+
 1. Run `cargo check`. This should update the lock file with new versions.
+
 1. Create a pull request with the changelog and version updates
+
 1. Merge the PR
+
 1. Run the [release workflow](https://github.com/astral-sh/ruff/actions/workflows/release.yml) with:
+
     - The new version number (without starting `v`)
+
 1. The release workflow will do the following:
+
     1. Build all the assets. If this fails (even though we tested in step 4), we haven't tagged or
         uploaded anything, you can restart after pushing a fix. If you just need to rerun the build,
         make sure you're [re-running all the failed
@@ -359,14 +342,25 @@ even patch releases may contain [non-backwards-compatible changes](https://semve
     1. Attach artifacts to draft GitHub release
     1. Trigger downstream repositories. This can fail non-catastrophically, as we can run any
         downstream jobs manually if needed.
+
 1. Verify the GitHub release:
+
     1. The Changelog should match the content of `CHANGELOG.md`
     1. Append the contributors from the `scripts/release.sh` script
+
 1. If needed, [update the schemastore](https://github.com/astral-sh/ruff/blob/main/scripts/update_schemastore.py).
+
     1. One can determine if an update is needed when
         `git diff old-version-tag new-version-tag -- ruff.schema.json` returns a non-empty diff.
     1. Once run successfully, you should follow the link in the output to create a PR.
-1. If needed, update the `ruff-lsp` and `ruff-vscode` repositories.
+
+1. If needed, update the [`ruff-lsp`](https://github.com/astral-sh/ruff-lsp) and
+    [`ruff-vscode`](https://github.com/astral-sh/ruff-vscode) repositories and follow
+    the release instructions in those repositories. `ruff-lsp` should always be updated
+    before `ruff-vscode`.
+
+    This step is generally not required for a patch release, but should always be done
+    for a minor release.
 
 ## Ecosystem CI
 
@@ -389,7 +383,7 @@ We have several ways of benchmarking and profiling Ruff:
 - Microbenchmarks which run the linter or the formatter on individual files. These run on pull requests.
 - Profiling the linter on either the microbenchmarks or entire projects
 
-> \[!NOTE\]
+> **Note**
 > When running benchmarks, ensure that your CPU is otherwise idle (e.g., close any background
 > applications, like web browsers). You may also want to switch your CPU to a "performance"
 > mode, if it exists, especially when benchmarking short-lived processes.
@@ -403,12 +397,18 @@ which makes it a good target for benchmarking.
 git clone --branch 3.10 https://github.com/python/cpython.git crates/ruff_linter/resources/test/cpython
 ```
 
+Install `hyperfine`:
+
+```shell
+cargo install hyperfine
+```
+
 To benchmark the release build:
 
 ```shell
 cargo build --release && hyperfine --warmup 10 \
-  "./target/release/ruff ./crates/ruff_linter/resources/test/cpython/ --no-cache -e" \
-  "./target/release/ruff ./crates/ruff_linter/resources/test/cpython/ -e"
+  "./target/release/ruff check ./crates/ruff_linter/resources/test/cpython/ --no-cache -e" \
+  "./target/release/ruff check ./crates/ruff_linter/resources/test/cpython/ -e"
 
 Benchmark 1: ./target/release/ruff ./crates/ruff_linter/resources/test/cpython/ --no-cache
   Time (mean ± σ):     293.8 ms ±   3.2 ms    [User: 2384.6 ms, System: 90.3 ms]
@@ -427,7 +427,7 @@ To benchmark against the ecosystem's existing tools:
 
 ```shell
 hyperfine --ignore-failure --warmup 5 \
-  "./target/release/ruff ./crates/ruff_linter/resources/test/cpython/ --no-cache" \
+  "./target/release/ruff check ./crates/ruff_linter/resources/test/cpython/ --no-cache" \
   "pyflakes crates/ruff_linter/resources/test/cpython" \
   "autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython" \
   "pycodestyle crates/ruff_linter/resources/test/cpython" \
@@ -473,7 +473,7 @@ To benchmark a subset of rules, e.g. `LineTooLong` and `DocLineTooLong`:
 
 ```shell
 cargo build --release && hyperfine --warmup 10 \
-  "./target/release/ruff ./crates/ruff_linter/resources/test/cpython/ --no-cache -e --select W505,E501"
+  "./target/release/ruff check ./crates/ruff_linter/resources/test/cpython/ --no-cache -e --select W505,E501"
 ```
 
 You can run `poetry install` from `./scripts/benchmarks` to create a working environment for the

Cargo.lock

@@ -1935,6 +1935,7 @@ dependencies = [
  "smallvec",
  "static_assertions",
  "tempfile",
+ "thiserror",
  "tracing",
  "walkdir",
  "zip",
@@ -1950,10 +1951,8 @@ dependencies = [
  "libc",
  "lsp-server",
  "lsp-types",
- "red_knot_python_semantic",
  "red_knot_workspace",
  "ruff_db",
- "ruff_linter",
  "ruff_notebook",
  "ruff_python_ast",
  "ruff_source_file",
@@ -1996,7 +1995,6 @@ dependencies = [
  "ruff_text_size",
  "rustc-hash 2.0.0",
  "salsa",
- "thiserror",
  "tracing",
 ]
 
@@ -2742,7 +2740,7 @@ checksum = "e86697c916019a8588c99b5fac3cead74ec0b4b819707a682fd4d23fa0ce1ba1"
 [[package]]
 name = "salsa"
 version = "0.18.0"
-source = "git+https://github.com/MichaReiser/salsa.git?tag=red-knot-0.0.1#ece083e15b79f155f9e4368ec1318cec9a08d88b"
+source = "git+https://github.com/MichaReiser/salsa.git?rev=74a4de43dc5b41a23114f889b91f3f730269c369#74a4de43dc5b41a23114f889b91f3f730269c369"
 dependencies = [
  "append-only-vec",
  "arc-swap",
@@ -2762,12 +2760,12 @@ dependencies = [
 [[package]]
 name = "salsa-macro-rules"
 version = "0.1.0"
-source = "git+https://github.com/MichaReiser/salsa.git?tag=red-knot-0.0.1#ece083e15b79f155f9e4368ec1318cec9a08d88b"
+source = "git+https://github.com/MichaReiser/salsa.git?rev=74a4de43dc5b41a23114f889b91f3f730269c369#74a4de43dc5b41a23114f889b91f3f730269c369"
 
 [[package]]
 name = "salsa-macros"
 version = "0.18.0"
-source = "git+https://github.com/MichaReiser/salsa.git?tag=red-knot-0.0.1#ece083e15b79f155f9e4368ec1318cec9a08d88b"
+source = "git+https://github.com/MichaReiser/salsa.git?rev=74a4de43dc5b41a23114f889b91f3f730269c369#74a4de43dc5b41a23114f889b91f3f730269c369"
 dependencies = [
  "heck",
  "proc-macro2",

Cargo.toml

@@ -108,7 +108,7 @@ rand = { version = "0.8.5" }
 rayon = { version = "1.10.0" }
 regex = { version = "1.10.2" }
 rustc-hash = { version = "2.0.0" }
-salsa = { git = "https://github.com/MichaReiser/salsa.git", tag = "red-knot-0.0.1" }
+salsa = { git = "https://github.com/MichaReiser/salsa.git", rev = "74a4de43dc5b41a23114f889b91f3f730269c369" }
 schemars = { version = "0.8.16" }
 seahash = { version = "4.1.0" }
 serde = { version = "1.0.197", features = ["derive"] }

crates/red_knot/src/logging.rs

@@ -5,8 +5,8 @@ use colored::Colorize;
 use std::fmt;
 use std::fs::File;
 use std::io::BufWriter;
-use tracing::log::LevelFilter;
 use tracing::{Event, Subscriber};
+use tracing_subscriber::filter::LevelFilter;
 use tracing_subscriber::fmt::format::Writer;
 use tracing_subscriber::fmt::{FmtContext, FormatEvent, FormatFields};
 use tracing_subscriber::registry::LookupSpan;
@@ -60,10 +60,10 @@ pub(crate) enum VerbosityLevel {
 impl VerbosityLevel {
     const fn level_filter(self) -> LevelFilter {
         match self {
-            VerbosityLevel::Default => LevelFilter::Warn,
-            VerbosityLevel::Verbose => LevelFilter::Info,
-            VerbosityLevel::ExtraVerbose => LevelFilter::Debug,
-            VerbosityLevel::Trace => LevelFilter::Trace,
+            VerbosityLevel::Default => LevelFilter::WARN,
+            VerbosityLevel::Verbose => LevelFilter::INFO,
+            VerbosityLevel::ExtraVerbose => LevelFilter::DEBUG,
+            VerbosityLevel::Trace => LevelFilter::TRACE,
         }
     }
 
@@ -88,7 +88,7 @@ pub(crate) fn setup_tracing(level: VerbosityLevel) -> anyhow::Result<TracingGuar
         match level {
             VerbosityLevel::Default => {
                 // Show warning traces
-                EnvFilter::default().add_directive(tracing::level_filters::LevelFilter::WARN.into())
+                EnvFilter::default().add_directive(LevelFilter::WARN.into())
             }
             level => {
                 let level_filter = level.level_filter();

crates/red_knot/src/main.rs

@@ -7,12 +7,12 @@ use colored::Colorize;
 use crossbeam::channel as crossbeam_channel;
 use salsa::plumbing::ZalsaDatabase;
 
-use red_knot_python_semantic::{ProgramSettings, SearchPathSettings};
+use red_knot_python_semantic::SitePackages;
 use red_knot_server::run_server;
 use red_knot_workspace::db::RootDatabase;
-use red_knot_workspace::site_packages::VirtualEnvironment;
 use red_knot_workspace::watch;
 use red_knot_workspace::watch::WorkspaceWatcher;
+use red_knot_workspace::workspace::settings::Configuration;
 use red_knot_workspace::workspace::WorkspaceMetadata;
 use ruff_db::system::{OsSystem, System, SystemPath, SystemPathBuf};
 use target_version::TargetVersion;
@@ -65,15 +65,14 @@ to resolve type information for the project's third-party dependencies.",
         value_name = "PATH",
         help = "Additional path to use as a module-resolution source (can be passed multiple times)"
     )]
-    extra_search_path: Vec<SystemPathBuf>,
+    extra_search_path: Option<Vec<SystemPathBuf>>,
 
     #[arg(
         long,
         help = "Python version to assume when resolving types",
-        default_value_t = TargetVersion::default(),
-        value_name="VERSION")
-    ]
-    target_version: TargetVersion,
+        value_name = "VERSION"
+    )]
+    target_version: Option<TargetVersion>,
 
     #[clap(flatten)]
     verbosity: Verbosity,
@@ -86,6 +85,36 @@ to resolve type information for the project's third-party dependencies.",
     watch: bool,
 }
 
+impl Args {
+    fn to_configuration(&self, cli_cwd: &SystemPath) -> Configuration {
+        let mut configuration = Configuration::default();
+
+        if let Some(target_version) = self.target_version {
+            configuration.target_version = Some(target_version.into());
+        }
+
+        if let Some(venv_path) = &self.venv_path {
+            configuration.search_paths.site_packages = Some(SitePackages::Derived {
+                venv_path: SystemPath::absolute(venv_path, cli_cwd),
+            });
+        }
+
+        if let Some(custom_typeshed_dir) = &self.custom_typeshed_dir {
+            configuration.search_paths.custom_typeshed =
+                Some(SystemPath::absolute(custom_typeshed_dir, cli_cwd));
+        }
+
+        if let Some(extra_search_paths) = &self.extra_search_path {
+            configuration.search_paths.extra_paths = extra_search_paths
+                .iter()
+                .map(|path| Some(SystemPath::absolute(path, cli_cwd)))
+                .collect();
+        }
+
+        configuration
+    }
+}
+
 #[derive(Debug, clap::Subcommand)]
 pub enum Command {
     /// Start the language server
@@ -115,22 +144,13 @@ pub fn main() -> ExitStatus {
 }
 
 fn run() -> anyhow::Result<ExitStatus> {
-    let Args {
-        command,
-        current_directory,
-        custom_typeshed_dir,
-        extra_search_path: extra_paths,
-        venv_path,
-        target_version,
-        verbosity,
-        watch,
-    } = Args::parse_from(std::env::args().collect::<Vec<_>>());
+    let args = Args::parse_from(std::env::args().collect::<Vec<_>>());
 
-    if matches!(command, Some(Command::Server)) {
+    if matches!(args.command, Some(Command::Server)) {
         return run_server().map(|()| ExitStatus::Success);
     }
 
-    let verbosity = verbosity.level();
+    let verbosity = args.verbosity.level();
     countme::enable(verbosity.is_trace());
     let _guard = setup_tracing(verbosity)?;
 
@@ -146,10 +166,12 @@ fn run() -> anyhow::Result<ExitStatus> {
             })?
     };
 
-    let cwd = current_directory
+    let cwd = args
+        .current_directory
+        .as_ref()
         .map(|cwd| {
             if cwd.as_std_path().is_dir() {
-                Ok(SystemPath::absolute(&cwd, &cli_base_path))
+                Ok(SystemPath::absolute(cwd, &cli_base_path))
             } else {
                 Err(anyhow!(
                     "Provided current-directory path '{cwd}' is not a directory."
@@ -160,33 +182,18 @@ fn run() -> anyhow::Result<ExitStatus> {
         .unwrap_or_else(|| cli_base_path.clone());
 
     let system = OsSystem::new(cwd.clone());
-    let workspace_metadata = WorkspaceMetadata::from_path(system.current_directory(), &system)?;
-
-    // TODO: Verify the remaining search path settings eagerly.
-    let site_packages = venv_path
-        .map(|path| {
-            VirtualEnvironment::new(path, &OsSystem::new(cli_base_path))
-                .and_then(|venv| venv.site_packages_directories(&system))
-        })
-        .transpose()?
-        .unwrap_or_default();
-
-    // TODO: Respect the settings from the workspace metadata. when resolving the program settings.
-    let program_settings = ProgramSettings {
-        target_version: target_version.into(),
-        search_paths: SearchPathSettings {
-            extra_paths,
-            src_root: workspace_metadata.root().to_path_buf(),
-            custom_typeshed: custom_typeshed_dir,
-            site_packages,
-        },
-    };
+    let cli_configuration = args.to_configuration(&cwd);
+    let workspace_metadata = WorkspaceMetadata::from_path(
+        system.current_directory(),
+        &system,
+        Some(cli_configuration.clone()),
+    )?;
 
     // TODO: Use the `program_settings` to compute the key for the database's persistent
     //   cache and load the cache if it exists.
-    let mut db = RootDatabase::new(workspace_metadata, program_settings, system)?;
+    let mut db = RootDatabase::new(workspace_metadata, system)?;
 
-    let (main_loop, main_loop_cancellation_token) = MainLoop::new();
+    let (main_loop, main_loop_cancellation_token) = MainLoop::new(cli_configuration);
 
     // Listen to Ctrl+C and abort the watch mode.
     let main_loop_cancellation_token = Mutex::new(Some(main_loop_cancellation_token));
@@ -198,7 +205,7 @@ fn run() -> anyhow::Result<ExitStatus> {
         }
     })?;
 
-    let exit_status = if watch {
+    let exit_status = if args.watch {
         main_loop.watch(&mut db)?
     } else {
         main_loop.run(&mut db)
@@ -238,10 +245,12 @@ struct MainLoop {
 
     /// The file system watcher, if running in watch mode.
     watcher: Option<WorkspaceWatcher>,
+
+    cli_configuration: Configuration,
 }
 
 impl MainLoop {
-    fn new() -> (Self, MainLoopCancellationToken) {
+    fn new(cli_configuration: Configuration) -> (Self, MainLoopCancellationToken) {
         let (sender, receiver) = crossbeam_channel::bounded(10);
 
         (
@@ -249,6 +258,7 @@ impl MainLoop {
                 sender: sender.clone(),
                 receiver,
                 watcher: None,
+                cli_configuration,
             },
             MainLoopCancellationToken { sender },
         )
@@ -331,7 +341,7 @@ impl MainLoop {
                 MainLoopMessage::ApplyChanges(changes) => {
                     revision += 1;
                     // Automatically cancels any pending queries and waits for them to complete.
-                    db.apply_changes(changes);
+                    db.apply_changes(changes, Some(&self.cli_configuration));
                     if let Some(watcher) = self.watcher.as_mut() {
                         watcher.update(db);
                     }

crates/red_knot/tests/file_watching.rs

@@ -5,12 +5,11 @@ use std::time::Duration;
 
 use anyhow::{anyhow, Context};
 
-use red_knot_python_semantic::{
-    resolve_module, ModuleName, Program, ProgramSettings, PythonVersion, SearchPathSettings,
-};
+use red_knot_python_semantic::{resolve_module, ModuleName, Program, PythonVersion, SitePackages};
 use red_knot_workspace::db::RootDatabase;
 use red_knot_workspace::watch;
 use red_knot_workspace::watch::{directory_watcher, WorkspaceWatcher};
+use red_knot_workspace::workspace::settings::{Configuration, SearchPathConfiguration};
 use red_knot_workspace::workspace::WorkspaceMetadata;
 use ruff_db::files::{system_path_to_file, File, FileError};
 use ruff_db::source::source_text;
@@ -25,7 +24,7 @@ struct TestCase {
     /// We need to hold on to it in the test case or the temp files get deleted.
     _temp_dir: tempfile::TempDir,
     root_dir: SystemPathBuf,
-    search_path_settings: SearchPathSettings,
+    configuration: Configuration,
 }
 
 impl TestCase {
@@ -41,10 +40,6 @@ impl TestCase {
         &self.db
     }
 
-    fn db_mut(&mut self) -> &mut RootDatabase {
-        &mut self.db
-    }
-
     fn stop_watch(&mut self) -> Vec<watch::ChangeEvent> {
         self.try_stop_watch(Duration::from_secs(10))
             .expect("Expected watch changes but observed none.")
@@ -105,16 +100,20 @@ impl TestCase {
         Some(all_events)
     }
 
+    fn apply_changes(&mut self, changes: Vec<watch::ChangeEvent>) {
+        self.db.apply_changes(changes, Some(&self.configuration));
+    }
+
     fn update_search_path_settings(
         &mut self,
-        f: impl FnOnce(&SearchPathSettings) -> SearchPathSettings,
+        configuration: SearchPathConfiguration,
     ) -> anyhow::Result<()> {
         let program = Program::get(self.db());
 
-        let new_settings = f(&self.search_path_settings);
+        self.configuration.search_paths = configuration.clone();
+        let new_settings = configuration.into_settings(self.db.workspace().root(&self.db));
 
-        program.update_search_paths(&mut self.db, new_settings.clone())?;
-        self.search_path_settings = new_settings;
+        program.update_search_paths(&mut self.db, &new_settings)?;
 
         if let Some(watcher) = &mut self.watcher {
             watcher.update(&self.db);
@@ -127,7 +126,6 @@ impl TestCase {
     fn collect_package_files(&self, path: &SystemPath) -> Vec<File> {
         let package = self.db().workspace().package(self.db(), path).unwrap();
         let files = package.files(self.db());
-        let files = files.read();
         let mut collected: Vec<_> = files.into_iter().collect();
         collected.sort_unstable_by_key(|file| file.path(self.db()).as_system_path().unwrap());
         collected
@@ -180,17 +178,14 @@ fn setup<F>(setup_files: F) -> anyhow::Result<TestCase>
 where
     F: SetupFiles,
 {
-    setup_with_search_paths(setup_files, |_root, workspace_path| SearchPathSettings {
-        extra_paths: vec![],
-        src_root: workspace_path.to_path_buf(),
-        custom_typeshed: None,
-        site_packages: vec![],
+    setup_with_search_paths(setup_files, |_root, _workspace_path| {
+        SearchPathConfiguration::default()
     })
 }
 
 fn setup_with_search_paths<F>(
     setup_files: F,
-    create_search_paths: impl FnOnce(&SystemPath, &SystemPath) -> SearchPathSettings,
+    create_search_paths: impl FnOnce(&SystemPath, &SystemPath) -> SearchPathConfiguration,
 ) -> anyhow::Result<TestCase>
 where
     F: SetupFiles,
@@ -222,25 +217,34 @@ where
 
     let system = OsSystem::new(&workspace_path);
 
-    let workspace = WorkspaceMetadata::from_path(&workspace_path, &system)?;
-    let search_path_settings = create_search_paths(&root_path, workspace.root());
+    let search_paths = create_search_paths(&root_path, &workspace_path);
 
-    for path in search_path_settings
+    for path in search_paths
         .extra_paths
         .iter()
-        .chain(search_path_settings.site_packages.iter())
-        .chain(search_path_settings.custom_typeshed.iter())
+        .flatten()
+        .chain(search_paths.custom_typeshed.iter())
+        .chain(search_paths.site_packages.iter().flat_map(|site_packages| {
+            if let SitePackages::Known(path) = site_packages {
+                path.as_slice()
+            } else {
+                &[]
+            }
+        }))
     {
         std::fs::create_dir_all(path.as_std_path())
             .with_context(|| format!("Failed to create search path '{path}'"))?;
     }
 
-    let settings = ProgramSettings {
-        target_version: PythonVersion::default(),
-        search_paths: search_path_settings.clone(),
+    let configuration = Configuration {
+        target_version: Some(PythonVersion::PY312),
+        search_paths,
     };
 
-    let db = RootDatabase::new(workspace, settings, system)?;
+    let workspace =
+        WorkspaceMetadata::from_path(&workspace_path, &system, Some(configuration.clone()))?;
+
+    let db = RootDatabase::new(workspace, system)?;
 
     let (sender, receiver) = crossbeam::channel::unbounded();
     let watcher = directory_watcher(move |events| sender.send(events).unwrap())
@@ -255,7 +259,7 @@ where
         watcher: Some(watcher),
         _temp_dir: temp_dir,
         root_dir: root_path,
-        search_path_settings,
+        configuration,
     };
 
     // Sometimes the file watcher reports changes for events that happened before the watcher was started.
@@ -308,7 +312,7 @@ fn new_file() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     let foo = case.system_file(&foo_path).expect("foo.py to exist.");
 
@@ -331,7 +335,7 @@ fn new_ignored_file() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     assert!(case.system_file(&foo_path).is_ok());
     assert_eq!(&case.collect_package_files(&bar_path), &[bar_file]);
@@ -355,7 +359,7 @@ fn changed_file() -> anyhow::Result<()> {
 
     assert!(!changes.is_empty());
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     assert_eq!(source_text(case.db(), foo).as_str(), "print('Version 2')");
     assert_eq!(&case.collect_package_files(&foo_path), &[foo]);
@@ -378,7 +382,7 @@ fn deleted_file() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     assert!(!foo.exists(case.db()));
     assert_eq!(&case.collect_package_files(&foo_path), &[] as &[File]);
@@ -410,7 +414,7 @@ fn move_file_to_trash() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     assert!(!foo.exists(case.db()));
     assert_eq!(&case.collect_package_files(&foo_path), &[] as &[File]);
@@ -442,7 +446,7 @@ fn move_file_to_workspace() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     let foo_in_workspace = case.system_file(&foo_in_workspace_path)?;
 
@@ -470,7 +474,7 @@ fn rename_file() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     assert!(!foo.exists(case.db()));
 
@@ -511,7 +515,7 @@ fn directory_moved_to_workspace() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     let init_file = case
         .system_file(sub_new_path.join("__init__.py"))
@@ -562,7 +566,7 @@ fn directory_moved_to_trash() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     // `import sub.a` should no longer resolve
     assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_none());
@@ -616,7 +620,7 @@ fn directory_renamed() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     // `import sub.a` should no longer resolve
     assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_none());
@@ -681,7 +685,7 @@ fn directory_deleted() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     // `import sub.a` should no longer resolve
     assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_none());
@@ -695,15 +699,13 @@ fn directory_deleted() -> anyhow::Result<()> {
 
 #[test]
 fn search_path() -> anyhow::Result<()> {
-    let mut case =
-        setup_with_search_paths([("bar.py", "import sub.a")], |root_path, workspace_path| {
-            SearchPathSettings {
-                extra_paths: vec![],
-                src_root: workspace_path.to_path_buf(),
-                custom_typeshed: None,
-                site_packages: vec![root_path.join("site_packages")],
-            }
-        })?;
+    let mut case = setup_with_search_paths(
+        [("bar.py", "import sub.a")],
+        |root_path, _workspace_path| SearchPathConfiguration {
+            site_packages: Some(SitePackages::Known(vec![root_path.join("site_packages")])),
+            ..SearchPathConfiguration::default()
+        },
+    )?;
 
     let site_packages = case.root_path().join("site_packages");
 
@@ -716,7 +718,7 @@ fn search_path() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     assert!(resolve_module(case.db().upcast(), ModuleName::new_static("a").unwrap()).is_some());
     assert_eq!(
@@ -737,9 +739,9 @@ fn add_search_path() -> anyhow::Result<()> {
     assert!(resolve_module(case.db().upcast(), ModuleName::new_static("a").unwrap()).is_none());
 
     // Register site-packages as a search path.
-    case.update_search_path_settings(|settings| SearchPathSettings {
-        site_packages: vec![site_packages.clone()],
-        ..settings.clone()
+    case.update_search_path_settings(SearchPathConfiguration {
+        site_packages: Some(SitePackages::Known(vec![site_packages.clone()])),
+        ..SearchPathConfiguration::default()
     })
     .expect("Search path settings to be valid");
 
@@ -747,7 +749,7 @@ fn add_search_path() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     assert!(resolve_module(case.db().upcast(), ModuleName::new_static("a").unwrap()).is_some());
 
@@ -756,21 +758,19 @@ fn add_search_path() -> anyhow::Result<()> {
 
 #[test]
 fn remove_search_path() -> anyhow::Result<()> {
-    let mut case =
-        setup_with_search_paths([("bar.py", "import sub.a")], |root_path, workspace_path| {
-            SearchPathSettings {
-                extra_paths: vec![],
-                src_root: workspace_path.to_path_buf(),
-                custom_typeshed: None,
-                site_packages: vec![root_path.join("site_packages")],
-            }
-        })?;
+    let mut case = setup_with_search_paths(
+        [("bar.py", "import sub.a")],
+        |root_path, _workspace_path| SearchPathConfiguration {
+            site_packages: Some(SitePackages::Known(vec![root_path.join("site_packages")])),
+            ..SearchPathConfiguration::default()
+        },
+    )?;
 
     // Remove site packages from the search path settings.
     let site_packages = case.root_path().join("site_packages");
-    case.update_search_path_settings(|settings| SearchPathSettings {
-        site_packages: vec![],
-        ..settings.clone()
+    case.update_search_path_settings(SearchPathConfiguration {
+        site_packages: None,
+        ..SearchPathConfiguration::default()
     })
     .expect("Search path settings to be valid");
 
@@ -783,6 +783,48 @@ fn remove_search_path() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[test]
+fn changed_versions_file() -> anyhow::Result<()> {
+    let mut case = setup_with_search_paths(
+        |root_path: &SystemPath, workspace_path: &SystemPath| {
+            std::fs::write(workspace_path.join("bar.py").as_std_path(), "import sub.a")?;
+            std::fs::create_dir_all(root_path.join("typeshed/stdlib").as_std_path())?;
+            std::fs::write(root_path.join("typeshed/stdlib/VERSIONS").as_std_path(), "")?;
+            std::fs::write(
+                root_path.join("typeshed/stdlib/os.pyi").as_std_path(),
+                "# not important",
+            )?;
+
+            Ok(())
+        },
+        |root_path, _workspace_path| SearchPathConfiguration {
+            custom_typeshed: Some(root_path.join("typeshed")),
+            ..SearchPathConfiguration::default()
+        },
+    )?;
+
+    // Unset the custom typeshed directory.
+    assert_eq!(
+        resolve_module(case.db(), ModuleName::new("os").unwrap()),
+        None
+    );
+
+    std::fs::write(
+        case.root_path()
+            .join("typeshed/stdlib/VERSIONS")
+            .as_std_path(),
+        "os: 3.0-",
+    )?;
+
+    let changes = case.stop_watch();
+
+    case.apply_changes(changes);
+
+    assert!(resolve_module(case.db(), ModuleName::new("os").unwrap()).is_some());
+
+    Ok(())
+}
+
 /// Watch a workspace that contains two files where one file is a hardlink to another.
 ///
 /// Setup:
@@ -829,7 +871,7 @@ fn hard_links_in_workspace() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     assert_eq!(source_text(case.db(), foo).as_str(), "print('Version 2')");
 
@@ -900,7 +942,7 @@ fn hard_links_to_target_outside_workspace() -> anyhow::Result<()> {
 
     let changes = case.stop_watch();
 
-    case.db_mut().apply_changes(changes);
+    case.apply_changes(changes);
 
     assert_eq!(source_text(case.db(), bar).as_str(), "print('Version 2')");
 
@@ -939,7 +981,7 @@ mod unix {
 
         let changes = case.stop_watch();
 
-        case.db_mut().apply_changes(changes);
+        case.apply_changes(changes);
 
         assert_eq!(
             foo.permissions(case.db()),
@@ -1024,7 +1066,7 @@ mod unix {
 
         let changes = case.take_watch_changes();
 
-        case.db_mut().apply_changes(changes);
+        case.apply_changes(changes);
 
         assert_eq!(
             source_text(case.db(), baz.file()).as_str(),
@@ -1037,7 +1079,7 @@ mod unix {
 
         let changes = case.stop_watch();
 
-        case.db_mut().apply_changes(changes);
+        case.apply_changes(changes);
 
         assert_eq!(
             source_text(case.db(), baz.file()).as_str(),
@@ -1108,7 +1150,7 @@ mod unix {
 
         let changes = case.stop_watch();
 
-        case.db_mut().apply_changes(changes);
+        case.apply_changes(changes);
 
         // The file watcher is guaranteed to emit one event for the changed file, but it isn't specified
         // if the event is emitted for the "original" or linked path because both paths are watched.
@@ -1177,11 +1219,11 @@ mod unix {
 
                 Ok(())
             },
-            |_root, workspace| SearchPathSettings {
-                extra_paths: vec![],
-                src_root: workspace.to_path_buf(),
-                custom_typeshed: None,
-                site_packages: vec![workspace.join(".venv/lib/python3.12/site-packages")],
+            |_root, workspace| SearchPathConfiguration {
+                site_packages: Some(SitePackages::Known(vec![
+                    workspace.join(".venv/lib/python3.12/site-packages")
+                ])),
+                ..SearchPathConfiguration::default()
             },
         )?;
 
@@ -1216,7 +1258,7 @@ mod unix {
 
         let changes = case.stop_watch();
 
-        case.db_mut().apply_changes(changes);
+        case.apply_changes(changes);
 
         assert_eq!(
             source_text(case.db(), baz_original_file).as_str(),

crates/red_knot_python_semantic/Cargo.toml

@@ -26,6 +26,7 @@ countme = { workspace = true }
 once_cell = { workspace = true }
 ordermap = { workspace = true }
 salsa = { workspace = true }
+thiserror = { workspace = true }
 tracing = { workspace = true }
 rustc-hash = { workspace = true }
 hashbrown = { workspace = true }

crates/red_knot_python_semantic/src/db.rs

@@ -1,15 +1,18 @@
+use ruff_db::files::File;
 use ruff_db::{Db as SourceDb, Upcast};
 
 /// Database giving access to semantic information about a Python program.
 #[salsa::db]
-pub trait Db: SourceDb + Upcast<dyn SourceDb> {}
+pub trait Db: SourceDb + Upcast<dyn SourceDb> {
+    fn is_file_open(&self, file: File) -> bool;
+}
 
 #[cfg(test)]
 pub(crate) mod tests {
     use std::sync::Arc;
 
     use crate::module_resolver::vendored_typeshed_stubs;
-    use ruff_db::files::Files;
+    use ruff_db::files::{File, Files};
     use ruff_db::system::{DbWithTestSystem, System, TestSystem};
     use ruff_db::vendored::VendoredFileSystem;
     use ruff_db::{Db as SourceDb, Upcast};
@@ -91,7 +94,11 @@ pub(crate) mod tests {
     }
 
     #[salsa::db]
-    impl Db for TestDb {}
+    impl Db for TestDb {
+        fn is_file_open(&self, file: File) -> bool {
+            !file.path(self).is_vendored_path()
+        }
+    }
 
     #[salsa::db]
     impl salsa::Database for TestDb {

crates/red_knot_python_semantic/src/lib.rs

@@ -5,7 +5,7 @@ use rustc_hash::FxHasher;
 pub use db::Db;
 pub use module_name::ModuleName;
 pub use module_resolver::{resolve_module, system_module_search_paths, vendored_typeshed_stubs};
-pub use program::{Program, ProgramSettings, SearchPathSettings};
+pub use program::{Program, ProgramSettings, SearchPathSettings, SitePackages};
 pub use python_version::PythonVersion;
 pub use semantic_model::{HasTy, SemanticModel};
 
@@ -19,6 +19,7 @@ mod program;
 mod python_version;
 pub mod semantic_index;
 mod semantic_model;
+pub(crate) mod site_packages;
 pub mod types;
 
 type FxOrderSet<V> = ordermap::set::OrderSet<V, BuildHasherDefault<FxHasher>>;

crates/red_knot_python_semantic/src/module_resolver/mod.rs

@@ -13,7 +13,6 @@ use resolver::SearchPathIterator;
 mod module;
 mod path;
 mod resolver;
-mod state;
 mod typeshed;
 
 #[cfg(test)]

crates/red_knot_python_semantic/src/module_resolver/path.rs

@@ -9,11 +9,11 @@ use ruff_db::files::{system_path_to_file, vendored_path_to_file, File, FileError
 use ruff_db::system::{System, SystemPath, SystemPathBuf};
 use ruff_db::vendored::{VendoredPath, VendoredPathBuf};
 
+use super::typeshed::{typeshed_versions, TypeshedVersionsParseError, TypeshedVersionsQueryResult};
 use crate::db::Db;
 use crate::module_name::ModuleName;
-
-use super::state::ResolverState;
-use super::typeshed::{TypeshedVersionsParseError, TypeshedVersionsQueryResult};
+use crate::module_resolver::resolver::ResolverContext;
+use crate::site_packages::SitePackagesDiscoveryError;
 
 /// A path that points to a Python module.
 ///
@@ -60,7 +60,7 @@ impl ModulePath {
     }
 
     #[must_use]
-    pub(crate) fn is_directory(&self, resolver: &ResolverState) -> bool {
+    pub(super) fn is_directory(&self, resolver: &ResolverContext) -> bool {
         let ModulePath {
             search_path,
             relative_path,
@@ -74,7 +74,7 @@ impl ModulePath {
                     == Err(FileError::IsADirectory)
             }
             SearchPathInner::StandardLibraryCustom(stdlib_root) => {
-                match query_stdlib_version(Some(stdlib_root), relative_path, resolver) {
+                match query_stdlib_version(relative_path, resolver) {
                     TypeshedVersionsQueryResult::DoesNotExist => false,
                     TypeshedVersionsQueryResult::Exists
                     | TypeshedVersionsQueryResult::MaybeExists => {
@@ -84,7 +84,7 @@ impl ModulePath {
                 }
             }
             SearchPathInner::StandardLibraryVendored(stdlib_root) => {
-                match query_stdlib_version(None, relative_path, resolver) {
+                match query_stdlib_version(relative_path, resolver) {
                     TypeshedVersionsQueryResult::DoesNotExist => false,
                     TypeshedVersionsQueryResult::Exists
                     | TypeshedVersionsQueryResult::MaybeExists => resolver
@@ -96,7 +96,7 @@ impl ModulePath {
     }
 
     #[must_use]
-    pub(crate) fn is_regular_package(&self, resolver: &ResolverState) -> bool {
+    pub(super) fn is_regular_package(&self, resolver: &ResolverContext) -> bool {
         let ModulePath {
             search_path,
             relative_path,
@@ -113,7 +113,7 @@ impl ModulePath {
                         .is_ok()
             }
             SearchPathInner::StandardLibraryCustom(search_path) => {
-                match query_stdlib_version(Some(search_path), relative_path, resolver) {
+                match query_stdlib_version(relative_path, resolver) {
                     TypeshedVersionsQueryResult::DoesNotExist => false,
                     TypeshedVersionsQueryResult::Exists
                     | TypeshedVersionsQueryResult::MaybeExists => system_path_to_file(
@@ -124,7 +124,7 @@ impl ModulePath {
                 }
             }
             SearchPathInner::StandardLibraryVendored(search_path) => {
-                match query_stdlib_version(None, relative_path, resolver) {
+                match query_stdlib_version(relative_path, resolver) {
                     TypeshedVersionsQueryResult::DoesNotExist => false,
                     TypeshedVersionsQueryResult::Exists
                     | TypeshedVersionsQueryResult::MaybeExists => resolver
@@ -136,7 +136,7 @@ impl ModulePath {
     }
 
     #[must_use]
-    pub(crate) fn to_file(&self, resolver: &ResolverState) -> Option<File> {
+    pub(super) fn to_file(&self, resolver: &ResolverContext) -> Option<File> {
         let db = resolver.db.upcast();
         let ModulePath {
             search_path,
@@ -150,7 +150,7 @@ impl ModulePath {
                 system_path_to_file(db, search_path.join(relative_path)).ok()
             }
             SearchPathInner::StandardLibraryCustom(stdlib_root) => {
-                match query_stdlib_version(Some(stdlib_root), relative_path, resolver) {
+                match query_stdlib_version(relative_path, resolver) {
                     TypeshedVersionsQueryResult::DoesNotExist => None,
                     TypeshedVersionsQueryResult::Exists
                     | TypeshedVersionsQueryResult::MaybeExists => {
@@ -159,7 +159,7 @@ impl ModulePath {
                 }
             }
             SearchPathInner::StandardLibraryVendored(stdlib_root) => {
-                match query_stdlib_version(None, relative_path, resolver) {
+                match query_stdlib_version(relative_path, resolver) {
                     TypeshedVersionsQueryResult::DoesNotExist => None,
                     TypeshedVersionsQueryResult::Exists
                     | TypeshedVersionsQueryResult::MaybeExists => {
@@ -273,19 +273,15 @@ fn stdlib_path_to_module_name(relative_path: &Utf8Path) -> Option<ModuleName> {
 
 #[must_use]
 fn query_stdlib_version(
-    custom_stdlib_root: Option<&SystemPath>,
     relative_path: &Utf8Path,
-    resolver: &ResolverState,
+    context: &ResolverContext,
 ) -> TypeshedVersionsQueryResult {
     let Some(module_name) = stdlib_path_to_module_name(relative_path) else {
         return TypeshedVersionsQueryResult::DoesNotExist;
     };
-    let ResolverState {
-        db,
-        typeshed_versions,
-        target_version,
-    } = resolver;
-    typeshed_versions.query_module(*db, &module_name, custom_stdlib_root, *target_version)
+    let ResolverContext { db, target_version } = context;
+
+    typeshed_versions(*db).query_module(&module_name, *target_version)
 }
 
 /// Enumeration describing the various ways in which validation of a search path might fail.
@@ -293,7 +289,7 @@ fn query_stdlib_version(
 /// If validation fails for a search path derived from the user settings,
 /// a message must be displayed to the user,
 /// as type checking cannot be done reliably in these circumstances.
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Debug)]
 pub(crate) enum SearchPathValidationError {
     /// The path provided by the user was not a directory
     NotADirectory(SystemPathBuf),
@@ -304,18 +300,20 @@ pub(crate) enum SearchPathValidationError {
     NoStdlibSubdirectory(SystemPathBuf),
 
     /// The typeshed path provided by the user is a directory,
-    /// but no `stdlib/VERSIONS` file exists.
+    /// but `stdlib/VERSIONS` could not be read.
     /// (This is only relevant for stdlib search paths.)
-    NoVersionsFile(SystemPathBuf),
-
-    /// `stdlib/VERSIONS` is a directory.
-    /// (This is only relevant for stdlib search paths.)
-    VersionsIsADirectory(SystemPathBuf),
+    FailedToReadVersionsFile {
+        path: SystemPathBuf,
+        error: std::io::Error,
+    },
 
     /// The path provided by the user is a directory,
     /// and a `stdlib/VERSIONS` file exists, but it fails to parse.
     /// (This is only relevant for stdlib search paths.)
     VersionsParseError(TypeshedVersionsParseError),
+
+    /// Failed to discover the site-packages for the configured virtual environment.
+    SitePackagesDiscovery(SitePackagesDiscoveryError),
 }
 
 impl fmt::Display for SearchPathValidationError {
@@ -325,9 +323,16 @@ impl fmt::Display for SearchPathValidationError {
             Self::NoStdlibSubdirectory(path) => {
                 write!(f, "The directory at {path} has no `stdlib/` subdirectory")
             }
-            Self::NoVersionsFile(path) => write!(f, "Expected a file at {path}/stdlib/VERSIONS"),
-            Self::VersionsIsADirectory(path) => write!(f, "{path}/stdlib/VERSIONS is a directory."),
+            Self::FailedToReadVersionsFile { path, error } => {
+                write!(
+                    f,
+                    "Failed to read the custom typeshed versions file '{path}': {error}"
+                )
+            }
             Self::VersionsParseError(underlying_error) => underlying_error.fmt(f),
+            SearchPathValidationError::SitePackagesDiscovery(error) => {
+                write!(f, "Failed to discover the site-packages directory: {error}")
+            }
         }
     }
 }
@@ -342,6 +347,18 @@ impl std::error::Error for SearchPathValidationError {
     }
 }
 
+impl From<TypeshedVersionsParseError> for SearchPathValidationError {
+    fn from(value: TypeshedVersionsParseError) -> Self {
+        Self::VersionsParseError(value)
+    }
+}
+
+impl From<SitePackagesDiscoveryError> for SearchPathValidationError {
+    fn from(value: SitePackagesDiscoveryError) -> Self {
+        Self::SitePackagesDiscovery(value)
+    }
+}
+
 type SearchPathResult<T> = Result<T, SearchPathValidationError>;
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -384,11 +401,10 @@ pub(crate) struct SearchPath(Arc<SearchPathInner>);
 
 impl SearchPath {
     fn directory_path(system: &dyn System, root: SystemPathBuf) -> SearchPathResult<SystemPathBuf> {
-        let canonicalized = system.canonicalize_path(&root).unwrap_or(root);
-        if system.is_directory(&canonicalized) {
-            Ok(canonicalized)
+        if system.is_directory(&root) {
+            Ok(root)
         } else {
-            Err(SearchPathValidationError::NotADirectory(canonicalized))
+            Err(SearchPathValidationError::NotADirectory(root))
         }
     }
 
@@ -407,32 +423,22 @@ impl SearchPath {
     }
 
     /// Create a new standard-library search path pointing to a custom directory on disk
-    pub(crate) fn custom_stdlib(db: &dyn Db, typeshed: SystemPathBuf) -> SearchPathResult<Self> {
+    pub(crate) fn custom_stdlib(db: &dyn Db, typeshed: &SystemPath) -> SearchPathResult<Self> {
         let system = db.system();
-        if !system.is_directory(&typeshed) {
+        if !system.is_directory(typeshed) {
             return Err(SearchPathValidationError::NotADirectory(
                 typeshed.to_path_buf(),
             ));
         }
+
         let stdlib =
             Self::directory_path(system, typeshed.join("stdlib")).map_err(|err| match err {
-                SearchPathValidationError::NotADirectory(path) => {
-                    SearchPathValidationError::NoStdlibSubdirectory(path)
+                SearchPathValidationError::NotADirectory(_) => {
+                    SearchPathValidationError::NoStdlibSubdirectory(typeshed.to_path_buf())
                 }
                 err => err,
             })?;
-        let typeshed_versions =
-            system_path_to_file(db.upcast(), stdlib.join("VERSIONS")).map_err(|err| match err {
-                FileError::NotFound => SearchPathValidationError::NoVersionsFile(typeshed),
-                FileError::IsADirectory => {
-                    SearchPathValidationError::VersionsIsADirectory(typeshed)
-                }
-            })?;
-        super::typeshed::parse_typeshed_versions(db, typeshed_versions)
-            .as_ref()
-            .map_err(|validation_error| {
-                SearchPathValidationError::VersionsParseError(validation_error.clone())
-            })?;
+
         Ok(Self(Arc::new(SearchPathInner::StandardLibraryCustom(
             stdlib,
         ))))
@@ -623,11 +629,11 @@ mod tests {
     use ruff_db::Db;
 
     use crate::db::tests::TestDb;
-
-    use super::*;
     use crate::module_resolver::testing::{FileSpec, MockedTypeshed, TestCase, TestCaseBuilder};
     use crate::python_version::PythonVersion;
 
+    use super::*;
+
     impl ModulePath {
         #[must_use]
         fn join(&self, component: &str) -> ModulePath {
@@ -638,15 +644,6 @@ mod tests {
     }
 
     impl SearchPath {
-        #[must_use]
-        pub(crate) fn is_stdlib_search_path(&self) -> bool {
-            matches!(
-                &*self.0,
-                SearchPathInner::StandardLibraryCustom(_)
-                    | SearchPathInner::StandardLibraryVendored(_)
-            )
-        }
-
         fn join(&self, component: &str) -> ModulePath {
             self.to_module_path().join(component)
         }
@@ -661,7 +658,7 @@ mod tests {
             .build();
 
         assert_eq!(
-            SearchPath::custom_stdlib(&db, stdlib.parent().unwrap().to_path_buf())
+            SearchPath::custom_stdlib(&db, stdlib.parent().unwrap())
                 .unwrap()
                 .to_module_path()
                 .with_py_extension(),
@@ -669,7 +666,7 @@ mod tests {
         );
 
         assert_eq!(
-            &SearchPath::custom_stdlib(&db, stdlib.parent().unwrap().to_path_buf())
+            &SearchPath::custom_stdlib(&db, stdlib.parent().unwrap())
                 .unwrap()
                 .join("foo")
                 .with_pyi_extension(),
@@ -780,7 +777,7 @@ mod tests {
         let TestCase { db, stdlib, .. } = TestCaseBuilder::new()
             .with_custom_typeshed(MockedTypeshed::default())
             .build();
-        SearchPath::custom_stdlib(&db, stdlib.parent().unwrap().to_path_buf())
+        SearchPath::custom_stdlib(&db, stdlib.parent().unwrap())
             .unwrap()
             .to_module_path()
             .push("bar.py");
@@ -792,7 +789,7 @@ mod tests {
         let TestCase { db, stdlib, .. } = TestCaseBuilder::new()
             .with_custom_typeshed(MockedTypeshed::default())
             .build();
-        SearchPath::custom_stdlib(&db, stdlib.parent().unwrap().to_path_buf())
+        SearchPath::custom_stdlib(&db, stdlib.parent().unwrap())
             .unwrap()
             .to_module_path()
             .push("bar.rs");
@@ -824,7 +821,7 @@ mod tests {
             .with_custom_typeshed(MockedTypeshed::default())
             .build();
 
-        let root = SearchPath::custom_stdlib(&db, stdlib.parent().unwrap().to_path_buf()).unwrap();
+        let root = SearchPath::custom_stdlib(&db, stdlib.parent().unwrap()).unwrap();
 
         // Must have a `.pyi` extension or no extension:
         let bad_absolute_path = SystemPath::new("foo/stdlib/x.py");
@@ -872,8 +869,7 @@ mod tests {
             .with_custom_typeshed(typeshed)
             .with_target_version(target_version)
             .build();
-        let stdlib =
-            SearchPath::custom_stdlib(&db, stdlib.parent().unwrap().to_path_buf()).unwrap();
+        let stdlib = SearchPath::custom_stdlib(&db, stdlib.parent().unwrap()).unwrap();
         (db, stdlib)
     }
 
@@ -898,7 +894,7 @@ mod tests {
         };
 
         let (db, stdlib_path) = py38_typeshed_test_case(TYPESHED);
-        let resolver = ResolverState::new(&db, PythonVersion::PY38);
+        let resolver = ResolverContext::new(&db, PythonVersion::PY38);
 
         let asyncio_regular_package = stdlib_path.join("asyncio");
         assert!(asyncio_regular_package.is_directory(&resolver));
@@ -926,7 +922,7 @@ mod tests {
         };
 
         let (db, stdlib_path) = py38_typeshed_test_case(TYPESHED);
-        let resolver = ResolverState::new(&db, PythonVersion::PY38);
+        let resolver = ResolverContext::new(&db, PythonVersion::PY38);
 
         let xml_namespace_package = stdlib_path.join("xml");
         assert!(xml_namespace_package.is_directory(&resolver));
@@ -948,7 +944,7 @@ mod tests {
         };
 
         let (db, stdlib_path) = py38_typeshed_test_case(TYPESHED);
-        let resolver = ResolverState::new(&db, PythonVersion::PY38);
+        let resolver = ResolverContext::new(&db, PythonVersion::PY38);
 
         let functools_module = stdlib_path.join("functools.pyi");
         assert!(functools_module.to_file(&resolver).is_some());
@@ -964,7 +960,7 @@ mod tests {
         };
 
         let (db, stdlib_path) = py38_typeshed_test_case(TYPESHED);
-        let resolver = ResolverState::new(&db, PythonVersion::PY38);
+        let resolver = ResolverContext::new(&db, PythonVersion::PY38);
 
         let collections_regular_package = stdlib_path.join("collections");
         assert_eq!(collections_regular_package.to_file(&resolver), None);
@@ -980,7 +976,7 @@ mod tests {
         };
 
         let (db, stdlib_path) = py38_typeshed_test_case(TYPESHED);
-        let resolver = ResolverState::new(&db, PythonVersion::PY38);
+        let resolver = ResolverContext::new(&db, PythonVersion::PY38);
 
         let importlib_namespace_package = stdlib_path.join("importlib");
         assert_eq!(importlib_namespace_package.to_file(&resolver), None);
@@ -1001,7 +997,7 @@ mod tests {
         };
 
         let (db, stdlib_path) = py38_typeshed_test_case(TYPESHED);
-        let resolver = ResolverState::new(&db, PythonVersion::PY38);
+        let resolver = ResolverContext::new(&db, PythonVersion::PY38);
 
         let non_existent = stdlib_path.join("doesnt_even_exist");
         assert_eq!(non_existent.to_file(&resolver), None);
@@ -1029,7 +1025,7 @@ mod tests {
         };
 
         let (db, stdlib_path) = py39_typeshed_test_case(TYPESHED);
-        let resolver = ResolverState::new(&db, PythonVersion::PY39);
+        let resolver = ResolverContext::new(&db, PythonVersion::PY39);
 
         // Since we've set the target version to Py39,
         // `collections` should now exist as a directory, according to VERSIONS...
@@ -1058,7 +1054,7 @@ mod tests {
         };
 
         let (db, stdlib_path) = py39_typeshed_test_case(TYPESHED);
-        let resolver = ResolverState::new(&db, PythonVersion::PY39);
+        let resolver = ResolverContext::new(&db, PythonVersion::PY39);
 
         // The `importlib` directory now also exists
         let importlib_namespace_package = stdlib_path.join("importlib");
@@ -1082,7 +1078,7 @@ mod tests {
         };
 
         let (db, stdlib_path) = py39_typeshed_test_case(TYPESHED);
-        let resolver = ResolverState::new(&db, PythonVersion::PY39);
+        let resolver = ResolverContext::new(&db, PythonVersion::PY39);
 
         // The `xml` package no longer exists on py39:
         let xml_namespace_package = stdlib_path.join("xml");

crates/red_knot_python_semantic/src/module_resolver/resolver.rs

@@ -1,19 +1,19 @@
+use rustc_hash::{FxBuildHasher, FxHashSet};
 use std::borrow::Cow;
 use std::iter::FusedIterator;
-
-use rustc_hash::{FxBuildHasher, FxHashSet};
+use std::ops::Deref;
 
 use ruff_db::files::{File, FilePath, FileRootKind};
-use ruff_db::system::{DirectoryEntry, SystemPath, SystemPathBuf};
-use ruff_db::vendored::VendoredPath;
-
-use crate::db::Db;
-use crate::module_name::ModuleName;
-use crate::{Program, SearchPathSettings};
+use ruff_db::system::{DirectoryEntry, System, SystemPath, SystemPathBuf};
+use ruff_db::vendored::{VendoredFileSystem, VendoredPath};
 
 use super::module::{Module, ModuleKind};
 use super::path::{ModulePath, SearchPath, SearchPathValidationError};
-use super::state::ResolverState;
+use crate::db::Db;
+use crate::module_name::ModuleName;
+use crate::module_resolver::typeshed::{vendored_typeshed_versions, TypeshedVersions};
+use crate::site_packages::VirtualEnvironment;
+use crate::{Program, PythonVersion, SearchPathSettings, SitePackages};
 
 /// Resolves a module name to a module.
 pub fn resolve_module(db: &dyn Db, module_name: ModuleName) -> Option<Module> {
@@ -41,7 +41,7 @@ pub(crate) fn resolve_module_query<'db>(
 
     let module = Module::new(name.clone(), kind, search_path, module_file);
 
-    tracing::debug!(
+    tracing::trace!(
         "Resolved module '{name}' to '{path}'.",
         path = module_file.path(db)
     );
@@ -122,7 +122,7 @@ pub(crate) fn search_paths(db: &dyn Db) -> SearchPathIterator {
     Program::get(db).search_paths(db).iter(db)
 }
 
-#[derive(Debug, PartialEq, Eq, Default)]
+#[derive(Debug, PartialEq, Eq)]
 pub(crate) struct SearchPaths {
     /// Search paths that have been statically determined purely from reading Ruff's configuration settings.
     /// These shouldn't ever change unless the config settings themselves change.
@@ -135,6 +135,8 @@ pub(crate) struct SearchPaths {
     /// in terms of module-resolution priority until we've discovered the editable installs
     /// for the first `site-packages` path
     site_packages: Vec<SearchPath>,
+
+    typeshed_versions: ResolvedTypeshedVersions,
 }
 
 impl SearchPaths {
@@ -146,8 +148,14 @@ impl SearchPaths {
     /// [module resolution order]: https://typing.readthedocs.io/en/latest/spec/distributing.html#import-resolution-ordering
     pub(crate) fn from_settings(
         db: &dyn Db,
-        settings: SearchPathSettings,
+        settings: &SearchPathSettings,
     ) -> Result<Self, SearchPathValidationError> {
+        fn canonicalize(path: &SystemPath, system: &dyn System) -> SystemPathBuf {
+            system
+                .canonicalize_path(path)
+                .unwrap_or_else(|_| path.to_path_buf())
+        }
+
         let SearchPathSettings {
             extra_paths,
             src_root,
@@ -161,45 +169,65 @@ impl SearchPaths {
         let mut static_paths = vec![];
 
         for path in extra_paths {
-            tracing::debug!("Adding static extra search-path '{path}'");
+            let path = canonicalize(path, system);
+            files.try_add_root(db.upcast(), &path, FileRootKind::LibrarySearchPath);
+            tracing::debug!("Adding extra search-path '{path}'");
 
-            let search_path = SearchPath::extra(system, path)?;
-            files.try_add_root(
-                db.upcast(),
-                search_path.as_system_path().unwrap(),
-                FileRootKind::LibrarySearchPath,
-            );
-            static_paths.push(search_path);
+            static_paths.push(SearchPath::extra(system, path)?);
         }
 
-        tracing::debug!("Adding static search path '{src_root}'");
-        static_paths.push(SearchPath::first_party(system, src_root)?);
+        tracing::debug!("Adding first-party search path '{src_root}'");
+        static_paths.push(SearchPath::first_party(system, src_root.to_path_buf())?);
 
-        static_paths.push(if let Some(custom_typeshed) = custom_typeshed {
-            tracing::debug!("Adding static custom-sdtlib search-path '{custom_typeshed}'");
+        let (typeshed_versions, stdlib_path) = if let Some(custom_typeshed) = custom_typeshed {
+            let custom_typeshed = canonicalize(custom_typeshed, system);
+            tracing::debug!("Adding custom-stdlib search path '{custom_typeshed}'");
 
-            let search_path = SearchPath::custom_stdlib(db, custom_typeshed)?;
             files.try_add_root(
                 db.upcast(),
-                search_path.as_system_path().unwrap(),
+                &custom_typeshed,
                 FileRootKind::LibrarySearchPath,
             );
-            search_path
+
+            let versions_path = custom_typeshed.join("stdlib/VERSIONS");
+
+            let versions_content = system.read_to_string(&versions_path).map_err(|error| {
+                SearchPathValidationError::FailedToReadVersionsFile {
+                    path: versions_path,
+                    error,
+                }
+            })?;
+
+            let parsed: TypeshedVersions = versions_content.parse()?;
+
+            let search_path = SearchPath::custom_stdlib(db, &custom_typeshed)?;
+
+            (ResolvedTypeshedVersions::Custom(parsed), search_path)
         } else {
-            SearchPath::vendored_stdlib()
-        });
+            tracing::debug!("Using vendored stdlib");
+            (
+                ResolvedTypeshedVersions::Vendored(vendored_typeshed_versions()),
+                SearchPath::vendored_stdlib(),
+            )
+        };
+
+        static_paths.push(stdlib_path);
+
+        let site_packages_paths = match site_packages_paths {
+            SitePackages::Derived { venv_path } => VirtualEnvironment::new(venv_path, system)
+                .and_then(|venv| venv.site_packages_directories(system))?,
+            SitePackages::Known(paths) => paths
+                .iter()
+                .map(|path| canonicalize(path, system))
+                .collect(),
+        };
 
         let mut site_packages: Vec<_> = Vec::with_capacity(site_packages_paths.len());
 
         for path in site_packages_paths {
-            tracing::debug!("Adding site-package path '{path}'");
-            let search_path = SearchPath::site_packages(system, path)?;
-            files.try_add_root(
-                db.upcast(),
-                search_path.as_system_path().unwrap(),
-                FileRootKind::LibrarySearchPath,
-            );
-            site_packages.push(search_path);
+            tracing::debug!("Adding site-packages search path '{path}'");
+            files.try_add_root(db.upcast(), &path, FileRootKind::LibrarySearchPath);
+            site_packages.push(SearchPath::site_packages(system, path)?);
         }
 
         // TODO vendor typeshed's third-party stubs as well as the stdlib and fallback to them as a final step
@@ -224,16 +252,48 @@ impl SearchPaths {
         Ok(SearchPaths {
             static_paths,
             site_packages,
+            typeshed_versions,
         })
     }
 
-    pub(crate) fn iter<'a>(&'a self, db: &'a dyn Db) -> SearchPathIterator<'a> {
+    pub(super) fn iter<'a>(&'a self, db: &'a dyn Db) -> SearchPathIterator<'a> {
         SearchPathIterator {
             db,
             static_paths: self.static_paths.iter(),
             dynamic_paths: None,
         }
     }
+
+    pub(crate) fn custom_stdlib(&self) -> Option<&SystemPath> {
+        self.static_paths.iter().find_map(|search_path| {
+            if search_path.is_standard_library() {
+                search_path.as_system_path()
+            } else {
+                None
+            }
+        })
+    }
+
+    pub(super) fn typeshed_versions(&self) -> &TypeshedVersions {
+        &self.typeshed_versions
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+enum ResolvedTypeshedVersions {
+    Vendored(&'static TypeshedVersions),
+    Custom(TypeshedVersions),
+}
+
+impl Deref for ResolvedTypeshedVersions {
+    type Target = TypeshedVersions;
+
+    fn deref(&self) -> &Self::Target {
+        match self {
+            ResolvedTypeshedVersions::Vendored(versions) => versions,
+            ResolvedTypeshedVersions::Custom(versions) => versions,
+        }
+    }
 }
 
 /// Collect all dynamic search paths. For each `site-packages` path:
@@ -251,6 +311,7 @@ pub(crate) fn dynamic_resolution_paths(db: &dyn Db) -> Vec<SearchPath> {
     let SearchPaths {
         static_paths,
         site_packages,
+        typeshed_versions: _,
     } = Program::get(db).search_paths(db);
 
     let mut dynamic_paths = Vec::new();
@@ -315,12 +376,16 @@ pub(crate) fn dynamic_resolution_paths(db: &dyn Db) -> Vec<SearchPath> {
         let installations = all_pth_files.iter().flat_map(PthFile::items);
 
         for installation in installations {
+            let installation = system
+                .canonicalize_path(&installation)
+                .unwrap_or(installation);
+
             if existing_paths.insert(Cow::Owned(installation.clone())) {
-                match SearchPath::editable(system, installation) {
+                match SearchPath::editable(system, installation.clone()) {
                     Ok(search_path) => {
                         tracing::debug!(
                             "Adding editable installation to module resolution path {path}",
-                            path = search_path.as_system_path().unwrap()
+                            path = installation
                         );
                         dynamic_paths.push(search_path);
                     }
@@ -482,7 +547,7 @@ struct ModuleNameIngredient<'db> {
 fn resolve_name(db: &dyn Db, name: &ModuleName) -> Option<(SearchPath, File, ModuleKind)> {
     let program = Program::get(db);
     let target_version = program.target_version(db);
-    let resolver_state = ResolverState::new(db, target_version);
+    let resolver_state = ResolverContext::new(db, target_version);
     let is_builtin_module =
         ruff_python_stdlib::sys::is_builtin_module(target_version.minor, name.as_str());
 
@@ -545,7 +610,7 @@ fn resolve_name(db: &dyn Db, name: &ModuleName) -> Option<(SearchPath, File, Mod
 fn resolve_package<'a, 'db, I>(
     module_search_path: &SearchPath,
     components: I,
-    resolver_state: &ResolverState<'db>,
+    resolver_state: &ResolverContext<'db>,
 ) -> Result<ResolvedPackage, PackageKind>
 where
     I: Iterator<Item = &'a str>,
@@ -627,6 +692,21 @@ impl PackageKind {
     }
 }
 
+pub(super) struct ResolverContext<'db> {
+    pub(super) db: &'db dyn Db,
+    pub(super) target_version: PythonVersion,
+}
+
+impl<'db> ResolverContext<'db> {
+    pub(super) fn new(db: &'db dyn Db, target_version: PythonVersion) -> Self {
+        Self { db, target_version }
+    }
+
+    pub(super) fn vendored(&self) -> &VendoredFileSystem {
+        self.db.vendored()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use ruff_db::files::{system_path_to_file, File, FilePath};
@@ -781,7 +861,7 @@ mod tests {
                 "Search path for {module_name} was unexpectedly {search_path:?}"
             );
             assert!(
-                search_path.is_stdlib_search_path(),
+                search_path.is_standard_library(),
                 "Expected a stdlib search path, but got {search_path:?}"
             );
         }
@@ -877,7 +957,7 @@ mod tests {
                 "Search path for {module_name} was unexpectedly {search_path:?}"
             );
             assert!(
-                search_path.is_stdlib_search_path(),
+                search_path.is_standard_library(),
                 "Expected a stdlib search path, but got {search_path:?}"
             );
         }
@@ -1194,13 +1274,13 @@ mod tests {
 
         Program::from_settings(
             &db,
-            ProgramSettings {
+            &ProgramSettings {
                 target_version: PythonVersion::PY38,
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
                     src_root: src.clone(),
                     custom_typeshed: Some(custom_typeshed.clone()),
-                    site_packages: vec![site_packages],
+                    site_packages: SitePackages::Known(vec![site_packages]),
                 },
             },
         )
@@ -1699,13 +1779,16 @@ not_a_directory
 
         Program::from_settings(
             &db,
-            ProgramSettings {
+            &ProgramSettings {
                 target_version: PythonVersion::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
                     src_root: SystemPathBuf::from("/src"),
                     custom_typeshed: None,
-                    site_packages: vec![venv_site_packages, system_site_packages],
+                    site_packages: SitePackages::Known(vec![
+                        venv_site_packages,
+                        system_site_packages,
+                    ]),
                 },
             },
         )

crates/red_knot_python_semantic/src/module_resolver/state.rs

@@ -1,25 +0,0 @@
-use ruff_db::vendored::VendoredFileSystem;
-
-use super::typeshed::LazyTypeshedVersions;
-use crate::db::Db;
-use crate::python_version::PythonVersion;
-
-pub(crate) struct ResolverState<'db> {
-    pub(crate) db: &'db dyn Db,
-    pub(crate) typeshed_versions: LazyTypeshedVersions<'db>,
-    pub(crate) target_version: PythonVersion,
-}
-
-impl<'db> ResolverState<'db> {
-    pub(crate) fn new(db: &'db dyn Db, target_version: PythonVersion) -> Self {
-        Self {
-            db,
-            typeshed_versions: LazyTypeshedVersions::new(),
-            target_version,
-        }
-    }
-
-    pub(crate) fn vendored(&self) -> &VendoredFileSystem {
-        self.db.vendored()
-    }
-}

crates/red_knot_python_semantic/src/module_resolver/testing.rs

@@ -4,7 +4,7 @@ use ruff_db::vendored::VendoredPathBuf;
 use crate::db::tests::TestDb;
 use crate::program::{Program, SearchPathSettings};
 use crate::python_version::PythonVersion;
-use crate::ProgramSettings;
+use crate::{ProgramSettings, SitePackages};
 
 /// A test case for the module resolver.
 ///
@@ -179,6 +179,7 @@ impl TestCaseBuilder<UnspecifiedTypeshed> {
             first_party_files,
             site_packages_files,
         } = self;
+
         TestCaseBuilder {
             typeshed_option: typeshed,
             target_version,
@@ -195,6 +196,7 @@ impl TestCaseBuilder<UnspecifiedTypeshed> {
             site_packages,
             target_version,
         } = self.with_custom_typeshed(MockedTypeshed::default()).build();
+
         TestCase {
             db,
             src,
@@ -223,13 +225,13 @@ impl TestCaseBuilder<MockedTypeshed> {
 
         Program::from_settings(
             &db,
-            ProgramSettings {
+            &ProgramSettings {
                 target_version,
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
                     src_root: src.clone(),
                     custom_typeshed: Some(typeshed.clone()),
-                    site_packages: vec![site_packages.clone()],
+                    site_packages: SitePackages::Known(vec![site_packages.clone()]),
                 },
             },
         )
@@ -279,13 +281,11 @@ impl TestCaseBuilder<VendoredTypeshed> {
 
         Program::from_settings(
             &db,
-            ProgramSettings {
+            &ProgramSettings {
                 target_version,
                 search_paths: SearchPathSettings {
-                    extra_paths: vec![],
-                    src_root: src.clone(),
-                    custom_typeshed: None,
-                    site_packages: vec![site_packages.clone()],
+                    site_packages: SitePackages::Known(vec![site_packages.clone()]),
+                    ..SearchPathSettings::new(src.clone())
                 },
             },
         )

crates/red_knot_python_semantic/src/module_resolver/typeshed/mod.rs

@@ -1,6 +1,6 @@
 pub use self::vendored::vendored_typeshed_stubs;
 pub(super) use self::versions::{
-    parse_typeshed_versions, LazyTypeshedVersions, TypeshedVersionsParseError,
+    typeshed_versions, vendored_typeshed_versions, TypeshedVersions, TypeshedVersionsParseError,
     TypeshedVersionsQueryResult,
 };
 

crates/red_knot_python_semantic/src/module_resolver/typeshed/versions.rs

@@ -1,4 +1,3 @@
-use std::cell::OnceCell;
 use std::collections::BTreeMap;
 use std::fmt;
 use std::num::{NonZeroU16, NonZeroUsize};
@@ -6,78 +5,12 @@ use std::ops::{RangeFrom, RangeInclusive};
 use std::str::FromStr;
 
 use once_cell::sync::Lazy;
-use ruff_db::system::SystemPath;
 use rustc_hash::FxHashMap;
 
-use ruff_db::files::{system_path_to_file, File};
-
 use super::vendored::vendored_typeshed_stubs;
 use crate::db::Db;
 use crate::module_name::ModuleName;
-use crate::python_version::PythonVersion;
-
-#[derive(Debug)]
-pub(crate) struct LazyTypeshedVersions<'db>(OnceCell<&'db TypeshedVersions>);
-
-impl<'db> LazyTypeshedVersions<'db> {
-    #[must_use]
-    pub(crate) fn new() -> Self {
-        Self(OnceCell::new())
-    }
-
-    /// Query whether a module exists at runtime in the stdlib on a certain Python version.
-    ///
-    /// Simply probing whether a file exists in typeshed is insufficient for this question,
-    /// as a module in the stdlib may have been added in Python 3.10, but the typeshed stub
-    /// will still be available (either in a custom typeshed dir or in our vendored copy)
-    /// even if the user specified Python 3.8 as the target version.
-    ///
-    /// For top-level modules and packages, the VERSIONS file can always provide an unambiguous answer
-    /// as to whether the module exists on the specified target version. However, VERSIONS does not
-    /// provide comprehensive information on all submodules, meaning that this method sometimes
-    /// returns [`TypeshedVersionsQueryResult::MaybeExists`].
-    /// See [`TypeshedVersionsQueryResult`] for more details.
-    #[must_use]
-    pub(crate) fn query_module(
-        &self,
-        db: &'db dyn Db,
-        module: &ModuleName,
-        stdlib_root: Option<&SystemPath>,
-        target_version: PythonVersion,
-    ) -> TypeshedVersionsQueryResult {
-        let versions = self.0.get_or_init(|| {
-            let versions_path = if let Some(system_path) = stdlib_root {
-                system_path.join("VERSIONS")
-            } else {
-                return &VENDORED_VERSIONS;
-            };
-            let Ok(versions_file) = system_path_to_file(db.upcast(), &versions_path) else {
-                todo!(
-                    "Still need to figure out how to handle VERSIONS files being deleted \
-                    from custom typeshed directories! Expected a file to exist at {versions_path}"
-                )
-            };
-            // TODO(Alex/Micha): If VERSIONS is invalid,
-            // this should invalidate not just the specific module resolution we're currently attempting,
-            // but all type inference that depends on any standard-library types.
-            // Unwrapping here is not correct...
-            parse_typeshed_versions(db, versions_file).as_ref().unwrap()
-        });
-        versions.query_module(module, target_version)
-    }
-}
-
-#[salsa::tracked(return_ref)]
-pub(crate) fn parse_typeshed_versions(
-    db: &dyn Db,
-    versions_file: File,
-) -> Result<TypeshedVersions, TypeshedVersionsParseError> {
-    // TODO: Handle IO errors
-    let file_content = versions_file
-        .read_to_string(db.upcast())
-        .unwrap_or_default();
-    file_content.parse()
-}
+use crate::{Program, PythonVersion};
 
 static VENDORED_VERSIONS: Lazy<TypeshedVersions> = Lazy::new(|| {
     TypeshedVersions::from_str(
@@ -88,6 +21,14 @@ static VENDORED_VERSIONS: Lazy<TypeshedVersions> = Lazy::new(|| {
     .unwrap()
 });
 
+pub(crate) fn vendored_typeshed_versions() -> &'static TypeshedVersions {
+    &VENDORED_VERSIONS
+}
+
+pub(crate) fn typeshed_versions(db: &dyn Db) -> &TypeshedVersions {
+    Program::get(db).search_paths(db).typeshed_versions()
+}
+
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub(crate) struct TypeshedVersionsParseError {
     line_number: Option<NonZeroU16>,
@@ -174,7 +115,7 @@ impl TypeshedVersions {
     }
 
     #[must_use]
-    fn query_module(
+    pub(in crate::module_resolver) fn query_module(
         &self,
         module: &ModuleName,
         target_version: PythonVersion,
@@ -204,7 +145,7 @@ impl TypeshedVersions {
     }
 }
 
-/// Possible answers [`LazyTypeshedVersions::query_module()`] could give to the question:
+/// Possible answers [`TypeshedVersions::query_module()`] could give to the question:
 /// "Does this module exist in the stdlib at runtime on a certain target version?"
 #[derive(Debug, Copy, PartialEq, Eq, Clone, Hash)]
 pub(crate) enum TypeshedVersionsQueryResult {

crates/red_knot_python_semantic/src/program.rs

@@ -3,7 +3,7 @@ use anyhow::Context;
 use salsa::Durability;
 use salsa::Setter;
 
-use ruff_db::system::SystemPathBuf;
+use ruff_db::system::{SystemPath, SystemPathBuf};
 
 use crate::module_resolver::SearchPaths;
 use crate::Db;
@@ -12,33 +12,31 @@ use crate::Db;
 pub struct Program {
     pub target_version: PythonVersion,
 
-    #[default]
     #[return_ref]
     pub(crate) search_paths: SearchPaths,
 }
 
 impl Program {
-    pub fn from_settings(db: &dyn Db, settings: ProgramSettings) -> anyhow::Result<Self> {
+    pub fn from_settings(db: &dyn Db, settings: &ProgramSettings) -> anyhow::Result<Self> {
         let ProgramSettings {
             target_version,
             search_paths,
         } = settings;
 
-        tracing::info!("Target version: {target_version}");
+        tracing::info!("Target version: Python {target_version}");
 
         let search_paths = SearchPaths::from_settings(db, search_paths)
             .with_context(|| "Invalid search path settings")?;
 
-        Ok(Program::builder(settings.target_version)
+        Ok(Program::builder(settings.target_version, search_paths)
             .durability(Durability::HIGH)
-            .search_paths(search_paths)
             .new(db))
     }
 
     pub fn update_search_paths(
-        &self,
+        self,
         db: &mut dyn Db,
-        search_path_settings: SearchPathSettings,
+        search_path_settings: &SearchPathSettings,
     ) -> anyhow::Result<()> {
         let search_paths = SearchPaths::from_settings(db, search_path_settings)?;
 
@@ -49,16 +47,20 @@ impl Program {
 
         Ok(())
     }
+
+    pub fn custom_stdlib_search_path(self, db: &dyn Db) -> Option<&SystemPath> {
+        self.search_paths(db).custom_stdlib()
+    }
 }
 
-#[derive(Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub struct ProgramSettings {
     pub target_version: PythonVersion,
     pub search_paths: SearchPathSettings,
 }
 
 /// Configures the search paths for module resolution.
-#[derive(Eq, PartialEq, Debug, Clone, Default)]
+#[derive(Eq, PartialEq, Debug, Clone)]
 pub struct SearchPathSettings {
     /// List of user-provided paths that should take first priority in the module resolution.
     /// Examples in other type checkers are mypy's MYPYPATH environment variable,
@@ -74,5 +76,25 @@ pub struct SearchPathSettings {
     pub custom_typeshed: Option<SystemPathBuf>,
 
     /// The path to the user's `site-packages` directory, where third-party packages from ``PyPI`` are installed.
-    pub site_packages: Vec<SystemPathBuf>,
+    pub site_packages: SitePackages,
+}
+
+impl SearchPathSettings {
+    pub fn new(src_root: SystemPathBuf) -> Self {
+        Self {
+            src_root,
+            extra_paths: vec![],
+            custom_typeshed: None,
+            site_packages: SitePackages::Known(vec![]),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub enum SitePackages {
+    Derived {
+        venv_path: SystemPathBuf,
+    },
+    /// Resolved site packages paths
+    Known(Vec<SystemPathBuf>),
 }

crates/red_knot_python_semantic/src/semantic_index.rs

@@ -154,6 +154,10 @@ impl<'db> SemanticIndex<'db> {
         &self.scopes[id]
     }
 
+    pub(crate) fn scope_ids(&self) -> impl Iterator<Item = ScopeId> {
+        self.scope_ids_by_scope.iter().copied()
+    }
+
     /// Returns the id of the parent scope.
     pub(crate) fn parent_scope_id(&self, scope_id: FileScopeId) -> Option<FileScopeId> {
         let scope = self.scope(scope_id);
@@ -463,6 +467,25 @@ mod tests {
         ));
     }
 
+    #[test]
+    fn augmented_assignment() {
+        let TestCase { db, file } = test_case("x += 1");
+        let scope = global_scope(&db, file);
+        let global_table = symbol_table(&db, scope);
+
+        assert_eq!(names(&global_table), vec!["x"]);
+
+        let use_def = use_def_map(&db, scope);
+        let definition = use_def
+            .first_public_definition(global_table.symbol_id_by_name("x").unwrap())
+            .unwrap();
+
+        assert!(matches!(
+            definition.node(&db),
+            DefinitionKind::AugmentedAssignment(_)
+        ));
+    }
+
     #[test]
     fn class_scope() {
         let TestCase { db, file } = test_case(
@@ -767,6 +790,56 @@ def f(a: str, /, b: str, c: int = 1, *args, d: int = 2, **kwargs):
         assert_eq!(names(&inner_comprehension_symbol_table), vec!["x"]);
     }
 
+    #[test]
+    fn with_item_definition() {
+        let TestCase { db, file } = test_case(
+            "
+with item1 as x, item2 as y:
+    pass
+",
+        );
+
+        let index = semantic_index(&db, file);
+        let global_table = index.symbol_table(FileScopeId::global());
+
+        assert_eq!(names(&global_table), vec!["item1", "x", "item2", "y"]);
+
+        let use_def = index.use_def_map(FileScopeId::global());
+        for name in ["x", "y"] {
+            let Some(definition) = use_def.first_public_definition(
+                global_table.symbol_id_by_name(name).expect("symbol exists"),
+            ) else {
+                panic!("Expected with item definition for {name}");
+            };
+            assert!(matches!(definition.node(&db), DefinitionKind::WithItem(_)));
+        }
+    }
+
+    #[test]
+    fn with_item_unpacked_definition() {
+        let TestCase { db, file } = test_case(
+            "
+with context() as (x, y):
+    pass
+",
+        );
+
+        let index = semantic_index(&db, file);
+        let global_table = index.symbol_table(FileScopeId::global());
+
+        assert_eq!(names(&global_table), vec!["context", "x", "y"]);
+
+        let use_def = index.use_def_map(FileScopeId::global());
+        for name in ["x", "y"] {
+            let Some(definition) = use_def.first_public_definition(
+                global_table.symbol_id_by_name(name).expect("symbol exists"),
+            ) else {
+                panic!("Expected with item definition for {name}");
+            };
+            assert!(matches!(definition.node(&db), DefinitionKind::WithItem(_)));
+        }
+    }
+
     #[test]
     fn dupes() {
         let TestCase { db, file } = test_case(
@@ -998,4 +1071,28 @@ def x():
             vec!["bar", "foo", "Test", "<module>"]
         );
     }
+
+    #[test]
+    fn match_stmt_symbols() {
+        let TestCase { db, file } = test_case(
+            "
+match subject:
+    case a: ...
+    case [b, c, *d]: ...
+    case e as f: ...
+    case {'x': g, **h}: ...
+    case Foo(i, z=j): ...
+    case k | l: ...
+    case _: ...
+",
+        );
+
+        let global_table = symbol_table(&db, global_scope(&db, file));
+
+        assert!(global_table.symbol_by_name("Foo").unwrap().is_used());
+        assert_eq!(
+            names(&global_table),
+            vec!["subject", "a", "b", "c", "d", "f", "e", "h", "g", "Foo", "i", "j", "k", "l"]
+        );
+    }
 }

crates/red_knot_python_semantic/src/semantic_index/builder.rs

@@ -7,7 +7,7 @@ use ruff_db::parsed::ParsedModule;
 use ruff_index::IndexVec;
 use ruff_python_ast as ast;
 use ruff_python_ast::name::Name;
-use ruff_python_ast::visitor::{walk_expr, walk_stmt, Visitor};
+use ruff_python_ast::visitor::{walk_expr, walk_pattern, walk_stmt, Visitor};
 use ruff_python_ast::AnyParameterRef;
 
 use crate::ast_node_ref::AstNodeRef;
@@ -26,6 +26,8 @@ use crate::semantic_index::use_def::{FlowSnapshot, UseDefMapBuilder};
 use crate::semantic_index::SemanticIndex;
 use crate::Db;
 
+use super::definition::WithItemDefinitionNodeRef;
+
 pub(super) struct SemanticIndexBuilder<'db> {
     // Builder state
     db: &'db dyn Db,
@@ -495,6 +497,20 @@ where
                 self.visit_expr(&node.target);
                 self.current_assignment = None;
             }
+            ast::Stmt::AugAssign(
+                aug_assign @ ast::StmtAugAssign {
+                    range: _,
+                    target,
+                    op: _,
+                    value,
+                },
+            ) => {
+                debug_assert!(self.current_assignment.is_none());
+                self.visit_expr(value);
+                self.current_assignment = Some(aug_assign.into());
+                self.visit_expr(target);
+                self.current_assignment = None;
+            }
             ast::Stmt::If(node) => {
                 self.visit_expr(&node.test);
                 let pre_if = self.flow_snapshot();
@@ -547,6 +563,18 @@ where
                     self.flow_merge(break_state);
                 }
             }
+            ast::Stmt::With(ast::StmtWith { items, body, .. }) => {
+                for item in items {
+                    self.visit_expr(&item.context_expr);
+                    if let Some(optional_vars) = item.optional_vars.as_deref() {
+                        self.add_standalone_expression(&item.context_expr);
+                        self.current_assignment = Some(item.into());
+                        self.visit_expr(optional_vars);
+                        self.current_assignment = None;
+                    }
+                }
+                self.visit_body(body);
+            }
             ast::Stmt::Break(_) => {
                 self.loop_break_states.push(self.flow_snapshot());
             }
@@ -563,12 +591,21 @@ where
 
         match expr {
             ast::Expr::Name(name_node @ ast::ExprName { id, ctx, .. }) => {
-                let flags = match ctx {
+                let mut flags = match ctx {
                     ast::ExprContext::Load => SymbolFlags::IS_USED,
                     ast::ExprContext::Store => SymbolFlags::IS_DEFINED,
                     ast::ExprContext::Del => SymbolFlags::IS_DEFINED,
                     ast::ExprContext::Invalid => SymbolFlags::empty(),
                 };
+                if matches!(
+                    self.current_assignment,
+                    Some(CurrentAssignment::AugAssign(_))
+                ) && !ctx.is_invalid()
+                {
+                    // For augmented assignment, the target expression is also used, so we should
+                    // record that as a use.
+                    flags |= SymbolFlags::IS_USED;
+                }
                 let symbol = self.add_or_update_symbol(id.clone(), flags);
                 if flags.contains(SymbolFlags::IS_DEFINED) {
                     match self.current_assignment {
@@ -584,6 +621,9 @@ where
                         Some(CurrentAssignment::AnnAssign(ann_assign)) => {
                             self.add_definition(symbol, ann_assign);
                         }
+                        Some(CurrentAssignment::AugAssign(aug_assign)) => {
+                            self.add_definition(symbol, aug_assign);
+                        }
                         Some(CurrentAssignment::Named(named)) => {
                             // TODO(dhruvmanila): If the current scope is a comprehension, then the
                             // named expression is implicitly nonlocal. This is yet to be
@@ -596,6 +636,15 @@ where
                                 ComprehensionDefinitionNodeRef { node, first },
                             );
                         }
+                        Some(CurrentAssignment::WithItem(with_item)) => {
+                            self.add_definition(
+                                symbol,
+                                WithItemDefinitionNodeRef {
+                                    node: with_item,
+                                    target: name_node,
+                                },
+                            );
+                        }
                         None => {}
                     }
                 }
@@ -721,17 +770,38 @@ where
             self.visit_parameter(parameter);
         }
     }
+
+    fn visit_pattern(&mut self, pattern: &'ast ast::Pattern) {
+        if let ast::Pattern::MatchAs(ast::PatternMatchAs {
+            name: Some(name), ..
+        })
+        | ast::Pattern::MatchStar(ast::PatternMatchStar {
+            name: Some(name),
+            range: _,
+        })
+        | ast::Pattern::MatchMapping(ast::PatternMatchMapping {
+            rest: Some(name), ..
+        }) = pattern
+        {
+            // TODO(dhruvmanila): Add definition
+            self.add_or_update_symbol(name.id.clone(), SymbolFlags::IS_DEFINED);
+        }
+
+        walk_pattern(self, pattern);
+    }
 }
 
 #[derive(Copy, Clone, Debug)]
 enum CurrentAssignment<'a> {
     Assign(&'a ast::StmtAssign),
     AnnAssign(&'a ast::StmtAnnAssign),
+    AugAssign(&'a ast::StmtAugAssign),
     Named(&'a ast::ExprNamed),
     Comprehension {
         node: &'a ast::Comprehension,
         first: bool,
     },
+    WithItem(&'a ast::WithItem),
 }
 
 impl<'a> From<&'a ast::StmtAssign> for CurrentAssignment<'a> {
@@ -746,8 +816,20 @@ impl<'a> From<&'a ast::StmtAnnAssign> for CurrentAssignment<'a> {
     }
 }
 
+impl<'a> From<&'a ast::StmtAugAssign> for CurrentAssignment<'a> {
+    fn from(value: &'a ast::StmtAugAssign) -> Self {
+        Self::AugAssign(value)
+    }
+}
+
 impl<'a> From<&'a ast::ExprNamed> for CurrentAssignment<'a> {
     fn from(value: &'a ast::ExprNamed) -> Self {
         Self::Named(value)
     }
 }
+
+impl<'a> From<&'a ast::WithItem> for CurrentAssignment<'a> {
+    fn from(value: &'a ast::WithItem) -> Self {
+        Self::WithItem(value)
+    }
+}

crates/red_knot_python_semantic/src/semantic_index/definition.rs

@@ -44,8 +44,10 @@ pub(crate) enum DefinitionNodeRef<'a> {
     NamedExpression(&'a ast::ExprNamed),
     Assignment(AssignmentDefinitionNodeRef<'a>),
     AnnotatedAssignment(&'a ast::StmtAnnAssign),
+    AugmentedAssignment(&'a ast::StmtAugAssign),
     Comprehension(ComprehensionDefinitionNodeRef<'a>),
     Parameter(ast::AnyParameterRef<'a>),
+    WithItem(WithItemDefinitionNodeRef<'a>),
 }
 
 impl<'a> From<&'a ast::StmtFunctionDef> for DefinitionNodeRef<'a> {
@@ -72,6 +74,12 @@ impl<'a> From<&'a ast::StmtAnnAssign> for DefinitionNodeRef<'a> {
     }
 }
 
+impl<'a> From<&'a ast::StmtAugAssign> for DefinitionNodeRef<'a> {
+    fn from(node: &'a ast::StmtAugAssign) -> Self {
+        Self::AugmentedAssignment(node)
+    }
+}
+
 impl<'a> From<&'a ast::Alias> for DefinitionNodeRef<'a> {
     fn from(node_ref: &'a ast::Alias) -> Self {
         Self::Import(node_ref)
@@ -90,6 +98,12 @@ impl<'a> From<AssignmentDefinitionNodeRef<'a>> for DefinitionNodeRef<'a> {
     }
 }
 
+impl<'a> From<WithItemDefinitionNodeRef<'a>> for DefinitionNodeRef<'a> {
+    fn from(node_ref: WithItemDefinitionNodeRef<'a>) -> Self {
+        Self::WithItem(node_ref)
+    }
+}
+
 impl<'a> From<ComprehensionDefinitionNodeRef<'a>> for DefinitionNodeRef<'a> {
     fn from(node: ComprehensionDefinitionNodeRef<'a>) -> Self {
         Self::Comprehension(node)
@@ -114,6 +128,12 @@ pub(crate) struct AssignmentDefinitionNodeRef<'a> {
     pub(crate) target: &'a ast::ExprName,
 }
 
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct WithItemDefinitionNodeRef<'a> {
+    pub(crate) node: &'a ast::WithItem,
+    pub(crate) target: &'a ast::ExprName,
+}
+
 #[derive(Copy, Clone, Debug)]
 pub(crate) struct ComprehensionDefinitionNodeRef<'a> {
     pub(crate) node: &'a ast::Comprehension,
@@ -151,6 +171,9 @@ impl DefinitionNodeRef<'_> {
             DefinitionNodeRef::AnnotatedAssignment(assign) => {
                 DefinitionKind::AnnotatedAssignment(AstNodeRef::new(parsed, assign))
             }
+            DefinitionNodeRef::AugmentedAssignment(augmented_assignment) => {
+                DefinitionKind::AugmentedAssignment(AstNodeRef::new(parsed, augmented_assignment))
+            }
             DefinitionNodeRef::Comprehension(ComprehensionDefinitionNodeRef { node, first }) => {
                 DefinitionKind::Comprehension(ComprehensionDefinitionKind {
                     node: AstNodeRef::new(parsed, node),
@@ -165,6 +188,12 @@ impl DefinitionNodeRef<'_> {
                     DefinitionKind::ParameterWithDefault(AstNodeRef::new(parsed, parameter))
                 }
             },
+            DefinitionNodeRef::WithItem(WithItemDefinitionNodeRef { node, target }) => {
+                DefinitionKind::WithItem(WithItemDefinitionKind {
+                    node: AstNodeRef::new(parsed.clone(), node),
+                    target: AstNodeRef::new(parsed, target),
+                })
+            }
         }
     }
 
@@ -182,11 +211,13 @@ impl DefinitionNodeRef<'_> {
                 target,
             }) => target.into(),
             Self::AnnotatedAssignment(node) => node.into(),
+            Self::AugmentedAssignment(node) => node.into(),
             Self::Comprehension(ComprehensionDefinitionNodeRef { node, first: _ }) => node.into(),
             Self::Parameter(node) => match node {
                 ast::AnyParameterRef::Variadic(parameter) => parameter.into(),
                 ast::AnyParameterRef::NonVariadic(parameter) => parameter.into(),
             },
+            Self::WithItem(WithItemDefinitionNodeRef { node: _, target }) => target.into(),
         }
     }
 }
@@ -200,9 +231,11 @@ pub enum DefinitionKind {
     NamedExpression(AstNodeRef<ast::ExprNamed>),
     Assignment(AssignmentDefinitionKind),
     AnnotatedAssignment(AstNodeRef<ast::StmtAnnAssign>),
+    AugmentedAssignment(AstNodeRef<ast::StmtAugAssign>),
     Comprehension(ComprehensionDefinitionKind),
     Parameter(AstNodeRef<ast::Parameter>),
     ParameterWithDefault(AstNodeRef<ast::ParameterWithDefault>),
+    WithItem(WithItemDefinitionKind),
 }
 
 #[derive(Clone, Debug)]
@@ -238,7 +271,6 @@ impl ImportFromDefinitionKind {
 }
 
 #[derive(Clone, Debug)]
-#[allow(dead_code)]
 pub struct AssignmentDefinitionKind {
     assignment: AstNodeRef<ast::StmtAssign>,
     target: AstNodeRef<ast::ExprName>,
@@ -254,6 +286,22 @@ impl AssignmentDefinitionKind {
     }
 }
 
+#[derive(Clone, Debug)]
+pub struct WithItemDefinitionKind {
+    node: AstNodeRef<ast::WithItem>,
+    target: AstNodeRef<ast::ExprName>,
+}
+
+impl WithItemDefinitionKind {
+    pub(crate) fn node(&self) -> &ast::WithItem {
+        self.node.node()
+    }
+
+    pub(crate) fn target(&self) -> &ast::ExprName {
+        self.target.node()
+    }
+}
+
 #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
 pub(crate) struct DefinitionNodeKey(NodeKey);
 
@@ -293,6 +341,12 @@ impl From<&ast::StmtAnnAssign> for DefinitionNodeKey {
     }
 }
 
+impl From<&ast::StmtAugAssign> for DefinitionNodeKey {
+    fn from(node: &ast::StmtAugAssign) -> Self {
+        Self(NodeKey::from_node(node))
+    }
+}
+
 impl From<&ast::Comprehension> for DefinitionNodeKey {
     fn from(node: &ast::Comprehension) -> Self {
         Self(NodeKey::from_node(node))

crates/red_knot_python_semantic/src/semantic_model.rs

@@ -184,14 +184,9 @@ mod tests {
 
         Program::from_settings(
             &db,
-            ProgramSettings {
+            &ProgramSettings {
                 target_version: PythonVersion::default(),
-                search_paths: SearchPathSettings {
-                    extra_paths: vec![],
-                    src_root: SystemPathBuf::from("/src"),
-                    site_packages: vec![],
-                    custom_typeshed: None,
-                },
+                search_paths: SearchPathSettings::new(SystemPathBuf::from("/src")),
             },
         )?;
 

crates/red_knot_python_semantic/src/site_packages.rs

@@ -13,9 +13,10 @@ use std::io;
 use std::num::NonZeroUsize;
 use std::ops::Deref;
 
-use red_knot_python_semantic::PythonVersion;
 use ruff_db::system::{System, SystemPath, SystemPathBuf};
 
+use crate::PythonVersion;
+
 type SitePackagesDiscoveryResult<T> = Result<T, SitePackagesDiscoveryError>;
 
 /// Abstraction for a Python virtual environment.
@@ -24,7 +25,7 @@ type SitePackagesDiscoveryResult<T> = Result<T, SitePackagesDiscoveryError>;
 /// The format of this file is not defined anywhere, and exactly which keys are present
 /// depends on the tool that was used to create the virtual environment.
 #[derive(Debug)]
-pub struct VirtualEnvironment {
+pub(crate) struct VirtualEnvironment {
     venv_path: SysPrefixPath,
     base_executable_home_path: PythonHomePath,
     include_system_site_packages: bool,
@@ -41,7 +42,7 @@ pub struct VirtualEnvironment {
 }
 
 impl VirtualEnvironment {
-    pub fn new(
+    pub(crate) fn new(
         path: impl AsRef<SystemPath>,
         system: &dyn System,
     ) -> SitePackagesDiscoveryResult<Self> {
@@ -55,7 +56,7 @@ impl VirtualEnvironment {
 
         let venv_path = SysPrefixPath::new(path, system)?;
         let pyvenv_cfg_path = venv_path.join("pyvenv.cfg");
-        tracing::debug!("Attempting to parse virtual environment metadata at {pyvenv_cfg_path}");
+        tracing::debug!("Attempting to parse virtual environment metadata at '{pyvenv_cfg_path}'");
 
         let pyvenv_cfg = system
             .read_to_string(&pyvenv_cfg_path)
@@ -157,7 +158,7 @@ impl VirtualEnvironment {
     /// Return a list of `site-packages` directories that are available from this virtual environment
     ///
     /// See the documentation for `site_packages_dir_from_sys_prefix` for more details.
-    pub fn site_packages_directories(
+    pub(crate) fn site_packages_directories(
         &self,
         system: &dyn System,
     ) -> SitePackagesDiscoveryResult<Vec<SystemPathBuf>> {
@@ -191,7 +192,7 @@ impl VirtualEnvironment {
             } else {
                 tracing::warn!(
                     "Failed to resolve `sys.prefix` of the system Python installation \
-from the `home` value in the `pyvenv.cfg` file at {}. \
+from the `home` value in the `pyvenv.cfg` file at '{}'. \
 System site-packages will not be used for module resolution.",
                     venv_path.join("pyvenv.cfg")
                 );
@@ -204,7 +205,7 @@ System site-packages will not be used for module resolution.",
 }
 
 #[derive(Debug, thiserror::Error)]
-pub enum SitePackagesDiscoveryError {
+pub(crate) enum SitePackagesDiscoveryError {
     #[error("Invalid --venv-path argument: {0} could not be canonicalized")]
     VenvDirCanonicalizationError(SystemPathBuf, #[source] io::Error),
     #[error("Invalid --venv-path argument: {0} does not point to a directory on disk")]
@@ -221,7 +222,7 @@ pub enum SitePackagesDiscoveryError {
 
 /// The various ways in which parsing a `pyvenv.cfg` file could fail
 #[derive(Debug)]
-pub enum PyvenvCfgParseErrorKind {
+pub(crate) enum PyvenvCfgParseErrorKind {
     TooManyEquals { line_number: NonZeroUsize },
     MalformedKeyValuePair { line_number: NonZeroUsize },
     NoHomeKey,
@@ -370,7 +371,7 @@ fn site_packages_directory_from_sys_prefix(
 ///
 /// [`sys.prefix`]: https://docs.python.org/3/library/sys.html#sys.prefix
 #[derive(Debug, PartialEq, Eq, Clone)]
-pub struct SysPrefixPath(SystemPathBuf);
+pub(crate) struct SysPrefixPath(SystemPathBuf);
 
 impl SysPrefixPath {
     fn new(
@@ -425,7 +426,7 @@ impl Deref for SysPrefixPath {
 
 impl fmt::Display for SysPrefixPath {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "`sys.prefix` path {}", self.0)
+        write!(f, "`sys.prefix` path '{}'", self.0)
     }
 }
 
@@ -482,7 +483,7 @@ impl Deref for PythonHomePath {
 
 impl fmt::Display for PythonHomePath {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "`home` location {}", self.0)
+        write!(f, "`home` location '{}'", self.0)
     }
 }
 

crates/red_knot_python_semantic/src/types.rs

@@ -5,21 +5,37 @@ use crate::builtins::builtins_scope;
 use crate::semantic_index::definition::Definition;
 use crate::semantic_index::symbol::{ScopeId, ScopedSymbolId};
 use crate::semantic_index::{
-    global_scope, symbol_table, use_def_map, DefinitionWithConstraints,
+    global_scope, semantic_index, symbol_table, use_def_map, DefinitionWithConstraints,
     DefinitionWithConstraintsIterator,
 };
 use crate::types::narrow::narrowing_constraint;
 use crate::{Db, FxOrderSet};
 
+pub(crate) use self::builder::{IntersectionBuilder, UnionBuilder};
+pub(crate) use self::diagnostic::TypeCheckDiagnostics;
+pub(crate) use self::infer::{
+    infer_definition_types, infer_expression_types, infer_scope_types, TypeInference,
+};
+
 mod builder;
+mod diagnostic;
 mod display;
 mod infer;
 mod narrow;
 
-pub(crate) use self::builder::{IntersectionBuilder, UnionBuilder};
-pub(crate) use self::infer::{
-    infer_definition_types, infer_expression_types, infer_scope_types, TypeInference,
-};
+pub fn check_types(db: &dyn Db, file: File) -> TypeCheckDiagnostics {
+    let _span = tracing::trace_span!("check_types", file=?file.path(db)).entered();
+
+    let index = semantic_index(db, file);
+    let mut diagnostics = TypeCheckDiagnostics::new();
+
+    for scope_id in index.scope_ids() {
+        let result = infer_scope_types(db, scope_id);
+        diagnostics.extend(result.diagnostics());
+    }
+
+    diagnostics
+}
 
 /// Infer the public type of a symbol (its type as seen from outside its scope).
 pub(crate) fn symbol_ty<'db>(
@@ -206,20 +222,42 @@ impl<'db> Type<'db> {
         }
     }
 
+    /// Resolve a member access of a type.
+    ///
+    /// For example, if `foo` is `Type::Instance(<Bar>)`,
+    /// `foo.member(&db, "baz")` returns the type of `baz` attributes
+    /// as accessed from instances of the `Bar` class.
+    ///
+    /// TODO: use of this method currently requires manually checking
+    /// whether the returned type is `Unknown`/`Unbound`
+    /// (or a union with `Unknown`/`Unbound`) in many places.
+    /// Ideally we'd use a more type-safe pattern, such as returning
+    /// an `Option` or a `Result` from this method, which would force
+    /// us to explicitly consider whether to handle an error or propagate
+    /// it up the call stack.
     #[must_use]
     pub fn member(&self, db: &'db dyn Db, name: &Name) -> Type<'db> {
         match self {
             Type::Any => Type::Any,
-            Type::Never => todo!("attribute lookup on Never type"),
+            Type::Never => {
+                // TODO: attribute lookup on Never type
+                Type::Unknown
+            }
             Type::Unknown => Type::Unknown,
             Type::Unbound => Type::Unbound,
-            Type::None => todo!("attribute lookup on None type"),
-            Type::Function(_) => todo!("attribute lookup on Function type"),
+            Type::None => {
+                // TODO: attribute lookup on None type
+                Type::Unknown
+            }
+            Type::Function(_) => {
+                // TODO: attribute lookup on function type
+                Type::Unknown
+            }
             Type::Module(file) => global_symbol_ty_by_name(db, *file, name),
             Type::Class(class) => class.class_member(db, name),
             Type::Instance(_) => {
                 // TODO MRO? get_own_instance_member, get_instance_member
-                todo!("attribute lookup on Instance type")
+                Type::Unknown
             }
             Type::Union(union) => union
                 .elements(db)
@@ -231,7 +269,7 @@ impl<'db> Type<'db> {
             Type::Intersection(_) => {
                 // TODO perform the get_member on each type in the intersection
                 // TODO return the intersection of those results
-                todo!("attribute lookup on Intersection type")
+                Type::Unknown
             }
             Type::IntLiteral(_) => {
                 // TODO raise error
@@ -333,3 +371,110 @@ pub struct IntersectionType<'db> {
     /// directly in intersections rather than as a separate type.
     negative: FxOrderSet<Type<'db>>,
 }
+
+#[cfg(test)]
+mod tests {
+    use anyhow::Context;
+
+    use ruff_db::files::system_path_to_file;
+    use ruff_db::system::{DbWithTestSystem, SystemPathBuf};
+
+    use crate::db::tests::TestDb;
+    use crate::{Program, ProgramSettings, PythonVersion, SearchPathSettings};
+
+    use super::TypeCheckDiagnostics;
+
+    fn setup_db() -> TestDb {
+        let db = TestDb::new();
+        db.memory_file_system()
+            .create_directory_all("/src")
+            .unwrap();
+
+        Program::from_settings(
+            &db,
+            &ProgramSettings {
+                target_version: PythonVersion::default(),
+                search_paths: SearchPathSettings::new(SystemPathBuf::from("/src")),
+            },
+        )
+        .expect("Valid search path settings");
+
+        db
+    }
+
+    fn assert_diagnostic_messages(diagnostics: &TypeCheckDiagnostics, expected: &[&str]) {
+        let messages: Vec<&str> = diagnostics
+            .iter()
+            .map(|diagnostic| diagnostic.message())
+            .collect();
+        assert_eq!(&messages, expected);
+    }
+
+    #[test]
+    fn unresolved_import_statement() -> anyhow::Result<()> {
+        let mut db = setup_db();
+
+        db.write_file("src/foo.py", "import bar\n")
+            .context("Failed to write foo.py")?;
+
+        let foo = system_path_to_file(&db, "src/foo.py").context("Failed to resolve foo.py")?;
+
+        let diagnostics = super::check_types(&db, foo);
+        assert_diagnostic_messages(&diagnostics, &["Import 'bar' could not be resolved."]);
+
+        Ok(())
+    }
+
+    #[test]
+    fn unresolved_import_from_statement() {
+        let mut db = setup_db();
+
+        db.write_file("src/foo.py", "from bar import baz\n")
+            .unwrap();
+        let foo = system_path_to_file(&db, "src/foo.py").unwrap();
+        let diagnostics = super::check_types(&db, foo);
+        assert_diagnostic_messages(&diagnostics, &["Import 'bar' could not be resolved."]);
+    }
+
+    #[test]
+    fn unresolved_import_from_resolved_module() {
+        let mut db = setup_db();
+
+        db.write_files([("/src/a.py", ""), ("/src/b.py", "from a import thing")])
+            .unwrap();
+
+        let b_file = system_path_to_file(&db, "/src/b.py").unwrap();
+        let b_file_diagnostics = super::check_types(&db, b_file);
+        assert_diagnostic_messages(
+            &b_file_diagnostics,
+            &["Could not resolve import of 'thing' from 'a'"],
+        );
+    }
+
+    #[ignore = "\
+A spurious second 'Unresolved import' diagnostic message is emitted on `b.py`, \
+despite the symbol existing in the symbol table for `a.py`"]
+    #[test]
+    fn resolved_import_of_symbol_from_unresolved_import() {
+        let mut db = setup_db();
+
+        db.write_files([
+            ("/src/a.py", "import foo as foo"),
+            ("/src/b.py", "from a import foo"),
+        ])
+        .unwrap();
+
+        let a_file = system_path_to_file(&db, "/src/a.py").unwrap();
+        let a_file_diagnostics = super::check_types(&db, a_file);
+        assert_diagnostic_messages(
+            &a_file_diagnostics,
+            &["Import 'foo' could not be resolved."],
+        );
+
+        // Importing the unresolved import into a second first-party file should not trigger
+        // an additional "unresolved import" violation
+        let b_file = system_path_to_file(&db, "/src/b.py").unwrap();
+        let b_file_diagnostics = super::check_types(&db, b_file);
+        assert_eq!(&*b_file_diagnostics, &[]);
+    }
+}

crates/red_knot_python_semantic/src/types/diagnostic.rs

@@ -0,0 +1,111 @@
+use ruff_db::files::File;
+use ruff_text_size::{Ranged, TextRange};
+use std::fmt::Formatter;
+use std::ops::Deref;
+use std::sync::Arc;
+
+#[derive(Debug, Eq, PartialEq)]
+pub struct TypeCheckDiagnostic {
+    // TODO: Don't use string keys for rules
+    pub(super) rule: String,
+    pub(super) message: String,
+    pub(super) range: TextRange,
+    pub(super) file: File,
+}
+
+impl TypeCheckDiagnostic {
+    pub fn rule(&self) -> &str {
+        &self.rule
+    }
+
+    pub fn message(&self) -> &str {
+        &self.message
+    }
+
+    pub fn file(&self) -> File {
+        self.file
+    }
+}
+
+impl Ranged for TypeCheckDiagnostic {
+    fn range(&self) -> TextRange {
+        self.range
+    }
+}
+
+/// A collection of type check diagnostics.
+///
+/// The diagnostics are wrapped in an `Arc` because they need to be cloned multiple times
+/// when going from `infer_expression` to `check_file`. We could consider
+/// making [`TypeCheckDiagnostic`] a Salsa struct to have them Arena-allocated (once the Tables refactor is done).
+/// Using Salsa struct does have the downside that it leaks the Salsa dependency into diagnostics and
+/// each Salsa-struct comes with an overhead.
+#[derive(Default, Eq, PartialEq)]
+pub struct TypeCheckDiagnostics {
+    inner: Vec<std::sync::Arc<TypeCheckDiagnostic>>,
+}
+
+impl TypeCheckDiagnostics {
+    pub fn new() -> Self {
+        Self { inner: Vec::new() }
+    }
+
+    pub(super) fn push(&mut self, diagnostic: TypeCheckDiagnostic) {
+        self.inner.push(Arc::new(diagnostic));
+    }
+
+    pub(crate) fn shrink_to_fit(&mut self) {
+        self.inner.shrink_to_fit();
+    }
+}
+
+impl Extend<TypeCheckDiagnostic> for TypeCheckDiagnostics {
+    fn extend<T: IntoIterator<Item = TypeCheckDiagnostic>>(&mut self, iter: T) {
+        self.inner.extend(iter.into_iter().map(std::sync::Arc::new));
+    }
+}
+
+impl Extend<std::sync::Arc<TypeCheckDiagnostic>> for TypeCheckDiagnostics {
+    fn extend<T: IntoIterator<Item = Arc<TypeCheckDiagnostic>>>(&mut self, iter: T) {
+        self.inner.extend(iter);
+    }
+}
+
+impl<'a> Extend<&'a std::sync::Arc<TypeCheckDiagnostic>> for TypeCheckDiagnostics {
+    fn extend<T: IntoIterator<Item = &'a Arc<TypeCheckDiagnostic>>>(&mut self, iter: T) {
+        self.inner
+            .extend(iter.into_iter().map(std::sync::Arc::clone));
+    }
+}
+
+impl std::fmt::Debug for TypeCheckDiagnostics {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        self.inner.fmt(f)
+    }
+}
+
+impl Deref for TypeCheckDiagnostics {
+    type Target = [std::sync::Arc<TypeCheckDiagnostic>];
+
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+impl IntoIterator for TypeCheckDiagnostics {
+    type Item = Arc<TypeCheckDiagnostic>;
+    type IntoIter = std::vec::IntoIter<std::sync::Arc<TypeCheckDiagnostic>>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.inner.into_iter()
+    }
+}
+
+impl<'a> IntoIterator for &'a TypeCheckDiagnostics {
+    type Item = &'a Arc<TypeCheckDiagnostic>;
+    type IntoIter = std::slice::Iter<'a, std::sync::Arc<TypeCheckDiagnostic>>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.inner.iter()
+    }
+}

crates/red_knot_python_semantic/src/types/infer.rs

@@ -29,7 +29,8 @@ use salsa::plumbing::AsId;
 use ruff_db::files::File;
 use ruff_db::parsed::parsed_module;
 use ruff_python_ast as ast;
-use ruff_python_ast::{Expr, ExprContext};
+use ruff_python_ast::{AnyNodeRef, ExprContext};
+use ruff_text_size::Ranged;
 
 use crate::builtins::builtins_scope;
 use crate::module_name::ModuleName;
@@ -40,6 +41,7 @@ use crate::semantic_index::expression::Expression;
 use crate::semantic_index::semantic_index;
 use crate::semantic_index::symbol::{FileScopeId, NodeWithScopeKind, NodeWithScopeRef, ScopeId};
 use crate::semantic_index::SemanticIndex;
+use crate::types::diagnostic::{TypeCheckDiagnostic, TypeCheckDiagnostics};
 use crate::types::{
     builtins_symbol_ty_by_name, definitions_ty, global_symbol_ty_by_name, ClassType, FunctionType,
     Name, Type, UnionBuilder,
@@ -123,13 +125,16 @@ pub(crate) enum InferenceRegion<'db> {
 }
 
 /// The inferred types for a single region.
-#[derive(Debug, Eq, PartialEq, Default, Clone)]
+#[derive(Debug, Eq, PartialEq, Default)]
 pub(crate) struct TypeInference<'db> {
     /// The types of every expression in this region.
     expressions: FxHashMap<ScopedExpressionId, Type<'db>>,
 
     /// The types of every definition in this region.
     definitions: FxHashMap<Definition<'db>, Type<'db>>,
+
+    /// The diagnostics for this region.
+    diagnostics: TypeCheckDiagnostics,
 }
 
 impl<'db> TypeInference<'db> {
@@ -142,9 +147,14 @@ impl<'db> TypeInference<'db> {
         self.definitions[&definition]
     }
 
+    pub(crate) fn diagnostics(&self) -> &[std::sync::Arc<TypeCheckDiagnostic>] {
+        &self.diagnostics
+    }
+
     fn shrink_to_fit(&mut self) {
         self.expressions.shrink_to_fit();
         self.definitions.shrink_to_fit();
+        self.diagnostics.shrink_to_fit();
     }
 }
 
@@ -235,6 +245,7 @@ impl<'db> TypeInferenceBuilder<'db> {
     fn extend(&mut self, inference: &TypeInference<'db>) {
         self.types.definitions.extend(inference.definitions.iter());
         self.types.expressions.extend(inference.expressions.iter());
+        self.types.diagnostics.extend(&inference.diagnostics);
     }
 
     /// Infers types in the given [`InferenceRegion`].
@@ -303,6 +314,9 @@ impl<'db> TypeInferenceBuilder<'db> {
             DefinitionKind::AnnotatedAssignment(annotated_assignment) => {
                 self.infer_annotated_assignment_definition(annotated_assignment.node(), definition);
             }
+            DefinitionKind::AugmentedAssignment(augmented_assignment) => {
+                self.infer_augment_assignment_definition(augmented_assignment.node(), definition);
+            }
             DefinitionKind::NamedExpression(named_expression) => {
                 self.infer_named_expression_definition(named_expression.node(), definition);
             }
@@ -319,6 +333,9 @@ impl<'db> TypeInferenceBuilder<'db> {
             DefinitionKind::ParameterWithDefault(parameter_with_default) => {
                 self.infer_parameter_with_default_definition(parameter_with_default, definition);
             }
+            DefinitionKind::WithItem(with_item) => {
+                self.infer_with_item_definition(with_item.target(), with_item.node(), definition);
+            }
         }
     }
 
@@ -604,13 +621,42 @@ impl<'db> TypeInferenceBuilder<'db> {
         } = with_statement;
 
         for item in items {
-            self.infer_expression(&item.context_expr);
-            self.infer_optional_expression(item.optional_vars.as_deref());
+            match item.optional_vars.as_deref() {
+                Some(ast::Expr::Name(name)) => {
+                    self.infer_definition(name);
+                }
+                _ => {
+                    // TODO infer definitions in unpacking assignment
+                    self.infer_expression(&item.context_expr);
+                }
+            }
         }
 
         self.infer_body(body);
     }
 
+    fn infer_with_item_definition(
+        &mut self,
+        target: &ast::ExprName,
+        with_item: &ast::WithItem,
+        definition: Definition<'db>,
+    ) {
+        let expression = self.index.expression(&with_item.context_expr);
+        let result = infer_expression_types(self.db, expression);
+        self.extend(result);
+
+        // TODO(dhruvmanila): The correct type inference here is the return type of the __enter__
+        // method of the context manager.
+        let context_expr_ty = self
+            .types
+            .expression_ty(with_item.context_expr.scoped_ast_id(self.db, self.scope));
+
+        self.types
+            .expressions
+            .insert(target.scoped_ast_id(self.db, self.scope), context_expr_ty);
+        self.types.definitions.insert(definition, context_expr_ty);
+    }
+
     fn infer_match_statement(&mut self, match_statement: &ast::StmtMatch) {
         let ast::StmtMatch {
             range: _,
@@ -763,15 +809,35 @@ impl<'db> TypeInferenceBuilder<'db> {
     }
 
     fn infer_augmented_assignment_statement(&mut self, assignment: &ast::StmtAugAssign) {
-        // TODO this should be a Definition
+        if assignment.target.is_name_expr() {
+            self.infer_definition(assignment);
+        } else {
+            // TODO currently we don't consider assignments to non-Names to be Definitions
+            self.infer_augment_assignment(assignment);
+        }
+    }
+
+    fn infer_augment_assignment_definition(
+        &mut self,
+        assignment: &ast::StmtAugAssign,
+        definition: Definition<'db>,
+    ) {
+        let target_ty = self.infer_augment_assignment(assignment);
+        self.types.definitions.insert(definition, target_ty);
+    }
+
+    fn infer_augment_assignment(&mut self, assignment: &ast::StmtAugAssign) -> Type<'db> {
         let ast::StmtAugAssign {
             range: _,
             target,
             op: _,
             value,
         } = assignment;
-        self.infer_expression(target);
         self.infer_expression(value);
+        self.infer_expression(target);
+
+        // TODO(dhruvmanila): Resolve the target type using the value type and the operator
+        Type::Unknown
     }
 
     fn infer_type_alias_statement(&mut self, type_alias_statement: &ast::StmtTypeAlias) {
@@ -832,7 +898,26 @@ impl<'db> TypeInferenceBuilder<'db> {
             asname: _,
         } = alias;
 
-        let module_ty = self.module_ty_from_name(ModuleName::new(name));
+        let module_ty = ModuleName::new(name)
+            .ok_or(ModuleResolutionError::InvalidSyntax)
+            .and_then(|module_name| self.module_ty_from_name(module_name));
+
+        let module_ty = match module_ty {
+            Ok(ty) => ty,
+            Err(ModuleResolutionError::InvalidSyntax) => {
+                tracing::debug!("Failed to resolve import due to invalid syntax");
+                Type::Unknown
+            }
+            Err(ModuleResolutionError::UnresolvedModule) => {
+                self.add_diagnostic(
+                    AnyNodeRef::Alias(alias),
+                    "unresolved-import",
+                    format_args!("Import '{name}' could not be resolved."),
+                );
+                Type::Unknown
+            }
+        };
+
         self.types.definitions.insert(definition, module_ty);
     }
 
@@ -880,10 +965,18 @@ impl<'db> TypeInferenceBuilder<'db> {
     /// - `tail` is the relative module name stripped of all leading dots:
     ///   - `from .foo import bar` => `tail == "foo"`
     ///   - `from ..foo.bar import baz` => `tail == "foo.bar"`
-    fn relative_module_name(&self, tail: Option<&str>, level: NonZeroU32) -> Option<ModuleName> {
+    fn relative_module_name(
+        &self,
+        tail: Option<&str>,
+        level: NonZeroU32,
+    ) -> Result<ModuleName, ModuleResolutionError> {
         let Some(module) = file_to_module(self.db, self.file) else {
-            tracing::debug!("Failed to resolve file {:?} to a module", self.file);
-            return None;
+            tracing::debug!(
+                "Relative module resolution '{}' failed; could not resolve file '{}' to a module",
+                format_import_from_module(level.get(), tail),
+                self.file.path(self.db)
+            );
+            return Err(ModuleResolutionError::UnresolvedModule);
         };
         let mut level = level.get();
         if module.kind().is_package() {
@@ -891,17 +984,19 @@ impl<'db> TypeInferenceBuilder<'db> {
         }
         let mut module_name = module.name().to_owned();
         for _ in 0..level {
-            module_name = module_name.parent()?;
+            module_name = module_name
+                .parent()
+                .ok_or(ModuleResolutionError::UnresolvedModule)?;
         }
         if let Some(tail) = tail {
             if let Some(valid_tail) = ModuleName::new(tail) {
                 module_name.extend(&valid_tail);
             } else {
-                tracing::debug!("Failed to resolve relative import due to invalid syntax");
-                return None;
+                tracing::debug!("Relative module resolution failed: invalid syntax");
+                return Err(ModuleResolutionError::InvalidSyntax);
             }
         }
-        Some(module_name)
+        Ok(module_name)
     }
 
     fn infer_import_from_definition(
@@ -921,16 +1016,27 @@ impl<'db> TypeInferenceBuilder<'db> {
         // `follow_nonexistent_import_bare_to_module()`.
         let ast::StmtImportFrom { module, level, .. } = import_from;
         tracing::trace!("Resolving imported object {alias:?} from statement {import_from:?}");
+        let module = module.as_deref();
         let module_name = if let Some(level) = NonZeroU32::new(*level) {
-            self.relative_module_name(module.as_deref(), level)
+            tracing::trace!(
+                "Resolving imported object '{}' from module '{}' relative to file '{}'",
+                alias.name,
+                format_import_from_module(level.get(), module),
+                self.file.path(self.db),
+            );
+            self.relative_module_name(module, level)
         } else {
-            let module_name = module
-                .as_ref()
-                .expect("Non-relative import should always have a non-None `module`!");
-            ModuleName::new(module_name)
+            tracing::trace!(
+                "Resolving imported object '{}' from module '{}'",
+                alias.name,
+                format_import_from_module(*level, module),
+            );
+            module
+                .and_then(ModuleName::new)
+                .ok_or(ModuleResolutionError::InvalidSyntax)
         };
 
-        let module_ty = self.module_ty_from_name(module_name);
+        let module_ty = module_name.and_then(|module_name| self.module_ty_from_name(module_name));
 
         let ast::Alias {
             range: _,
@@ -943,11 +1049,34 @@ impl<'db> TypeInferenceBuilder<'db> {
         // the runtime error will occur immediately (rather than when the symbol is *used*,
         // as would be the case for a symbol with type `Unbound`), so it's appropriate to
         // think of the type of the imported symbol as `Unknown` rather than `Unbound`
-        let ty = module_ty
+        let member_ty = module_ty
+            .unwrap_or(Type::Unbound)
             .member(self.db, &Name::new(&name.id))
             .replace_unbound_with(self.db, Type::Unknown);
 
-        self.types.definitions.insert(definition, ty);
+        if matches!(module_ty, Err(ModuleResolutionError::UnresolvedModule)) {
+            self.add_diagnostic(
+                AnyNodeRef::StmtImportFrom(import_from),
+                "unresolved-import",
+                format_args!(
+                    "Import '{}{}' could not be resolved.",
+                    ".".repeat(*level as usize),
+                    module.unwrap_or_default()
+                ),
+            );
+        } else if module_ty.is_ok() && member_ty.is_unknown() {
+            self.add_diagnostic(
+                AnyNodeRef::Alias(alias),
+                "unresolved-import",
+                format_args!(
+                    "Could not resolve import of '{name}' from '{}{}'",
+                    ".".repeat(*level as usize),
+                    module.unwrap_or_default()
+                ),
+            );
+        }
+
+        self.types.definitions.insert(definition, member_ty);
     }
 
     fn infer_return_statement(&mut self, ret: &ast::StmtReturn) {
@@ -961,10 +1090,13 @@ impl<'db> TypeInferenceBuilder<'db> {
         }
     }
 
-    fn module_ty_from_name(&self, module_name: Option<ModuleName>) -> Type<'db> {
-        module_name
-            .and_then(|module_name| resolve_module(self.db, module_name))
-            .map_or(Type::Unknown, |module| Type::Module(module.file()))
+    fn module_ty_from_name(
+        &self,
+        module_name: ModuleName,
+    ) -> Result<Type<'db>, ModuleResolutionError> {
+        resolve_module(self.db, module_name)
+            .map(|module| Type::Module(module.file()))
+            .ok_or(ModuleResolutionError::UnresolvedModule)
     }
 
     fn infer_decorator(&mut self, decorator: &ast::Decorator) -> Type<'db> {
@@ -1036,7 +1168,7 @@ impl<'db> TypeInferenceBuilder<'db> {
             ast::Expr::Yield(yield_expression) => self.infer_yield_expression(yield_expression),
             ast::Expr::YieldFrom(yield_from) => self.infer_yield_from_expression(yield_from),
             ast::Expr::Await(await_expression) => self.infer_await_expression(await_expression),
-            Expr::IpyEscapeCommand(_) => todo!("Implement Ipy escape command support"),
+            ast::Expr::IpyEscapeCommand(_) => todo!("Implement Ipy escape command support"),
         };
 
         let expr_id = expression.scoped_ast_id(self.db, self.scope);
@@ -1094,21 +1226,7 @@ impl<'db> TypeInferenceBuilder<'db> {
                         flags: _,
                     } = fstring;
                     for element in elements {
-                        match element {
-                            ast::FStringElement::Literal(_) => {
-                                // TODO string literal type
-                            }
-                            ast::FStringElement::Expression(expr_element) => {
-                                let ast::FStringExpressionElement {
-                                    range: _,
-                                    expression,
-                                    debug_text: _,
-                                    conversion: _,
-                                    format_spec: _,
-                                } = expr_element;
-                                self.infer_expression(expression);
-                            }
-                        }
+                        self.infer_fstring_element(element);
                     }
                 }
             }
@@ -1118,6 +1236,30 @@ impl<'db> TypeInferenceBuilder<'db> {
         Type::Unknown
     }
 
+    fn infer_fstring_element(&mut self, element: &ast::FStringElement) {
+        match element {
+            ast::FStringElement::Literal(_) => {
+                // TODO string literal type
+            }
+            ast::FStringElement::Expression(expr_element) => {
+                let ast::FStringExpressionElement {
+                    range: _,
+                    expression,
+                    debug_text: _,
+                    conversion: _,
+                    format_spec,
+                } = expr_element;
+                self.infer_expression(expression);
+
+                if let Some(format_spec) = format_spec {
+                    for spec_element in &format_spec.elements {
+                        self.infer_fstring_element(spec_element);
+                    }
+                }
+            }
+        }
+    }
+
     #[allow(clippy::unused_self)]
     fn infer_ellipsis_literal_expression(
         &mut self,
@@ -1683,6 +1825,28 @@ impl<'db> TypeInferenceBuilder<'db> {
         }
     }
 
+    /// Adds a new diagnostic.
+    ///
+    /// The diagnostic does not get added if the rule isn't enabled for this file.
+    fn add_diagnostic(&mut self, node: AnyNodeRef, rule: &str, message: std::fmt::Arguments) {
+        if !self.db.is_file_open(self.file) {
+            return;
+        }
+
+        // TODO: Don't emit the diagnostic if:
+        // * The enclosing node contains any syntax errors
+        // * The rule is disabled for this file. We probably want to introduce a new query that
+        //   returns a rule selector for a given file that respects the package's settings,
+        //   any global pragma comments in the file, and any per-file-ignores.
+
+        self.types.diagnostics.push(TypeCheckDiagnostic {
+            file: self.file,
+            rule: rule.to_string(),
+            message: message.to_string(),
+            range: node.range(),
+        });
+    }
+
     pub(super) fn finish(mut self) -> TypeInference<'db> {
         self.infer_region();
         self.types.shrink_to_fit();
@@ -1690,6 +1854,20 @@ impl<'db> TypeInferenceBuilder<'db> {
     }
 }
 
+fn format_import_from_module(level: u32, module: Option<&str>) -> String {
+    format!(
+        "{}{}",
+        ".".repeat(level as usize),
+        module.unwrap_or_default()
+    )
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+enum ModuleResolutionError {
+    InvalidSyntax,
+    UnresolvedModule,
+}
+
 #[cfg(test)]
 mod tests {
     use anyhow::Context;
@@ -1720,14 +1898,9 @@ mod tests {
 
         Program::from_settings(
             &db,
-            ProgramSettings {
+            &ProgramSettings {
                 target_version: PythonVersion::default(),
-                search_paths: SearchPathSettings {
-                    extra_paths: Vec::new(),
-                    src_root,
-                    site_packages: vec![],
-                    custom_typeshed: None,
-                },
+                search_paths: SearchPathSettings::new(src_root),
             },
         )
         .expect("Valid search path settings");
@@ -1747,13 +1920,11 @@ mod tests {
 
         Program::from_settings(
             &db,
-            ProgramSettings {
+            &ProgramSettings {
                 target_version: PythonVersion::default(),
                 search_paths: SearchPathSettings {
-                    extra_paths: Vec::new(),
-                    src_root,
-                    site_packages: vec![],
                     custom_typeshed: Some(SystemPathBuf::from(typeshed)),
+                    ..SearchPathSettings::new(src_root)
                 },
             },
         )
@@ -1943,6 +2114,16 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn from_import_with_no_module_name() -> anyhow::Result<()> {
+        // This test checks that invalid syntax in a `StmtImportFrom` node
+        // leads to the type being inferred as `Unknown`
+        let mut db = setup_db();
+        db.write_file("src/foo.py", "from import bar")?;
+        assert_public_ty(&db, "src/foo.py", "bar", "Unknown");
+        Ok(())
+    }
+
     #[test]
     fn resolve_base_class_by_name() -> anyhow::Result<()> {
         let mut db = setup_db();

crates/red_knot_server/Cargo.toml

@@ -11,10 +11,8 @@ repository = { workspace = true }
 license = { workspace = true }
 
 [dependencies]
-red_knot_python_semantic = { workspace = true }
 red_knot_workspace = { workspace = true }
 ruff_db = { workspace = true }
-ruff_linter = { workspace = true }
 ruff_notebook = { workspace = true }
 ruff_python_ast = { workspace = true }
 ruff_source_file = { workspace = true }

crates/red_knot_server/src/session.rs

@@ -8,7 +8,6 @@ use std::sync::Arc;
 use anyhow::anyhow;
 use lsp_types::{ClientCapabilities, Url};
 
-use red_knot_python_semantic::{ProgramSettings, PythonVersion, SearchPathSettings};
 use red_knot_workspace::db::RootDatabase;
 use red_knot_workspace::workspace::WorkspaceMetadata;
 use ruff_db::files::{system_path_to_file, File};
@@ -67,19 +66,10 @@ impl Session {
                 .ok_or_else(|| anyhow!("Workspace path is not a valid UTF-8 path: {:?}", path))?;
             let system = LSPSystem::new(index.clone());
 
-            let metadata = WorkspaceMetadata::from_path(system_path, &system)?;
             // TODO(dhruvmanila): Get the values from the client settings
-            let program_settings = ProgramSettings {
-                target_version: PythonVersion::default(),
-                search_paths: SearchPathSettings {
-                    extra_paths: vec![],
-                    src_root: system_path.to_path_buf(),
-                    site_packages: vec![],
-                    custom_typeshed: None,
-                },
-            };
+            let metadata = WorkspaceMetadata::from_path(system_path, &system, None)?;
             // TODO(micha): Handle the case where the program settings are incorrect more gracefully.
-            workspaces.insert(path, RootDatabase::new(metadata, program_settings, system)?);
+            workspaces.insert(path, RootDatabase::new(metadata, system)?);
         }
 
         Ok(Self {

crates/red_knot_server/src/session/capabilities.rs

@@ -1,5 +1,4 @@
 use lsp_types::ClientCapabilities;
-use ruff_linter::display_settings;
 
 #[derive(Debug, Clone, PartialEq, Eq, Default)]
 #[allow(clippy::struct_excessive_bools)]
@@ -66,20 +65,3 @@ impl ResolvedClientCapabilities {
         }
     }
 }
-
-impl std::fmt::Display for ResolvedClientCapabilities {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        display_settings! {
-            formatter = f,
-            namespace = "capabilities",
-            fields = [
-                self.code_action_deferred_edit_resolution,
-                self.apply_edit,
-                self.document_changes,
-                self.workspace_refresh,
-                self.pull_diagnostics,
-            ]
-        };
-        Ok(())
-    }
-}

crates/red_knot_server/src/session/index.rs

@@ -278,18 +278,6 @@ impl DocumentQuery {
         }
     }
 
-    /// Generate a source kind used by the linter.
-    pub(crate) fn make_source_kind(&self) -> ruff_linter::source_kind::SourceKind {
-        match self {
-            Self::Text { document, .. } => {
-                ruff_linter::source_kind::SourceKind::Python(document.contents().to_string())
-            }
-            Self::Notebook { notebook, .. } => {
-                ruff_linter::source_kind::SourceKind::IpyNotebook(notebook.make_ruff_notebook())
-            }
-        }
-    }
-
     /// Attempts to access the underlying notebook document that this query is selecting.
     pub fn as_notebook(&self) -> Option<&NotebookDocument> {
         match self {

crates/red_knot_wasm/src/lib.rs

@@ -3,8 +3,8 @@ use std::any::Any;
 use js_sys::Error;
 use wasm_bindgen::prelude::*;
 
-use red_knot_python_semantic::{ProgramSettings, SearchPathSettings};
 use red_knot_workspace::db::RootDatabase;
+use red_knot_workspace::workspace::settings::Configuration;
 use red_knot_workspace::workspace::WorkspaceMetadata;
 use ruff_db::files::{system_path_to_file, File};
 use ruff_db::system::walk_directory::WalkDirectoryBuilder;
@@ -41,16 +41,17 @@ impl Workspace {
     #[wasm_bindgen(constructor)]
     pub fn new(root: &str, settings: &Settings) -> Result<Workspace, Error> {
         let system = WasmSystem::new(SystemPath::new(root));
-        let workspace =
-            WorkspaceMetadata::from_path(SystemPath::new(root), &system).map_err(into_error)?;
+        let workspace = WorkspaceMetadata::from_path(
+            SystemPath::new(root),
+            &system,
+            Some(Configuration {
+                target_version: Some(settings.target_version.into()),
+                ..Configuration::default()
+            }),
+        )
+        .map_err(into_error)?;
 
-        let program_settings = ProgramSettings {
-            target_version: settings.target_version.into(),
-            search_paths: SearchPathSettings::default(),
-        };
-
-        let db =
-            RootDatabase::new(workspace, program_settings, system.clone()).map_err(into_error)?;
+        let db = RootDatabase::new(workspace, system.clone()).map_err(into_error)?;
 
         Ok(Self { db, system })
     }
@@ -109,7 +110,7 @@ impl Workspace {
     pub fn check_file(&self, file_id: &FileHandle) -> Result<Vec<String>, Error> {
         let result = self.db.check_file(file_id.file).map_err(into_error)?;
 
-        Ok(result.to_vec())
+        Ok(result.clone())
     }
 
     /// Checks all open files

crates/red_knot_wasm/tests/api.rs

@@ -17,5 +17,8 @@ fn check() {
 
     let result = workspace.check_file(&test).expect("Check to succeed");
 
-    assert_eq!(result, vec!["/test.py:1:8: Unresolved import 'random22'"]);
+    assert_eq!(
+        result,
+        vec!["/test.py:1:8: Import 'random22' could not be resolved.",]
+    );
 }

crates/red_knot_workspace/Cargo.toml

@@ -24,10 +24,10 @@ crossbeam = { workspace = true }
 notify = { workspace = true }
 rustc-hash = { workspace = true }
 salsa = { workspace = true }
-thiserror = { workspace = true }
 tracing = { workspace = true }
 
 [dev-dependencies]
+ruff_db = { workspace = true, features = ["testing"]}
 
 [lints]
 workspace = true

crates/red_knot_workspace/src/db.rs

@@ -1,17 +1,15 @@
 use std::panic::RefUnwindSafe;
 use std::sync::Arc;
 
-use red_knot_python_semantic::{
-    vendored_typeshed_stubs, Db as SemanticDb, Program, ProgramSettings,
-};
+use salsa::plumbing::ZalsaDatabase;
+use salsa::{Cancelled, Event};
+
+use red_knot_python_semantic::{vendored_typeshed_stubs, Db as SemanticDb, Program};
 use ruff_db::files::{File, Files};
 use ruff_db::system::System;
 use ruff_db::vendored::VendoredFileSystem;
 use ruff_db::{Db as SourceDb, Upcast};
-use salsa::plumbing::ZalsaDatabase;
-use salsa::{Cancelled, Event};
 
-use crate::lint::Diagnostics;
 use crate::workspace::{check_file, Workspace, WorkspaceMetadata};
 
 mod changes;
@@ -28,11 +26,7 @@ pub struct RootDatabase {
 }
 
 impl RootDatabase {
-    pub fn new<S>(
-        workspace: WorkspaceMetadata,
-        settings: ProgramSettings,
-        system: S,
-    ) -> anyhow::Result<Self>
+    pub fn new<S>(workspace: WorkspaceMetadata, system: S) -> anyhow::Result<Self>
     where
         S: System + 'static + Send + Sync + RefUnwindSafe,
     {
@@ -43,11 +37,11 @@ impl RootDatabase {
             system: Arc::new(system),
         };
 
-        let workspace = Workspace::from_metadata(&db, workspace);
         // Initialize the `Program` singleton
-        Program::from_settings(&db, settings)?;
+        Program::from_settings(&db, workspace.settings().program())?;
+
+        db.workspace = Some(Workspace::from_metadata(&db, workspace));
 
-        db.workspace = Some(workspace);
         Ok(db)
     }
 
@@ -61,7 +55,7 @@ impl RootDatabase {
         self.with_db(|db| db.workspace().check(db))
     }
 
-    pub fn check_file(&self, file: File) -> Result<Diagnostics, Cancelled> {
+    pub fn check_file(&self, file: File) -> Result<Vec<String>, Cancelled> {
         self.with_db(|db| check_file(db, file))
     }
 
@@ -115,7 +109,15 @@ impl Upcast<dyn SourceDb> for RootDatabase {
 }
 
 #[salsa::db]
-impl SemanticDb for RootDatabase {}
+impl SemanticDb for RootDatabase {
+    fn is_file_open(&self, file: File) -> bool {
+        let Some(workspace) = &self.workspace else {
+            return false;
+        };
+
+        workspace.is_file_open(self, file)
+    }
+}
 
 #[salsa::db]
 impl SourceDb for RootDatabase {
@@ -153,9 +155,10 @@ impl Db for RootDatabase {}
 
 #[cfg(test)]
 pub(crate) mod tests {
-    use salsa::Event;
     use std::sync::Arc;
 
+    use salsa::Event;
+
     use red_knot_python_semantic::{vendored_typeshed_stubs, Db as SemanticDb};
     use ruff_db::files::Files;
     use ruff_db::system::{DbWithTestSystem, System, TestSystem};
@@ -242,7 +245,12 @@ pub(crate) mod tests {
     }
 
     #[salsa::db]
-    impl red_knot_python_semantic::Db for TestDb {}
+    impl red_knot_python_semantic::Db for TestDb {
+        fn is_file_open(&self, file: ruff_db::files::File) -> bool {
+            !file.path(self).is_vendored_path()
+        }
+    }
+
     #[salsa::db]
     impl Db for TestDb {}
 

crates/red_knot_workspace/src/db/changes.rs

@@ -1,22 +1,33 @@
-use rustc_hash::FxHashSet;
-
+use red_knot_python_semantic::Program;
 use ruff_db::files::{system_path_to_file, File, Files};
 use ruff_db::system::walk_directory::WalkState;
 use ruff_db::system::SystemPath;
 use ruff_db::Db;
+use rustc_hash::FxHashSet;
 
 use crate::db::RootDatabase;
 use crate::watch;
 use crate::watch::{CreatedKind, DeletedKind};
+use crate::workspace::settings::Configuration;
 use crate::workspace::WorkspaceMetadata;
 
 impl RootDatabase {
-    #[tracing::instrument(level = "debug", skip(self, changes))]
-    pub fn apply_changes(&mut self, changes: Vec<watch::ChangeEvent>) {
+    #[tracing::instrument(level = "debug", skip(self, changes, base_configuration))]
+    pub fn apply_changes(
+        &mut self,
+        changes: Vec<watch::ChangeEvent>,
+        base_configuration: Option<&Configuration>,
+    ) {
         let workspace = self.workspace();
         let workspace_path = workspace.root(self).to_path_buf();
+        let program = Program::get(self);
+        let custom_stdlib_versions_path = program
+            .custom_stdlib_search_path(self)
+            .map(|path| path.join("VERSIONS"));
 
         let mut workspace_change = false;
+        // Changes to a custom stdlib path's VERSIONS
+        let mut custom_stdlib_change = false;
         // Packages that need reloading
         let mut changed_packages = FxHashSet::default();
         // Paths that were added
@@ -54,6 +65,10 @@ impl RootDatabase {
 
                     continue;
                 }
+
+                if Some(path) == custom_stdlib_versions_path.as_deref() {
+                    custom_stdlib_change = true;
+                }
             }
 
             match change {
@@ -100,7 +115,13 @@ impl RootDatabase {
                     } else {
                         sync_recursively(self, &path);
 
-                        // TODO: Remove after converting `package.files()` to a salsa query.
+                        if custom_stdlib_versions_path
+                            .as_ref()
+                            .is_some_and(|versions_path| versions_path.starts_with(&path))
+                        {
+                            custom_stdlib_change = true;
+                        }
+
                         if let Some(package) = workspace.package(self, &path) {
                             changed_packages.insert(package);
                         } else {
@@ -118,9 +139,13 @@ impl RootDatabase {
         }
 
         if workspace_change {
-            match WorkspaceMetadata::from_path(&workspace_path, self.system()) {
+            match WorkspaceMetadata::from_path(
+                &workspace_path,
+                self.system(),
+                base_configuration.cloned(),
+            ) {
                 Ok(metadata) => {
-                    tracing::debug!("Reload workspace after structural change.");
+                    tracing::debug!("Reloading workspace after structural change.");
                     // TODO: Handle changes in the program settings.
                     workspace.reload(self, metadata);
                 }
@@ -130,6 +155,11 @@ impl RootDatabase {
             }
 
             return;
+        } else if custom_stdlib_change {
+            let search_paths = workspace.search_path_settings(self).clone();
+            if let Err(error) = program.update_search_paths(self, &search_paths) {
+                tracing::error!("Failed to set the new search paths: {error}");
+            }
         }
 
         let mut added_paths = added_paths.into_iter().filter(|path| {

crates/red_knot_workspace/src/lib.rs

@@ -1,5 +1,4 @@
 pub mod db;
 pub mod lint;
-pub mod site_packages;
 pub mod watch;
 pub mod workspace;

crates/red_knot_workspace/src/lint.rs

@@ -1,5 +1,4 @@
 use std::cell::RefCell;
-use std::ops::Deref;
 use std::time::Duration;
 
 use tracing::debug_span;
@@ -22,7 +21,7 @@ use crate::db::Db;
 pub(crate) fn unwind_if_cancelled(db: &dyn Db) {}
 
 #[salsa::tracked(return_ref)]
-pub(crate) fn lint_syntax(db: &dyn Db, file_id: File) -> Diagnostics {
+pub(crate) fn lint_syntax(db: &dyn Db, file_id: File) -> Vec<String> {
     #[allow(clippy::print_stdout)]
     if std::env::var("RED_KNOT_SLOW_LINT").is_ok() {
         for i in 0..10 {
@@ -64,7 +63,7 @@ pub(crate) fn lint_syntax(db: &dyn Db, file_id: File) -> Diagnostics {
         }));
     }
 
-    Diagnostics::from(diagnostics)
+    diagnostics
 }
 
 fn lint_lines(source: &str, diagnostics: &mut Vec<String>) {
@@ -86,7 +85,7 @@ fn lint_lines(source: &str, diagnostics: &mut Vec<String>) {
 
 #[allow(unreachable_pub)]
 #[salsa::tracked(return_ref)]
-pub fn lint_semantic(db: &dyn Db, file_id: File) -> Diagnostics {
+pub fn lint_semantic(db: &dyn Db, file_id: File) -> Vec<String> {
     let _span = debug_span!("lint_semantic", file=%file_id.path(db)).entered();
 
     let source = source_text(db.upcast(), file_id);
@@ -94,7 +93,7 @@ pub fn lint_semantic(db: &dyn Db, file_id: File) -> Diagnostics {
     let semantic = SemanticModel::new(db.upcast(), file_id);
 
     if !parsed.is_valid() {
-        return Diagnostics::Empty;
+        return vec![];
     }
 
     let context = SemanticLintContext {
@@ -106,7 +105,7 @@ pub fn lint_semantic(db: &dyn Db, file_id: File) -> Diagnostics {
 
     SemanticVisitor { context: &context }.visit_body(parsed.suite());
 
-    Diagnostics::from(context.diagnostics.take())
+    context.diagnostics.take()
 }
 
 fn format_diagnostic(context: &SemanticLintContext, message: &str, start: TextSize) -> String {
@@ -116,48 +115,13 @@ fn format_diagnostic(context: &SemanticLintContext, message: &str, start: TextSi
         .source_location(start, context.source_text());
     format!(
         "{}:{}:{}: {}",
-        context.semantic.file_path().as_str(),
+        context.semantic.file_path(),
         source_location.row,
         source_location.column,
         message,
     )
 }
 
-fn lint_unresolved_imports(context: &SemanticLintContext, import: AnyImportRef) {
-    // TODO: this treats any symbol with `Type::Unknown` as an unresolved import,
-    // which isn't really correct: if it exists but has `Type::Unknown` in the
-    // module we're importing it from, we shouldn't really emit a diagnostic here,
-    // but currently do.
-    match import {
-        AnyImportRef::Import(import) => {
-            for alias in &import.names {
-                let ty = alias.ty(&context.semantic);
-
-                if ty.is_unknown() {
-                    context.push_diagnostic(format_diagnostic(
-                        context,
-                        &format!("Unresolved import '{}'", &alias.name),
-                        alias.start(),
-                    ));
-                }
-            }
-        }
-        AnyImportRef::ImportFrom(import) => {
-            for alias in &import.names {
-                let ty = alias.ty(&context.semantic);
-
-                if ty.is_unknown() {
-                    context.push_diagnostic(format_diagnostic(
-                        context,
-                        &format!("Unresolved import '{}'", &alias.name),
-                        alias.start(),
-                    ));
-                }
-            }
-        }
-    }
-}
-
 fn lint_maybe_undefined(context: &SemanticLintContext, name: &ast::ExprName) {
     if !matches!(name.ctx, ast::ExprContext::Load) {
         return;
@@ -280,17 +244,8 @@ struct SemanticVisitor<'a> {
 
 impl Visitor<'_> for SemanticVisitor<'_> {
     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
-        match stmt {
-            ast::Stmt::ClassDef(class) => {
-                lint_bad_override(self.context, class);
-            }
-            ast::Stmt::Import(import) => {
-                lint_unresolved_imports(self.context, AnyImportRef::Import(import));
-            }
-            ast::Stmt::ImportFrom(import) => {
-                lint_unresolved_imports(self.context, AnyImportRef::ImportFrom(import));
-            }
-            _ => {}
+        if let ast::Stmt::ClassDef(class) = stmt {
+            lint_bad_override(self.context, class);
         }
 
         walk_stmt(self, stmt);
@@ -308,53 +263,6 @@ impl Visitor<'_> for SemanticVisitor<'_> {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum Diagnostics {
-    Empty,
-    List(Vec<String>),
-}
-
-impl Diagnostics {
-    pub fn as_slice(&self) -> &[String] {
-        match self {
-            Diagnostics::Empty => &[],
-            Diagnostics::List(list) => list.as_slice(),
-        }
-    }
-}
-
-impl Deref for Diagnostics {
-    type Target = [String];
-    fn deref(&self) -> &Self::Target {
-        self.as_slice()
-    }
-}
-
-impl From<Vec<String>> for Diagnostics {
-    fn from(value: Vec<String>) -> Self {
-        if value.is_empty() {
-            Diagnostics::Empty
-        } else {
-            Diagnostics::List(value)
-        }
-    }
-}
-
-#[derive(Copy, Clone, Debug)]
-enum AnyImportRef<'a> {
-    Import(&'a ast::StmtImport),
-    ImportFrom(&'a ast::StmtImportFrom),
-}
-
-impl Ranged for AnyImportRef<'_> {
-    fn range(&self) -> ruff_text_size::TextRange {
-        match self {
-            AnyImportRef::Import(import) => import.range(),
-            AnyImportRef::ImportFrom(import) => import.range(),
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use red_knot_python_semantic::{Program, ProgramSettings, PythonVersion, SearchPathSettings};
@@ -363,7 +271,7 @@ mod tests {
 
     use crate::db::tests::TestDb;
 
-    use super::{lint_semantic, Diagnostics};
+    use super::lint_semantic;
 
     fn setup_db() -> TestDb {
         setup_db_with_root(SystemPathBuf::from("/src"))
@@ -378,14 +286,9 @@ mod tests {
 
         Program::from_settings(
             &db,
-            ProgramSettings {
+            &ProgramSettings {
                 target_version: PythonVersion::default(),
-                search_paths: SearchPathSettings {
-                    extra_paths: Vec::new(),
-                    src_root,
-                    site_packages: vec![],
-                    custom_typeshed: None,
-                },
+                search_paths: SearchPathSettings::new(src_root),
             },
         )
         .expect("Valid program settings");
@@ -409,9 +312,9 @@ mod tests {
         .unwrap();
 
         let file = system_path_to_file(&db, "/src/a.py").expect("file to exist");
-        let Diagnostics::List(messages) = lint_semantic(&db, file) else {
-            panic!("expected some diagnostics");
-        };
+        let messages = lint_semantic(&db, file);
+
+        assert_ne!(messages, &[] as &[String], "expected some diagnostics");
 
         assert_eq!(
             *messages,

crates/red_knot_workspace/src/watch/watcher.rs

@@ -109,7 +109,7 @@ struct WatcherInner {
 impl Watcher {
     /// Sets up file watching for `path`.
     pub fn watch(&mut self, path: &SystemPath) -> notify::Result<()> {
-        tracing::debug!("Watching path: {path}.");
+        tracing::debug!("Watching path: '{path}'.");
 
         self.inner_mut()
             .watcher
@@ -118,7 +118,7 @@ impl Watcher {
 
     /// Stops file watching for `path`.
     pub fn unwatch(&mut self, path: &SystemPath) -> notify::Result<()> {
-        tracing::debug!("Unwatching path: {path}.");
+        tracing::debug!("Unwatching path: '{path}'.");
 
         self.inner_mut().watcher.unwatch(path.as_std_path())
     }
@@ -351,7 +351,7 @@ impl Debouncer {
             }
 
             EventKind::Any => {
-                tracing::debug!("Skip any FS event for {path}.");
+                tracing::debug!("Skipping any FS event for '{path}'.");
                 return;
             }
         };

crates/red_knot_workspace/src/workspace.rs

@@ -4,21 +4,25 @@ use rustc_hash::{FxBuildHasher, FxHashSet};
 use salsa::{Durability, Setter as _};
 
 pub use metadata::{PackageMetadata, WorkspaceMetadata};
-use ruff_db::source::{source_text, SourceDiagnostic};
+use red_knot_python_semantic::types::check_types;
+use red_knot_python_semantic::SearchPathSettings;
+use ruff_db::source::{line_index, source_text, SourceDiagnostic};
 use ruff_db::{
     files::{system_path_to_file, File},
     system::{walk_directory::WalkState, SystemPath, SystemPathBuf},
 };
 use ruff_python_ast::{name::Name, PySourceType};
+use ruff_text_size::Ranged;
 
-use crate::workspace::files::{Index, IndexedFiles, PackageFiles};
+use crate::workspace::files::{Index, Indexed, PackageFiles};
 use crate::{
     db::Db,
-    lint::{lint_semantic, lint_syntax, Diagnostics},
+    lint::{lint_semantic, lint_syntax},
 };
 
 mod files;
 mod metadata;
+pub mod settings;
 
 /// The project workspace as a Salsa ingredient.
 ///
@@ -79,6 +83,10 @@ pub struct Workspace {
     /// The (first-party) packages in this workspace.
     #[return_ref]
     package_tree: BTreeMap<SystemPathBuf, Package>,
+
+    /// The unresolved search path configuration.
+    #[return_ref]
+    pub search_path_settings: SearchPathSettings,
 }
 
 /// A first-party package in a workspace.
@@ -92,8 +100,8 @@ pub struct Package {
     root_buf: SystemPathBuf,
 
     /// The files that are part of this package.
-    #[return_ref]
     #[default]
+    #[return_ref]
     file_set: PackageFiles,
     // TODO: Add the loaded settings.
 }
@@ -107,10 +115,14 @@ impl Workspace {
             packages.insert(package.root.clone(), Package::from_metadata(db, package));
         }
 
-        Workspace::builder(metadata.root, packages)
-            .durability(Durability::MEDIUM)
-            .open_fileset_durability(Durability::LOW)
-            .new(db)
+        Workspace::builder(
+            metadata.root,
+            packages,
+            metadata.settings.program.search_paths,
+        )
+        .durability(Durability::MEDIUM)
+        .open_fileset_durability(Durability::LOW)
+        .new(db)
     }
 
     pub fn root(self, db: &dyn Db) -> &SystemPath {
@@ -141,9 +153,12 @@ impl Workspace {
             new_packages.insert(path, package);
         }
 
-        self.set_package_tree(db)
-            .with_durability(Durability::MEDIUM)
-            .to(new_packages);
+        if &metadata.settings.program.search_paths != self.search_path_settings(db) {
+            self.set_search_path_settings(db)
+                .to(metadata.settings.program.search_paths);
+        }
+
+        self.set_package_tree(db).to(new_packages);
     }
 
     pub fn update_package(self, db: &mut dyn Db, metadata: PackageMetadata) -> anyhow::Result<()> {
@@ -197,7 +212,7 @@ impl Workspace {
     ///
     /// This changes the behavior of `check` to only check the open files rather than all files in the workspace.
     pub fn open_file(self, db: &mut dyn Db, file: File) {
-        tracing::debug!("Opening file {}", file.path(db));
+        tracing::debug!("Opening file '{}'", file.path(db));
 
         let mut open_files = self.take_open_files(db);
         open_files.insert(file);
@@ -206,7 +221,7 @@ impl Workspace {
 
     /// Closes a file in the workspace.
     pub fn close_file(self, db: &mut dyn Db, file: File) -> bool {
-        tracing::debug!("Closing file {}", file.path(db));
+        tracing::debug!("Closing file '{}'", file.path(db));
 
         let mut open_files = self.take_open_files(db);
         let removed = open_files.remove(&file);
@@ -249,6 +264,23 @@ impl Workspace {
             FxHashSet::default()
         }
     }
+
+    /// Returns `true` if the file is open in the workspace.
+    ///
+    /// A file is considered open when:
+    /// * explicitly set as an open file using [`open_file`](Self::open_file)
+    /// * It has a [`SystemPath`] and belongs to a package's `src` files
+    /// * It has a [`SystemVirtualPath`](ruff_db::system::SystemVirtualPath)
+    pub fn is_file_open(self, db: &dyn Db, file: File) -> bool {
+        if let Some(open_files) = self.open_files(db) {
+            open_files.contains(&file)
+        } else if let Some(system_path) = file.path(db).as_system_path() {
+            self.package(db, system_path)
+                .map_or(false, |package| package.contains_file(db, file))
+        } else {
+            file.path(db).is_system_virtual_path()
+        }
+    }
 }
 
 #[salsa::tracked]
@@ -259,13 +291,13 @@ impl Package {
 
     /// Returns `true` if `file` is a first-party file part of this package.
     pub fn contains_file(self, db: &dyn Db, file: File) -> bool {
-        self.files(db).read().contains(&file)
+        self.files(db).contains(&file)
     }
 
     #[tracing::instrument(level = "debug", skip(db))]
     pub fn remove_file(self, db: &mut dyn Db, file: File) {
         tracing::debug!(
-            "Remove file {} from package {}",
+            "Removing file '{}' from package '{}'",
             file.path(db),
             self.name(db)
         );
@@ -278,7 +310,11 @@ impl Package {
     }
 
     pub fn add_file(self, db: &mut dyn Db, file: File) {
-        tracing::debug!("Add file {} to package {}", file.path(db), self.name(db));
+        tracing::debug!(
+            "Adding file '{}' to package '{}'",
+            file.path(db),
+            self.name(db)
+        );
 
         let Some(mut index) = PackageFiles::indexed_mut(db, self) else {
             return;
@@ -289,10 +325,10 @@ impl Package {
 
     #[tracing::instrument(level = "debug", skip(db))]
     pub(crate) fn check(self, db: &dyn Db) -> Vec<String> {
-        tracing::debug!("Checking package {}", self.root(db));
+        tracing::debug!("Checking package '{}'", self.root(db));
 
         let mut result = Vec::new();
-        for file in &self.files(db).read() {
+        for file in &self.files(db) {
             let diagnostics = check_file(db, file);
             result.extend_from_slice(&diagnostics);
         }
@@ -301,15 +337,16 @@ impl Package {
     }
 
     /// Returns the files belonging to this package.
-    #[salsa::tracked]
-    pub fn files(self, db: &dyn Db) -> IndexedFiles {
-        let _entered = tracing::debug_span!("files").entered();
+    pub fn files(self, db: &dyn Db) -> Indexed<'_> {
         let files = self.file_set(db);
 
         let indexed = match files.get() {
             Index::Lazy(vacant) => {
-                tracing::debug!("Indexing files for package {}", self.name(db));
+                let _entered =
+                    tracing::debug_span!("index_package_files", package = %self.name(db)).entered();
+
                 let files = discover_package_files(db, self.root(db));
+                tracing::info!("Found {} files in package '{}'", files.len(), self.name(db));
                 vacant.set(files)
             }
             Index::Indexed(indexed) => indexed,
@@ -330,14 +367,12 @@ impl Package {
         assert_eq!(root, metadata.root());
 
         if self.name(db) != metadata.name() {
-            self.set_name(db)
-                .with_durability(Durability::MEDIUM)
-                .to(metadata.name);
+            self.set_name(db).to(metadata.name);
         }
     }
 
     pub fn reload_files(self, db: &mut dyn Db) {
-        tracing::debug!("Reload files for package {}", self.name(db));
+        tracing::debug!("Reloading files for package '{}'", self.name(db));
 
         if !self.file_set(db).is_lazy() {
             // Force a re-index of the files in the next revision.
@@ -347,10 +382,10 @@ impl Package {
 }
 
 #[salsa::tracked]
-pub(super) fn check_file(db: &dyn Db, file: File) -> Diagnostics {
+pub(super) fn check_file(db: &dyn Db, file: File) -> Vec<String> {
     let path = file.path(db);
     let _span = tracing::debug_span!("check_file", file=%path).entered();
-    tracing::debug!("Checking file {path}");
+    tracing::debug!("Checking file '{path}'");
 
     let mut diagnostics = Vec::new();
 
@@ -363,13 +398,25 @@ pub(super) fn check_file(db: &dyn Db, file: File) -> Diagnostics {
     );
 
     // Abort checking if there are IO errors.
-    if source_text(db.upcast(), file).has_read_error() {
-        return Diagnostics::from(diagnostics);
+    let source = source_text(db.upcast(), file);
+
+    if source.has_read_error() {
+        return diagnostics;
+    }
+
+    for diagnostic in check_types(db.upcast(), file) {
+        let index = line_index(db.upcast(), diagnostic.file());
+        let location = index.source_location(diagnostic.start(), source.as_str());
+        diagnostics.push(format!(
+            "{path}:{location}: {message}",
+            path = file.path(db),
+            message = diagnostic.message()
+        ));
     }
 
     diagnostics.extend_from_slice(lint_syntax(db, file));
     diagnostics.extend_from_slice(lint_semantic(db, file));
-    Diagnostics::from(diagnostics)
+    diagnostics
 }
 
 fn discover_package_files(db: &dyn Db, path: &SystemPath) -> FxHashSet<File> {
@@ -423,7 +470,7 @@ mod tests {
     use ruff_db::testing::assert_function_query_was_not_run;
 
     use crate::db::tests::TestDb;
-    use crate::lint::{lint_syntax, Diagnostics};
+    use crate::lint::lint_syntax;
     use crate::workspace::check_file;
 
     #[test]
@@ -441,9 +488,7 @@ mod tests {
         assert_eq!(source_text(&db, file).as_str(), "");
         assert_eq!(
             check_file(&db, file),
-            Diagnostics::List(vec![
-                "Failed to read file: No such file or directory".to_string()
-            ])
+            vec!["Failed to read file: No such file or directory".to_string()]
         );
 
         let events = db.take_salsa_events();
@@ -454,7 +499,7 @@ mod tests {
         db.write_file(path, "").unwrap();
 
         assert_eq!(source_text(&db, file).as_str(), "");
-        assert_eq!(check_file(&db, file), Diagnostics::Empty);
+        assert_eq!(check_file(&db, file), vec![] as Vec<String>);
 
         Ok(())
     }

crates/red_knot_workspace/src/workspace/files.rs

@@ -1,4 +1,4 @@
-use std::iter::FusedIterator;
+use std::marker::PhantomData;
 use std::ops::Deref;
 use std::sync::Arc;
 
@@ -10,6 +10,9 @@ use ruff_db::files::File;
 use crate::db::Db;
 use crate::workspace::Package;
 
+/// Cheap cloneable hash set of files.
+type FileSet = Arc<FxHashSet<File>>;
+
 /// The indexed files of a package.
 ///
 /// The indexing happens lazily, but the files are then cached for subsequent reads.
@@ -18,7 +21,7 @@ use crate::workspace::Package;
 /// The implementation uses internal mutability to transition between the lazy and indexed state
 /// without triggering a new salsa revision. This is safe because the initial indexing happens on first access,
 /// so no query can be depending on the contents of the indexed files before that. All subsequent mutations to
-/// the indexed files must go through `IndexedFilesMut`, which uses the Salsa setter `package.set_file_set` to
+/// the indexed files must go through `IndexedMut`, which uses the Salsa setter `package.set_file_set` to
 /// ensure that Salsa always knows when the set of indexed files have changed.
 #[derive(Debug)]
 pub struct PackageFiles {
@@ -32,46 +35,67 @@ impl PackageFiles {
         }
     }
 
-    fn indexed(indexed_files: IndexedFiles) -> Self {
+    fn indexed(files: FileSet) -> Self {
         Self {
-            state: std::sync::Mutex::new(State::Indexed(indexed_files)),
+            state: std::sync::Mutex::new(State::Indexed(files)),
         }
     }
 
-    pub fn get(&self) -> Index {
+    pub(super) fn get(&self) -> Index {
         let state = self.state.lock().unwrap();
 
         match &*state {
             State::Lazy => Index::Lazy(LazyFiles { files: state }),
-            State::Indexed(files) => Index::Indexed(files.clone()),
+            State::Indexed(files) => Index::Indexed(Indexed {
+                files: Arc::clone(files),
+                _lifetime: PhantomData,
+            }),
         }
     }
 
-    pub fn is_lazy(&self) -> bool {
+    pub(super) fn is_lazy(&self) -> bool {
         matches!(*self.state.lock().unwrap(), State::Lazy)
     }
 
     /// Returns a mutable view on the index that allows cheap in-place mutations.
     ///
     /// The changes are automatically written back to the database once the view is dropped.
-    pub fn indexed_mut(db: &mut dyn Db, package: Package) -> Option<IndexedFilesMut> {
+    pub(super) fn indexed_mut(db: &mut dyn Db, package: Package) -> Option<IndexedMut> {
         // Calling `zalsa_mut` cancels all pending salsa queries. This ensures that there are no pending
         // reads to the file set.
         // TODO: Use a non-internal API instead https://salsa.zulipchat.com/#narrow/stream/333573-salsa-3.2E0/topic/Expose.20an.20API.20to.20cancel.20other.20queries
         let _ = db.as_dyn_database_mut().zalsa_mut();
 
-        let files = package.file_set(db);
-
-        let indexed = match &*files.state.lock().unwrap() {
-            State::Lazy => return None,
-            State::Indexed(indexed) => indexed.clone(),
+        // Replace the state with lazy. The `IndexedMut` guard restores the state
+        // to `State::Indexed`  or sets a new `PackageFiles` when it gets dropped to ensure the state
+        // is restored to how it has been before replacing the value.
+        //
+        // It isn't necessary to hold on to the lock after this point:
+        // * The above call to `zalsa_mut` guarantees that there's exactly **one** DB reference.
+        // * `Indexed` has a `'db` lifetime, and this method requires a `&mut db`.
+        //   This means that there can't be any pending reference to `Indexed` because Rust
+        //   doesn't allow borrowing `db` as mutable (to call this method) and immutable (`Indexed<'db>`) at the same time.
+        //   There can't be any other `Indexed<'db>` references created by clones of this DB because
+        //   all clones must have been dropped at this point and the `Indexed`
+        //   can't outlive the database (constrained by the `db` lifetime).
+        let state = {
+            let files = package.file_set(db);
+            let mut locked = files.state.lock().unwrap();
+            std::mem::replace(&mut *locked, State::Lazy)
         };
 
-        Some(IndexedFilesMut {
+        let indexed = match state {
+            // If it's already lazy, just return. We also don't need to restore anything because the
+            // replace above was a no-op.
+            State::Lazy => return None,
+            State::Indexed(indexed) => indexed,
+        };
+
+        Some(IndexedMut {
             db: Some(db),
             package,
-            new_revision: indexed.revision,
-            indexed,
+            files: indexed,
+            did_change: false,
         })
     }
 }
@@ -88,152 +112,93 @@ enum State {
     Lazy,
 
     /// The files are indexed. Stores the known files of a package.
-    Indexed(IndexedFiles),
+    Indexed(FileSet),
 }
 
-pub enum Index<'a> {
+pub(super) enum Index<'db> {
     /// The index has not yet been computed. Allows inserting the files.
-    Lazy(LazyFiles<'a>),
+    Lazy(LazyFiles<'db>),
 
-    Indexed(IndexedFiles),
+    Indexed(Indexed<'db>),
 }
 
 /// Package files that have not been indexed yet.
-pub struct LazyFiles<'a> {
-    files: std::sync::MutexGuard<'a, State>,
+pub(super) struct LazyFiles<'db> {
+    files: std::sync::MutexGuard<'db, State>,
 }
 
-impl<'a> LazyFiles<'a> {
+impl<'db> LazyFiles<'db> {
     /// Sets the indexed files of a package to `files`.
-    pub fn set(mut self, files: FxHashSet<File>) -> IndexedFiles {
-        let files = IndexedFiles::new(files);
-        *self.files = State::Indexed(files.clone());
+    pub(super) fn set(mut self, files: FxHashSet<File>) -> Indexed<'db> {
+        let files = Indexed {
+            files: Arc::new(files),
+            _lifetime: PhantomData,
+        };
+        *self.files = State::Indexed(Arc::clone(&files.files));
         files
     }
 }
 
 /// The indexed files of a package.
 ///
-/// # Salsa integration
-/// The type is cheap clonable and allows for in-place mutation of the files. The in-place mutation requires
-/// extra care because the type is used as the result of Salsa queries and Salsa relies on a type's equality
-/// to determine if the output has changed. This is accomplished by using a `revision` that gets incremented
-/// whenever the files are changed. The revision ensures that salsa's comparison of the
-/// previous [`IndexedFiles`] with the next [`IndexedFiles`] returns false even though they both
-/// point to the same underlying hash set.
-///
-/// # Equality
-/// Two [`IndexedFiles`] are only equal if they have the same revision and point to the **same** (identity) hash set.
-#[derive(Debug, Clone)]
-pub struct IndexedFiles {
-    revision: u64,
-    files: Arc<std::sync::Mutex<FxHashSet<File>>>,
+/// Note: This type is intentionally non-cloneable. Making it cloneable requires
+/// revisiting the locking behavior in [`PackageFiles::indexed_mut`].
+#[derive(Debug, PartialEq, Eq)]
+pub struct Indexed<'db> {
+    files: FileSet,
+    // Preserve the lifetime of `PackageFiles`.
+    _lifetime: PhantomData<&'db ()>,
 }
 
-impl IndexedFiles {
-    fn new(files: FxHashSet<File>) -> Self {
-        Self {
-            files: Arc::new(std::sync::Mutex::new(files)),
-            revision: 0,
-        }
-    }
-
-    /// Locks the file index for reading.
-    pub fn read(&self) -> IndexedFilesGuard {
-        IndexedFilesGuard {
-            guard: self.files.lock().unwrap(),
-        }
-    }
-}
-
-impl PartialEq for IndexedFiles {
-    fn eq(&self, other: &Self) -> bool {
-        self.revision == other.revision && Arc::ptr_eq(&self.files, &other.files)
-    }
-}
-
-impl Eq for IndexedFiles {}
-
-pub struct IndexedFilesGuard<'a> {
-    guard: std::sync::MutexGuard<'a, FxHashSet<File>>,
-}
-
-impl Deref for IndexedFilesGuard<'_> {
+impl Deref for Indexed<'_> {
     type Target = FxHashSet<File>;
 
     fn deref(&self) -> &Self::Target {
-        &self.guard
+        &self.files
     }
 }
 
-impl<'a> IntoIterator for &'a IndexedFilesGuard<'a> {
+impl<'a> IntoIterator for &'a Indexed<'_> {
     type Item = File;
-    type IntoIter = IndexedFilesIter<'a>;
+    type IntoIter = std::iter::Copied<std::collections::hash_set::Iter<'a, File>>;
 
     fn into_iter(self) -> Self::IntoIter {
-        IndexedFilesIter {
-            inner: self.guard.iter(),
-        }
+        self.files.iter().copied()
     }
 }
 
-/// Iterator over the indexed files.
-///
-/// # Locks
-/// Holding on to the iterator locks the file index for reading.
-pub struct IndexedFilesIter<'a> {
-    inner: std::collections::hash_set::Iter<'a, File>,
-}
-
-impl<'a> Iterator for IndexedFilesIter<'a> {
-    type Item = File;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        self.inner.next().copied()
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        self.inner.size_hint()
-    }
-}
-
-impl FusedIterator for IndexedFilesIter<'_> {}
-
-impl ExactSizeIterator for IndexedFilesIter<'_> {}
-
 /// A Mutable view of a package's indexed files.
 ///
 /// Allows in-place mutation of the files without deep cloning the hash set.
 /// The changes are written back when the mutable view is dropped or by calling [`Self::set`] manually.
-pub struct IndexedFilesMut<'db> {
+pub(super) struct IndexedMut<'db> {
     db: Option<&'db mut dyn Db>,
     package: Package,
-    indexed: IndexedFiles,
-    new_revision: u64,
+    files: FileSet,
+    did_change: bool,
 }
 
-impl IndexedFilesMut<'_> {
-    pub fn insert(&mut self, file: File) -> bool {
-        if self.indexed.files.lock().unwrap().insert(file) {
-            self.new_revision += 1;
+impl IndexedMut<'_> {
+    pub(super) fn insert(&mut self, file: File) -> bool {
+        if self.files_mut().insert(file) {
+            self.did_change = true;
             true
         } else {
             false
         }
     }
 
-    pub fn remove(&mut self, file: File) -> bool {
-        if self.indexed.files.lock().unwrap().remove(&file) {
-            self.new_revision += 1;
+    pub(super) fn remove(&mut self, file: File) -> bool {
+        if self.files_mut().remove(&file) {
+            self.did_change = true;
             true
         } else {
             false
         }
     }
 
-    /// Writes the changes back to the database.
-    pub fn set(mut self) {
-        self.set_impl();
+    fn files_mut(&mut self) -> &mut FxHashSet<File> {
+        Arc::get_mut(&mut self.files).expect("All references to `FilesSet` to have been dropped")
     }
 
     fn set_impl(&mut self) {
@@ -241,19 +206,70 @@ impl IndexedFilesMut<'_> {
             return;
         };
 
-        if self.indexed.revision != self.new_revision {
+        let files = Arc::clone(&self.files);
+
+        if self.did_change {
+            // If there are changes, set the new file_set to trigger a salsa revision change.
             self.package
                 .set_file_set(db)
-                .to(PackageFiles::indexed(IndexedFiles {
-                    revision: self.new_revision,
-                    files: self.indexed.files.clone(),
-                }));
+                .to(PackageFiles::indexed(files));
+        } else {
+            // The `indexed_mut` replaced the `state` with Lazy. Restore it back to the indexed state.
+            *self.package.file_set(db).state.lock().unwrap() = State::Indexed(files);
         }
     }
 }
 
-impl Drop for IndexedFilesMut<'_> {
+impl Drop for IndexedMut<'_> {
     fn drop(&mut self) {
         self.set_impl();
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use rustc_hash::FxHashSet;
+
+    use ruff_db::files::system_path_to_file;
+    use ruff_db::system::{DbWithTestSystem, SystemPathBuf};
+    use ruff_python_ast::name::Name;
+
+    use crate::db::tests::TestDb;
+    use crate::workspace::files::Index;
+    use crate::workspace::Package;
+
+    #[test]
+    fn re_entrance() -> anyhow::Result<()> {
+        let mut db = TestDb::new();
+
+        db.write_file("test.py", "")?;
+
+        let package = Package::new(&db, Name::new("test"), SystemPathBuf::from("/test"));
+
+        let file = system_path_to_file(&db, "test.py").unwrap();
+
+        let files = match package.file_set(&db).get() {
+            Index::Lazy(lazy) => lazy.set(FxHashSet::from_iter([file])),
+            Index::Indexed(files) => files,
+        };
+
+        // Calling files a second time should not dead-lock.
+        // This can e.g. happen when `check_file` iterates over all files and
+        // `is_file_open` queries the open files.
+        let files_2 = package.file_set(&db).get();
+
+        match files_2 {
+            Index::Lazy(_) => {
+                panic!("Expected indexed files, got lazy files");
+            }
+            Index::Indexed(files_2) => {
+                assert_eq!(
+                    files_2.iter().collect::<Vec<_>>(),
+                    files.iter().collect::<Vec<_>>()
+                );
+            }
+        }
+
+        Ok(())
+    }
+}

crates/red_knot_workspace/src/workspace/metadata.rs

@@ -1,3 +1,4 @@
+use crate::workspace::settings::{Configuration, WorkspaceSettings};
 use ruff_db::system::{System, SystemPath, SystemPathBuf};
 use ruff_python_ast::name::Name;
 
@@ -7,6 +8,8 @@ pub struct WorkspaceMetadata {
 
     /// The (first-party) packages in this workspace.
     pub(super) packages: Vec<PackageMetadata>,
+
+    pub(super) settings: WorkspaceSettings,
 }
 
 /// A first-party package in a workspace.
@@ -21,7 +24,11 @@ pub struct PackageMetadata {
 
 impl WorkspaceMetadata {
     /// Discovers the closest workspace at `path` and returns its metadata.
-    pub fn from_path(path: &SystemPath, system: &dyn System) -> anyhow::Result<WorkspaceMetadata> {
+    pub fn from_path(
+        path: &SystemPath,
+        system: &dyn System,
+        base_configuration: Option<Configuration>,
+    ) -> anyhow::Result<WorkspaceMetadata> {
         assert!(
             system.is_directory(path),
             "Workspace root path must be a directory"
@@ -38,9 +45,20 @@ impl WorkspaceMetadata {
             root: root.clone(),
         };
 
+        // TODO: Load the configuration from disk.
+        let mut configuration = Configuration::default();
+
+        if let Some(base_configuration) = base_configuration {
+            configuration.extend(base_configuration);
+        }
+
+        // TODO: Respect the package configurations when resolving settings (e.g. for the target version).
+        let settings = configuration.into_workspace_settings(&root);
+
         let workspace = WorkspaceMetadata {
             root,
             packages: vec![package],
+            settings,
         };
 
         Ok(workspace)
@@ -53,6 +71,10 @@ impl WorkspaceMetadata {
     pub fn packages(&self) -> &[PackageMetadata] {
         &self.packages
     }
+
+    pub fn settings(&self) -> &WorkspaceSettings {
+        &self.settings
+    }
 }
 
 impl PackageMetadata {

crates/red_knot_workspace/src/workspace/settings.rs

@@ -0,0 +1,89 @@
+use red_knot_python_semantic::{ProgramSettings, PythonVersion, SearchPathSettings, SitePackages};
+use ruff_db::system::{SystemPath, SystemPathBuf};
+
+/// The resolved configurations.
+///
+/// The main difference to [`Configuration`] is that default values are filled in.
+#[derive(Debug, Clone)]
+pub struct WorkspaceSettings {
+    pub(super) program: ProgramSettings,
+}
+
+impl WorkspaceSettings {
+    pub fn program(&self) -> &ProgramSettings {
+        &self.program
+    }
+}
+
+/// The configuration for the workspace or a package.
+#[derive(Debug, Default, Clone)]
+pub struct Configuration {
+    pub target_version: Option<PythonVersion>,
+    pub search_paths: SearchPathConfiguration,
+}
+
+impl Configuration {
+    /// Extends this configuration by using the values from `with` for all values that are absent in `self`.
+    pub fn extend(&mut self, with: Configuration) {
+        self.target_version = self.target_version.or(with.target_version);
+        self.search_paths.extend(with.search_paths);
+    }
+
+    pub fn into_workspace_settings(self, workspace_root: &SystemPath) -> WorkspaceSettings {
+        WorkspaceSettings {
+            program: ProgramSettings {
+                target_version: self.target_version.unwrap_or_default(),
+                search_paths: self.search_paths.into_settings(workspace_root),
+            },
+        }
+    }
+}
+
+#[derive(Debug, Default, Clone, Eq, PartialEq)]
+pub struct SearchPathConfiguration {
+    /// List of user-provided paths that should take first priority in the module resolution.
+    /// Examples in other type checkers are mypy's MYPYPATH environment variable,
+    /// or pyright's stubPath configuration setting.
+    pub extra_paths: Option<Vec<SystemPathBuf>>,
+
+    /// The root of the workspace, used for finding first-party modules.
+    pub src_root: Option<SystemPathBuf>,
+
+    /// Optional path to a "custom typeshed" directory on disk for us to use for standard-library types.
+    /// If this is not provided, we will fallback to our vendored typeshed stubs for the stdlib,
+    /// bundled as a zip file in the binary
+    pub custom_typeshed: Option<SystemPathBuf>,
+
+    /// The path to the user's `site-packages` directory, where third-party packages from ``PyPI`` are installed.
+    pub site_packages: Option<SitePackages>,
+}
+
+impl SearchPathConfiguration {
+    pub fn into_settings(self, workspace_root: &SystemPath) -> SearchPathSettings {
+        let site_packages = self.site_packages.unwrap_or(SitePackages::Known(vec![]));
+
+        SearchPathSettings {
+            extra_paths: self.extra_paths.unwrap_or_default(),
+            src_root: self
+                .src_root
+                .unwrap_or_else(|| workspace_root.to_path_buf()),
+            custom_typeshed: self.custom_typeshed,
+            site_packages,
+        }
+    }
+
+    pub fn extend(&mut self, with: SearchPathConfiguration) {
+        if let Some(extra_paths) = with.extra_paths {
+            self.extra_paths.get_or_insert(extra_paths);
+        }
+        if let Some(src_root) = with.src_root {
+            self.src_root.get_or_insert(src_root);
+        }
+        if let Some(custom_typeshed) = with.custom_typeshed {
+            self.custom_typeshed.get_or_insert(custom_typeshed);
+        }
+        if let Some(site_packages) = with.site_packages {
+            self.site_packages.get_or_insert(site_packages);
+        }
+    }
+}

crates/red_knot_workspace/tests/check.rs

@@ -1,6 +1,7 @@
-use red_knot_python_semantic::{
-    HasTy, ProgramSettings, PythonVersion, SearchPathSettings, SemanticModel,
-};
+use std::fs;
+use std::path::PathBuf;
+
+use red_knot_python_semantic::{HasTy, SemanticModel};
 use red_knot_workspace::db::RootDatabase;
 use red_knot_workspace::workspace::WorkspaceMetadata;
 use ruff_db::files::{system_path_to_file, File};
@@ -9,23 +10,11 @@ use ruff_db::system::{OsSystem, SystemPath, SystemPathBuf};
 use ruff_python_ast::visitor::source_order;
 use ruff_python_ast::visitor::source_order::SourceOrderVisitor;
 use ruff_python_ast::{Alias, Expr, Parameter, ParameterWithDefault, Stmt};
-use std::fs;
-use std::path::PathBuf;
 
-fn setup_db(workspace_root: SystemPathBuf) -> anyhow::Result<RootDatabase> {
-    let system = OsSystem::new(&workspace_root);
-    let workspace = WorkspaceMetadata::from_path(&workspace_root, &system)?;
-    let search_paths = SearchPathSettings {
-        extra_paths: vec![],
-        src_root: workspace_root,
-        custom_typeshed: None,
-        site_packages: vec![],
-    };
-    let settings = ProgramSettings {
-        target_version: PythonVersion::default(),
-        search_paths,
-    };
-    RootDatabase::new(workspace, settings, system)
+fn setup_db(workspace_root: &SystemPath) -> anyhow::Result<RootDatabase> {
+    let system = OsSystem::new(workspace_root);
+    let workspace = WorkspaceMetadata::from_path(workspace_root, &system, None)?;
+    RootDatabase::new(workspace, system)
 }
 
 /// Test that all snippets in testcorpus can be checked without panic
@@ -33,8 +22,9 @@ fn setup_db(workspace_root: SystemPathBuf) -> anyhow::Result<RootDatabase> {
 #[allow(clippy::print_stdout)]
 fn corpus_no_panic() -> anyhow::Result<()> {
     let corpus = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("resources/test/corpus");
-    let system_corpus = SystemPath::from_std_path(&corpus).expect("corpus path to be UTF8");
-    let db = setup_db(system_corpus.to_path_buf())?;
+    let system_corpus =
+        SystemPathBuf::from_path_buf(corpus.clone()).expect("corpus path to be UTF8");
+    let db = setup_db(&system_corpus)?;
 
     for path in fs::read_dir(&corpus).expect("corpus to be a directory") {
         let path = path.expect("path to not be an error").path();

crates/ruff_benchmark/benches/red_knot.rs

@@ -1,7 +1,9 @@
 #![allow(clippy::disallowed_names)]
 
-use red_knot_python_semantic::{ProgramSettings, PythonVersion, SearchPathSettings};
+use red_knot_python_semantic::PythonVersion;
 use red_knot_workspace::db::RootDatabase;
+use red_knot_workspace::watch::{ChangeEvent, ChangedKind};
+use red_knot_workspace::workspace::settings::Configuration;
 use red_knot_workspace::workspace::WorkspaceMetadata;
 use ruff_benchmark::criterion::{criterion_group, criterion_main, BatchSize, Criterion};
 use ruff_benchmark::TestFile;
@@ -12,13 +14,53 @@ use ruff_db::system::{MemoryFileSystem, SystemPath, TestSystem};
 struct Case {
     db: RootDatabase,
     fs: MemoryFileSystem,
-    parser: File,
     re: File,
     re_path: &'static SystemPath,
 }
 
 const TOMLLIB_312_URL: &str = "https://raw.githubusercontent.com/python/cpython/8e8a4baf652f6e1cee7acde9d78c4b6154539748/Lib/tomllib";
 
+// This first "unresolved import" is because we don't understand `*` imports yet.
+// The following "unresolved import" violations are because we can't distinguish currently from
+// "Symbol exists in the module but its type is unknown" and
+// "Symbol does not exist in the module"
+static EXPECTED_DIAGNOSTICS: &[&str] = &[
+    "/src/tomllib/_parser.py:7:29: Could not resolve import of 'Iterable' from 'collections.abc'",
+    "/src/tomllib/_parser.py:10:20: Could not resolve import of 'Any' from 'typing'",
+    "/src/tomllib/_parser.py:13:5: Could not resolve import of 'RE_DATETIME' from '._re'",
+    "/src/tomllib/_parser.py:14:5: Could not resolve import of 'RE_LOCALTIME' from '._re'",
+    "/src/tomllib/_parser.py:15:5: Could not resolve import of 'RE_NUMBER' from '._re'",
+    "/src/tomllib/_parser.py:20:21: Could not resolve import of 'Key' from '._types'",
+    "/src/tomllib/_parser.py:20:26: Could not resolve import of 'ParseFloat' from '._types'",
+    "Line 69 is too long (89 characters)",
+    "Use double quotes for strings",
+    "Use double quotes for strings",
+    "Use double quotes for strings",
+    "Use double quotes for strings",
+    "Use double quotes for strings",
+    "Use double quotes for strings",
+    "Use double quotes for strings",
+    "/src/tomllib/_parser.py:153:22: Name 'key' used when not defined.",
+    "/src/tomllib/_parser.py:153:27: Name 'flag' used when not defined.",
+    "/src/tomllib/_parser.py:159:16: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:161:25: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:168:16: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:169:22: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:170:25: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:180:16: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:182:31: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:206:16: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:207:22: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:208:25: Name 'k' used when not defined.",
+    "/src/tomllib/_parser.py:330:32: Name 'header' used when not defined.",
+    "/src/tomllib/_parser.py:330:41: Name 'key' used when not defined.",
+    "/src/tomllib/_parser.py:333:26: Name 'cont_key' used when not defined.",
+    "/src/tomllib/_parser.py:334:71: Name 'cont_key' used when not defined.",
+    "/src/tomllib/_parser.py:337:31: Name 'cont_key' used when not defined.",
+    "/src/tomllib/_parser.py:628:75: Name 'e' used when not defined.",
+    "/src/tomllib/_parser.py:686:23: Name 'parse_float' used when not defined.",
+];
+
 fn get_test_file(name: &str) -> TestFile {
     let path = format!("tomllib/{name}");
     let url = format!("{TOMLLIB_312_URL}/{name}");
@@ -28,31 +70,34 @@ fn get_test_file(name: &str) -> TestFile {
 fn setup_case() -> Case {
     let system = TestSystem::default();
     let fs = system.memory_file_system().clone();
-    let init_path = SystemPath::new("/src/tomllib/__init__.py");
     let parser_path = SystemPath::new("/src/tomllib/_parser.py");
     let re_path = SystemPath::new("/src/tomllib/_re.py");
-    let types_path = SystemPath::new("/src/tomllib/_types.py");
     fs.write_files([
-        (init_path, get_test_file("__init__.py").code()),
+        (
+            SystemPath::new("/src/tomllib/__init__.py"),
+            get_test_file("__init__.py").code(),
+        ),
         (parser_path, get_test_file("_parser.py").code()),
         (re_path, get_test_file("_re.py").code()),
-        (types_path, get_test_file("_types.py").code()),
+        (
+            SystemPath::new("/src/tomllib/_types.py"),
+            get_test_file("_types.py").code(),
+        ),
     ])
     .unwrap();
 
     let src_root = SystemPath::new("/src");
-    let metadata = WorkspaceMetadata::from_path(src_root, &system).unwrap();
-    let settings = ProgramSettings {
-        target_version: PythonVersion::PY312,
-        search_paths: SearchPathSettings {
-            extra_paths: vec![],
-            src_root: src_root.to_path_buf(),
-            site_packages: vec![],
-            custom_typeshed: None,
-        },
-    };
+    let metadata = WorkspaceMetadata::from_path(
+        src_root,
+        &system,
+        Some(Configuration {
+            target_version: Some(PythonVersion::PY312),
+            ..Configuration::default()
+        }),
+    )
+    .unwrap();
 
-    let mut db = RootDatabase::new(metadata, settings, system).unwrap();
+    let mut db = RootDatabase::new(metadata, system).unwrap();
     let parser = system_path_to_file(&db, parser_path).unwrap();
 
     db.workspace().open_file(&mut db, parser);
@@ -62,7 +107,6 @@ fn setup_case() -> Case {
     Case {
         db,
         fs,
-        parser,
         re,
         re_path,
     }
@@ -72,8 +116,8 @@ fn benchmark_incremental(criterion: &mut Criterion) {
     criterion.bench_function("red_knot_check_file[incremental]", |b| {
         b.iter_batched_ref(
             || {
-                let mut case = setup_case();
-                case.db.check_file(case.parser).unwrap();
+                let case = setup_case();
+                case.db.check().unwrap();
 
                 case.fs
                     .write_file(
@@ -82,14 +126,22 @@ fn benchmark_incremental(criterion: &mut Criterion) {
                     )
                     .unwrap();
 
-                case.re.sync(&mut case.db);
                 case
             },
             |case| {
-                let Case { db, parser, .. } = case;
-                let result = db.check_file(*parser).unwrap();
+                let Case { db, .. } = case;
 
-                assert_eq!(result.len(), 34);
+                db.apply_changes(
+                    vec![ChangeEvent::Changed {
+                        path: case.re_path.to_path_buf(),
+                        kind: ChangedKind::FileContent,
+                    }],
+                    None,
+                );
+
+                let result = db.check().unwrap();
+
+                assert_eq!(result, EXPECTED_DIAGNOSTICS);
             },
             BatchSize::SmallInput,
         );
@@ -101,10 +153,10 @@ fn benchmark_cold(criterion: &mut Criterion) {
         b.iter_batched_ref(
             setup_case,
             |case| {
-                let Case { db, parser, .. } = case;
-                let result = db.check_file(*parser).unwrap();
+                let Case { db, .. } = case;
+                let result = db.check().unwrap();
 
-                assert_eq!(result.len(), 34);
+                assert_eq!(result, EXPECTED_DIAGNOSTICS);
             },
             BatchSize::SmallInput,
         );

crates/ruff_db/src/files.rs

@@ -85,7 +85,7 @@ impl Files {
             .system_by_path
             .entry(absolute.clone())
             .or_insert_with(|| {
-                tracing::trace!("Adding file {path}");
+                tracing::trace!("Adding file '{path}'");
 
                 let metadata = db.system().path_metadata(path);
                 let durability = self
@@ -131,7 +131,7 @@ impl Files {
                     Err(_) => return Err(FileError::NotFound),
                 };
 
-                tracing::trace!("Adding vendored file {}", path);
+                tracing::trace!("Adding vendored file '{}'", path);
                 let file = File::builder(FilePath::Vendored(path.to_path_buf()))
                     .permissions(Some(0o444))
                     .revision(metadata.revision())
@@ -158,7 +158,7 @@ impl Files {
             Entry::Vacant(entry) => {
                 let metadata = db.system().virtual_path_metadata(path).ok()?;
 
-                tracing::trace!("Adding virtual file {}", path);
+                tracing::trace!("Adding virtual file '{}'", path);
 
                 let file = File::builder(FilePath::SystemVirtual(path.to_path_buf()))
                     .revision(metadata.revision())
@@ -211,7 +211,7 @@ impl Files {
     /// That's why [`File::sync_path`] and [`File::sync_path`] is preferred if it is known that the path is a file.
     pub fn sync_recursively(db: &mut dyn Db, path: &SystemPath) {
         let path = SystemPath::absolute(path, db.system().current_directory());
-        tracing::debug!("Syncing all files in {path}");
+        tracing::debug!("Syncing all files in '{path}'");
 
         let inner = Arc::clone(&db.files().inner);
         for entry in inner.system_by_path.iter_mut() {
@@ -224,9 +224,7 @@ impl Files {
 
         for root in roots.all() {
             if root.path(db).starts_with(&path) {
-                root.set_revision(db)
-                    .with_durability(Durability::HIGH)
-                    .to(FileRevision::now());
+                root.set_revision(db).to(FileRevision::now());
             }
         }
     }
@@ -249,9 +247,7 @@ impl Files {
         let roots = inner.roots.read().unwrap();
 
         for root in roots.all() {
-            root.set_revision(db)
-                .with_durability(Durability::HIGH)
-                .to(FileRevision::now());
+            root.set_revision(db).to(FileRevision::now());
         }
     }
 
@@ -381,23 +377,17 @@ impl File {
             return;
         };
         let metadata = db.system().path_metadata(path);
-        let durability = db.files().root(db, path).map(|root| root.durability(db));
-        Self::sync_impl(db, metadata, file, durability);
+        Self::sync_impl(db, metadata, file);
     }
 
     fn sync_system_virtual_path(db: &mut dyn Db, path: &SystemVirtualPath, file: File) {
         let metadata = db.system().virtual_path_metadata(path);
-        Self::sync_impl(db, metadata, file, None);
+        Self::sync_impl(db, metadata, file);
     }
 
     /// Private method providing the implementation for [`Self::sync_system_path`] and
     /// [`Self::sync_system_virtual_path`].
-    fn sync_impl(
-        db: &mut dyn Db,
-        metadata: crate::system::Result<Metadata>,
-        file: File,
-        durability: Option<Durability>,
-    ) {
+    fn sync_impl(db: &mut dyn Db, metadata: crate::system::Result<Metadata>, file: File) {
         let (status, revision, permission) = match metadata {
             Ok(metadata) if metadata.file_type().is_file() => (
                 FileStatus::Exists,
@@ -410,25 +400,19 @@ impl File {
             _ => (FileStatus::NotFound, FileRevision::zero(), None),
         };
 
-        let durability = durability.unwrap_or_default();
-
         if file.status(db) != status {
-            tracing::debug!("Updating the status of {}", file.path(db),);
-            file.set_status(db).with_durability(durability).to(status);
+            tracing::debug!("Updating the status of '{}'", file.path(db),);
+            file.set_status(db).to(status);
         }
 
         if file.revision(db) != revision {
-            tracing::debug!("Updating the revision of {}", file.path(db));
-            file.set_revision(db)
-                .with_durability(durability)
-                .to(revision);
+            tracing::debug!("Updating the revision of '{}'", file.path(db));
+            file.set_revision(db).to(revision);
         }
 
         if file.permissions(db) != permission {
-            tracing::debug!("Updating the permissions of {}", file.path(db),);
-            file.set_permissions(db)
-                .with_durability(durability)
-                .to(permission);
+            tracing::debug!("Updating the permissions of '{}'", file.path(db),);
+            file.set_permissions(db).to(permission);
         }
     }
 

crates/ruff_db/src/source.rs

@@ -22,7 +22,7 @@ pub fn source_text(db: &dyn Db, file: File) -> SourceText {
     let kind = if is_notebook(file.path(db)) {
         file.read_to_notebook(db)
             .unwrap_or_else(|error| {
-                tracing::debug!("Failed to read notebook {path}: {error}");
+                tracing::debug!("Failed to read notebook '{path}': {error}");
 
                 has_read_error = true;
                 SourceDiagnostic(Arc::new(SourceTextError::FailedToReadNotebook(error)))
@@ -33,7 +33,7 @@ pub fn source_text(db: &dyn Db, file: File) -> SourceText {
     } else {
         file.read_to_string(db)
             .unwrap_or_else(|error| {
-                tracing::debug!("Failed to read file {path}: {error}");
+                tracing::debug!("Failed to read file '{path}': {error}");
 
                 has_read_error = true;
                 SourceDiagnostic(Arc::new(SourceTextError::FailedToReadFile(error))).accumulate(db);

crates/ruff_db/src/testing.rs

@@ -31,10 +31,20 @@ pub fn assert_const_function_query_was_not_run<Db, Q, QDb, R>(
     Db: salsa::Database,
     Q: Fn(QDb) -> R,
 {
-    let (query_name, will_execute_event) = find_will_execute_event(db, query, (), events);
+    // Salsa now interns singleton ingredients. But we know that it is a singleton, so we can just search for
+    // any event of that ingredient.
+    let query_name = query_name(&query);
+
+    let event = events.iter().find(|event| {
+        if let salsa::EventKind::WillExecute { database_key } = event.kind {
+            db.ingredient_debug_name(database_key.ingredient_index()) == query_name
+        } else {
+            false
+        }
+    });
 
     db.attach(|_| {
-        if let Some(will_execute_event) = will_execute_event {
+        if let Some(will_execute_event) = event {
             panic!(
                 "Expected query {query_name}() not to have run but it did: {will_execute_event:?}"
             );

crates/ruff_db/src/vendored.rs

@@ -97,7 +97,16 @@ impl VendoredFileSystem {
         fn read_to_string(fs: &VendoredFileSystem, path: &VendoredPath) -> Result<String> {
             let mut archive = fs.lock_archive();
             let mut zip_file = archive.lookup_path(&NormalizedVendoredPath::from(path))?;
-            let mut buffer = String::new();
+
+            // Pre-allocate the buffer with the size specified in the ZIP file metadata
+            // because `read_to_string` passes `None` as the size hint.
+            // But let's not trust the zip file metadata (even though it's vendored)
+            // and limit it to a reasonable size.
+            let mut buffer = String::with_capacity(
+                usize::try_from(zip_file.size())
+                    .unwrap_or(usize::MAX)
+                    .min(10_000_000),
+            );
             zip_file.read_to_string(&mut buffer)?;
             Ok(buffer)
         }

crates/ruff_linter/resources/test/fixtures/flake8_pyi/PYI053.pyi

@@ -66,3 +66,6 @@ def not_warnings_dot_deprecated(
 def not_a_deprecated_function() -> None: ...
 
 fbaz: str = f"51 character {foo} stringgggggggggggggggggggggggggg"  # Error: PYI053
+
+# see https://github.com/astral-sh/ruff/issues/12995
+def foo(bar: typing.Literal["a", "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"]):...

crates/ruff_linter/resources/test/fixtures/ruff/RUF032.py

@@ -0,0 +1,120 @@
+import decimal
+
+# Tests with fully qualified import
+decimal.Decimal(0)
+
+decimal.Decimal(0.0)  # Should error
+
+decimal.Decimal("0.0")
+
+decimal.Decimal(10)
+
+decimal.Decimal(10.0)  # Should error
+
+decimal.Decimal("10.0")
+
+decimal.Decimal(-10)
+
+decimal.Decimal(-10.0)  # Should error
+
+decimal.Decimal("-10.0")
+
+a = 10.0
+
+decimal.Decimal(a)
+
+
+# Tests with relative import
+from decimal import Decimal
+
+
+val = Decimal(0)
+
+val = Decimal(0.0)  # Should error
+
+val = Decimal("0.0")
+
+val = Decimal(10)
+
+val = Decimal(10.0)  # Should error
+
+val = Decimal("10.0")
+
+val = Decimal(-10)
+
+val = Decimal(-10.0)  # Should error
+
+val = Decimal("-10.0")
+
+a = 10.0
+
+val = Decimal(a)
+
+
+# Tests with shadowed name
+class Decimal():
+    value: float | int | str
+
+    def __init__(self, value: float | int | str) -> None:
+        self.value = value
+
+
+val = Decimal(0.0)
+
+val = Decimal("0.0")
+
+val = Decimal(10.0)
+
+val = Decimal("10.0")
+
+val = Decimal(-10.0)
+
+val = Decimal("-10.0")
+
+a = 10.0
+
+val = Decimal(a)
+
+
+# Retest with fully qualified import
+
+val = decimal.Decimal(0.0)  # Should error
+
+val = decimal.Decimal("0.0")
+
+val = decimal.Decimal(10.0)  # Should error
+
+val = decimal.Decimal("10.0")
+
+val = decimal.Decimal(-10.0)  # Should error
+
+val = decimal.Decimal("-10.0")
+
+a = 10.0
+
+val = decimal.Decimal(a)
+
+
+class decimal():
+    class Decimal():
+        value: float | int | str
+
+        def __init__(self, value: float | int | str) -> None:
+            self.value = value
+
+
+val = decimal.Decimal(0.0)
+
+val = decimal.Decimal("0.0")
+
+val = decimal.Decimal(10.0)
+
+val = decimal.Decimal("10.0")
+
+val = decimal.Decimal(-10.0)
+
+val = decimal.Decimal("-10.0")
+
+a = 10.0
+
+val = decimal.Decimal(a)

crates/ruff_linter/src/checkers/ast/analyze/expression.rs

@@ -1011,6 +1011,9 @@ pub(crate) fn expression(expr: &Expr, checker: &mut Checker) {
             if checker.enabled(Rule::UnnecessaryIterableAllocationForFirstElement) {
                 ruff::rules::unnecessary_iterable_allocation_for_first_element(checker, expr);
             }
+            if checker.enabled(Rule::DecimalFromFloatLiteral) {
+                ruff::rules::decimal_from_float_literal_syntax(checker, call);
+            }
             if checker.enabled(Rule::IntOnSlicedStr) {
                 refurb::rules::int_on_sliced_str(checker, call);
             }

crates/ruff_linter/src/codes.rs

@@ -959,6 +959,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Ruff, "029") => (RuleGroup::Preview, rules::ruff::rules::UnusedAsync),
         (Ruff, "030") => (RuleGroup::Preview, rules::ruff::rules::AssertWithPrintMessage),
         (Ruff, "031") => (RuleGroup::Preview, rules::ruff::rules::IncorrectlyParenthesizedTupleInSubscript),
+        (Ruff, "032") => (RuleGroup::Preview, rules::ruff::rules::DecimalFromFloatLiteral),
         (Ruff, "100") => (RuleGroup::Stable, rules::ruff::rules::UnusedNOQA),
         (Ruff, "101") => (RuleGroup::Stable, rules::ruff::rules::RedirectedNOQA),
 

crates/ruff_linter/src/rules/flake8_pyi/rules/string_or_bytes_too_long.rs

@@ -59,6 +59,10 @@ pub(crate) fn string_or_bytes_too_long(checker: &mut Checker, string: StringLike
         return;
     }
 
+    if semantic.in_annotation() {
+        return;
+    }
+
     let length = match string {
         StringLike::String(ast::ExprStringLiteral { value, .. }) => value.chars().count(),
         StringLike::Bytes(ast::ExprBytesLiteral { value, .. }) => value.len(),

crates/ruff_linter/src/rules/flake8_pyi/snapshots/ruff_linter__rules__flake8_pyi__tests__PYI053_PYI053.pyi.snap

@@ -152,6 +152,8 @@ PYI053.pyi:68:13: PYI053 [*] String and bytes literals longer than 50 characters
 67 | 
 68 | fbaz: str = f"51 character {foo} stringgggggggggggggggggggggggggg"  # Error: PYI053
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PYI053
+69 | 
+70 | # see https://github.com/astral-sh/ruff/issues/12995
    |
    = help: Replace with `...`
 
@@ -161,3 +163,6 @@ PYI053.pyi:68:13: PYI053 [*] String and bytes literals longer than 50 characters
 67 67 | 
 68    |-fbaz: str = f"51 character {foo} stringgggggggggggggggggggggggggg"  # Error: PYI053
    68 |+fbaz: str = ...  # Error: PYI053
+69 69 | 
+70 70 | # see https://github.com/astral-sh/ruff/issues/12995
+71 71 | def foo(bar: typing.Literal["a", "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"]):...

crates/ruff_linter/src/rules/flake8_pytest_style/rules/fixture.rs

@@ -42,7 +42,7 @@ use super::helpers::{
 /// import pytest
 ///
 ///
-/// @pytest.fixture
+/// @pytest.fixture()
 /// def my_fixture(): ...
 /// ```
 ///
@@ -52,7 +52,7 @@ use super::helpers::{
 /// import pytest
 ///
 ///
-/// @pytest.fixture()
+/// @pytest.fixture
 /// def my_fixture(): ...
 /// ```
 ///

crates/ruff_linter/src/rules/flake8_type_checking/rules/typing_only_runtime_import.rs

@@ -300,7 +300,7 @@ pub(crate) fn typing_only_runtime_import(
             // Categorize the import, using coarse-grained categorization.
             let import_type = match categorize(
                 &qualified_name.to_string(),
-                0,
+                qualified_name.is_unresolved_import(),
                 &checker.settings.src,
                 checker.package(),
                 checker.settings.isort.detect_same_package,

crates/ruff_linter/src/rules/isort/categorize.rs

@@ -91,7 +91,7 @@ enum Reason<'a> {
 #[allow(clippy::too_many_arguments)]
 pub(crate) fn categorize<'a>(
     module_name: &str,
-    level: u32,
+    is_relative: bool,
     src: &[PathBuf],
     package: Option<&Path>,
     detect_same_package: bool,
@@ -103,14 +103,14 @@ pub(crate) fn categorize<'a>(
 ) -> &'a ImportSection {
     let module_base = module_name.split('.').next().unwrap();
     let (mut import_type, mut reason) = {
-        if level == 0 && module_base == "__future__" {
+        if !is_relative && module_base == "__future__" {
             (&ImportSection::Known(ImportType::Future), Reason::Future)
         } else if no_sections {
             (
                 &ImportSection::Known(ImportType::FirstParty),
                 Reason::NoSections,
             )
-        } else if level > 0 {
+        } else if is_relative {
             (
                 &ImportSection::Known(ImportType::LocalFolder),
                 Reason::NonZeroLevel,
@@ -132,7 +132,7 @@ pub(crate) fn categorize<'a>(
                 &ImportSection::Known(ImportType::FirstParty),
                 Reason::SourceMatch(src),
             )
-        } else if level == 0 && module_name == "__main__" {
+        } else if !is_relative && module_name == "__main__" {
             (
                 &ImportSection::Known(ImportType::FirstParty),
                 Reason::KnownFirstParty,
@@ -190,7 +190,7 @@ pub(crate) fn categorize_imports<'a>(
     for (alias, comments) in block.import {
         let import_type = categorize(
             &alias.module_name(),
-            0,
+            false,
             src,
             package,
             detect_same_package,
@@ -210,7 +210,7 @@ pub(crate) fn categorize_imports<'a>(
     for (import_from, aliases) in block.import_from {
         let classification = categorize(
             &import_from.module_name(),
-            import_from.level,
+            import_from.level > 0,
             src,
             package,
             detect_same_package,
@@ -230,7 +230,7 @@ pub(crate) fn categorize_imports<'a>(
     for ((import_from, alias), aliases) in block.import_from_as {
         let classification = categorize(
             &import_from.module_name(),
-            import_from.level,
+            import_from.level > 0,
             src,
             package,
             detect_same_package,
@@ -250,7 +250,7 @@ pub(crate) fn categorize_imports<'a>(
     for (import_from, comments) in block.import_from_star {
         let classification = categorize(
             &import_from.module_name(),
-            import_from.level,
+            import_from.level > 0,
             src,
             package,
             detect_same_package,

crates/ruff_linter/src/rules/pydocstyle/rules/not_missing.rs

@@ -218,6 +218,9 @@ impl Violation for UndocumentedPublicClass {
 ///             raise ValueError("Tried to greet an unhappy cat.")
 /// ```
 ///
+/// ## Options
+/// - `lint.pydocstyle.ignore-decorators`
+///
 /// ## References
 /// - [PEP 257 – Docstring Conventions](https://peps.python.org/pep-0257/)
 /// - [PEP 287 – reStructuredText Docstring Format](https://peps.python.org/pep-0287/)
@@ -305,6 +308,9 @@ impl Violation for UndocumentedPublicMethod {
 ///         raise FasterThanLightError from exc
 /// ```
 ///
+/// ## Options
+/// - `lint.pydocstyle.ignore-decorators`
+///
 /// ## References
 /// - [PEP 257 – Docstring Conventions](https://peps.python.org/pep-0257/)
 /// - [PEP 287 – reStructuredText Docstring Format](https://peps.python.org/pep-0287/)
@@ -402,6 +408,9 @@ impl Violation for UndocumentedPublicPackage {
 /// print(cat)  # "Cat: Dusty"
 /// ```
 ///
+/// ## Options
+/// - `lint.pydocstyle.ignore-decorators`
+///
 /// ## References
 /// - [PEP 257 – Docstring Conventions](https://peps.python.org/pep-0257/)
 /// - [PEP 287 – reStructuredText Docstring Format](https://peps.python.org/pep-0287/)
@@ -502,6 +511,9 @@ impl Violation for UndocumentedPublicNestedClass {
 ///         self.population: int = population
 /// ```
 ///
+/// ## Options
+/// - `lint.pydocstyle.ignore-decorators`
+///
 /// ## References
 /// - [PEP 257 – Docstring Conventions](https://peps.python.org/pep-0257/)
 /// - [PEP 287 – reStructuredText Docstring Format](https://peps.python.org/pep-0287/)

crates/ruff_linter/src/rules/pyflakes/rules/unused_import.rs

@@ -6,8 +6,7 @@ use std::collections::BTreeMap;
 
 use ruff_diagnostics::{Applicability, Diagnostic, Fix, FixAvailability, Violation};
 use ruff_macros::{derive_message_formats, violation};
-use ruff_python_ast as ast;
-use ruff_python_ast::{Stmt, StmtImportFrom};
+use ruff_python_ast::{self as ast, Stmt};
 use ruff_python_semantic::{
     AnyImport, BindingKind, Exceptions, Imported, NodeId, Scope, SemanticModel, SubmoduleImport,
 };
@@ -218,10 +217,11 @@ enum UnusedImportContext {
     Other,
 }
 
-fn is_first_party(qualified_name: &str, level: u32, checker: &Checker) -> bool {
+fn is_first_party(import: &AnyImport, checker: &Checker) -> bool {
+    let qualified_name = import.qualified_name();
     let category = isort::categorize(
-        qualified_name,
-        level,
+        &qualified_name.to_string(),
+        qualified_name.is_unresolved_import(),
         &checker.settings.src,
         checker.package(),
         checker.settings.isort.detect_same_package,
@@ -343,13 +343,6 @@ pub(crate) fn unused_import(checker: &Checker, scope: &Scope, diagnostics: &mut
         let in_except_handler =
             exceptions.intersects(Exceptions::MODULE_NOT_FOUND_ERROR | Exceptions::IMPORT_ERROR);
         let multiple = bindings.len() > 1;
-        let level = match checker.semantic().statement(import_statement) {
-            Stmt::Import(_) => 0,
-            Stmt::ImportFrom(StmtImportFrom { level, .. }) => *level,
-            _ => {
-                continue;
-            }
-        };
 
         // pair each binding with context; divide them by how we want to fix them
         let (to_reexport, to_remove): (Vec<_>, Vec<_>) = bindings
@@ -357,9 +350,7 @@ pub(crate) fn unused_import(checker: &Checker, scope: &Scope, diagnostics: &mut
             .map(|binding| {
                 let context = if in_except_handler {
                     UnusedImportContext::ExceptHandler
-                } else if in_init
-                    && is_first_party(&binding.import.qualified_name().to_string(), level, checker)
-                {
+                } else if in_init && is_first_party(&binding.import, checker) {
                     UnusedImportContext::DunderInitFirstParty {
                         dunder_all_count: DunderAllCount::from(dunder_all_exprs.len()),
                         submodule_import: binding.import.is_submodule_import(),

crates/ruff_linter/src/rules/ruff/mod.rs

@@ -57,6 +57,7 @@ mod tests {
     #[test_case(Rule::UnusedAsync, Path::new("RUF029.py"))]
     #[test_case(Rule::AssertWithPrintMessage, Path::new("RUF030.py"))]
     #[test_case(Rule::IncorrectlyParenthesizedTupleInSubscript, Path::new("RUF031.py"))]
+    #[test_case(Rule::DecimalFromFloatLiteral, Path::new("RUF032.py"))]
     #[test_case(Rule::RedirectedNOQA, Path::new("RUF101.py"))]
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());

crates/ruff_linter/src/rules/ruff/rules/decimal_from_float_literal.rs

@@ -0,0 +1,85 @@
+use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::{self as ast};
+use ruff_python_codegen::Stylist;
+use ruff_text_size::{Ranged, TextRange};
+
+use crate::checkers::ast::Checker;
+
+/// ## What it does
+/// Checks for `Decimal` calls passing a float literal.
+///
+/// ## Why is this bad?
+/// Float literals have limited precision that can lead to unexpected results.
+/// The `Decimal` class is designed to handle numbers with fixed-point precision,
+/// so a string literal should be used instead.
+///
+/// ## Example
+///
+/// ```python
+/// num = Decimal(1.2345)
+/// ```
+///
+/// Use instead:
+/// ```python
+/// num = Decimal("1.2345")
+/// ```
+///
+/// ## Fix Safety
+/// This rule's fix is marked as unsafe because it changes the underlying value
+/// of the `Decimal` instance that is constructed. This can lead to unexpected
+/// behavior if your program relies on the previous value (whether deliberately or not).
+#[violation]
+pub struct DecimalFromFloatLiteral;
+
+impl AlwaysFixableViolation for DecimalFromFloatLiteral {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("`Decimal()` called with float literal argument")
+    }
+
+    fn fix_title(&self) -> String {
+        "Use a string literal instead".to_string()
+    }
+}
+
+/// RUF032: `Decimal()` called with float literal argument
+pub(crate) fn decimal_from_float_literal_syntax(checker: &mut Checker, call: &ast::ExprCall) {
+    let Some(arg) = call.arguments.args.first() else {
+        return;
+    };
+
+    if !is_arg_float_literal(arg) {
+        return;
+    }
+
+    if checker
+        .semantic()
+        .resolve_qualified_name(call.func.as_ref())
+        .is_some_and(|qualified_name| matches!(qualified_name.segments(), ["decimal", "Decimal"]))
+    {
+        let diagnostic =
+            Diagnostic::new(DecimalFromFloatLiteral, arg.range()).with_fix(fix_float_literal(
+                arg.range(),
+                &checker.generator().expr(arg),
+                checker.stylist(),
+            ));
+        checker.diagnostics.push(diagnostic);
+    }
+}
+
+fn is_arg_float_literal(arg: &ast::Expr) -> bool {
+    match arg {
+        ast::Expr::NumberLiteral(ast::ExprNumberLiteral {
+            value: ast::Number::Float(_),
+            ..
+        }) => true,
+        ast::Expr::UnaryOp(ast::ExprUnaryOp { operand, .. }) => is_arg_float_literal(operand),
+        _ => false,
+    }
+}
+
+fn fix_float_literal(range: TextRange, float_literal: &str, stylist: &Stylist) -> Fix {
+    let content = format!("{quote}{float_literal}{quote}", quote = stylist.quote());
+    Fix::unsafe_edit(Edit::range_replacement(content, range))
+}

crates/ruff_linter/src/rules/ruff/rules/mod.rs

@@ -3,6 +3,7 @@ pub(crate) use assert_with_print_message::*;
 pub(crate) use assignment_in_assert::*;
 pub(crate) use asyncio_dangling_task::*;
 pub(crate) use collection_literal_concatenation::*;
+pub(crate) use decimal_from_float_literal::*;
 pub(crate) use default_factory_kwarg::*;
 pub(crate) use explicit_f_string_type_conversion::*;
 pub(crate) use function_call_in_dataclass_default::*;
@@ -36,6 +37,7 @@ mod assignment_in_assert;
 mod asyncio_dangling_task;
 mod collection_literal_concatenation;
 mod confusables;
+mod decimal_from_float_literal;
 mod default_factory_kwarg;
 mod explicit_f_string_type_conversion;
 mod function_call_in_dataclass_default;

crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF032_RUF032.py.snap

@@ -0,0 +1,191 @@
+---
+source: crates/ruff_linter/src/rules/ruff/mod.rs
+---
+RUF032.py:6:17: RUF032 [*] `Decimal()` called with float literal argument
+  |
+4 | decimal.Decimal(0)
+5 | 
+6 | decimal.Decimal(0.0)  # Should error
+  |                 ^^^ RUF032
+7 | 
+8 | decimal.Decimal("0.0")
+  |
+  = help: Use a string literal instead
+
+ℹ Unsafe fix
+3 3 | # Tests with fully qualified import
+4 4 | decimal.Decimal(0)
+5 5 | 
+6   |-decimal.Decimal(0.0)  # Should error
+  6 |+decimal.Decimal("0.0")  # Should error
+7 7 | 
+8 8 | decimal.Decimal("0.0")
+9 9 | 
+
+RUF032.py:12:17: RUF032 [*] `Decimal()` called with float literal argument
+   |
+10 | decimal.Decimal(10)
+11 | 
+12 | decimal.Decimal(10.0)  # Should error
+   |                 ^^^^ RUF032
+13 | 
+14 | decimal.Decimal("10.0")
+   |
+   = help: Use a string literal instead
+
+ℹ Unsafe fix
+9  9  | 
+10 10 | decimal.Decimal(10)
+11 11 | 
+12    |-decimal.Decimal(10.0)  # Should error
+   12 |+decimal.Decimal("10.0")  # Should error
+13 13 | 
+14 14 | decimal.Decimal("10.0")
+15 15 | 
+
+RUF032.py:18:17: RUF032 [*] `Decimal()` called with float literal argument
+   |
+16 | decimal.Decimal(-10)
+17 | 
+18 | decimal.Decimal(-10.0)  # Should error
+   |                 ^^^^^ RUF032
+19 | 
+20 | decimal.Decimal("-10.0")
+   |
+   = help: Use a string literal instead
+
+ℹ Unsafe fix
+15 15 | 
+16 16 | decimal.Decimal(-10)
+17 17 | 
+18    |-decimal.Decimal(-10.0)  # Should error
+   18 |+decimal.Decimal("-10.0")  # Should error
+19 19 | 
+20 20 | decimal.Decimal("-10.0")
+21 21 | 
+
+RUF032.py:33:15: RUF032 [*] `Decimal()` called with float literal argument
+   |
+31 | val = Decimal(0)
+32 | 
+33 | val = Decimal(0.0)  # Should error
+   |               ^^^ RUF032
+34 | 
+35 | val = Decimal("0.0")
+   |
+   = help: Use a string literal instead
+
+ℹ Unsafe fix
+30 30 | 
+31 31 | val = Decimal(0)
+32 32 | 
+33    |-val = Decimal(0.0)  # Should error
+   33 |+val = Decimal("0.0")  # Should error
+34 34 | 
+35 35 | val = Decimal("0.0")
+36 36 | 
+
+RUF032.py:39:15: RUF032 [*] `Decimal()` called with float literal argument
+   |
+37 | val = Decimal(10)
+38 | 
+39 | val = Decimal(10.0)  # Should error
+   |               ^^^^ RUF032
+40 | 
+41 | val = Decimal("10.0")
+   |
+   = help: Use a string literal instead
+
+ℹ Unsafe fix
+36 36 | 
+37 37 | val = Decimal(10)
+38 38 | 
+39    |-val = Decimal(10.0)  # Should error
+   39 |+val = Decimal("10.0")  # Should error
+40 40 | 
+41 41 | val = Decimal("10.0")
+42 42 | 
+
+RUF032.py:45:15: RUF032 [*] `Decimal()` called with float literal argument
+   |
+43 | val = Decimal(-10)
+44 | 
+45 | val = Decimal(-10.0)  # Should error
+   |               ^^^^^ RUF032
+46 | 
+47 | val = Decimal("-10.0")
+   |
+   = help: Use a string literal instead
+
+ℹ Unsafe fix
+42 42 | 
+43 43 | val = Decimal(-10)
+44 44 | 
+45    |-val = Decimal(-10.0)  # Should error
+   45 |+val = Decimal("-10.0")  # Should error
+46 46 | 
+47 47 | val = Decimal("-10.0")
+48 48 | 
+
+RUF032.py:81:23: RUF032 [*] `Decimal()` called with float literal argument
+   |
+79 | # Retest with fully qualified import
+80 | 
+81 | val = decimal.Decimal(0.0)  # Should error
+   |                       ^^^ RUF032
+82 | 
+83 | val = decimal.Decimal("0.0")
+   |
+   = help: Use a string literal instead
+
+ℹ Unsafe fix
+78 78 | 
+79 79 | # Retest with fully qualified import
+80 80 | 
+81    |-val = decimal.Decimal(0.0)  # Should error
+   81 |+val = decimal.Decimal("0.0")  # Should error
+82 82 | 
+83 83 | val = decimal.Decimal("0.0")
+84 84 | 
+
+RUF032.py:85:23: RUF032 [*] `Decimal()` called with float literal argument
+   |
+83 | val = decimal.Decimal("0.0")
+84 | 
+85 | val = decimal.Decimal(10.0)  # Should error
+   |                       ^^^^ RUF032
+86 | 
+87 | val = decimal.Decimal("10.0")
+   |
+   = help: Use a string literal instead
+
+ℹ Unsafe fix
+82 82 | 
+83 83 | val = decimal.Decimal("0.0")
+84 84 | 
+85    |-val = decimal.Decimal(10.0)  # Should error
+   85 |+val = decimal.Decimal("10.0")  # Should error
+86 86 | 
+87 87 | val = decimal.Decimal("10.0")
+88 88 | 
+
+RUF032.py:89:23: RUF032 [*] `Decimal()` called with float literal argument
+   |
+87 | val = decimal.Decimal("10.0")
+88 | 
+89 | val = decimal.Decimal(-10.0)  # Should error
+   |                       ^^^^^ RUF032
+90 | 
+91 | val = decimal.Decimal("-10.0")
+   |
+   = help: Use a string literal instead
+
+ℹ Unsafe fix
+86 86 | 
+87 87 | val = decimal.Decimal("10.0")
+88 88 | 
+89    |-val = decimal.Decimal(-10.0)  # Should error
+   89 |+val = decimal.Decimal("-10.0")  # Should error
+90 90 | 
+91 91 | val = decimal.Decimal("-10.0")
+92 92 |

crates/ruff_server/src/session/index/ruff_settings.rs

@@ -3,6 +3,7 @@ use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
 
+use anyhow::Context;
 use ignore::{WalkBuilder, WalkState};
 
 use ruff_linter::{
@@ -100,7 +101,7 @@ impl RuffSettings {
 
 impl RuffSettingsIndex {
     pub(super) fn new(root: &Path, editor_settings: &ResolvedEditorSettings) -> Self {
-        let mut error = false;
+        let mut has_error = false;
         let mut index = BTreeMap::default();
         let mut respect_gitignore = None;
 
@@ -127,20 +128,27 @@ impl RuffSettingsIndex {
                             );
                             break;
                         }
-                        Err(err) => {
+                        error => {
                             tracing::error!(
-                                "Error while resolving settings from {}: {err}",
-                                pyproject.display()
+                                "{:#}",
+                                error
+                                    .with_context(|| {
+                                        format!(
+                                            "Failed to resolve settings for {}",
+                                            pyproject.display()
+                                        )
+                                    })
+                                    .unwrap_err()
                             );
-                            error = true;
+                            has_error = true;
                             continue;
                         }
                     }
                 }
                 Ok(None) => continue,
                 Err(err) => {
-                    tracing::error!("{err}");
-                    error = true;
+                    tracing::error!("{err:#}");
+                    has_error = true;
                     continue;
                 }
             }
@@ -162,7 +170,7 @@ impl RuffSettingsIndex {
         let walker = builder.build_parallel();
 
         let index = std::sync::RwLock::new(index);
-        let error = AtomicBool::new(error);
+        let has_error = AtomicBool::new(has_error);
 
         walker.run(|| {
             Box::new(|result| {
@@ -224,19 +232,26 @@ impl RuffSettingsIndex {
                                     }),
                                 );
                             }
-                            Err(err) => {
+                            error => {
                                 tracing::error!(
-                                    "Error while resolving settings from {}: {err}",
-                                    pyproject.display()
+                                    "{:#}",
+                                    error
+                                        .with_context(|| {
+                                            format!(
+                                                "Failed to resolve settings for {}",
+                                                pyproject.display()
+                                            )
+                                        })
+                                        .unwrap_err()
                                 );
-                                error.store(true, Ordering::Relaxed);
+                                has_error.store(true, Ordering::Relaxed);
                             }
                         }
                     }
                     Ok(None) => {}
                     Err(err) => {
-                        tracing::error!("{err}");
-                        error.store(true, Ordering::Relaxed);
+                        tracing::error!("{err:#}");
+                        has_error.store(true, Ordering::Relaxed);
                     }
                 }
 
@@ -244,7 +259,7 @@ impl RuffSettingsIndex {
             })
         });
 
-        if error.load(Ordering::Relaxed) {
+        if has_error.load(Ordering::Relaxed) {
             let root = root.display();
             show_err_msg!(
                 "Error while resolving settings from workspace {root}. Please refer to the logs for more details.",

crates/ruff_source_file/src/lib.rs

@@ -254,6 +254,12 @@ impl Debug for SourceLocation {
     }
 }
 
+impl std::fmt::Display for SourceLocation {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{row}:{column}", row = self.row, column = self.column)
+    }
+}
+
 #[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 pub enum SourceRow {
     /// A row within a cell in a Jupyter Notebook.

crates/ruff_workspace/src/options.rs

@@ -47,7 +47,7 @@ pub struct Options {
     /// This setting will override even the `RUFF_CACHE_DIR` environment
     /// variable, if set.
     #[option(
-        default = ".ruff_cache",
+        default = r#"".ruff_cache""#,
         value_type = "str",
         example = r#"cache-dir = "~/.cache/ruff""#
     )]
@@ -553,7 +553,7 @@ pub struct LintCommonOptions {
     /// default expression matches `_`, `__`, and `_var`, but not `_var_`.
     #[option(
         default = r#""^(_+|(_+[a-zA-Z0-9_]*[a-zA-Z0-9]+?))$""#,
-        value_type = "re.Pattern",
+        value_type = "str",
         example = r#"
             # Only ignore variables named "_".
             dummy-variable-rgx = "^_$"
@@ -1171,7 +1171,7 @@ pub struct Flake8CopyrightOptions {
     /// - `Copyright (C) 2021-2023`
     /// - `Copyright (C) 2021, 2023`
     #[option(
-        default = r#"(?i)Copyright\s+((?:\(C\)|©)\s+)?\d{4}((-|,\s)\d{4})*"#,
+        default = r#""(?i)Copyright\s+((?:\(C\)|©)\s+)?\d{4}((-|,\s)\d{4})*""#,
         value_type = "str",
         example = r#"notice-rgx = "(?i)Copyright \\(C\\) \\d{4}""#
     )]
@@ -2029,7 +2029,7 @@ pub struct IsortOptions {
     /// this to "closest-to-furthest" is equivalent to isort's
     /// `reverse-relative = true`.
     #[option(
-        default = r#"furthest-to-closest"#,
+        default = r#""furthest-to-closest""#,
         value_type = r#""furthest-to-closest" | "closest-to-furthest""#,
         example = r#"
             relative-imports-order = "closest-to-furthest"
@@ -2146,7 +2146,7 @@ pub struct IsortOptions {
 
     /// Define a default section for any imports that don't fit into the specified [`section-order`](#lint_isort_section-order).
     #[option(
-        default = r#"third-party"#,
+        default = r#""third-party""#,
         value_type = "str",
         example = r#"
             default-section = "first-party"
@@ -2660,8 +2660,8 @@ pub struct PycodestyleOptions {
     pub max_doc_length: Option<LineLength>,
 
     /// Whether line-length violations (`E501`) should be triggered for
-    /// comments starting with [`task-tags`](#lint_task-tags) (by default: \["TODO", "FIXME",
-    /// and "XXX"\]).
+    /// comments starting with [`task-tags`](#lint_task-tags) (by default: "TODO", "FIXME",
+    /// and "XXX").
     #[option(
         default = "false",
         value_type = "bool",
@@ -3059,7 +3059,7 @@ pub struct FormatOptions {
     ///
     /// See [`indent-width`](#indent-width) to configure the number of spaces per indentation and the tab width.
     #[option(
-        default = "space",
+        default = r#""space""#,
         value_type = r#""space" | "tab""#,
         example = r#"
             # Use tabs instead of 4 space indentation.
@@ -3092,7 +3092,7 @@ pub struct FormatOptions {
     /// a mixture of single and double quotes and can't migrate to the `double` or `single` style.
     /// The quote style `preserve` leaves the quotes of all strings unchanged.
     #[option(
-        default = r#"double"#,
+        default = r#""double""#,
         value_type = r#""double" | "single" | "preserve""#,
         example = r#"
             # Prefer single quotes over double quotes.
@@ -3136,7 +3136,7 @@ pub struct FormatOptions {
     /// * `cr-lf`: Line endings will be converted to `\r\n`. The default line ending on Windows.
     /// * `native`: Line endings will be converted to `\n` on Unix and `\r\n` on Windows.
     #[option(
-        default = r#"auto"#,
+        default = r#""auto""#,
         value_type = r#""auto" | "lf" | "cr-lf" | "native""#,
         example = r#"
             # Use `\n` line endings for all files

crates/ruff_workspace/src/resolver.rs

@@ -253,7 +253,7 @@ fn is_package_with_cache<'a>(
 /// Applies a transformation to a [`Configuration`].
 ///
 /// Used to override options with the values provided by the CLI.
-pub trait ConfigurationTransformer: Sync {
+pub trait ConfigurationTransformer {
     fn transform(&self, config: Configuration) -> Configuration;
 }
 
@@ -334,7 +334,7 @@ pub fn resolve_root_settings(
 pub fn python_files_in_path<'a>(
     paths: &[PathBuf],
     pyproject_config: &'a PyprojectConfig,
-    transformer: &dyn ConfigurationTransformer,
+    transformer: &(dyn ConfigurationTransformer + Sync),
 ) -> Result<(Vec<Result<ResolvedFile, ignore::Error>>, Resolver<'a>)> {
     // Normalize every path (e.g., convert from relative to absolute).
     let mut paths: Vec<PathBuf> = paths.iter().map(fs::normalize_path).unique().collect();
@@ -430,12 +430,12 @@ impl<'config> WalkPythonFilesState<'config> {
 
 struct PythonFilesVisitorBuilder<'s, 'config> {
     state: &'s WalkPythonFilesState<'config>,
-    transformer: &'s dyn ConfigurationTransformer,
+    transformer: &'s (dyn ConfigurationTransformer + Sync),
 }
 
 impl<'s, 'config> PythonFilesVisitorBuilder<'s, 'config> {
     fn new(
-        transformer: &'s dyn ConfigurationTransformer,
+        transformer: &'s (dyn ConfigurationTransformer + Sync),
         state: &'s WalkPythonFilesState<'config>,
     ) -> Self {
         Self { state, transformer }
@@ -446,7 +446,7 @@ struct PythonFilesVisitor<'s, 'config> {
     local_files: Vec<Result<ResolvedFile, ignore::Error>>,
     local_error: Result<()>,
     global: &'s WalkPythonFilesState<'config>,
-    transformer: &'s dyn ConfigurationTransformer,
+    transformer: &'s (dyn ConfigurationTransformer + Sync),
 }
 
 impl<'config, 's> ignore::ParallelVisitorBuilder<'s> for PythonFilesVisitorBuilder<'s, 'config>

docs/editors/setup.md

@@ -310,7 +310,12 @@ See [LSP Client documentation](https://docs.kde.org/stable5/en/kate/kate/kate-ap
 on how to configure the server from there.
 
 !!! important
-    Kate's LSP Client plugin does not support multiple servers for the same language.
+    Kate's LSP Client plugin does not support multiple servers for the same language. As a
+    workaround, you can use the [`python-lsp-server`](https://github.com/python-lsp/python-lsp-server)
+    along with the [`python-lsp-ruff`](https://github.com/python-lsp/python-lsp-ruff) plugin to
+    use Ruff alongside another language server. Note that this setup won't use the [server settings](settings.md)
+    because the [`python-lsp-ruff`](https://github.com/python-lsp/python-lsp-ruff) plugin uses the
+    `ruff` executable and not the language server.
 
 ## Sublime Text
 

mkdocs.template.yml

@@ -71,3 +71,8 @@ not_in_nav: |
 extra:
   analytics:
     provider: fathom
+validation:
+  omitted_files: warn
+  absolute_links: warn
+  unrecognized_links: warn
+  anchors: warn

playground/.eslintrc

@@ -1,6 +1,6 @@
 {
   "parser": "@typescript-eslint/parser",
-  "plugins": ["@typescript-eslint", "prettier"],
+  "plugins": ["@typescript-eslint"],
   "extends": [
     "eslint:recommended",
     "plugin:@typescript-eslint/eslint-recommended",
@@ -9,8 +9,7 @@
     "plugin:react/jsx-runtime",
     "plugin:react-hooks/recommended",
     "plugin:import/recommended",
-    "plugin:import/typescript",
-    "plugin:prettier/recommended"
+    "plugin:import/typescript"
   ],
   "rules": {
     // Disable some recommended rules that we don't want to enforce.

playground/api/package-lock.json

@@ -16,7 +16,7 @@
         "@cloudflare/workers-types": "^4.20230801.0",
         "miniflare": "^3.20230801.1",
         "typescript": "^5.1.6",
-        "wrangler": "3.70.0"
+        "wrangler": "3.72.0"
       }
     },
     "node_modules/@cloudflare/kv-asset-handler": {
@@ -118,15 +118,19 @@
       }
     },
     "node_modules/@cloudflare/workers-shared": {
-      "version": "0.1.0",
-      "resolved": "https://registry.npmjs.org/@cloudflare/workers-shared/-/workers-shared-0.1.0.tgz",
-      "integrity": "sha512-SyD4iw6jM4anZaG+ujgVETV4fulF2KHBOW31eavbVN7TNpk2l4aJgwY1YSPK00IKSWsoQuH2TigR446KuT5lqQ==",
-      "dev": true
+      "version": "0.2.0",
+      "resolved": "https://registry.npmjs.org/@cloudflare/workers-shared/-/workers-shared-0.2.0.tgz",
+      "integrity": "sha512-tIWLooWkBMuoKRk72lr6YrEtVlVdUTtAGVmPOnUroMrnri/9YLx+mVawL0/egDgSGmPbmvkdBFsUGRuI+aZmxg==",
+      "dev": true,
+      "license": "MIT OR Apache-2.0",
+      "engines": {
+        "node": ">=16.7.0"
+      }
     },
     "node_modules/@cloudflare/workers-types": {
-      "version": "4.20240806.0",
-      "resolved": "https://registry.npmjs.org/@cloudflare/workers-types/-/workers-types-4.20240806.0.tgz",
-      "integrity": "sha512-8lvgrwXGTZEBsUQJ8YUnMk72Anh9omwr6fqWLw/EwVgcw1nQxs/bfdadBEbdP48l9fWXjE4E5XERLUrrFuEpsg==",
+      "version": "4.20240815.0",
+      "resolved": "https://registry.npmjs.org/@cloudflare/workers-types/-/workers-types-4.20240815.0.tgz",
+      "integrity": "sha512-H/IXCOahT1lr4RKzsiCkyjM7+LCPLtl2wjxyLG8xMTNERR0XuD1Vcfns6TraE0cd5+IcKe7j3rpzBlSCjZ+61A==",
       "dev": true,
       "license": "MIT OR Apache-2.0"
     },
@@ -1111,9 +1115,9 @@
       }
     },
     "node_modules/miniflare": {
-      "version": "3.20240806.0",
-      "resolved": "https://registry.npmjs.org/miniflare/-/miniflare-3.20240806.0.tgz",
-      "integrity": "sha512-jDsXBJOLUVpIQXHsluX3xV0piDxXolTCsxdje2Ex2LTC9PsSoBIkMwvCmnCxe9wpJJCq8rb0UMyeEn3KOF3LOw==",
+      "version": "3.20240806.1",
+      "resolved": "https://registry.npmjs.org/miniflare/-/miniflare-3.20240806.1.tgz",
+      "integrity": "sha512-wJq3YQYx9k83L2CNYtxvwWvXSi+uHrC6aFoXYSbzhxIDlUWvMEqippj+3HeKLgsggC31nHJab3b1Pifg9IxIFQ==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
@@ -1599,21 +1603,21 @@
       }
     },
     "node_modules/wrangler": {
-      "version": "3.70.0",
-      "resolved": "https://registry.npmjs.org/wrangler/-/wrangler-3.70.0.tgz",
-      "integrity": "sha512-aMtCEXmH02SIxbxOFGGuJ8ZemmG9W+IcNRh5D4qIKgzSxqy0mt9mRoPNPSv1geGB2/8YAyeLGPf+tB4lxz+ssg==",
+      "version": "3.72.0",
+      "resolved": "https://registry.npmjs.org/wrangler/-/wrangler-3.72.0.tgz",
+      "integrity": "sha512-9sryHTCtCj48vUC5y/M3Dsx02U1bT6mK9E41TXBCpSJgWh8UvWG/xgmu2dY93Mqj9aJIvK/kwwIBRlNFRwF7Hw==",
       "dev": true,
       "license": "MIT OR Apache-2.0",
       "dependencies": {
         "@cloudflare/kv-asset-handler": "0.3.4",
-        "@cloudflare/workers-shared": "0.1.0",
+        "@cloudflare/workers-shared": "0.2.0",
         "@esbuild-plugins/node-globals-polyfill": "^0.2.3",
         "@esbuild-plugins/node-modules-polyfill": "^0.2.2",
         "blake3-wasm": "^2.1.5",
         "chokidar": "^3.5.3",
         "date-fns": "^3.6.0",
         "esbuild": "0.17.19",
-        "miniflare": "3.20240806.0",
+        "miniflare": "3.20240806.1",
         "nanoid": "^3.3.3",
         "path-to-regexp": "^6.2.0",
         "resolve": "^1.22.8",

playground/api/package.json

@@ -5,7 +5,7 @@
     "@cloudflare/workers-types": "^4.20230801.0",
     "miniflare": "^3.20230801.1",
     "typescript": "^5.1.6",
-    "wrangler": "3.70.0"
+    "wrangler": "3.72.0"
   },
   "private": true,
   "scripts": {

playground/package-lock.json

@@ -26,7 +26,6 @@
         "eslint": "^8.30.0",
         "eslint-config-prettier": "^9.0.0",
         "eslint-plugin-import": "^2.29.1",
-        "eslint-plugin-prettier": "^5.0.0",
         "eslint-plugin-react": "^7.31.11",
         "eslint-plugin-react-hooks": "^4.6.0",
         "postcss": "^8.4.20",
@@ -650,18 +649,6 @@
         "node": ">= 8"
       }
     },
-    "node_modules/@pkgr/core": {
-      "version": "0.1.1",
-      "resolved": "https://registry.npmjs.org/@pkgr/core/-/core-0.1.1.tgz",
-      "integrity": "sha512-cq8o4cWH0ibXh9VGi5P20Tu9XF/0fFXl9EUinr9QfTM7a7p0oTA4iJRCQWppXR1Pg8dSM0UCItCkPwsk9qWWYA==",
-      "dev": true,
-      "engines": {
-        "node": "^12.20.0 || ^14.18.0 || >=16.0.0"
-      },
-      "funding": {
-        "url": "https://opencollective.com/unts"
-      }
-    },
     "node_modules/@rollup/rollup-android-arm-eabi": {
       "version": "4.13.0",
       "resolved": "https://registry.npmjs.org/@rollup/rollup-android-arm-eabi/-/rollup-android-arm-eabi-4.13.0.tgz",
@@ -1096,17 +1083,17 @@
       }
     },
     "node_modules/@typescript-eslint/eslint-plugin": {
-      "version": "8.0.1",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/eslint-plugin/-/eslint-plugin-8.0.1.tgz",
-      "integrity": "sha512-5g3Y7GDFsJAnY4Yhvk8sZtFfV6YNF2caLzjrRPUBzewjPCaj0yokePB4LJSobyCzGMzjZZYFbwuzbfDHlimXbQ==",
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/eslint-plugin/-/eslint-plugin-8.1.0.tgz",
+      "integrity": "sha512-LlNBaHFCEBPHyD4pZXb35mzjGkuGKXU5eeCA1SxvHfiRES0E82dOounfVpL4DCqYvJEKab0bZIA0gCRpdLKkCw==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
         "@eslint-community/regexpp": "^4.10.0",
-        "@typescript-eslint/scope-manager": "8.0.1",
-        "@typescript-eslint/type-utils": "8.0.1",
-        "@typescript-eslint/utils": "8.0.1",
-        "@typescript-eslint/visitor-keys": "8.0.1",
+        "@typescript-eslint/scope-manager": "8.1.0",
+        "@typescript-eslint/type-utils": "8.1.0",
+        "@typescript-eslint/utils": "8.1.0",
+        "@typescript-eslint/visitor-keys": "8.1.0",
         "graphemer": "^1.4.0",
         "ignore": "^5.3.1",
         "natural-compare": "^1.4.0",
@@ -1130,16 +1117,16 @@
       }
     },
     "node_modules/@typescript-eslint/parser": {
-      "version": "8.0.1",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/parser/-/parser-8.0.1.tgz",
-      "integrity": "sha512-5IgYJ9EO/12pOUwiBKFkpU7rS3IU21mtXzB81TNwq2xEybcmAZrE9qwDtsb5uQd9aVO9o0fdabFyAmKveXyujg==",
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/parser/-/parser-8.1.0.tgz",
+      "integrity": "sha512-U7iTAtGgJk6DPX9wIWPPOlt1gO57097G06gIcl0N0EEnNw8RGD62c+2/DiP/zL7KrkqnnqF7gtFGR7YgzPllTA==",
       "dev": true,
       "license": "BSD-2-Clause",
       "dependencies": {
-        "@typescript-eslint/scope-manager": "8.0.1",
-        "@typescript-eslint/types": "8.0.1",
-        "@typescript-eslint/typescript-estree": "8.0.1",
-        "@typescript-eslint/visitor-keys": "8.0.1",
+        "@typescript-eslint/scope-manager": "8.1.0",
+        "@typescript-eslint/types": "8.1.0",
+        "@typescript-eslint/typescript-estree": "8.1.0",
+        "@typescript-eslint/visitor-keys": "8.1.0",
         "debug": "^4.3.4"
       },
       "engines": {
@@ -1159,14 +1146,14 @@
       }
     },
     "node_modules/@typescript-eslint/scope-manager": {
-      "version": "8.0.1",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/scope-manager/-/scope-manager-8.0.1.tgz",
-      "integrity": "sha512-NpixInP5dm7uukMiRyiHjRKkom5RIFA4dfiHvalanD2cF0CLUuQqxfg8PtEUo9yqJI2bBhF+pcSafqnG3UBnRQ==",
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/scope-manager/-/scope-manager-8.1.0.tgz",
+      "integrity": "sha512-DsuOZQji687sQUjm4N6c9xABJa7fjvfIdjqpSIIVOgaENf2jFXiM9hIBZOL3hb6DHK9Nvd2d7zZnoMLf9e0OtQ==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
-        "@typescript-eslint/types": "8.0.1",
-        "@typescript-eslint/visitor-keys": "8.0.1"
+        "@typescript-eslint/types": "8.1.0",
+        "@typescript-eslint/visitor-keys": "8.1.0"
       },
       "engines": {
         "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
@@ -1177,14 +1164,14 @@
       }
     },
     "node_modules/@typescript-eslint/type-utils": {
-      "version": "8.0.1",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/type-utils/-/type-utils-8.0.1.tgz",
-      "integrity": "sha512-+/UT25MWvXeDX9YaHv1IS6KI1fiuTto43WprE7pgSMswHbn1Jm9GEM4Txp+X74ifOWV8emu2AWcbLhpJAvD5Ng==",
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/type-utils/-/type-utils-8.1.0.tgz",
+      "integrity": "sha512-oLYvTxljVvsMnldfl6jIKxTaU7ok7km0KDrwOt1RHYu6nxlhN3TIx8k5Q52L6wR33nOwDgM7VwW1fT1qMNfFIA==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
-        "@typescript-eslint/typescript-estree": "8.0.1",
-        "@typescript-eslint/utils": "8.0.1",
+        "@typescript-eslint/typescript-estree": "8.1.0",
+        "@typescript-eslint/utils": "8.1.0",
         "debug": "^4.3.4",
         "ts-api-utils": "^1.3.0"
       },
@@ -1202,9 +1189,9 @@
       }
     },
     "node_modules/@typescript-eslint/types": {
-      "version": "8.0.1",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/types/-/types-8.0.1.tgz",
-      "integrity": "sha512-PpqTVT3yCA/bIgJ12czBuE3iBlM3g4inRSC5J0QOdQFAn07TYrYEQBBKgXH1lQpglup+Zy6c1fxuwTk4MTNKIw==",
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/types/-/types-8.1.0.tgz",
+      "integrity": "sha512-q2/Bxa0gMOu/2/AKALI0tCKbG2zppccnRIRCW6BaaTlRVaPKft4oVYPp7WOPpcnsgbr0qROAVCVKCvIQ0tbWog==",
       "dev": true,
       "license": "MIT",
       "engines": {
@@ -1216,14 +1203,14 @@
       }
     },
     "node_modules/@typescript-eslint/typescript-estree": {
-      "version": "8.0.1",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/typescript-estree/-/typescript-estree-8.0.1.tgz",
-      "integrity": "sha512-8V9hriRvZQXPWU3bbiUV4Epo7EvgM6RTs+sUmxp5G//dBGy402S7Fx0W0QkB2fb4obCF8SInoUzvTYtc3bkb5w==",
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/typescript-estree/-/typescript-estree-8.1.0.tgz",
+      "integrity": "sha512-NTHhmufocEkMiAord/g++gWKb0Fr34e9AExBRdqgWdVBaKoei2dIyYKD9Q0jBnvfbEA5zaf8plUFMUH6kQ0vGg==",
       "dev": true,
       "license": "BSD-2-Clause",
       "dependencies": {
-        "@typescript-eslint/types": "8.0.1",
-        "@typescript-eslint/visitor-keys": "8.0.1",
+        "@typescript-eslint/types": "8.1.0",
+        "@typescript-eslint/visitor-keys": "8.1.0",
         "debug": "^4.3.4",
         "globby": "^11.1.0",
         "is-glob": "^4.0.3",
@@ -1271,16 +1258,16 @@
       }
     },
     "node_modules/@typescript-eslint/utils": {
-      "version": "8.0.1",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/utils/-/utils-8.0.1.tgz",
-      "integrity": "sha512-CBFR0G0sCt0+fzfnKaciu9IBsKvEKYwN9UZ+eeogK1fYHg4Qxk1yf/wLQkLXlq8wbU2dFlgAesxt8Gi76E8RTA==",
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/utils/-/utils-8.1.0.tgz",
+      "integrity": "sha512-ypRueFNKTIFwqPeJBfeIpxZ895PQhNyH4YID6js0UoBImWYoSjBsahUn9KMiJXh94uOjVBgHD9AmkyPsPnFwJA==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
         "@eslint-community/eslint-utils": "^4.4.0",
-        "@typescript-eslint/scope-manager": "8.0.1",
-        "@typescript-eslint/types": "8.0.1",
-        "@typescript-eslint/typescript-estree": "8.0.1"
+        "@typescript-eslint/scope-manager": "8.1.0",
+        "@typescript-eslint/types": "8.1.0",
+        "@typescript-eslint/typescript-estree": "8.1.0"
       },
       "engines": {
         "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
@@ -1294,13 +1281,13 @@
       }
     },
     "node_modules/@typescript-eslint/visitor-keys": {
-      "version": "8.0.1",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/visitor-keys/-/visitor-keys-8.0.1.tgz",
-      "integrity": "sha512-W5E+o0UfUcK5EgchLZsyVWqARmsM7v54/qEq6PY3YI5arkgmCzHiuk0zKSJJbm71V0xdRna4BGomkCTXz2/LkQ==",
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/visitor-keys/-/visitor-keys-8.1.0.tgz",
+      "integrity": "sha512-ba0lNI19awqZ5ZNKh6wCModMwoZs457StTebQ0q1NP58zSi2F6MOZRXwfKZy+jB78JNJ/WH8GSh2IQNzXX8Nag==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
-        "@typescript-eslint/types": "8.0.1",
+        "@typescript-eslint/types": "8.1.0",
         "eslint-visitor-keys": "^3.4.3"
       },
       "engines": {
@@ -2453,37 +2440,6 @@
         "semver": "bin/semver.js"
       }
     },
-    "node_modules/eslint-plugin-prettier": {
-      "version": "5.2.1",
-      "resolved": "https://registry.npmjs.org/eslint-plugin-prettier/-/eslint-plugin-prettier-5.2.1.tgz",
-      "integrity": "sha512-gH3iR3g4JfF+yYPaJYkN7jEl9QbweL/YfkoRlNnuIEHEz1vHVlCmWOS+eGGiRuzHQXdJFCOTxRgvju9b8VUmrw==",
-      "dev": true,
-      "license": "MIT",
-      "dependencies": {
-        "prettier-linter-helpers": "^1.0.0",
-        "synckit": "^0.9.1"
-      },
-      "engines": {
-        "node": "^14.18.0 || >=16.0.0"
-      },
-      "funding": {
-        "url": "https://opencollective.com/eslint-plugin-prettier"
-      },
-      "peerDependencies": {
-        "@types/eslint": ">=8.0.0",
-        "eslint": ">=8.0.0",
-        "eslint-config-prettier": "*",
-        "prettier": ">=3.0.0"
-      },
-      "peerDependenciesMeta": {
-        "@types/eslint": {
-          "optional": true
-        },
-        "eslint-config-prettier": {
-          "optional": true
-        }
-      }
-    },
     "node_modules/eslint-plugin-react": {
       "version": "7.35.0",
       "resolved": "https://registry.npmjs.org/eslint-plugin-react/-/eslint-plugin-react-7.35.0.tgz",
@@ -2663,12 +2619,6 @@
       "integrity": "sha512-f3qQ9oQy9j2AhBe/H9VC91wLmKBCCU/gDOnKNAYG5hswO7BLKj09Hc5HYNz9cGI++xlpDCIgDaitVs03ATR84Q==",
       "dev": true
     },
-    "node_modules/fast-diff": {
-      "version": "1.3.0",
-      "resolved": "https://registry.npmjs.org/fast-diff/-/fast-diff-1.3.0.tgz",
-      "integrity": "sha512-VxPP4NqbUjj6MaAOafWeUn2cXWLcCtljklUtZf0Ind4XQ+QPtmA0b18zZy0jIQx+ExRVCR/ZQpBmik5lXshNsw==",
-      "dev": true
-    },
     "node_modules/fast-glob": {
       "version": "3.3.0",
       "resolved": "https://registry.npmjs.org/fast-glob/-/fast-glob-3.3.0.tgz",
@@ -4215,18 +4165,6 @@
         "url": "https://github.com/prettier/prettier?sponsor=1"
       }
     },
-    "node_modules/prettier-linter-helpers": {
-      "version": "1.0.0",
-      "resolved": "https://registry.npmjs.org/prettier-linter-helpers/-/prettier-linter-helpers-1.0.0.tgz",
-      "integrity": "sha512-GbK2cP9nraSSUF9N2XwUwqfzlAFlMNYYl+ShE/V+H8a9uNl/oUqB1w2EL54Jh0OlyRSd8RfWYJ3coVS4TROP2w==",
-      "dev": true,
-      "dependencies": {
-        "fast-diff": "^1.1.2"
-      },
-      "engines": {
-        "node": ">=6.0.0"
-      }
-    },
     "node_modules/prop-types": {
       "version": "15.8.1",
       "resolved": "https://registry.npmjs.org/prop-types/-/prop-types-15.8.1.tgz",
@@ -4297,9 +4235,9 @@
       "dev": true
     },
     "node_modules/react-resizable-panels": {
-      "version": "2.0.23",
-      "resolved": "https://registry.npmjs.org/react-resizable-panels/-/react-resizable-panels-2.0.23.tgz",
-      "integrity": "sha512-8ZKTwTU11t/FYwiwhMdtZYYyFxic5U5ysRu2YwfkAgDbUJXFvnWSJqhnzkSlW+mnDoNAzDCrJhdOSXBPA76wug==",
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/react-resizable-panels/-/react-resizable-panels-2.1.0.tgz",
+      "integrity": "sha512-k2gGjGyCNF9xq8gVkkHBK1mlWv6xetPtvRdEtD914gTdhJcy02TLF0xMPuVLlGRuLoWGv7Gd/O1rea2KIQb3Qw==",
       "license": "MIT",
       "peerDependencies": {
         "react": "^16.14.0 || ^17.0.0 || ^18.0.0",
@@ -4808,27 +4746,10 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
-    "node_modules/synckit": {
-      "version": "0.9.1",
-      "resolved": "https://registry.npmjs.org/synckit/-/synckit-0.9.1.tgz",
-      "integrity": "sha512-7gr8p9TQP6RAHusBOSLs46F4564ZrjV8xFmw5zCmgmhGUcw2hxsShhJ6CEiHQMgPDwAQ1fWHPM0ypc4RMAig4A==",
-      "dev": true,
-      "license": "MIT",
-      "dependencies": {
-        "@pkgr/core": "^0.1.0",
-        "tslib": "^2.6.2"
-      },
-      "engines": {
-        "node": "^14.18.0 || >=16.0.0"
-      },
-      "funding": {
-        "url": "https://opencollective.com/unts"
-      }
-    },
     "node_modules/tailwindcss": {
-      "version": "3.4.9",
-      "resolved": "https://registry.npmjs.org/tailwindcss/-/tailwindcss-3.4.9.tgz",
-      "integrity": "sha512-1SEOvRr6sSdV5IDf9iC+NU4dhwdqzF4zKKq3sAbasUWHEM6lsMhX+eNN5gkPx1BvLFEnZQEUFbXnGj8Qlp83Pg==",
+      "version": "3.4.10",
+      "resolved": "https://registry.npmjs.org/tailwindcss/-/tailwindcss-3.4.10.tgz",
+      "integrity": "sha512-KWZkVPm7yJRhdu4SRSl9d4AK2wM3a50UsvgHZO7xY77NQr2V+fIrEuoDGQcbvswWvFGbS2f6e+jC/6WJm1Dl0w==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
@@ -4932,12 +4853,6 @@
         "strip-bom": "^3.0.0"
       }
     },
-    "node_modules/tslib": {
-      "version": "2.6.2",
-      "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.6.2.tgz",
-      "integrity": "sha512-AEYxH93jGFPn/a2iVAwW87VuUIkR1FVUKB77NwMF7nBTDkDrrT/Hpt/IrCJ0QXhW27jTBDcf5ZY7w6RiqTMw2Q==",
-      "dev": true
-    },
     "node_modules/type-check": {
       "version": "0.4.0",
       "resolved": "https://registry.npmjs.org/type-check/-/type-check-0.4.0.tgz",
@@ -5111,14 +5026,14 @@
       "dev": true
     },
     "node_modules/vite": {
-      "version": "5.4.0",
-      "resolved": "https://registry.npmjs.org/vite/-/vite-5.4.0.tgz",
-      "integrity": "sha512-5xokfMX0PIiwCMCMb9ZJcMyh5wbBun0zUzKib+L65vAZ8GY9ePZMXxFrHbr/Kyll2+LSCY7xtERPpxkBDKngwg==",
+      "version": "5.4.1",
+      "resolved": "https://registry.npmjs.org/vite/-/vite-5.4.1.tgz",
+      "integrity": "sha512-1oE6yuNXssjrZdblI9AfBbHCC41nnyoVoEZxQnID6yvQZAFBzxxkqoFLtHUMkYunL8hwOLEjgTuxpkRxvba3kA==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
         "esbuild": "^0.21.3",
-        "postcss": "^8.4.40",
+        "postcss": "^8.4.41",
         "rollup": "^4.13.0"
       },
       "bin": {

playground/package.json

@@ -33,7 +33,6 @@
     "eslint": "^8.30.0",
     "eslint-config-prettier": "^9.0.0",
     "eslint-plugin-import": "^2.29.1",
-    "eslint-plugin-prettier": "^5.0.0",
     "eslint-plugin-react": "^7.31.11",
     "eslint-plugin-react-hooks": "^4.6.0",
     "postcss": "^8.4.20",

playground/src/Editor/Chrome.tsx

@@ -3,7 +3,7 @@ import Header from "./Header";
 import { persist, persistLocal, restore, stringify } from "./settings";
 import { useTheme } from "./theme";
 import { default as Editor, Source } from "./Editor";
-import initRuff, { Workspace } from "../pkg/ruff_wasm";
+import initRuff, { Workspace } from "../pkg";
 import { loader } from "@monaco-editor/react";
 import { setupMonaco } from "./setupMonaco";
 import { DEFAULT_PYTHON_SOURCE } from "../constants";

playground/src/Editor/Editor.tsx

@@ -1,6 +1,6 @@
 import { useDeferredValue, useMemo, useState } from "react";
 import { Panel, PanelGroup } from "react-resizable-panels";
-import { Diagnostic, Workspace } from "../pkg/ruff_wasm";
+import { Diagnostic, Workspace } from "../pkg";
 import { ErrorMessage } from "./ErrorMessage";
 import PrimarySideBar from "./PrimarySideBar";
 import { HorizontalResizeHandle } from "./ResizeHandle";

playground/src/Editor/SourceEditor.tsx

@@ -5,7 +5,7 @@
 import Editor, { BeforeMount, Monaco } from "@monaco-editor/react";
 import { MarkerSeverity, MarkerTag } from "monaco-editor";
 import { useCallback, useEffect, useRef } from "react";
-import { Diagnostic } from "../pkg/ruff_wasm";
+import { Diagnostic } from "../pkg";
 import { Theme } from "./theme";
 
 export default function SourceEditor({
@@ -83,7 +83,10 @@ export default function SourceEditor({
                   }
                 : undefined,
             }));
-          return { actions, dispose: () => {} };
+          return {
+            actions,
+            dispose: () => {},
+          };
         },
       },
     );

ruff.schema.json

@@ -2430,7 +2430,7 @@
       "type": "object",
       "properties": {
         "ignore-overlong-task-comments": {
-          "description": "Whether line-length violations (`E501`) should be triggered for comments starting with [`task-tags`](#lint_task-tags) (by default: \\[\"TODO\", \"FIXME\", and \"XXX\"\\]).",
+          "description": "Whether line-length violations (`E501`) should be triggered for comments starting with [`task-tags`](#lint_task-tags) (by default: \"TODO\", \"FIXME\", and \"XXX\").",
           "type": [
             "boolean",
             "null"
@@ -3738,6 +3738,7 @@
         "RUF03",
         "RUF030",
         "RUF031",
+        "RUF032",
         "RUF1",
         "RUF10",
         "RUF100",