ruff server now supports source.fixAll source action (#10597)

## Summary

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

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

## Test Plan




f4c07425-e68a-445f-a4ed-949c9197a6be

crates/ruff_server/src/edit.rs

@@ -2,11 +2,13 @@
 
 mod document;
 mod range;
+mod replacement;
 
 pub use document::Document;
 pub(crate) use document::DocumentVersion;
 use lsp_types::PositionEncodingKind;
 pub(crate) use range::{RangeExt, ToRangeExt};
+pub(crate) use replacement::Replacement;
 
 /// A convenient enumeration for supported text encodings. Can be converted to [`lsp_types::PositionEncodingKind`].
 // Please maintain the order from least to greatest priority for the derived `Ord` impl.

crates/ruff_server/src/edit/replacement.rs

@@ -0,0 +1,98 @@
+use ruff_text_size::{TextLen, TextRange, TextSize};
+
+pub(crate) struct Replacement {
+    pub(crate) source_range: TextRange,
+    pub(crate) modified_range: TextRange,
+}
+
+impl Replacement {
+    /// Creates a [`Replacement`] that describes the `source_range` of `source` to replace
+    /// with `modified` sliced by `modified_range`.
+    pub(crate) fn between(
+        source: &str,
+        source_line_starts: &[TextSize],
+        modified: &str,
+        modified_line_starts: &[TextSize],
+    ) -> Self {
+        let mut source_start = TextSize::default();
+        let mut replaced_start = TextSize::default();
+        let mut source_end = source.text_len();
+        let mut replaced_end = modified.text_len();
+        let mut line_iter = source_line_starts
+            .iter()
+            .copied()
+            .zip(modified_line_starts.iter().copied());
+        for (source_line_start, modified_line_start) in line_iter.by_ref() {
+            if source_line_start != modified_line_start
+                || source[TextRange::new(source_start, source_line_start)]
+                    != modified[TextRange::new(replaced_start, modified_line_start)]
+            {
+                break;
+            }
+            source_start = source_line_start;
+            replaced_start = modified_line_start;
+        }
+
+        let mut line_iter = line_iter.rev();
+
+        for (old_line_start, new_line_start) in line_iter.by_ref() {
+            if old_line_start <= source_start
+                || new_line_start <= replaced_start
+                || source[TextRange::new(old_line_start, source_end)]
+                    != modified[TextRange::new(new_line_start, replaced_end)]
+            {
+                break;
+            }
+            source_end = old_line_start;
+            replaced_end = new_line_start;
+        }
+
+        Replacement {
+            source_range: TextRange::new(source_start, source_end),
+            modified_range: TextRange::new(replaced_start, replaced_end),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use ruff_source_file::LineIndex;
+
+    use super::Replacement;
+
+    #[test]
+    fn find_replacement_range_works() {
+        let original = r#"
+         aaaa
+         bbbb
+         cccc
+         dddd
+         eeee
+         "#;
+        let original_index = LineIndex::from_source_text(original);
+        let new = r#"
+         bb
+         cccc
+         dd
+         "#;
+        let new_index = LineIndex::from_source_text(new);
+        let expected = r#"
+         bb
+         cccc
+         dd
+         "#;
+        let replacement = Replacement::between(
+            original,
+            original_index.line_starts(),
+            new,
+            new_index.line_starts(),
+        );
+        let mut test = original.to_string();
+        test.replace_range(
+            replacement.source_range.start().to_usize()..replacement.source_range.end().to_usize(),
+            &new[replacement.modified_range],
+        );
+
+        assert_eq!(expected, &test);
+    }
+}

crates/ruff_server/src/fix.rs

@@ -0,0 +1,79 @@
+use ruff_linter::{
+    linter::{FixerResult, LinterResult},
+    settings::{flags, types::UnsafeFixes, LinterSettings},
+    source_kind::SourceKind,
+};
+use ruff_python_ast::PySourceType;
+use ruff_source_file::LineIndex;
+use std::{borrow::Cow, path::Path};
+
+use crate::{
+    edit::{Replacement, ToRangeExt},
+    PositionEncoding,
+};
+
+pub(crate) fn fix_all(
+    document: &crate::edit::Document,
+    linter_settings: &LinterSettings,
+    encoding: PositionEncoding,
+) -> crate::Result<Vec<lsp_types::TextEdit>> {
+    let source = document.contents();
+
+    let source_type = PySourceType::default();
+
+    // TODO(jane): Support Jupyter Notebooks
+    let source_kind = SourceKind::Python(source.to_string());
+
+    // We need to iteratively apply all safe fixes onto a single file and then
+    // create a diff between the modified file and the original source to use as a single workspace
+    // edit.
+    // If we simply generated the diagnostics with `check_path` and then applied fixes individually,
+    // there's a possibility they could overlap or introduce new problems that need to be fixed,
+    // which is inconsistent with how `ruff check --fix` works.
+    let FixerResult {
+        transformed,
+        result: LinterResult { error, .. },
+        ..
+    } = ruff_linter::linter::lint_fix(
+        Path::new("<filename>"),
+        None,
+        flags::Noqa::Enabled,
+        UnsafeFixes::Disabled,
+        linter_settings,
+        &source_kind,
+        source_type,
+    )?;
+
+    if let Some(error) = error {
+        // abort early if a parsing error occurred
+        return Err(anyhow::anyhow!(
+            "A parsing error occurred during `fix_all`: {error}"
+        ));
+    }
+
+    // fast path: if `transformed` is still borrowed, no changes were made and we can return early
+    if let Cow::Borrowed(_) = transformed {
+        return Ok(vec![]);
+    }
+
+    let modified = transformed.source_code();
+
+    let modified_index = LineIndex::from_source_text(modified);
+
+    let source_index = document.index();
+
+    let Replacement {
+        source_range,
+        modified_range,
+    } = Replacement::between(
+        source,
+        source_index.line_starts(),
+        modified,
+        modified_index.line_starts(),
+    );
+
+    Ok(vec![lsp_types::TextEdit {
+        range: source_range.to_range(source, source_index, encoding),
+        new_text: modified[modified_range].to_owned(),
+    }])
+}

crates/ruff_server/src/lib.rs

@@ -1,9 +1,11 @@
 //! ## The Ruff Language Server
 
 pub use edit::{Document, PositionEncoding};
+use lsp_types::CodeActionKind;
 pub use server::Server;
 
 mod edit;
+mod fix;
 mod format;
 mod lint;
 mod server;
@@ -12,6 +14,10 @@ mod session;
 pub(crate) const SERVER_NAME: &str = "ruff";
 pub(crate) const DIAGNOSTIC_NAME: &str = "Ruff";
 
+pub(crate) const SOURCE_FIX_ALL_RUFF: CodeActionKind = CodeActionKind::new("source.fixAll.ruff");
+pub(crate) const SOURCE_ORGANIZE_IMPORTS_RUFF: CodeActionKind =
+    CodeActionKind::new("source.organizeImports.ruff");
+
 /// A common result type used in most cases where a
 /// result type is needed.
 pub(crate) type Result<T> = anyhow::Result<T>;

crates/ruff_server/src/lint.rs

@@ -16,14 +16,26 @@ use ruff_python_index::Indexer;
 use ruff_python_parser::lexer::LexResult;
 use ruff_python_parser::AsMode;
 use ruff_source_file::Locator;
+use ruff_text_size::Ranged;
 use serde::{Deserialize, Serialize};
 
 use crate::{edit::ToRangeExt, PositionEncoding, DIAGNOSTIC_NAME};
 
-#[derive(Serialize, Deserialize)]
-pub(crate) struct DiagnosticFix {
+/// This is serialized on the diagnostic `data` field.
+#[derive(Serialize, Deserialize, Debug, Clone)]
+pub(crate) struct AssociatedDiagnosticData {
     pub(crate) kind: DiagnosticKind,
     pub(crate) fix: Fix,
+    pub(crate) code: String,
+}
+
+/// Describes a fix for `fixed_diagnostic` that applies `document_edits` to the source.
+#[derive(Clone, Debug)]
+pub(crate) struct DiagnosticFix {
+    pub(crate) fixed_diagnostic: lsp_types::Diagnostic,
+    pub(crate) title: String,
+    pub(crate) code: String,
+    pub(crate) document_edits: Vec<lsp_types::TextDocumentEdit>,
 }
 
 pub(crate) fn check(
@@ -78,6 +90,56 @@ pub(crate) fn check(
         .collect()
 }
 
+pub(crate) fn fixes_for_diagnostics<'d>(
+    document: &'d crate::edit::Document,
+    url: &'d lsp_types::Url,
+    encoding: PositionEncoding,
+    version: crate::edit::DocumentVersion,
+    diagnostics: Vec<lsp_types::Diagnostic>,
+) -> crate::Result<Vec<DiagnosticFix>> {
+    diagnostics
+        .into_iter()
+        .map(move |mut diagnostic| {
+            let Some(data) = diagnostic.data.take() else {
+                return Ok(None);
+            };
+            let fixed_diagnostic = diagnostic;
+            let associated_data: crate::lint::AssociatedDiagnosticData =
+                serde_json::from_value(data).map_err(|err| {
+                    anyhow::anyhow!("failed to deserialize diagnostic data: {err}")
+                })?;
+            let edits = associated_data
+                .fix
+                .edits()
+                .iter()
+                .map(|edit| lsp_types::TextEdit {
+                    range: edit
+                        .range()
+                        .to_range(document.contents(), document.index(), encoding),
+                    new_text: edit.content().unwrap_or_default().to_string(),
+                });
+
+            let document_edits = vec![lsp_types::TextDocumentEdit {
+                text_document: lsp_types::OptionalVersionedTextDocumentIdentifier::new(
+                    url.clone(),
+                    version,
+                ),
+                edits: edits.map(lsp_types::OneOf::Left).collect(),
+            }];
+            Ok(Some(DiagnosticFix {
+                fixed_diagnostic,
+                code: associated_data.code,
+                title: associated_data
+                    .kind
+                    .suggestion
+                    .unwrap_or(associated_data.kind.name),
+                document_edits,
+            }))
+        })
+        .filter_map(crate::Result::transpose)
+        .collect()
+}
+
 fn to_lsp_diagnostic(
     diagnostic: Diagnostic,
     document: &crate::edit::Document,
@@ -92,9 +154,10 @@ fn to_lsp_diagnostic(
     let data = fix.and_then(|fix| {
         fix.applies(Applicability::Unsafe)
             .then(|| {
-                serde_json::to_value(&DiagnosticFix {
+                serde_json::to_value(&AssociatedDiagnosticData {
                     kind: kind.clone(),
                     fix,
+                    code: rule.noqa_code().to_string(),
                 })
                 .ok()
             })

crates/ruff_server/src/server.rs

@@ -72,10 +72,10 @@ impl Server {
 
         Ok(Self {
             conn,
-            client_capabilities,
             threads,
             worker_threads,
-            session: Session::new(&server_capabilities, &workspaces)?,
+            session: Session::new(&client_capabilities, &server_capabilities, &workspaces)?,
+            client_capabilities,
         })
     }
 
@@ -192,14 +192,15 @@ impl Server {
             position_encoding: Some(position_encoding.into()),
             code_action_provider: Some(types::CodeActionProviderCapability::Options(
                 CodeActionOptions {
-                    code_action_kinds: Some(vec![
-                        CodeActionKind::QUICKFIX,
-                        CodeActionKind::SOURCE_ORGANIZE_IMPORTS,
-                    ]),
+                    code_action_kinds: Some(
+                        SupportedCodeAction::all()
+                            .flat_map(|action| action.kinds().into_iter())
+                            .collect(),
+                    ),
                     work_done_progress_options: WorkDoneProgressOptions {
                         work_done_progress: Some(true),
                     },
-                    resolve_provider: Some(false),
+                    resolve_provider: Some(true),
                 },
             )),
             workspace: Some(types::WorkspaceServerCapabilities {
@@ -235,3 +236,56 @@ impl Server {
         }
     }
 }
+
+/// The code actions we support.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub(crate) enum SupportedCodeAction {
+    /// Maps to the `quickfix` code action kind. Quick fix code actions are shown under
+    /// their respective diagnostics. Quick fixes are only created where the fix applicability is
+    /// at least [`ruff_diagnostics::Applicability::Unsafe`].
+    QuickFix,
+    /// Maps to the `source.fixAll` and `source.fixAll.ruff` code action kinds.
+    /// This is a source action that applies all safe fixes to the currently open document.
+    SourceFixAll,
+    /// Maps to `source.organizeImports` and `source.organizeImports.ruff` code action kinds.
+    /// This is a source action that applies import sorting fixes to the currently open document.
+    #[allow(dead_code)] // TODO: remove
+    SourceOrganizeImports,
+}
+
+impl SupportedCodeAction {
+    /// Returns the possible LSP code action kind(s) that map to this code action.
+    fn kinds(self) -> Vec<CodeActionKind> {
+        match self {
+            Self::QuickFix => vec![CodeActionKind::QUICKFIX],
+            Self::SourceFixAll => vec![CodeActionKind::SOURCE_FIX_ALL, crate::SOURCE_FIX_ALL_RUFF],
+            Self::SourceOrganizeImports => vec![
+                CodeActionKind::SOURCE_ORGANIZE_IMPORTS,
+                crate::SOURCE_ORGANIZE_IMPORTS_RUFF,
+            ],
+        }
+    }
+
+    /// Returns all code actions kinds that the server currently supports.
+    fn all() -> impl Iterator<Item = Self> {
+        [
+            Self::QuickFix,
+            Self::SourceFixAll,
+            // Self::SourceOrganizeImports,
+        ]
+        .into_iter()
+    }
+}
+
+impl TryFrom<CodeActionKind> for SupportedCodeAction {
+    type Error = ();
+
+    fn try_from(kind: CodeActionKind) -> std::result::Result<Self, Self::Error> {
+        for supported_kind in Self::all() {
+            if supported_kind.kinds().contains(&kind) {
+                return Ok(supported_kind);
+            }
+        }
+        Err(())
+    }
+}

crates/ruff_server/src/server/api.rs

@@ -16,8 +16,8 @@ use super::{client::Responder, schedule::BackgroundSchedule, Result};
 /// given the parameter type used by the implementer.
 macro_rules! define_document_url {
     ($params:ident: &$p:ty) => {
-        fn document_url($params: &$p) -> &lsp_types::Url {
-            &$params.text_document.uri
+        fn document_url($params: &$p) -> std::borrow::Cow<lsp_types::Url> {
+            std::borrow::Cow::Borrowed(&$params.text_document.uri)
         }
     };
 }
@@ -28,10 +28,13 @@ pub(super) fn request<'a>(req: server::Request) -> Task<'a> {
     let id = req.id.clone();
 
     match req.method.as_str() {
-        request::CodeAction::METHOD => background_request_task::<request::CodeAction>(
+        request::CodeActions::METHOD => background_request_task::<request::CodeActions>(
             req,
             BackgroundSchedule::LatencySensitive,
         ),
+        request::CodeActionResolve::METHOD => {
+            background_request_task::<request::CodeActionResolve>(req, BackgroundSchedule::Worker)
+        }
         request::DocumentDiagnostic::METHOD => {
             background_request_task::<request::DocumentDiagnostic>(
                 req,
@@ -102,7 +105,7 @@ fn background_request_task<'a, R: traits::BackgroundDocumentRequestHandler>(
     let (id, params) = cast_request::<R>(req)?;
     Ok(Task::background(schedule, move |session: &Session| {
         // TODO(jane): we should log an error if we can't take a snapshot.
-        let Some(snapshot) = session.take_snapshot(R::document_url(&params)) else {
+        let Some(snapshot) = session.take_snapshot(&R::document_url(&params)) else {
             return Box::new(|_, _| {});
         };
         Box::new(move |notifier, responder| {
@@ -131,7 +134,7 @@ fn background_notification_thread<'a, N: traits::BackgroundDocumentNotificationH
     let (id, params) = cast_notification::<N>(req)?;
     Ok(Task::background(schedule, move |session: &Session| {
         // TODO(jane): we should log an error if we can't take a snapshot.
-        let Some(snapshot) = session.take_snapshot(N::document_url(&params)) else {
+        let Some(snapshot) = session.take_snapshot(&N::document_url(&params)) else {
             return Box::new(|_, _| {});
         };
         Box::new(move |notifier, _| {

crates/ruff_server/src/server/api/requests.rs

@@ -1,4 +1,5 @@
 mod code_action;
+mod code_action_resolve;
 mod diagnostic;
 mod format;
 mod format_range;
@@ -7,7 +8,8 @@ use super::{
     define_document_url,
     traits::{BackgroundDocumentRequestHandler, RequestHandler},
 };
-pub(super) use code_action::CodeAction;
+pub(super) use code_action::CodeActions;
+pub(super) use code_action_resolve::CodeActionResolve;
 pub(super) use diagnostic::DocumentDiagnostic;
 pub(super) use format::Format;
 pub(super) use format_range::FormatRange;

crates/ruff_server/src/server/api/requests/code_action.rs

@@ -1,81 +1,131 @@
-use crate::edit::ToRangeExt;
+use crate::lint::fixes_for_diagnostics;
 use crate::server::api::LSPResult;
+use crate::server::SupportedCodeAction;
 use crate::server::{client::Notifier, Result};
 use crate::session::DocumentSnapshot;
+use crate::DIAGNOSTIC_NAME;
+use lsp_server::ErrorCode;
 use lsp_types::{self as types, request as req};
-use ruff_text_size::Ranged;
+use rustc_hash::FxHashSet;
+use types::{CodeActionKind, CodeActionOrCommand};
 
-pub(crate) struct CodeAction;
+use super::code_action_resolve::resolve_edit_for_fix_all;
 
-impl super::RequestHandler for CodeAction {
+pub(crate) struct CodeActions;
+
+impl super::RequestHandler for CodeActions {
     type RequestType = req::CodeActionRequest;
 }
 
-impl super::BackgroundDocumentRequestHandler for CodeAction {
+impl super::BackgroundDocumentRequestHandler for CodeActions {
     super::define_document_url!(params: &types::CodeActionParams);
     fn run_with_snapshot(
         snapshot: DocumentSnapshot,
         _notifier: Notifier,
         params: types::CodeActionParams,
     ) -> Result<Option<types::CodeActionResponse>> {
-        let document = snapshot.document();
-        let url = snapshot.url();
-        let encoding = snapshot.encoding();
-        let version = document.version();
-        let actions: Result<Vec<_>> = params
-            .context
-            .diagnostics
-            .into_iter()
-            .map(|diagnostic| {
-                let Some(data) = diagnostic.data else {
-                    return Ok(None);
-                };
-                let diagnostic_fix: crate::lint::DiagnosticFix = serde_json::from_value(data)
-                    .map_err(|err| anyhow::anyhow!("failed to deserialize diagnostic data: {err}"))
-                    .with_failure_code(lsp_server::ErrorCode::ParseError)?;
-                let edits = diagnostic_fix
-                    .fix
-                    .edits()
-                    .iter()
-                    .map(|edit| types::TextEdit {
-                        range: edit.range().to_range(
-                            document.contents(),
-                            document.index(),
-                            encoding,
-                        ),
-                        new_text: edit.content().unwrap_or_default().to_string(),
-                    });
+        let mut response: types::CodeActionResponse = types::CodeActionResponse::default();
 
-                let changes = vec![types::TextDocumentEdit {
-                    text_document: types::OptionalVersionedTextDocumentIdentifier::new(
-                        url.clone(),
-                        version,
-                    ),
-                    edits: edits.map(types::OneOf::Left).collect(),
-                }];
+        let supported_code_actions = supported_code_actions(params.context.only);
 
-                let title = diagnostic_fix
-                    .kind
-                    .suggestion
-                    .unwrap_or(diagnostic_fix.kind.name);
-                Ok(Some(types::CodeAction {
-                    title,
-                    kind: Some(types::CodeActionKind::QUICKFIX),
-                    edit: Some(types::WorkspaceEdit {
-                        document_changes: Some(types::DocumentChanges::Edits(changes)),
-                        ..Default::default()
-                    }),
-                    ..Default::default()
-                }))
-            })
-            .collect();
+        if supported_code_actions.contains(&SupportedCodeAction::QuickFix) {
+            response.extend(
+                quick_fix(&snapshot, params.context.diagnostics)
+                    .with_failure_code(ErrorCode::InternalError)?,
+            );
+        }
 
-        Ok(Some(
-            actions?
-                .into_iter()
-                .flatten()
-                .map(types::CodeActionOrCommand::CodeAction)
-                .collect(),
-        ))
+        if supported_code_actions.contains(&SupportedCodeAction::SourceFixAll) {
+            response.push(fix_all(&snapshot).with_failure_code(ErrorCode::InternalError)?);
+        }
+
+        if supported_code_actions.contains(&SupportedCodeAction::SourceOrganizeImports) {
+            todo!("Implement the `source.organizeImports` code action");
+        }
+
+        Ok(Some(response))
     }
 }
+
+fn quick_fix(
+    snapshot: &DocumentSnapshot,
+    diagnostics: Vec<types::Diagnostic>,
+) -> crate::Result<impl Iterator<Item = CodeActionOrCommand> + '_> {
+    let document = snapshot.document();
+
+    let fixes = fixes_for_diagnostics(
+        document,
+        snapshot.url(),
+        snapshot.encoding(),
+        document.version(),
+        diagnostics,
+    )?;
+
+    Ok(fixes.into_iter().map(|fix| {
+        types::CodeActionOrCommand::CodeAction(types::CodeAction {
+            title: format!("{DIAGNOSTIC_NAME} ({}): {}", fix.code, fix.title),
+            kind: Some(types::CodeActionKind::QUICKFIX),
+            edit: Some(types::WorkspaceEdit {
+                document_changes: Some(types::DocumentChanges::Edits(fix.document_edits.clone())),
+                ..Default::default()
+            }),
+            diagnostics: Some(vec![fix.fixed_diagnostic.clone()]),
+            data: Some(serde_json::to_value(snapshot.url()).expect("document url to serialize")),
+            ..Default::default()
+        })
+    }))
+}
+
+fn fix_all(snapshot: &DocumentSnapshot) -> crate::Result<CodeActionOrCommand> {
+    let document = snapshot.document();
+
+    let (edit, data) = if snapshot
+        .resolved_client_capabilities()
+        .code_action_deferred_edit_resolution
+    {
+        // The editor will request the edit in a `CodeActionsResolve` request
+        (
+            None,
+            Some(serde_json::to_value(snapshot.url()).expect("document url to serialize")),
+        )
+    } else {
+        (
+            Some(resolve_edit_for_fix_all(
+                document,
+                snapshot.url(),
+                &snapshot.configuration().linter,
+                snapshot.encoding(),
+            )?),
+            None,
+        )
+    };
+    let action = types::CodeAction {
+        title: format!("{DIAGNOSTIC_NAME}: Fix all auto-fixable problems"),
+        kind: Some(types::CodeActionKind::SOURCE_FIX_ALL),
+        edit,
+        data,
+        ..Default::default()
+    };
+    Ok(types::CodeActionOrCommand::CodeAction(action))
+}
+
+/// If `action_filter` is `None`, this returns [`SupportedCodeActionKind::all()`]. Otherwise,
+/// the list is filtered.
+fn supported_code_actions(
+    action_filter: Option<Vec<CodeActionKind>>,
+) -> FxHashSet<SupportedCodeAction> {
+    let Some(action_filter) = action_filter else {
+        return SupportedCodeAction::all().collect();
+    };
+
+    SupportedCodeAction::all()
+        .filter(move |action| {
+            action_filter.iter().any(|filter| {
+                action
+                    .kinds()
+                    .iter()
+                    .any(|kind| kind.as_str().starts_with(filter.as_str()))
+            })
+        })
+        .collect()
+}

crates/ruff_server/src/server/api/requests/code_action_resolve.rs

@@ -0,0 +1,82 @@
+use std::borrow::Cow;
+
+use crate::server::api::LSPResult;
+use crate::server::SupportedCodeAction;
+use crate::server::{client::Notifier, Result};
+use crate::session::DocumentSnapshot;
+use crate::PositionEncoding;
+use lsp_server::ErrorCode;
+use lsp_types::{self as types, request as req};
+use ruff_linter::settings::LinterSettings;
+
+pub(crate) struct CodeActionResolve;
+
+impl super::RequestHandler for CodeActionResolve {
+    type RequestType = req::CodeActionResolveRequest;
+}
+
+impl super::BackgroundDocumentRequestHandler for CodeActionResolve {
+    fn document_url(params: &types::CodeAction) -> Cow<types::Url> {
+        let uri: lsp_types::Url = serde_json::from_value(params.data.clone().unwrap_or_default())
+            .expect("code actions should have a URI in their data fields");
+        std::borrow::Cow::Owned(uri)
+    }
+    fn run_with_snapshot(
+        snapshot: DocumentSnapshot,
+        _notifier: Notifier,
+        mut action: types::CodeAction,
+    ) -> Result<types::CodeAction> {
+        let document = snapshot.document();
+
+        let action_kind: SupportedCodeAction = action
+            .kind
+            .clone()
+            .ok_or(anyhow::anyhow!("No kind was given for code action"))
+            .with_failure_code(ErrorCode::InvalidParams)?
+            .try_into()
+            .map_err(|()| anyhow::anyhow!("Code action was of an invalid kind"))
+            .with_failure_code(ErrorCode::InvalidParams)?;
+
+        action.edit = match action_kind {
+            SupportedCodeAction::SourceFixAll => Some(
+                resolve_edit_for_fix_all(
+                    document,
+                    snapshot.url(),
+                    &snapshot.configuration().linter,
+                    snapshot.encoding(),
+                )
+                .with_failure_code(ErrorCode::InternalError)?,
+            ),
+            SupportedCodeAction::SourceOrganizeImports => {
+                todo!("Support `source.organizeImports`")
+            }
+            SupportedCodeAction::QuickFix => {
+                return Err(anyhow::anyhow!(
+                    "Got a code action that should not need additional resolution: {action_kind:?}"
+                ))
+                .with_failure_code(ErrorCode::InvalidParams)
+            }
+        };
+
+        Ok(action)
+    }
+}
+
+pub(super) fn resolve_edit_for_fix_all(
+    document: &crate::edit::Document,
+    url: &types::Url,
+    linter_settings: &LinterSettings,
+    encoding: PositionEncoding,
+) -> crate::Result<types::WorkspaceEdit> {
+    Ok(types::WorkspaceEdit {
+        changes: Some(
+            [(
+                url.clone(),
+                crate::fix::fix_all(document, linter_settings, encoding)?,
+            )]
+            .into_iter()
+            .collect(),
+        ),
+        ..Default::default()
+    })
+}

crates/ruff_server/src/server/api/requests/format.rs

@@ -1,10 +1,9 @@
-use crate::edit::ToRangeExt;
+use crate::edit::{Replacement, ToRangeExt};
 use crate::server::api::LSPResult;
 use crate::server::{client::Notifier, Result};
 use crate::session::DocumentSnapshot;
 use lsp_types::{self as types, request as req};
 use ruff_source_file::LineIndex;
-use ruff_text_size::{TextLen, TextRange, TextSize};
 use types::TextEdit;
 
 pub(crate) struct Format;
@@ -33,8 +32,8 @@ impl super::BackgroundDocumentRequestHandler for Format {
         let unformatted_index = doc.index();
 
         let Replacement {
-            source_range: replace_range,
-            formatted_range: replacement_text_range,
+            source_range,
+            modified_range: formatted_range,
         } = Replacement::between(
             source,
             unformatted_index.line_starts(),
@@ -43,105 +42,8 @@ impl super::BackgroundDocumentRequestHandler for Format {
         );
 
         Ok(Some(vec![TextEdit {
-            range: replace_range.to_range(source, unformatted_index, snapshot.encoding()),
-            new_text: formatted[replacement_text_range].to_owned(),
+            range: source_range.to_range(source, unformatted_index, snapshot.encoding()),
+            new_text: formatted[formatted_range].to_owned(),
         }]))
     }
 }
-
-struct Replacement {
-    source_range: TextRange,
-    formatted_range: TextRange,
-}
-
-impl Replacement {
-    /// Creates a [`Replacement`] that describes the `replace_range` of `old_text` to replace
-    /// with `new_text` sliced by `replacement_text_range`.
-    fn between(
-        source: &str,
-        source_line_starts: &[TextSize],
-        formatted: &str,
-        formatted_line_starts: &[TextSize],
-    ) -> Self {
-        let mut source_start = TextSize::default();
-        let mut formatted_start = TextSize::default();
-        let mut source_end = source.text_len();
-        let mut formatted_end = formatted.text_len();
-        let mut line_iter = source_line_starts
-            .iter()
-            .copied()
-            .zip(formatted_line_starts.iter().copied());
-        for (source_line_start, formatted_line_start) in line_iter.by_ref() {
-            if source_line_start != formatted_line_start
-                || source[TextRange::new(source_start, source_line_start)]
-                    != formatted[TextRange::new(formatted_start, formatted_line_start)]
-            {
-                break;
-            }
-            source_start = source_line_start;
-            formatted_start = formatted_line_start;
-        }
-
-        let mut line_iter = line_iter.rev();
-
-        for (old_line_start, new_line_start) in line_iter.by_ref() {
-            if old_line_start <= source_start
-                || new_line_start <= formatted_start
-                || source[TextRange::new(old_line_start, source_end)]
-                    != formatted[TextRange::new(new_line_start, formatted_end)]
-            {
-                break;
-            }
-            source_end = old_line_start;
-            formatted_end = new_line_start;
-        }
-
-        Replacement {
-            source_range: TextRange::new(source_start, source_end),
-            formatted_range: TextRange::new(formatted_start, formatted_end),
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use ruff_source_file::LineIndex;
-
-    use crate::server::api::requests::format::Replacement;
-
-    #[test]
-    fn find_replacement_range_works() {
-        let original = r#"
-         aaaa
-         bbbb
-         cccc
-         dddd
-         eeee
-         "#;
-        let original_index = LineIndex::from_source_text(original);
-        let new = r#"
-         bb
-         cccc
-         dd
-         "#;
-        let new_index = LineIndex::from_source_text(new);
-        let expected = r#"
-         bb
-         cccc
-         dd
-         "#;
-        let replacement = Replacement::between(
-            original,
-            original_index.line_starts(),
-            new,
-            new_index.line_starts(),
-        );
-        let mut test = original.to_string();
-        test.replace_range(
-            replacement.source_range.start().to_usize()..replacement.source_range.end().to_usize(),
-            &new[replacement.formatted_range],
-        );
-
-        assert_eq!(expected, &test);
-    }
-}

crates/ruff_server/src/server/api/traits.rs

@@ -31,7 +31,7 @@ pub(super) trait BackgroundDocumentRequestHandler: RequestHandler {
     /// implementation.
     fn document_url(
         params: &<<Self as RequestHandler>::RequestType as Request>::Params,
-    ) -> &lsp_types::Url;
+    ) -> std::borrow::Cow<lsp_types::Url>;
 
     fn run_with_snapshot(
         snapshot: DocumentSnapshot,
@@ -66,7 +66,7 @@ pub(super) trait BackgroundDocumentNotificationHandler: NotificationHandler {
     /// implementation.
     fn document_url(
         params: &<<Self as NotificationHandler>::NotificationType as LSPNotification>::Params,
-    ) -> &lsp_types::Url;
+    ) -> std::borrow::Cow<lsp_types::Url>;
 
     fn run_with_snapshot(
         snapshot: DocumentSnapshot,

crates/ruff_server/src/session.rs

@@ -1,34 +1,36 @@
 //! Data model, state management, and configuration resolution.
 
-mod types;
+mod settings;
 
 use std::collections::BTreeMap;
 use std::path::{Path, PathBuf};
 use std::{ops::Deref, sync::Arc};
 
 use anyhow::anyhow;
-use lsp_types::{ServerCapabilities, Url};
+use lsp_types::{ClientCapabilities, ServerCapabilities, Url};
 use ruff_workspace::resolver::{ConfigurationTransformer, Relativity};
 use rustc_hash::FxHashMap;
 
 use crate::edit::{Document, DocumentVersion};
 use crate::PositionEncoding;
 
+use self::settings::ResolvedClientCapabilities;
+
 /// The global state for the LSP
 pub(crate) struct Session {
     /// Workspace folders in the current session, which contain the state of all open files.
     workspaces: Workspaces,
     /// The global position encoding, negotiated during LSP initialization.
     position_encoding: PositionEncoding,
-    /// Extension-specific settings, set by the client, that apply to all workspace folders.
-    #[allow(dead_code)]
-    lsp_settings: types::ExtensionSettings,
+    /// Tracks what LSP features the client supports and doesn't support.
+    resolved_client_capabilities: Arc<ResolvedClientCapabilities>,
 }
 
 /// An immutable snapshot of `Session` that references
 /// a specific document.
 pub(crate) struct DocumentSnapshot {
     configuration: Arc<RuffConfiguration>,
+    resolved_client_capabilities: Arc<ResolvedClientCapabilities>,
     document_ref: DocumentRef,
     position_encoding: PositionEncoding,
     url: Url,
@@ -70,6 +72,7 @@ pub(crate) struct DocumentRef {
 
 impl Session {
     pub(crate) fn new(
+        client_capabilities: &ClientCapabilities,
         server_capabilities: &ServerCapabilities,
         workspaces: &[Url],
     ) -> crate::Result<Self> {
@@ -79,7 +82,9 @@ impl Session {
                 .as_ref()
                 .and_then(|encoding| encoding.try_into().ok())
                 .unwrap_or_default(),
-            lsp_settings: types::ExtensionSettings,
+            resolved_client_capabilities: Arc::new(ResolvedClientCapabilities::new(
+                client_capabilities,
+            )),
             workspaces: Workspaces::new(workspaces)?,
         })
     }
@@ -87,6 +92,7 @@ impl Session {
     pub(crate) fn take_snapshot(&self, url: &Url) -> Option<DocumentSnapshot> {
         Some(DocumentSnapshot {
             configuration: self.workspaces.configuration(url)?.clone(),
+            resolved_client_capabilities: self.resolved_client_capabilities.clone(),
             document_ref: self.workspaces.snapshot(url)?,
             position_encoding: self.position_encoding,
             url: url.clone(),
@@ -196,6 +202,10 @@ impl DocumentSnapshot {
         &self.configuration
     }
 
+    pub(crate) fn resolved_client_capabilities(&self) -> &ResolvedClientCapabilities {
+        &self.resolved_client_capabilities
+    }
+
     pub(crate) fn document(&self) -> &DocumentRef {
         &self.document_ref
     }

crates/ruff_server/src/session/settings.rs

@@ -0,0 +1,25 @@
+use lsp_types::ClientCapabilities;
+
+#[derive(Debug, Clone, PartialEq, Eq, Default)]
+pub(crate) struct ResolvedClientCapabilities {
+    pub(crate) code_action_deferred_edit_resolution: bool,
+}
+
+impl ResolvedClientCapabilities {
+    pub(super) fn new(client_capabilities: &ClientCapabilities) -> Self {
+        let code_action_settings = client_capabilities
+            .text_document
+            .as_ref()
+            .and_then(|doc_settings| doc_settings.code_action.as_ref());
+        let code_action_data_support = code_action_settings
+            .and_then(|code_action_settings| code_action_settings.data_support)
+            .unwrap_or_default();
+        let code_action_edit_resolution = code_action_settings
+            .and_then(|code_action_settings| code_action_settings.resolve_support.as_ref())
+            .is_some_and(|resolve_support| resolve_support.properties.contains(&"edit".into()));
+        Self {
+            code_action_deferred_edit_resolution: code_action_data_support
+                && code_action_edit_resolution,
+        }
+    }
+}

crates/ruff_server/src/session/types.rs

@@ -1,3 +0,0 @@
-#[allow(dead_code)] // TODO(jane): get this wired up after the pre-release
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
-pub(crate) struct ExtensionSettings;