feat: add Phase 5 document highlights provider

README.ja.md

@@ -80,7 +80,7 @@ VS Codeのフォーク。本家にはないUI/UX改善を追加した(してい
 | `coderm.workbench.editor.separateTerminalEditors` | `boolean`  | `true`                                           | ターミナルエディタとテキストエディタを同じグループに混在させない。Quick Open等のデフォルトの開く操作で、既存の同種グループ（なければ新規）に振り分ける |
 | `coderm.workbench.editor.singleTerminalEditorPerGroup` | `boolean`  | `true`                                           | 1つのエディタグループにターミナルエディタは1つだけ。新規ターミナルは空きグループ（なければ新規）に開き、既存ターミナルグループにタブを追加しない |
 | `coderm.workbench.editor.disableGroupLock`        | `boolean`  | `true`                                           | エディタグループのロック機能を完全に無効化。グループは自動・手動を問わずロックできず、常にロック解除状態で動作 |
-| `coderm.languageHost.enabled`                    | `boolean`  | `false`                                          | （実験的）ネイティブ（Rust）Language Host を有効化。設定した言語で tree-sitter ベースの documentSymbol・foldingRange・hover・definition・references を提供（Phase 4） |
+| `coderm.languageHost.enabled`                    | `boolean`  | `false`                                          | （実験的）ネイティブ（Rust）Language Host を有効化。設定した言語で tree-sitter ベースの documentSymbol・foldingRange・hover・definition・references・documentHighlights を提供（Phase 5） |
 | `coderm.languageHost.languages`                  | `array`    | `[]`                                             | （実験的）ネイティブ Host が扱う言語 ID（例: "typescript", "tsx"）。空の場合は機能無効 |
 
 ---

README.md

@@ -80,7 +80,7 @@ Settings unique to Coderm that are not available in upstream VS Code.
 | `coderm.workbench.editor.separateTerminalEditors` | `boolean`  | `true`                                           | Never mix terminal and text editors in one group; Quick Open and other default open paths route to an existing same-type group (or a new one) instead of mixing |
 | `coderm.workbench.editor.singleTerminalEditorPerGroup` | `boolean`  | `true`                                           | Limit each editor group to a single terminal editor; opening a new terminal routes to an empty group (or creates one) instead of adding a tab to an existing terminal group |
 | `coderm.workbench.editor.disableGroupLock`        | `boolean`  | `true`                                           | Completely disable the editor group lock feature — groups can never be locked (automatically or manually) and always behave as unlocked |
-| `coderm.languageHost.enabled`                    | `boolean`  | `false`                                          | _(experimental)_ Enable the native (Rust) Language Host. Provides tree-sitter-backed documentSymbol, foldingRange, hover, definition, and references for the configured languages (Phase 4) |
+| `coderm.languageHost.enabled`                    | `boolean`  | `false`                                          | _(experimental)_ Enable the native (Rust) Language Host. Provides tree-sitter-backed documentSymbol, foldingRange, hover, definition, references, and document highlights for the configured languages (Phase 5) |
 | `coderm.languageHost.languages`                  | `array`    | `[]`                                             | _(experimental)_ Language IDs handled by the native host (e.g. "typescript", "tsx"). Empty keeps the feature inert |
 
 ---

rust/crates/language-host/src/main.rs

@@ -1,17 +1,21 @@
-// Coderm Language Host (Phase 4: references + Phase 3: definition + Phase 2 hover + Phase 1.5 robustness).
+// Coderm Language Host (Phase 5: document highlights + Phase 4: references + Phase 3: definition + Phase 2 hover + Phase 1.5 robustness).
 //
 // Wire format: [4 bytes LE request_id][4 bytes LE length][payload(JSON)].
 //   request_id == 0  → notification (no response). Used for document sync.
 //   request_id  > 0  → request (response expected). Used for language features.
 // Payload is JSON tagged by "type":
-//   - document/open:    {type:"document/open",    uri, version, languageId, text}
-//   - document/change:  {type:"document/change",  uri, version, text}      // full-text replace
-//   - document/close:   {type:"document/close",   uri}
-//   - documentSymbol:   {type:"documentSymbol",   uri}  → [DocumentSymbol]
-//   - foldingRange:     {type:"foldingRange",     uri}  → [FoldingRange]
-//   - hover:            {type:"hover",            uri, line, column} → HoverResponse | null
-//   - definition:       {type:"definition",       uri, line, column} → DefinitionResponse | null
-//   - references:       {type:"references",       uri, line, column, includeDeclaration} → DefinitionResponse | null
+//   - document/open:      {type:"document/open",      uri, version, languageId, text}
+//   - document/change:    {type:"document/change",    uri, version, text}      // full-text replace
+//   - document/close:     {type:"document/close",     uri}
+//   - documentSymbol:     {type:"documentSymbol",     uri}  → [DocumentSymbol]
+//   - foldingRange:       {type:"foldingRange",       uri}  → [FoldingRange]
+//   - hover:              {type:"hover",              uri, line, column} → HoverResponse | null
+//   - definition:         {type:"definition",         uri, line, column} → DefinitionResponse | null
+//   - references:         {type:"references",         uri, line, column, includeDeclaration} → DefinitionResponse | null
+//   - documentHighlights: {type:"documentHighlights", uri, line, column} → DocumentHighlightsResponse | null
+//
+// Phase 5 additions:
+//   - documentHighlights: file-local identifier highlights (Write for declaration names, Read otherwise)
 //
 // Phase 4 additions:
 //   - references: file-local symbol references (find all references matching the identifier name)
@@ -74,6 +78,8 @@ enum Message {
         column: u32,
         include_declaration: bool,
     },
+    #[serde(rename = "documentHighlights", rename_all = "camelCase")]
+    DocumentHighlights { uri: String, line: u32, column: u32 },
 }
 
 struct Document {
@@ -133,6 +139,21 @@ struct Location {
     range: Range,
 }
 
+// Phase 5 document highlight response. `kind` mirrors VS Code's DocumentHighlightKind
+// (Text=0, Read=1, Write=2); Text is unused in v1.
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+struct DocumentHighlightsResponse {
+    highlights: Vec<DocumentHighlightResponse>,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+struct DocumentHighlightResponse {
+    range: Range,
+    kind: u32,
+}
+
 struct LanguageHost {
     documents: HashMap<String, Document>,
 }
@@ -213,6 +234,9 @@ impl LanguageHost {
                 column,
                 include_declaration,
             ))),
+            Message::DocumentHighlights { uri, line, column } => {
+                Ok(Some(self.document_highlights_json(&uri, line, column)))
+            }
         }
     }
 
@@ -276,6 +300,12 @@ impl LanguageHost {
             )
         })
     }
+
+    fn document_highlights_json(&self, uri: &str, line: u32, column: u32) -> String {
+        self.feature_json(uri, "document highlights", |doc| {
+            document_highlights_at_position(&doc.language_id, &doc.content, line, column)
+        })
+    }
 }
 
 fn parse_source(language_id: &str, content: &str) -> Result<tree_sitter::Tree, String> {
@@ -409,12 +439,7 @@ fn hover_at_position(
     column_1: u32,
 ) -> Result<Option<HoverResponse>, String> {
     let tree = parse_source(language_id, content)?;
-    let row_0 = line_1.saturating_sub(1) as usize;
-    let column_0_utf8 = utf16_column_to_utf8_byte(content, row_0, column_1)?;
-    let point = Point {
-        row: row_0,
-        column: column_0_utf8,
-    };
+    let point = point_for_position(content, line_1, column_1)?;
 
     // Deepest named node at the point, then walk up to the enclosing declaration.
     let leaf = match tree
@@ -478,6 +503,18 @@ fn utf16_column_to_utf8_byte(content: &str, row_0: usize, column_1: u32) -> Resu
     Ok(byte_offset)
 }
 
+// Resolve a renderer (line_1, column_1) Position to a tree-sitter Point. Wraps the
+// 1-indexed → 0-indexed row conversion and the UTF-16 → UTF-8 byte column reconciliation
+// performed by utf16_column_to_utf8_byte (see its comment for the per-row walk rationale).
+fn point_for_position(content: &str, line_1: u32, column_1: u32) -> Result<Point, String> {
+    let row_0 = line_1.saturating_sub(1) as usize;
+    let column_0_utf8 = utf16_column_to_utf8_byte(content, row_0, column_1)?;
+    Ok(Point {
+        row: row_0,
+        column: column_0_utf8,
+    })
+}
+
 fn walk_up_to_declaration<'a>(start: Node<'a>) -> Option<Node<'a>> {
     let mut cursor = Some(start);
     while let Some(n) = cursor {
@@ -588,12 +625,7 @@ fn find_identifier_at_position<'a>(
     column_1: u32,
 ) -> Result<Option<(tree_sitter::Tree, &'a str)>, String> {
     let tree = parse_source(language_id, content)?;
-    let row_0 = line_1.saturating_sub(1) as usize;
-    let column_0_utf8 = utf16_column_to_utf8_byte(content, row_0, column_1)?;
-    let point = Point {
-        row: row_0,
-        column: column_0_utf8,
-    };
+    let point = point_for_position(content, line_1, column_1)?;
 
     // Get the identifier at the cursor position.
     let leaf = match tree
@@ -789,6 +821,59 @@ fn is_declaration_name(node: Node) -> bool {
     false
 }
 
+// Phase 5: document highlights provider. Returns highlight ranges for all occurrences of the
+// identifier at the given position. File-local only. kind heuristic: declaration name →
+// Write(2), otherwise Read(1); Text(0) is unused in v1.
+fn document_highlights_at_position(
+    language_id: &str,
+    content: &str,
+    line_1: u32,
+    column_1: u32,
+) -> Result<Option<DocumentHighlightsResponse>, String> {
+    let (tree, identifier) =
+        match find_identifier_at_position(language_id, content, line_1, column_1)? {
+            Some(v) => v,
+            None => return Ok(None),
+        };
+
+    // Caution: name-based, not scope-aware — highlights every same-named identifier in the file
+    // (shadowed locals too), since Phase 5 is file-local only.
+    let mut highlights = Vec::new();
+    collect_document_highlights(tree.root_node(), content, identifier, &mut highlights);
+
+    if highlights.is_empty() {
+        Ok(None)
+    } else {
+        Ok(Some(DocumentHighlightsResponse { highlights }))
+    }
+}
+
+// Why recursive named-child walk: occurrences nest arbitrarily (methods inside classes,
+// references inside expressions), so we descend into named children like the other collect_*
+// helpers — a single goto_next() loop only visits one level of siblings.
+fn collect_document_highlights(
+    node: Node,
+    source: &str,
+    identifier: &str,
+    out: &mut Vec<DocumentHighlightResponse>,
+) {
+    if is_definition_trigger_kind(node.kind()) && node_text(node, source) == identifier {
+        // Declaration name (the identifier bound as a declaration's "name" field) is a Write
+        // site; every other occurrence is a Read.
+        let kind = if is_declaration_name(node) { 2 } else { 1 };
+        out.push(DocumentHighlightResponse {
+            range: range_from_points(node.start_position(), node.end_position()),
+            kind,
+        });
+    }
+    let count = node.named_child_count();
+    for i in 0..count {
+        if let Some(child) = node.named_child(i) {
+            collect_document_highlights(child, source, identifier, out);
+        }
+    }
+}
+
 // Emits one [reqId(4)][length(4)][payload] frame to stdout.
 fn write_frame(request_id: u32, payload: &[u8]) -> io::Result<()> {
     let mut header = [0u8; 8];

src/vs/workbench/services/languageHost/common/languageFeatures.ts

@@ -24,19 +24,24 @@ import {
 	HoverProvider,
 	ReferenceContext,
 	ReferenceProvider,
+	DocumentHighlight,
+	DocumentHighlightKind,
+	DocumentHighlightProvider,
 	SymbolKind,
 } from '../../../../editor/common/languages.js';
 import { IMarkdownString, MarkdownString } from '../../../../base/common/htmlContent.js';
+import { IRange } from '../../../../editor/common/core/range.js';
 import { Position } from '../../../../editor/common/core/position.js';
 import { ILanguageFeaturesService } from '../../../../editor/common/services/languageFeatures.js';
 import { ILanguageHostService } from './languageHost.js';
 
 // Shapes returned by the Rust host (camelCase, matching the renderer's DocumentSymbol/IRange).
+// `range` fields reuse the editor's IRange since the host emits the identical shape.
 interface DocumentSymbolResponse {
 	name: string;
 	kind: number;
-	range: { startLineNumber: number; startColumn: number; endLineNumber: number; endColumn: number };
-	selectionRange: { startLineNumber: number; startColumn: number; endLineNumber: number; endColumn: number };
+	range: IRange;
+	selectionRange: IRange;
 	children?: DocumentSymbolResponse[];
 }
 
@@ -48,11 +53,15 @@ interface FoldingRangeResponse {
 interface HoverResponse {
 	signature: string;
 	documentation: string;
-	range: { startLineNumber: number; startColumn: number; endLineNumber: number; endColumn: number };
+	range: IRange;
 }
 
 interface DefinitionResponse {
-	locations: Array<{ uri: string; range: { startLineNumber: number; startColumn: number; endLineNumber: number; endColumn: number } }>;
+	locations: Array<{ uri: string; range: IRange }>;
+}
+
+interface DocumentHighlightsResponse {
+	highlights: Array<{ range: IRange; kind: number }>;
 }
 
 class CodermDocumentSymbolProvider implements DocumentSymbolProvider {
@@ -163,6 +172,29 @@ class CodermReferenceProvider implements ReferenceProvider {
 	}
 }
 
+class CodermDocumentHighlightProvider implements DocumentHighlightProvider {
+	readonly displayName = 'Coderm Language Host';
+
+	constructor(private readonly languageHostService: ILanguageHostService) { }
+
+	async provideDocumentHighlights(model: ITextModel, position: Position, token: CancellationToken): Promise<DocumentHighlight[] | undefined> {
+		if (token.isCancellationRequested) {
+			return undefined;
+		}
+		try {
+			const json = await this.languageHostService.requestDocumentHighlights(
+				model.uri.toString(),
+				position.lineNumber,
+				position.column
+			);
+			return parseDocumentHighlights(json);
+		} catch (err) {
+			console.error('[CodermDocumentHighlightProvider] request failed', err);
+			return undefined;
+		}
+	}
+}
+
 // Parses a JSON array from the host's response. Returns [] on parse failure or a
 // non-array payload — a malformed host reply should not crash the provider.
 function parseJsonArray<T>(json: string): T[] {
@@ -252,6 +284,19 @@ function parseLocations(json: string): Location[] | undefined {
 	}));
 }
 
+// Note: kind mirrors VS Code's DocumentHighlightKind (Text=0, Read=1, Write=2). The host sends
+// numbers directly (no enum on the wire), so a plain cast is sufficient.
+function parseDocumentHighlights(json: string): DocumentHighlight[] | undefined {
+	const response = parseJsonObject<DocumentHighlightsResponse>(json);
+	if (!response) {
+		return undefined;
+	}
+	return response.highlights.map((h): DocumentHighlight => ({
+		range: h.range,
+		kind: h.kind as DocumentHighlightKind,
+	}));
+}
+
 export function registerLanguageFeatureProviders(
 	languageHostService: ILanguageHostService,
 	languages: string[],
@@ -262,6 +307,7 @@ export function registerLanguageFeatureProviders(
 	const hoverProvider = new CodermHoverProvider(languageHostService);
 	const definitionProvider = new CodermDefinitionProvider(languageHostService);
 	const referenceProvider = new CodermReferenceProvider(languageHostService);
+	const documentHighlightProvider = new CodermDocumentHighlightProvider(languageHostService);
 
 	// Why a flat string[] selector: each entry is a language id; VS Code invokes the provider
 	// only for models whose language matches, so no extra in-provider filtering is needed.
@@ -271,5 +317,6 @@ export function registerLanguageFeatureProviders(
 		languageFeaturesService.hoverProvider.register(languages, hoverProvider),
 		languageFeaturesService.definitionProvider.register(languages, definitionProvider),
 		languageFeaturesService.referenceProvider.register(languages, referenceProvider),
+		languageFeaturesService.documentHighlightProvider.register(languages, documentHighlightProvider),
 	);
 }

src/vs/workbench/services/languageHost/common/languageHost.ts

@@ -61,6 +61,12 @@ export interface ILanguageHostService {
 	 * Returns the host's JSON string (a DefinitionResponse shape or null).
 	 */
 	requestReferences(uri: string, line: number, column: number, includeDeclaration: boolean): Promise<string>;
+
+	/**
+	 * Request document highlights for a position in a synced document.
+	 * Returns the host's JSON string (a DocumentHighlightsResponse shape or null).
+	 */
+	requestDocumentHighlights(uri: string, line: number, column: number): Promise<string>;
 }
 
 // --- Coderm end ---

src/vs/workbench/services/languageHost/electron-browser/languageHostService.ts

@@ -115,6 +115,10 @@ export class NativeLanguageHostService extends Disposable implements ILanguageHo
 		return this.requestFeature({ type: 'references', uri, line, column, includeDeclaration });
 	}
 
+	async requestDocumentHighlights(uri: string, line: number, column: number): Promise<string> {
+		return this.requestFeature({ type: 'documentHighlights', uri, line, column });
+	}
+
 	private async requestFeature(message: { type: string; uri: string; line?: number; column?: number; includeDeclaration?: boolean }): Promise<string> {
 		if (!this.protocol) {
 			throw new Error('Language Host not ready');