fix(core): update language detection to use LSP 3.18 identifiers (#21931)

packages/core/src/code_assist/telemetry.test.ts

@@ -375,7 +375,7 @@ describe('telemetry', () => {
 
       expect(mockServer.recordConversationInteraction).toHaveBeenCalledWith(
         expect.objectContaining({
-          language: 'TypeScript',
+          language: 'typescript',
         }),
       );
     });
@@ -408,7 +408,7 @@ describe('telemetry', () => {
 
       expect(mockServer.recordConversationInteraction).toHaveBeenCalledWith(
         expect.objectContaining({
-          language: 'Python',
+          language: 'python',
         }),
       );
     });

packages/core/src/telemetry/telemetry-utils.test.ts

@@ -18,14 +18,14 @@ describe('getProgrammingLanguage', () => {
     {
       name: 'file_path is present',
       args: { file_path: 'src/test.ts' },
-      expected: 'TypeScript',
+      expected: 'typescript',
     },
     {
       name: 'absolute_path is present',
       args: { absolute_path: 'src/test.py' },
-      expected: 'Python',
+      expected: 'python',
     },
-    { name: 'path is present', args: { path: 'src/test.go' }, expected: 'Go' },
+    { name: 'path is present', args: { path: 'src/test.go' }, expected: 'go' },
     {
       name: 'no file path is present',
       args: {},

packages/core/src/utils/language-detection.test.ts

@@ -0,0 +1,44 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { getLanguageFromFilePath } from './language-detection.js';
+
+describe('language-detection', () => {
+  it('should return correct LSP identifiers for various extensions', () => {
+    expect(getLanguageFromFilePath('test.ts')).toBe('typescript');
+    expect(getLanguageFromFilePath('test.js')).toBe('javascript');
+    expect(getLanguageFromFilePath('test.py')).toBe('python');
+    expect(getLanguageFromFilePath('test.java')).toBe('java');
+    expect(getLanguageFromFilePath('test.go')).toBe('go');
+    expect(getLanguageFromFilePath('test.cs')).toBe('csharp');
+    expect(getLanguageFromFilePath('test.cpp')).toBe('cpp');
+    expect(getLanguageFromFilePath('test.sh')).toBe('shellscript');
+    expect(getLanguageFromFilePath('test.bat')).toBe('bat');
+    expect(getLanguageFromFilePath('test.json')).toBe('json');
+    expect(getLanguageFromFilePath('test.md')).toBe('markdown');
+    expect(getLanguageFromFilePath('test.tsx')).toBe('typescriptreact');
+    expect(getLanguageFromFilePath('test.jsx')).toBe('javascriptreact');
+  });
+
+  it('should handle uppercase extensions', () => {
+    expect(getLanguageFromFilePath('TEST.TS')).toBe('typescript');
+  });
+
+  it('should handle filenames without extensions but in map', () => {
+    expect(getLanguageFromFilePath('.gitignore')).toBe('ignore');
+    expect(getLanguageFromFilePath('.dockerfile')).toBe('dockerfile');
+    expect(getLanguageFromFilePath('Dockerfile')).toBe('dockerfile');
+  });
+
+  it('should return undefined for unknown extensions', () => {
+    expect(getLanguageFromFilePath('test.unknown')).toBeUndefined();
+  });
+
+  it('should return undefined for files without extension or known filename', () => {
+    expect(getLanguageFromFilePath('just_a_file')).toBeUndefined();
+  });
+});

packages/core/src/utils/language-detection.ts

@@ -6,98 +6,107 @@
 
 import * as path from 'node:path';
 
+/**
+ * Maps file extensions or filenames to LSP 3.18 language identifiers.
+ * See: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.18/specification/#textDocumentItem
+ */
 const extensionToLanguageMap: { [key: string]: string } = {
-  '.ts': 'TypeScript',
-  '.js': 'JavaScript',
-  '.mjs': 'JavaScript',
-  '.cjs': 'JavaScript',
-  '.jsx': 'JavaScript',
-  '.tsx': 'TypeScript',
-  '.py': 'Python',
-  '.java': 'Java',
-  '.go': 'Go',
-  '.rb': 'Ruby',
-  '.php': 'PHP',
-  '.phtml': 'PHP',
-  '.cs': 'C#',
-  '.cpp': 'C++',
-  '.cxx': 'C++',
-  '.cc': 'C++',
-  '.c': 'C',
-  '.h': 'C/C++',
-  '.hpp': 'C++',
-  '.swift': 'Swift',
-  '.kt': 'Kotlin',
-  '.rs': 'Rust',
-  '.m': 'Objective-C',
-  '.mm': 'Objective-C',
-  '.pl': 'Perl',
-  '.pm': 'Perl',
-  '.lua': 'Lua',
-  '.r': 'R',
-  '.scala': 'Scala',
-  '.sc': 'Scala',
-  '.sh': 'Shell',
-  '.ps1': 'PowerShell',
-  '.bat': 'Batch',
-  '.cmd': 'Batch',
-  '.sql': 'SQL',
-  '.html': 'HTML',
-  '.htm': 'HTML',
-  '.css': 'CSS',
-  '.less': 'Less',
-  '.sass': 'Sass',
-  '.scss': 'Sass',
-  '.json': 'JSON',
-  '.xml': 'XML',
-  '.yaml': 'YAML',
-  '.yml': 'YAML',
-  '.md': 'Markdown',
-  '.markdown': 'Markdown',
-  '.dockerfile': 'Dockerfile',
-  '.vim': 'Vim script',
-  '.vb': 'Visual Basic',
-  '.fs': 'F#',
-  '.clj': 'Clojure',
-  '.cljs': 'Clojure',
-  '.dart': 'Dart',
-  '.ex': 'Elixir',
-  '.erl': 'Erlang',
-  '.hs': 'Haskell',
-  '.lisp': 'Lisp',
-  '.rkt': 'Racket',
-  '.groovy': 'Groovy',
-  '.jl': 'Julia',
-  '.tex': 'LaTeX',
-  '.ino': 'Arduino',
-  '.asm': 'Assembly',
-  '.s': 'Assembly',
-  '.toml': 'TOML',
-  '.vue': 'Vue',
-  '.svelte': 'Svelte',
-  '.gohtml': 'Go Template',
-  '.hbs': 'Handlebars',
-  '.ejs': 'EJS',
-  '.erb': 'ERB',
-  '.jsp': 'JSP',
-  '.dockerignore': 'Docker',
-  '.gitignore': 'Git',
-  '.npmignore': 'npm',
-  '.editorconfig': 'EditorConfig',
-  '.prettierrc': 'Prettier',
-  '.eslintrc': 'ESLint',
-  '.babelrc': 'Babel',
-  '.tsconfig': 'TypeScript',
-  '.flow': 'Flow',
-  '.graphql': 'GraphQL',
-  '.proto': 'Protocol Buffers',
+  '.ts': 'typescript',
+  '.js': 'javascript',
+  '.mjs': 'javascript',
+  '.cjs': 'javascript',
+  '.jsx': 'javascriptreact',
+  '.tsx': 'typescriptreact',
+  '.py': 'python',
+  '.java': 'java',
+  '.go': 'go',
+  '.rb': 'ruby',
+  '.php': 'php',
+  '.phtml': 'php',
+  '.cs': 'csharp',
+  '.cpp': 'cpp',
+  '.cxx': 'cpp',
+  '.cc': 'cpp',
+  '.c': 'c',
+  '.h': 'c',
+  '.hpp': 'cpp',
+  '.swift': 'swift',
+  '.kt': 'kotlin',
+  '.rs': 'rust',
+  '.m': 'objective-c',
+  '.mm': 'objective-cpp',
+  '.pl': 'perl',
+  '.pm': 'perl',
+  '.lua': 'lua',
+  '.r': 'r',
+  '.scala': 'scala',
+  '.sc': 'scala',
+  '.sh': 'shellscript',
+  '.ps1': 'powershell',
+  '.bat': 'bat',
+  '.cmd': 'bat',
+  '.sql': 'sql',
+  '.html': 'html',
+  '.htm': 'html',
+  '.css': 'css',
+  '.less': 'less',
+  '.sass': 'sass',
+  '.scss': 'scss',
+  '.json': 'json',
+  '.xml': 'xml',
+  '.yaml': 'yaml',
+  '.yml': 'yaml',
+  '.md': 'markdown',
+  '.markdown': 'markdown',
+  '.dockerfile': 'dockerfile',
+  '.vim': 'vim',
+  '.vb': 'vb',
+  '.fs': 'fsharp',
+  '.clj': 'clojure',
+  '.cljs': 'clojure',
+  '.dart': 'dart',
+  '.ex': 'elixir',
+  '.erl': 'erlang',
+  '.hs': 'haskell',
+  '.lisp': 'lisp',
+  '.rkt': 'racket',
+  '.groovy': 'groovy',
+  '.jl': 'julia',
+  '.tex': 'latex',
+  '.ino': 'arduino',
+  '.asm': 'assembly',
+  '.s': 'assembly',
+  '.toml': 'toml',
+  '.vue': 'vue',
+  '.svelte': 'svelte',
+  '.gohtml': 'gohtml', // Not in standard LSP well-known list but kept for compatibility
+  '.hbs': 'handlebars',
+  '.ejs': 'ejs',
+  '.erb': 'erb',
+  '.jsp': 'jsp',
+  '.dockerignore': 'ignore',
+  '.gitignore': 'ignore',
+  '.npmignore': 'ignore',
+  '.editorconfig': 'properties',
+  '.prettierrc': 'json',
+  '.eslintrc': 'json',
+  '.babelrc': 'json',
+  '.tsconfig': 'json',
+  '.flow': 'javascript',
+  '.graphql': 'graphql',
+  '.proto': 'proto',
 };
 
 export function getLanguageFromFilePath(filePath: string): string | undefined {
-  const extension = path.extname(filePath).toLowerCase();
-  if (extension) {
-    return extensionToLanguageMap[extension];
-  }
   const filename = path.basename(filePath).toLowerCase();
-  return extensionToLanguageMap[`.${filename}`];
+  const extension = path.extname(filePath).toLowerCase();
+
+  const candidates = [
+    extension, // 1. Standard extension (e.g., '.js')
+    filename, // 2. Exact filename (e.g., 'dockerfile')
+    `.${filename}`, // 3. Dot-prefixed filename (e.g., '.gitignore')
+  ];
+  const match = candidates.find((key) => key in extensionToLanguageMap);
+
+  return match ? extensionToLanguageMap[match] : undefined;
 }