feat(i18n): Add Internationalization Support for UI and LLM Output (#1058)

Author: pomelo-nwu

docs/cli/commands.md

@@ -195,6 +195,16 @@ Slash commands provide meta-level control over the CLI itself.
 - **`/init`**
   - **Description:** Analyzes the current directory and creates a `QWEN.md` context file by default (or the filename specified by `contextFileName`). If a non-empty file already exists, no changes are made. The command seeds an empty file and prompts the model to populate it with project-specific instructions.
 
+- [**`/language`**](./language.md)
+  - **Description:** View or change the language setting for both UI and LLM output.
+  - **Sub-commands:**
+    - **`ui`**: Set the UI language (zh-CN or en-US)
+    - **`output`**: Set the LLM output language
+  - **Usage:** `/language [ui|output] [language]`
+  - **Examples:**
+    - `/language ui zh-CN` (set UI language to Simplified Chinese)
+    - `/language output English` (set LLM output language to English)
+
 ### Custom Commands
 
 For a quick start, see the [example](#example-a-pure-function-refactoring-command) below.

docs/cli/language.md

@@ -0,0 +1,71 @@
+# Language Command
+
+The `/language` command allows you to customize the language settings for both the Qwen Code user interface (UI) and the language model's output. This command supports two distinct functionalities:
+
+1. Setting the UI language for the Qwen Code interface
+2. Setting the output language for the language model (LLM)
+
+## UI Language Settings
+
+To change the UI language of Qwen Code, use the `ui` subcommand:
+
+```
+/language ui [zh-CN|en-US]
+```
+
+### Available UI Languages
+
+- **zh-CN**: Simplified Chinese (简体中文)
+- **en-US**: English
+
+### Examples
+
+```
+/language ui zh-CN    # Set UI language to Simplified Chinese
+/language ui en-US    # Set UI language to English
+```
+
+### UI Language Subcommands
+
+You can also use direct subcommands for convenience:
+
+- `/language ui zh-CN` or `/language ui zh` or `/language ui 中文`
+- `/language ui en-US` or `/language ui en` or `/language ui english`
+
+## LLM Output Language Settings
+
+To set the language for the language model's responses, use the `output` subcommand:
+
+```
+/language output <language>
+```
+
+This command generates a language rule file that instructs the LLM to respond in the specified language. The rule file is saved to `~/.qwen/output-language.md`.
+
+### Examples
+
+```
+/language output 中文      # Set LLM output language to Chinese
+/language output English   # Set LLM output language to English
+/language output 日本語    # Set LLM output language to Japanese
+```
+
+## Viewing Current Settings
+
+When used without arguments, the `/language` command displays the current language settings:
+
+```
+/language
+```
+
+This will show:
+
+- Current UI language
+- Current LLM output language (if set)
+- Available subcommands
+
+## Notes
+
+- UI language changes take effect immediately and reload all command descriptions
+- LLM output language settings are persisted in a rule file that is automatically included in the model's context
+- To request additional UI language packs, please open an issue on GitHub

package.json

@@ -46,6 +46,7 @@
     "lint:all": "node scripts/lint.js",
     "format": "prettier --experimental-cli --write .",
     "typecheck": "npm run typecheck --workspaces --if-present",
+    "check-i18n": "npm run check-i18n --workspace=packages/cli",
     "preflight": "npm run clean && npm ci && npm run format && npm run lint:ci && npm run build && npm run typecheck && npm run test:ci",
     "prepare": "husky && npm run bundle",
     "prepare:package": "node scripts/prepare-package.js",

packages/cli/package.json

@@ -26,7 +26,8 @@
     "format": "prettier --write .",
     "test": "vitest run",
     "test:ci": "vitest run",
-    "typecheck": "tsc --noEmit"
+    "typecheck": "tsc --noEmit",
+    "check-i18n": "tsx ../../scripts/check-i18n.ts"
   },
   "files": [
     "dist"

packages/cli/src/config/config.ts

@@ -23,6 +23,7 @@ import {
   WriteFileTool,
   resolveTelemetrySettings,
   FatalConfigError,
+  Storage,
   InputFormat,
   OutputFormat,
 } from '@qwen-code/qwen-code-core';
@@ -602,6 +603,20 @@ export async function loadCliConfig(
     (e) => e.contextFiles,
   );
 
+  // Automatically load output-language.md if it exists
+  const outputLanguageFilePath = path.join(
+    Storage.getGlobalQwenDir(),
+    'output-language.md',
+  );
+  if (fs.existsSync(outputLanguageFilePath)) {
+    extensionContextFilePaths.push(outputLanguageFilePath);
+    if (debugMode) {
+      logger.debug(
+        `Found output-language.md, adding to context files: ${outputLanguageFilePath}`,
+      );
+    }
+  }
+
   const fileService = new FileDiscoveryService(cwd);
 
   const fileFiltering = {

packages/cli/src/config/settingsSchema.ts

@@ -176,6 +176,23 @@ const SETTINGS_SCHEMA = {
         description: 'Enable debug logging of keystrokes to the console.',
         showInDialog: true,
       },
+      language: {
+        type: 'enum',
+        label: 'Language',
+        category: 'General',
+        requiresRestart: false,
+        default: 'auto',
+        description:
+          'The language for the user interface. Use "auto" to detect from system settings. ' +
+          'You can also use custom language codes (e.g., "es", "fr") by placing JS language files ' +
+          'in ~/.qwen/locales/ (e.g., ~/.qwen/locales/es.js).',
+        showInDialog: true,
+        options: [
+          { value: 'auto', label: 'Auto (detect from system)' },
+          { value: 'en', label: 'English' },
+          { value: 'zh', label: '中文 (Chinese)' },
+        ],
+      },
     },
   },
   output: {

packages/cli/src/core/initializer.ts

@@ -14,6 +14,7 @@ import {
 import { type LoadedSettings, SettingScope } from '../config/settings.js';
 import { performInitialAuth } from './auth.js';
 import { validateTheme } from './theme.js';
+import { initializeI18n } from '../i18n/index.js';
 
 export interface InitializationResult {
   authError: string | null;
@@ -33,6 +34,13 @@ export async function initializeApp(
   config: Config,
   settings: LoadedSettings,
 ): Promise<InitializationResult> {
+  // Initialize i18n system
+  const languageSetting =
+    process.env['QWEN_CODE_LANG'] ||
+    settings.merged.general?.language ||
+    'auto';
+  await initializeI18n(languageSetting);
+
   const authType = settings.merged.security?.auth?.selectedType;
   const authError = await performInitialAuth(config, authType);
 
@@ -44,7 +52,6 @@ export async function initializeApp(
       undefined,
     );
   }
-
   const themeError = validateTheme(settings);
 
   const shouldOpenAuthDialog =

packages/cli/src/core/theme.ts

@@ -6,6 +6,7 @@
 
 import { themeManager } from '../ui/themes/theme-manager.js';
 import { type LoadedSettings } from '../config/settings.js';
+import { t } from '../i18n/index.js';
 
 /**
  * Validates the configured theme.
@@ -15,7 +16,9 @@ import { type LoadedSettings } from '../config/settings.js';
 export function validateTheme(settings: LoadedSettings): string | null {
   const effectiveTheme = settings.merged.ui?.theme;
   if (effectiveTheme && !themeManager.findThemeByName(effectiveTheme)) {
-    return `Theme "${effectiveTheme}" not found.`;
+    return t('Theme "{{themeName}}" not found.', {
+      themeName: effectiveTheme,
+    });
   }
   return null;
 }