feat(cli): support LLM output language configuration in Settings Dialog

packages/cli/src/utils/languageUtils.ts

@@ -0,0 +1,190 @@
+/**
+ * @license
+ * Copyright 2025 Qwen team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Utilities for managing the LLM output language rule file.
+ * This file handles the creation and maintenance of ~/.qwen/output-language.md
+ * which instructs the LLM to respond in the user's preferred language.
+ */
+
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+import { Storage } from '@qwen-code/qwen-code-core';
+import {
+  detectSystemLanguage,
+  getLanguageNameFromLocale,
+} from '../i18n/index.js';
+
+const LLM_OUTPUT_LANGUAGE_RULE_FILENAME = 'output-language.md';
+const LLM_OUTPUT_LANGUAGE_MARKER_PREFIX = 'qwen-code:llm-output-language:';
+
+/** Special value meaning "detect from system settings" */
+export const OUTPUT_LANGUAGE_AUTO = 'auto';
+
+/**
+ * Checks if a value represents the "auto" setting.
+ */
+export function isAutoLanguage(value: string | undefined | null): boolean {
+  return !value || value.toLowerCase() === OUTPUT_LANGUAGE_AUTO;
+}
+
+/**
+ * Normalizes a language input to its canonical form.
+ * Converts known locale codes (e.g., "zh", "ru") to full names (e.g., "Chinese", "Russian").
+ * Unknown inputs are returned as-is to support any language name.
+ */
+export function normalizeOutputLanguage(language: string): string {
+  const lowered = language.toLowerCase();
+  const fullName = getLanguageNameFromLocale(lowered);
+  // getLanguageNameFromLocale returns 'English' as default for unknown codes.
+  // Only use the result if it's a known code or explicitly 'en'.
+  if (fullName !== 'English' || lowered === 'en') {
+    return fullName;
+  }
+  return language;
+}
+
+/**
+ * Resolves the output language, converting 'auto' to the detected system language.
+ */
+export function resolveOutputLanguage(
+  value: string | undefined | null,
+): string {
+  if (isAutoLanguage(value)) {
+    const detectedLocale = detectSystemLanguage();
+    return getLanguageNameFromLocale(detectedLocale);
+  }
+  return normalizeOutputLanguage(value!);
+}
+
+/**
+ * Returns the path to the LLM output language rule file (~/.qwen/output-language.md).
+ */
+function getOutputLanguageFilePath(): string {
+  return path.join(
+    Storage.getGlobalQwenDir(),
+    LLM_OUTPUT_LANGUAGE_RULE_FILENAME,
+  );
+}
+
+/**
+ * Sanitizes a language string for use in an HTML comment marker.
+ * Removes characters that could break HTML comment syntax.
+ */
+function sanitizeForMarker(language: string): string {
+  return language
+    .replace(/[\r\n]/g, ' ')
+    .replace(/--!?>/g, '')
+    .replace(/--/g, '');
+}
+
+/**
+ * Generates the content for the LLM output language rule file.
+ */
+function generateOutputLanguageFileContent(language: string): string {
+  const safeLanguage = sanitizeForMarker(language);
+  return `# Output language preference: ${language}
+<!-- ${LLM_OUTPUT_LANGUAGE_MARKER_PREFIX} ${safeLanguage} -->
+
+## Goal
+Prefer responding in **${language}** for normal assistant messages and explanations.
+
+## Keep technical artifacts unchanged
+Do **not** translate or rewrite:
+- Code blocks, CLI commands, file paths, stack traces, logs, JSON keys, identifiers
+- Exact quoted text from the user (keep quotes verbatim)
+
+## When a conflict exists
+If higher-priority instructions (system/developer) require a different behavior, follow them.
+
+## Tool / system outputs
+Raw tool/system outputs may contain fixed-format English. Preserve them verbatim, and if needed, add a short **${language}** explanation below.
+`;
+}
+
+/**
+ * Extracts the language from the content of an output language rule file.
+ * Supports both the new marker format and legacy heading format.
+ */
+function parseOutputLanguageFromContent(content: string): string | null {
+  // Primary: machine-readable marker (e.g., <!-- qwen-code:llm-output-language: 中文 -->)
+  const markerRegex = new RegExp(
+    String.raw`<!--\s*${LLM_OUTPUT_LANGUAGE_MARKER_PREFIX}\s*(.*?)\s*-->`,
+    'i',
+  );
+  const markerMatch = content.match(markerRegex);
+  if (markerMatch?.[1]?.trim()) {
+    return markerMatch[1].trim();
+  }
+
+  // Fallback: legacy heading format (e.g., # CRITICAL: Chinese Output Language Rule)
+  const headingMatch = content.match(
+    /^#.*?CRITICAL:\s*(.*?)\s+Output Language Rule\b/im,
+  );
+  if (headingMatch?.[1]?.trim()) {
+    return headingMatch[1].trim();
+  }
+
+  return null;
+}
+
+/**
+ * Reads the current output language from the rule file.
+ * Returns null if the file doesn't exist or can't be parsed.
+ */
+function readOutputLanguageFromFile(): string | null {
+  const filePath = getOutputLanguageFilePath();
+  if (!fs.existsSync(filePath)) {
+    return null;
+  }
+  try {
+    const content = fs.readFileSync(filePath, 'utf-8');
+    return parseOutputLanguageFromContent(content);
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Writes the output language rule file with the given language.
+ */
+export function writeOutputLanguageFile(language: string): void {
+  const filePath = getOutputLanguageFilePath();
+  const content = generateOutputLanguageFileContent(language);
+  const dir = path.dirname(filePath);
+  fs.mkdirSync(dir, { recursive: true });
+  fs.writeFileSync(filePath, content, 'utf-8');
+}
+
+/**
+ * Updates the LLM output language rule file based on the setting value.
+ * Resolves 'auto' to the detected system language before writing.
+ */
+export function updateOutputLanguageFile(settingValue: string): void {
+  const resolved = resolveOutputLanguage(settingValue);
+  writeOutputLanguageFile(resolved);
+}
+
+/**
+ * Initializes the LLM output language rule file on application startup.
+ *
+ * @param outputLanguage - The output language setting value (e.g., 'auto', 'Chinese', etc.)
+ *
+ * Behavior:
+ * - Resolves the setting value ('auto' -> detected system language, or use as-is)
+ * - Ensures the rule file matches the resolved language
+ * - Creates the file if it doesn't exist
+ */
+export function initializeLlmOutputLanguage(outputLanguage?: string): void {
+  // Resolve 'auto' or undefined to the detected system language
+  const resolved = resolveOutputLanguage(outputLanguage);
+  const currentFileLanguage = readOutputLanguageFromFile();
+
+  // Only write if the file doesn't match the resolved language
+  if (currentFileLanguage !== resolved) {
+    writeOutputLanguageFile(resolved);
+  }
+}