fix(i18n): respect browser preferred languages when supported (#6812)

* fix(i18n): respect browser preferred languages when supported

Instead of relying on the first browser language, the application now
iterates through navigator.languages and selects the first supported
locale, with a fallback to English.

* chore: add the release notes related file

* fix(i18n): check region locales support before falling back to base locale

* fix(i18n): make the unit test aligned with the region locales checking

packages/desktop-client/src/i18n.test.ts

@@ -71,7 +71,7 @@ describe('setI18NextLanguage', () => {
     setI18NextLanguage('uk-ZZ');
 
     expect(console.info).toHaveBeenCalledWith(
-      'Unknown locale uk-ZZ, falling back to uk',
+      'Unknown locale uk-ZZ, falling back to uk-zz',
     );
     expect(i18n.changeLanguage).toHaveBeenCalledWith('uk');
   });

packages/desktop-client/src/i18n.ts

@@ -40,44 +40,55 @@ i18n
     },
   });
 
+const resolveLanguage = (language: string) => {
+  // English is always available since we use natural-language keys.
+  if (language === 'en') return 'en';
+
+  if (isLanguageAvailable(language)) return language;
+
+  const lowercaseLanguage = language.toLowerCase();
+  if (lowercaseLanguage !== language) {
+    console.info(
+      `Unknown locale ${language}, falling back to ${lowercaseLanguage}`,
+    );
+    return resolveLanguage(lowercaseLanguage);
+  }
+
+  if (language.includes('-')) {
+    const fallback = language.split('-')[0];
+    console.info(`Unknown locale ${language}, falling back to ${fallback}`);
+    return resolveLanguage(fallback);
+  }
+
+  return undefined;
+};
+
 export const setI18NextLanguage = (language: string) => {
-  if (!language) {
-    // System default
-    setI18NextLanguage(navigator.language || 'en');
-    return;
+  const defaultLanguages = Array.isArray(navigator.languages)
+    ? navigator.languages
+    : [navigator.language || 'en'];
+  const languagesToTry = language ? [language] : defaultLanguages;
+
+  let resolved: string | undefined;
+
+  for (const lang of languagesToTry) {
+    resolved = resolveLanguage(lang);
+    if (resolved) break;
   }
 
-  if (!isLanguageAvailable(language)) {
-    if (language === 'en') {
-      // English is always available since we use natural-language keys.
-      return;
-    }
-
-    if (language.includes('-')) {
-      const fallback = language.split('-')[0];
-      console.info(`Unknown locale ${language}, falling back to ${fallback}`);
-      setI18NextLanguage(fallback);
-      return;
-    }
-
-    const lowercaseLanguage = language.toLowerCase();
-    if (lowercaseLanguage !== language) {
-      console.info(
-        `Unknown locale ${language}, falling back to ${lowercaseLanguage}`,
-      );
-      setI18NextLanguage(lowercaseLanguage);
-      return;
-    }
-
+  if (!resolved) {
     // Fall back to English
-    console.info(`Unknown locale ${language}, falling back to en`);
-    setI18NextLanguage('en');
-    return;
+    console.info(
+      language
+        ? `Unknown locale ${language}, falling back to en`
+        : `Unknown locales [${languagesToTry.join(', ')}] falling back to en`,
+    );
+    resolved = 'en';
   }
 
-  if (language === i18n.language) {
+  if (resolved === i18n.language) {
     return; // language is already set
   }
 
-  i18n.changeLanguage(language || 'en');
+  i18n.changeLanguage(resolved);
 };

upcoming-release-notes/6812.md

@@ -0,0 +1,6 @@
+---
+category: Bugfixes
+authors: [elevennprime]
+---
+
+The app now checks your preferred browser languages in order and uses the first one we support, otherwise English.