Guard language switching failures (#1002)

src/ui/AppShell.tsx

@@ -63,6 +63,7 @@ import { ConnectionsPanel } from "@/sidebar/ConnectionsPanel";
 import { TransferMonitor } from "@/features/file-manager/TransferMonitor.tsx";
 import { sshHostToHost } from "@/sidebar/HostManagerData";
 import { resolveHostTabType } from "@/lib/host-connection-tabs";
+import { changeAppLanguage } from "@/i18n/i18n";
 
 function buildHostTree(
   hosts: SSHHostWithStatus[],
@@ -618,8 +619,7 @@ export function AppShell({
             applyAccentColor(prefs.accentColor);
           }
           if (prefs.language && prefs.language !== i18n.language) {
-            localStorage.setItem("i18nextLng", prefs.language);
+            void changeAppLanguage(prefs.language);
-            void i18n.changeLanguage(prefs.language);
           }
           if (
             prefs.commandAutocomplete !== null &&

src/ui/auth/Auth.tsx

@@ -41,7 +41,7 @@ import type { SSOProviderPublic } from "@/types/index";
 import { ElectronServerConfig as ServerConfigComponent } from "@/auth/ElectronServerConfig";
 import { ElectronLoginForm } from "@/auth/ElectronLoginForm";
 import { Checkbox } from "@/components/checkbox";
-import i18n from "@/i18n/i18n";
+import { changeAppLanguage, normalizeLanguageCode } from "@/i18n/i18n";
 import {
   removeSilentSigninFromSearch,
   shouldTriggerSilentSignin,
@@ -238,14 +238,14 @@ export function Auth({ onLogin }: AuthProps) {
   const [confirmNewPassword, setConfirmNewPassword] = useState("");
   const [resetTempToken, setResetTempToken] = useState("");
 
-  const [language, setLanguage] = useState(
+  const [language, setLanguage] = useState(() =>
-    () => localStorage.getItem("i18nextLng") ?? "en",
+    normalizeLanguageCode(localStorage.getItem("i18nextLng")),
   );
 
   function handleLanguageChange(code: string) {
-    setLanguage(code);
+    void changeAppLanguage(code)
-    localStorage.setItem("i18nextLng", code);
+      .then((language) => setLanguage(language))
-    i18n.changeLanguage(code);
+      .catch(() => {});
   }
 
   const [registrationAllowed, setRegistrationAllowed] = useState(true);

src/ui/i18n/i18n.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, it, beforeEach } from "vitest";
+
+import { changeAppLanguage, normalizeLanguageCode } from "./i18n";
+
+describe("i18n language handling", () => {
+  beforeEach(() => {
+    localStorage.clear();
+  });
+
+  it("normalizes persisted desktop language codes", () => {
+    expect(normalizeLanguageCode("zh_CN")).toBe("zh-CN");
+    expect(normalizeLanguageCode("pt_br")).toBe("pt-BR");
+    expect(normalizeLanguageCode("EN-us")).toBe("en");
+    expect(normalizeLanguageCode("unknown")).toBe("en");
+  });
+
+  it("stores the normalized language after a successful switch", async () => {
+    await expect(changeAppLanguage("zh_CN")).resolves.toBe("zh-CN");
+    expect(localStorage.getItem("i18nextLng")).toBe("zh-CN");
+  });
+});

src/ui/i18n/i18n.ts

@@ -43,31 +43,43 @@ const localeLoaders = {
   "zh-TW": () => import("../locales/translated/zh_TW.json"),
 } satisfies Record<string, () => Promise<LocaleModule>>;
 
-const supportedLngs = ["en", ...Object.keys(localeLoaders)];
+export const supportedLngs = ["en", ...Object.keys(localeLoaders)];
+
+export function normalizeLanguageCode(language?: string | null): string {
+  if (!language) return "en";
+
+  const normalized = language.replaceAll("_", "-");
+  if (supportedLngs.includes(normalized)) return normalized;
+
+  const exactMatch = supportedLngs.find(
+    (supported) => supported.toLowerCase() === normalized.toLowerCase(),
+  );
+  if (exactMatch) return exactMatch;
+
+  const baseLanguage = normalized.split("-")[0];
+  return supportedLngs.includes(baseLanguage) ? baseLanguage : "en";
+}
 
 const localeBackend: BackendModule = {
   type: "backend",
   init: () => {},
   read: (language, _namespace, callback) => {
-    if (language === "en") {
+    const normalizedLanguage = normalizeLanguageCode(language);
+
+    if (normalizedLanguage === "en") {
       callback(null, enTranslation);
       return;
     }
 
-    const loadLocale = localeLoaders[language];
+    const loadLocale = localeLoaders[normalizedLanguage];
     if (!loadLocale) {
-      callback(new Error(`Unsupported language: ${language}`), false);
+      callback(null, enTranslation);
       return;
     }
 
     loadLocale()
       .then((module) => callback(null, module.default))
-      .catch((error: unknown) => {
+      .catch(() => callback(null, enTranslation));
-        callback(
-          error instanceof Error ? error : new Error(String(error)),
-          false,
-        );
-      });
   },
 };
 
@@ -104,4 +116,11 @@ i18n
     },
   });
 
+export async function changeAppLanguage(language: string): Promise<string> {
+  const normalizedLanguage = normalizeLanguageCode(language);
+  await i18n.changeLanguage(normalizedLanguage);
+  localStorage.setItem("i18nextLng", normalizedLanguage);
+  return normalizedLanguage;
+}
+
 export default i18n;

src/ui/sidebar/UserProfilePanel.tsx

@@ -78,7 +78,7 @@ import type { ApiKey } from "@/main-axios";
 import { useTheme } from "@/components/theme-provider";
 import type { FontSizeId, ThemeId } from "@/types/ui-types";
 import { toast } from "sonner";
-import i18n from "@/i18n/i18n";
+import { changeAppLanguage, normalizeLanguageCode } from "@/i18n/i18n";
 
 type UserProfileSection =
   | "account"
@@ -515,8 +515,8 @@ export function UserProfilePanel({
   const [fontSize, setFontSize] = useState<FontSizeId>(
     () => (localStorage.getItem("termix-font-size") as FontSizeId) ?? "md",
   );
-  const [language, setLanguage] = useState(
+  const [language, setLanguage] = useState(() =>
-    () => localStorage.getItem("i18nextLng") ?? "en",
+    normalizeLanguageCode(localStorage.getItem("i18nextLng")),
   );
   const [storageMode, setStorageMode] = useState<"local" | "cloud">(() =>
     userPrefs?.storageMode === "cloud" ? "cloud" : "local",
@@ -662,9 +662,8 @@ export function UserProfilePanel({
           applyAccentColor(prefs.accentColor);
         }
         if (prefs.language) {
-          setLanguage(prefs.language);
+          const language = await changeAppLanguage(prefs.language);
-          localStorage.setItem("i18nextLng", prefs.language);
+          setLanguage(language);
-          void i18n.changeLanguage(prefs.language);
         }
         if (prefs.commandAutocomplete != null) {
           setCommandAutocomplete(prefs.commandAutocomplete);
@@ -772,8 +771,7 @@ export function UserProfilePanel({
     localStorage.setItem("termix-accent", DEFAULT_ACCENT);
     applyAccentColor(DEFAULT_ACCENT);
     setLanguage("en");
-    localStorage.setItem("i18nextLng", "en");
+    void changeAppLanguage("en");
-    void i18n.changeLanguage("en");
     setCommandAutocomplete(false);
     localStorage.setItem("commandAutocomplete", "false");
     setCommandPaletteEnabled(true);
@@ -862,10 +860,9 @@ export function UserProfilePanel({
     localStorage.setItem("termix-accent", restoredAccent);
     applyAccentColor(restoredAccent);
 
-    const restoredLang = restore("i18nextLng", "en") ?? "en";
+    const restoredLang = normalizeLanguageCode(restore("i18nextLng", "en"));
     setLanguage(restoredLang);
-    localStorage.setItem("i18nextLng", restoredLang);
+    void changeAppLanguage(restoredLang);
-    void i18n.changeLanguage(restoredLang);
 
     const restoredAutocomplete =
       restore("commandAutocomplete", "false") === "true";
@@ -984,10 +981,12 @@ export function UserProfilePanel({
   }
 
   function handleLanguageChange(code: string) {
-    setLanguage(code);
+    void changeAppLanguage(code)
-    localStorage.setItem("i18nextLng", code);
+      .then((language) => {
-    i18n.changeLanguage(code);
+        setLanguage(language);
-    if (storageMode === "cloud") saveToCloud({ language: code });
+        if (storageMode === "cloud") saveToCloud({ language });
+      })
+      .catch(() => {});
   }
 
   function toggle(id: UserProfileSection) {

src/ui/user/LanguageSwitcher.tsx

@@ -9,6 +9,7 @@ import {
 } from "@/components/select.tsx";
 import { Globe } from "lucide-react";
 import { saveUserPreferences } from "@/main-axios";
+import { changeAppLanguage, normalizeLanguageCode } from "@/i18n/i18n";
 
 const languages = [
   { code: "en", name: "English", nativeName: "English" },
@@ -60,15 +61,18 @@ export function LanguageSwitcher() {
   const { i18n, t } = useTranslation();
 
   const handleLanguageChange = (value: string) => {
-    i18n.changeLanguage(value);
+    void changeAppLanguage(value)
-    localStorage.setItem("i18nextLng", value);
+      .then((language) => saveUserPreferences({ language }))
-    saveUserPreferences({ language: value }).catch(() => {});
+      .catch(() => {});
   };
 
   return (
     <div className="flex items-center gap-2 relative z-[99999]">
       <Globe className="h-4 w-4 text-muted-foreground" />
-      <Select value={i18n.language} onValueChange={handleLanguageChange}>
+      <Select
+        value={normalizeLanguageCode(i18n.resolvedLanguage || i18n.language)}
+        onValueChange={handleLanguageChange}
+      >
         <SelectTrigger className="w-[120px]">
           <SelectValue placeholder={t("placeholders.language")} />
         </SelectTrigger>