fix(settings): keep the language and save settings one after the other

src/pages/languageSwitch.test.jsx

@@ -0,0 +1,54 @@
+// @vitest-environment jsdom
+import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest';
+import {cleanup, render, screen} from '@testing-library/react';
+import {MemoryRouter, Route, Routes} from 'react-router-dom';
+import {switchLanguage} from '../test/i18n-mock.js';
+import {PreferencesProvider} from '../context/PreferencesContext.jsx';
+import Dashboard from './Dashboard.jsx';
+import GameDetail from './GameDetail.jsx';
+import GameLibrary from './GameLibrary.jsx';
+import PublicProfilePage from './PublicProfilePage.jsx';
+import SettingsPage from './SettingsPage.jsx';
+import WishlistPage from './WishlistPage.jsx';
+
+vi.mock('react-i18next', () => import('../test/i18n-mock.js'));
+
+const pages = [
+    ['Dashboard', '/', '/', <Dashboard/>, 'INFO.ERROR.LOAD_PROFILE'],
+    ['GameDetail', '/games/:appid', '/games/220', <GameDetail/>, 'GAME_DETAIL.ERROR_LOAD'],
+    ['GameLibrary', '/library', '/library', <GameLibrary/>, 'LIBRARY.ERROR_LOAD'],
+    ['PublicProfilePage', '/u/:name', '/u/Lobo', <PublicProfilePage/>, 'PROFILE.ERROR_LOAD'],
+    ['SettingsPage', '/settings', '/settings', <SettingsPage/>, 'INFO.ERROR.LOAD_PROFILE'],
+    ['WishlistPage', '/wishlist', '/wishlist', <WishlistPage/>, 'WISHLIST.ERROR_LOAD'],
+];
+
+beforeEach(() => {
+    localStorage.setItem('tbp_session', '1');
+    switchLanguage('de');
+    globalThis.fetch = vi.fn(async () => ({ok: false, status: 500, json: async () => ({})}));
+});
+
+afterEach(() => {
+    cleanup();
+    localStorage.clear();
+});
+
+describe('a language change', () => {
+    it.each(pages)('%s: loads nothing again and shows the error in the new language', async (name, path, url, page, errorKey) => {
+        const tree = () => (
+            <MemoryRouter initialEntries={[url]}>
+                <PreferencesProvider><Routes><Route path={path} element={page}/></Routes></PreferencesProvider>
+            </MemoryRouter>
+        );
+        const {rerender} = render(tree());
+        await screen.findByText(`de:${errorKey}`);
+        const requests = fetch.mock.calls.length;
+
+        switchLanguage('en');
+        rerender(tree());
+
+        expect(await screen.findByText(`en:${errorKey}`)).toBeTruthy();
+        await new Promise((resolve) => setTimeout(resolve, 50));
+        expect(fetch.mock.calls.length).toBe(requests);
+    });
+});