Refactor languageHandler to avoid import cycles (#33948)

* Refactor languageHandler to avoid import cycles

Also move its tests to vitest

* Small refactor

* Iterate

* Iterate

apps/web/src/test/setupGlobals.ts

@@ -0,0 +1,20 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { vi } from "vitest";
+
+import { mocks } from "../../test/setup/mocks.ts";
+
+// set up AudioContext API mock
+vi.stubGlobal("AudioContext", function () {
+    return mocks.AudioContext;
+});
+
+if (globalThis.window === undefined) {
+    // We are in a node environment, stub a basic window so singletons work
+    vi.stubGlobal("window", {});
+}

apps/web/src/test/setupLanguage.ts

@@ -0,0 +1,66 @@
+/*
+Copyright 2024 New Vector Ltd.
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import fetchMock from "@fetch-mock/vitest";
+import { merge } from "lodash";
+import { setMissingEntryGenerator, setLanguage } from "@element-hq/web-shared-components";
+
+import enElementWeb from "../i18n/strings/en_EN.json";
+import deElementWeb from "../i18n/strings/de_DE.json";
+// Cheat and import relatively here as these aren't exported by the module (should they be?)
+// eslint-disable-next-line no-restricted-imports
+import enSharedComponents from "../../../../packages/shared-components/src/i18n/strings/en_EN.json";
+// eslint-disable-next-line no-restricted-imports
+import deSharedComponents from "../../../../packages/shared-components/src/i18n/strings/de_DE.json";
+
+const lv = {
+    Save: "Saglabāt",
+    room: {
+        upload: {
+            uploading_multiple_file: {
+                one: "Качване на %(filename)s и %(count)s друг",
+            },
+        },
+    },
+};
+
+// Fake languages.json containing references to en_EN, de_DE and lv
+// en_EN.json
+// de_DE.json
+// lv.json - mock version with few translations, used to test fallback translation
+
+export function setupLanguageMock() {
+    // Pull the translations from shared components too as they have
+    // the strings for things like `humanizeTime` which do appear in
+    // snapshots (needs 'merge' which does a deep-merge rather than just
+    // replacing top-level keys).
+    const enTranslations = merge(enElementWeb, enSharedComponents);
+    const deTranslations = merge(deElementWeb, deSharedComponents);
+
+    fetchMock
+        .get(
+            "end:/i18n/languages.json",
+            {
+                en: "en_EN.json",
+                de: "de_DE.json",
+                lv: "lv.json",
+            },
+            { name: "languages" },
+        )
+        .get("end:en_EN.json", enTranslations)
+        .get("end:de_DE.json", deTranslations)
+        .get("end:lv.json", lv);
+}
+
+// Initialise the fetchMock before the test starts so the languageHandler.setLanguage call below can function
+fetchMock.mockGlobal();
+fetchMock.catch(404);
+setupLanguageMock();
+
+setLanguage("en");
+setMissingEntryGenerator((key) => key.split("|", 2)[1]);

apps/web/src/test/setupTests.ts

@@ -5,11 +5,12 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE files in the repository root for full details.
 */
 
-import { vi, beforeEach } from "vitest";
+import { beforeEach, afterEach } from "vitest";
 import fetchMock, { manageFetchMockGlobally } from "@fetch-mock/vitest";
 
-import { mocks } from "../../test/setup/mocks.ts";
 import SdkConfig, { DEFAULTS } from "../SdkConfig";
+import "./setupGlobals.ts";
+import { setupLanguageMock } from "./setupLanguage.ts";
 
 manageFetchMockGlobally();
 
@@ -18,17 +19,11 @@ beforeEach(() => {
     fetchMock.hardReset();
     fetchMock.catch(404);
     fetchMock.mockGlobal();
+
+    setupLanguageMock();
 });
 
-// set up AudioContext API mock
-vi.stubGlobal("AudioContext", function () {
-    return mocks.AudioContext;
-});
-
-if (globalThis.window === undefined) {
-    // We are in a node environment, stub a basic window so singletons work
-    vi.stubGlobal("window", {});
-}
+afterEach(() => fetchMock.callHistory.flush());
 
 // uninitialised SdkConfig causes lots of warnings in console, init with defaults
 SdkConfig.put(DEFAULTS);