test-utils: add built-in TranslationApi mock

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/test-utils/package.json

@@ -61,6 +61,7 @@
     "@testing-library/user-event": "^14.0.0",
     "@types/react": "^16.13.1 || ^17.0.0",
     "cross-fetch": "^3.1.5",
+    "i18next": "^22.4.15",
     "zen-observable": "^0.10.0"
   },
   "peerDependencies": {

packages/test-utils/src/testUtils/apis/TranslationApi/MockTranslationApi.ts

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  TranslationApi,
+  TranslationRef,
+  TranslationSnapshot,
+} from '@backstage/core-plugin-api/alpha';
+import { createInstance as createI18n, type i18n as I18n } from 'i18next';
+import ObservableImpl from 'zen-observable';
+
+import { Observable } from '@backstage/types';
+// Internal import to avoid code duplication, this will lead to duplication in build output
+// eslint-disable-next-line @backstage/no-relative-monorepo-imports
+import { toInternalTranslationRef } from '../../../../../core-plugin-api/src/translation/TranslationRef';
+
+const DEFAULT_LANGUAGE = 'en';
+
+/** @alpha */
+export class MockTranslationApi implements TranslationApi {
+  static create() {
+    const i18n = createI18n({
+      fallbackLng: DEFAULT_LANGUAGE,
+      supportedLngs: [DEFAULT_LANGUAGE],
+      interpolation: {
+        escapeValue: false,
+      },
+      ns: [],
+      defaultNS: false,
+      fallbackNS: false,
+    });
+
+    i18n.init();
+
+    return new MockTranslationApi(i18n);
+  }
+
+  #i18n: I18n;
+
+  private constructor(i18n: I18n) {
+    this.#i18n = i18n;
+  }
+
+  getTranslation<TMessages extends { [key in string]: string }>(
+    translationRef: TranslationRef<string, TMessages>,
+  ): TranslationSnapshot<TMessages> {
+    const internalRef = toInternalTranslationRef(translationRef);
+
+    const t = this.#i18n.getFixedT(null, internalRef.id);
+    const defaultMessages = internalRef.getDefaultMessages() as TMessages;
+
+    return {
+      ready: true,
+      t: (key, options) => {
+        return t(key as string, {
+          ...options,
+          defaultValue: defaultMessages[key],
+        });
+      },
+    };
+  }
+
+  translation$<TMessages extends { [key in string]: string }>(): Observable<
+    TranslationSnapshot<TMessages>
+  > {
+    // No need to implement, getTranslation will always return a ready snapshot
+    return new ObservableImpl<TranslationSnapshot<TMessages>>(_subscriber => {
+      return () => {};
+    });
+  }
+}

packages/test-utils/src/testUtils/apis/TranslationApi/index.ts

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export { MockTranslationApi } from './MockTranslationApi';

packages/test-utils/src/testUtils/apis/index.ts

@@ -20,3 +20,4 @@ export * from './ErrorApi';
 export * from './FetchApi';
 export * from './PermissionApi';
 export * from './StorageApi';
+export * from './TranslationApi';

packages/test-utils/src/testUtils/mockApis.ts

@@ -20,10 +20,17 @@ import {
   fetchApiRef,
   storageApiRef,
 } from '@backstage/core-plugin-api';
-import { MockErrorApi, MockFetchApi, MockStorageApi } from './apis';
+import { translationApiRef } from '@backstage/core-plugin-api/alpha';
+import {
+  MockErrorApi,
+  MockFetchApi,
+  MockStorageApi,
+  MockTranslationApi,
+} from './apis';
 
 export const mockApis = [
   createApiFactory(errorApiRef, new MockErrorApi()),
   createApiFactory(fetchApiRef, new MockFetchApi()),
   createApiFactory(storageApiRef, MockStorageApi.create()),
+  createApiFactory(translationApiRef, MockTranslationApi.create()),
 ];

yarn.lock

@@ -10063,6 +10063,7 @@ __metadata:
     "@testing-library/user-event": ^14.0.0
     "@types/react": ^16.13.1 || ^17.0.0
     cross-fetch: ^3.1.5
+    i18next: ^22.4.15
     msw: ^1.0.0
     zen-observable: ^0.10.0
   peerDependencies: