frontend-*-api: initial ComponentsApi implementation

Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Co-authored-by: Camila Belo <camilaibs@gmail.com>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/frontend-plugin-api/src/apis/definitions/ComponentsApi.ts

@@ -0,0 +1,37 @@
+/*
+ * 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 { ComponentRef } from '../../components';
+import { createApiRef } from '../system';
+
+/**
+ * API for looking up components based on component refs.
+ *
+ * @public
+ */
+export interface ComponentsApi {
+  // TODO: Should component refs also provide the default implementation so that we're guaranteed to get a component?
+  getComponent<T>(ref: ComponentRef<T>): T | undefined;
+}
+
+/**
+ * The `ApiRef` of {@link ComponentsApi}.
+ *
+ * @public
+ */
+export const componentsApiRef = createApiRef<ComponentsApi>({
+  id: 'core.components',
+});

packages/frontend-plugin-api/src/apis/definitions/index.ts

@@ -34,6 +34,7 @@ export * from './auth';
 
 export * from './AlertApi';
 export * from './AppThemeApi';
+export * from './ComponentsApi';
 export * from './ConfigApi';
 export * from './DiscoveryApi';
 export * from './ErrorApi';