backend-app-api: extract and add tests for createSpecializedBackend

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

packages/backend-app-api/src/wiring/createSpecializedBackend.test.ts

@@ -0,0 +1,62 @@
+/*
+ * 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 {
+  coreServices,
+  createServiceFactory,
+} from '@backstage/backend-plugin-api';
+import { createSpecializedBackend } from './createSpecializedBackend';
+
+describe('createSpecializedBackend', () => {
+  it('should create a backend without services', () => {
+    expect(() => createSpecializedBackend({ services: [] })).not.toThrow();
+  });
+
+  it('should throw on duplicate service implementations', () => {
+    expect(() =>
+      createSpecializedBackend({
+        services: [
+          createServiceFactory({
+            service: coreServices.rootLifecycle,
+            deps: {},
+            factory: async () => ({ addShutdownHook: () => {} }),
+          }),
+          createServiceFactory({
+            service: coreServices.rootLifecycle,
+            deps: {},
+            factory: async () => ({ addShutdownHook: () => {} }),
+          }),
+        ],
+      }),
+    ).toThrow(
+      'Duplicate service implementations provided for core.rootLifecycle',
+    );
+  });
+
+  it('should throw when providing a plugin metadata service implementation', () => {
+    expect(() =>
+      createSpecializedBackend({
+        services: [
+          createServiceFactory({
+            service: coreServices.pluginMetadata,
+            deps: {},
+            factory: async () => async () => ({ getId: () => 'test' }),
+          }),
+        ],
+      }),
+    ).toThrow('The core.plugin-metadata service cannot be overridden');
+  });
+});

packages/backend-app-api/src/wiring/createSpecializedBackend.ts

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2022 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 { coreServices } from '@backstage/backend-plugin-api';
+import { BackstageBackend } from './BackstageBackend';
+import { Backend, CreateSpecializedBackendOptions } from './types';
+
+/**
+ * @public
+ */
+export function createSpecializedBackend(
+  options: CreateSpecializedBackendOptions,
+): Backend {
+  const services = options.services.map(sf =>
+    typeof sf === 'function' ? sf() : sf,
+  );
+
+  const exists = new Set<string>();
+  const duplicates = new Set<string>();
+  for (const { service } of services) {
+    if (exists.has(service.id)) {
+      duplicates.add(service.id);
+    } else {
+      exists.add(service.id);
+    }
+  }
+  if (duplicates.size > 0) {
+    const ids = Array.from(duplicates).join(', ');
+    throw new Error(`Duplicate service implementations provided for ${ids}`);
+  }
+  if (exists.has(coreServices.pluginMetadata.id)) {
+    throw new Error(
+      `The ${coreServices.pluginMetadata.id} service cannot be overridden`,
+    );
+  }
+
+  return new BackstageBackend(services);
+}

packages/backend-app-api/src/wiring/index.ts

@@ -19,4 +19,4 @@ export type {
   CreateSpecializedBackendOptions,
   ServiceOrExtensionPoint,
 } from './types';
-export { createSpecializedBackend } from './types';
+export { createSpecializedBackend } from './createSpecializedBackend';

packages/backend-app-api/src/wiring/types.ts

@@ -15,13 +15,11 @@
  */
 
 import {
-  ServiceFactory,
   BackendFeature,
   ExtensionPoint,
+  ServiceFactory,
   ServiceRef,
-  coreServices,
 } from '@backstage/backend-plugin-api';
-import { BackstageBackend } from './BackstageBackend';
 
 /**
  * @public
@@ -58,38 +56,6 @@ export interface EnumerableServiceHolder extends ServiceHolder {
   getServiceRefs(): ServiceRef<unknown>[];
 }
 
-/**
- * @public
- */
-export function createSpecializedBackend(
-  options: CreateSpecializedBackendOptions,
-): Backend {
-  const services = options.services.map(sf =>
-    typeof sf === 'function' ? sf() : sf,
-  );
-
-  const exists = new Set<string>();
-  const duplicates = new Set<string>();
-  for (const { service } of services) {
-    if (exists.has(service.id)) {
-      duplicates.add(service.id);
-    } else {
-      exists.add(service.id);
-    }
-  }
-  if (duplicates.size > 0) {
-    const ids = Array.from(duplicates).join(', ');
-    throw new Error(`Duplicate service implementations provided for ${ids}`);
-  }
-  if (exists.has(coreServices.pluginMetadata.id)) {
-    throw new Error(
-      `The ${coreServices.pluginMetadata.id} service cannot be overridden`,
-    );
-  }
-
-  return new BackstageBackend(services);
-}
-
 /**
  * @public
  */