Add initializePerformance() to performance-exp (#4456)

* Add initializePerformance()

* add test for initializePerforamnce

Author: Feiyang1

packages-exp/performance-exp/src/index.test.ts

@@ -0,0 +1,50 @@
+/**
+ * @license
+ * Copyright 2020 Google LLC
+ *
+ * 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 { expect } from 'chai';
+import { stub } from 'sinon';
+import { initializePerformance } from './index';
+import { ERROR_FACTORY, ErrorCode } from './utils/errors';
+import * as firebase from '@firebase/app-exp';
+import { Provider } from '@firebase/component';
+import '../test/setup';
+
+const fakeFirebaseConfig = {
+  apiKey: 'api-key',
+  authDomain: 'project-id.firebaseapp.com',
+  databaseURL: 'https://project-id.firebaseio.com',
+  projectId: 'project-id',
+  storageBucket: 'project-id.appspot.com',
+  messagingSenderId: 'sender-id',
+  appId: '1:111:web:a1234'
+};
+
+const fakeFirebaseApp = ({
+  options: fakeFirebaseConfig
+} as unknown) as firebase.FirebaseApp;
+
+describe('Firebase Performance > initializePerformance()', () => {
+  it('throws if a perf instance has already been created', () => {
+    stub(firebase, '_getProvider').returns(({
+      isInitialized: () => true
+    } as unknown) as Provider<'performance-exp'>);
+    const expectedError = ERROR_FACTORY.create(ErrorCode.ALREADY_INITIALIZED);
+    expect(() => initializePerformance(fakeFirebaseApp)).to.throw(
+      expectedError.message
+    );
+  });
+});

packages-exp/performance-exp/src/index.ts

@@ -44,14 +44,32 @@ const DEFAULT_ENTRY_NAME = '[DEFAULT]';
 /**
  * Returns a FirebasePerformance instance for the given app.
  * @param app - The FirebaseApp to use.
+ * @public
+ */
+export function getPerformance(app: FirebaseApp): FirebasePerformance {
+  const provider = _getProvider(app, 'performance-exp');
+  const perfInstance = provider.getImmediate() as PerformanceController;
+  return perfInstance;
+}
+
+/**
+ * Returns a FirebasePerformance instance for the given app. Can only be called once.
+ * @param app - The FirebaseApp to use.
  * @param settings - Optional settings for the Performance instance.
  * @public
  */
-export function getPerformance(
+export function initializePerformance(
   app: FirebaseApp,
   settings?: PerformanceSettings
 ): FirebasePerformance {
   const provider = _getProvider(app, 'performance-exp');
+
+  // throw if an instance was already created.
+  // It could happen if initializePerformance() is called more than once, or getPerformance() is called first.
+  if (provider.isInitialized()) {
+    throw ERROR_FACTORY.create(ErrorCode.ALREADY_INITIALIZED);
+  }
+
   const perfInstance = provider.getImmediate() as PerformanceController;
   perfInstance._init(settings);
   return perfInstance;

packages-exp/performance-exp/src/utils/errors.ts

@@ -33,7 +33,8 @@ export const enum ErrorCode {
   INVALID_ATTRIBUTE_NAME = 'invalid attribute name',
   INVALID_ATTRIBUTE_VALUE = 'invalid attribute value',
   INVALID_CUSTOM_METRIC_NAME = 'invalid custom metric name',
-  INVALID_STRING_MERGER_PARAMETER = 'invalid String merger input'
+  INVALID_STRING_MERGER_PARAMETER = 'invalid String merger input',
+  ALREADY_INITIALIZED = 'already initialized'
 }
 
 const ERROR_DESCRIPTION_MAP: { readonly [key in ErrorCode]: string } = {
@@ -58,7 +59,8 @@ const ERROR_DESCRIPTION_MAP: { readonly [key in ErrorCode]: string } = {
   [ErrorCode.INVALID_CUSTOM_METRIC_NAME]:
     'Custom metric name {$customMetricName} is invalid',
   [ErrorCode.INVALID_STRING_MERGER_PARAMETER]:
-    'Input for String merger is invalid, contact support team to resolve.'
+    'Input for String merger is invalid, contact support team to resolve.',
+  [ErrorCode.ALREADY_INITIALIZED]: 'Performance can only be initialized once.'
 };
 
 interface ErrorParams {

packages-exp/performance-exp/src/utils/string_merger.test.ts

@@ -19,13 +19,11 @@ import { expect } from 'chai';
 
 import { mergeStrings } from './string_merger';
 import { FirebaseError } from '@firebase/util';
-// import { ERROR_FACTORY, ErrorCode } from './errors';
 import '../../test/setup';
 
 describe('Firebase Performance > string_merger', () => {
   describe('#mergeStrings', () => {
     it('Throws exception when string length has | diff | > 1', () => {
-      // const expectedError = ERROR_FACTORY.create(ErrorCode.INVALID_STRING_MERGER_PARAMETER);
       expect(() => mergeStrings('', '123')).to.throw(
         FirebaseError,
         'performance/invalid String merger input'

packages/component/src/provider.ts

@@ -186,6 +186,10 @@ export class Provider<T extends Name> {
     return this.component != null;
   }
 
+  isInitialized(identifier: string = DEFAULT_ENTRY_NAME): boolean {
+    return this.instances.has(identifier);
+  }
+
   private getOrInitializeService(
     identifier: string
   ): NameServiceMapping[T] | null {