Send Analytics measurement ID with script tag request

packages/analytics/index.test.ts

@@ -93,7 +93,12 @@ describe('FirebaseAnalytics instance tests', () => {
       );
     });
     it('Warns if config has no apiKey but does have a measurementId', () => {
+      // Since this is a warning and doesn't block the rest of initialization
+      // all the async stuff needs to be stubbed and cleaned up.
       const warnStub = stub(console, 'warn');
+      const docStub = stub(document, 'createElement');
+      stubFetch(200, { measurementId: fakeMeasurementId });
+      stubIdbOpen();
       const app = getFakeApp({
         appId: fakeAppParams.appId,
         measurementId: fakeMeasurementId
@@ -104,6 +109,11 @@ describe('FirebaseAnalytics instance tests', () => {
         `Falling back to the measurement ID ${fakeMeasurementId}`
       );
       warnStub.restore();
+      docStub.restore();
+      fetchStub.restore();
+      idbOpenStub.restore();
+      delete window['gtag'];
+      delete window['dataLayer'];
     });
     it('Throws if creating an instance with already-used appId', () => {
       const app = getFakeApp(fakeAppParams);
@@ -210,6 +220,7 @@ describe('FirebaseAnalytics instance tests', () => {
     afterEach(() => {
       delete window['gtag'];
       delete window['dataLayer'];
+      removeGtagScript();
       fetchStub.restore();
       clock.restore();
       warnStub.restore();

packages/analytics/src/factory.ts

@@ -29,12 +29,7 @@ import {
   setUserProperties,
   setAnalyticsCollectionEnabled
 } from './functions';
-import {
-  insertScriptTag,
-  getOrCreateDataLayer,
-  wrapOrCreateGtag,
-  findGtagScriptOnPage
-} from './helpers';
+import { getOrCreateDataLayer, wrapOrCreateGtag } from './helpers';
 import { AnalyticsError, ERROR_FACTORY } from './errors';
 import { FirebaseApp } from '@firebase/app-types';
 import { FirebaseInstallations } from '@firebase/installations-types';
@@ -61,9 +56,9 @@ let initializationPromisesMap: {
  * wait on all these to be complete in order to determine if it can selectively
  * wait for only certain initialization (FID) promises or if it must wait for all.
  */
-let dynamicConfigPromisesList: Array<Promise<
-  DynamicConfig | MinimalDynamicConfig
->> = [];
+let dynamicConfigPromisesList: Array<
+  Promise<DynamicConfig | MinimalDynamicConfig>
+> = [];
 
 /**
  * Maps fetched measurementIds to appId. Populated when the app's dynamic config
@@ -202,10 +197,6 @@ export function factory(
     // Steps here should only be done once per page: creation or wrapping
     // of dataLayer and global gtag function.
 
-    // Detect if user has already put the gtag <script> tag on this page.
-    if (!findGtagScriptOnPage()) {
-      insertScriptTag(dataLayerName);
-    }
     getOrCreateDataLayer(dataLayerName);
 
     const { wrappedGtag, gtagCore } = wrapOrCreateGtag(
@@ -227,7 +218,8 @@ export function factory(
     dynamicConfigPromisesList,
     measurementIdToAppId,
     installations,
-    gtagCoreFunction
+    gtagCoreFunction,
+    dataLayerName
   );
 
   const analyticsInstance: FirebaseAnalyticsInternal = {

packages/analytics/src/helpers.test.ts

@@ -56,10 +56,11 @@ describe('Gtag wrapping functions', () => {
 
   it('insertScriptIfNeeded inserts script tag', () => {
     expect(findGtagScriptOnPage()).to.be.null;
-    insertScriptTag('customDataLayerName');
+    insertScriptTag('customDataLayerName', fakeMeasurementId);
     const scriptTag = findGtagScriptOnPage();
     expect(scriptTag).to.not.be.null;
     expect(scriptTag!.src).to.contain(`l=customDataLayerName`);
+    expect(scriptTag!.src).to.contain(`id=${fakeMeasurementId}`);
   });
 
   describe('wrapOrCreateGtag() when user has not previously inserted a gtag script tag on this page', () => {

packages/analytics/src/helpers.ts

@@ -31,11 +31,12 @@ import { logger } from './logger';
  * Inserts gtag script tag into the page to asynchronously download gtag.
  * @param dataLayerName Name of datalayer (most often the default, "_dataLayer").
  */
-export function insertScriptTag(dataLayerName: string): void {
+export function insertScriptTag(
+  dataLayerName: string,
+  measurementId: string
+): void {
   const script = document.createElement('script');
-  // We are not providing an analyticsId in the URL because it would trigger a `page_view`
-  // without fid. We will initialize ga-id using gtag (config) command together with fid.
-  script.src = `${GTAG_URL}?l=${dataLayerName}`;
+  script.src = `${GTAG_URL}?l=${dataLayerName}&id=${measurementId}`;
   script.async = true;
   document.head.appendChild(script);
 }

packages/analytics/src/initialize-ids.test.ts

@@ -28,6 +28,7 @@ import { DynamicConfig } from '@firebase/analytics-types';
 import { FirebaseInstallations } from '@firebase/installations-types';
 import { FirebaseApp } from '@firebase/app-types';
 import { Deferred } from '@firebase/util';
+import { removeGtagScript } from '../testing/gtag-script-util';
 
 const fakeMeasurementId = 'abcd-efgh-ijkl';
 const fakeFid = 'fid-1234-zyxw';
@@ -60,6 +61,7 @@ describe('initializeIds()', () => {
   });
   afterEach(() => {
     fetchStub.restore();
+    removeGtagScript();
   });
   it('gets FID and measurement ID and calls gtag config with them', async () => {
     stubFetch();
@@ -68,7 +70,8 @@ describe('initializeIds()', () => {
       dynamicPromisesList,
       measurementIdToAppId,
       installations,
-      gtagStub
+      gtagStub,
+      'dataLayer'
     );
     expect(gtagStub).to.be.calledWith(GtagCommand.CONFIG, fakeMeasurementId, {
       'firebase_id': fakeFid,
@@ -83,7 +86,8 @@ describe('initializeIds()', () => {
       dynamicPromisesList,
       measurementIdToAppId,
       installations,
-      gtagStub
+      gtagStub,
+      'dataLayer'
     );
     const dynamicPromiseResult = await dynamicPromisesList[0];
     expect(dynamicPromiseResult.measurementId).to.equal(fakeMeasurementId);
@@ -96,7 +100,8 @@ describe('initializeIds()', () => {
       dynamicPromisesList,
       measurementIdToAppId,
       installations,
-      gtagStub
+      gtagStub,
+      'dataLayer'
     );
     expect(measurementIdToAppId[fakeMeasurementId]).to.equal(fakeAppId);
   });
@@ -108,7 +113,8 @@ describe('initializeIds()', () => {
       dynamicPromisesList,
       measurementIdToAppId,
       installations,
-      gtagStub
+      gtagStub,
+      'dataLayer'
     );
     expect(consoleStub.args[0][1]).to.include(fakeMeasurementId);
     expect(consoleStub.args[0][1]).to.include('old-measurement-id');

packages/analytics/src/initialize-ids.ts

@@ -30,6 +30,7 @@ import {
   validateIndexedDBOpenable
 } from '@firebase/util';
 import { ERROR_FACTORY, AnalyticsError } from './errors';
+import { findGtagScriptOnPage, insertScriptTag } from './helpers';
 
 async function validateIndexedDB(): Promise<boolean> {
   if (!isIndexedDBAvailable()) {
@@ -74,7 +75,8 @@ export async function initializeIds(
   >,
   measurementIdToAppId: { [key: string]: string },
   installations: FirebaseInstallations,
-  gtagCore: Gtag
+  gtagCore: Gtag,
+  dataLayerName: string
 ): Promise<string> {
   const dynamicConfigPromise = fetchDynamicConfigWithRetry(app);
   // Once fetched, map measurementIds to appId, for ease of lookup in wrapped gtag function.
@@ -113,6 +115,11 @@ export async function initializeIds(
     fidPromise
   ]);
 
+  // Detect if user has already put the gtag <script> tag on this page.
+  if (!findGtagScriptOnPage()) {
+    insertScriptTag(dataLayerName, dynamicConfig.measurementId);
+  }
+
   // This command initializes gtag.js and only needs to be called once for the entire web app,
   // but since it is idempotent, we can call it multiple times.
   // We keep it together with other initialization logic for better code structure.
@@ -131,6 +138,8 @@ export async function initializeIds(
 
   // It should be the first config command called on this GA-ID
   // Initialize this GA-ID and set FID on it using the gtag config API.
+  // Note: This will trigger a page_view event unless 'send_page_view' is set to false in
+  // `configProperties`.
   gtagCore(GtagCommand.CONFIG, dynamicConfig.measurementId, configProperties);
   return dynamicConfig.measurementId;
 }