Update to allow for multiple instance of gtag with different datalayer names (#6655)

* Update to look for datalayer of gtag script

* Update tests and remove console.logs

* Update doc string to reflect function changes

* Update function name to more accurately reflect usage

* Adding changeset

Author: dwyfrequency

.changeset/slow-forks-tease.md

@@ -0,0 +1,5 @@
+---
+'@firebase/analytics': patch
+---
+
+Update to allow for multiple instance of gtag with different datalayer names

packages/analytics/src/helpers.test.ts

@@ -29,6 +29,7 @@ import {
 import { GtagCommand } from './constants';
 import { Deferred } from '@firebase/util';
 import { ConsentSettings } from './public-types';
+import { removeGtagScripts } from '../testing/gtag-script-util';
 
 const fakeMeasurementId = 'abcd-efgh-ijkl';
 const fakeAppId = 'my-test-app-1234';
@@ -46,6 +47,10 @@ const fakeDynamicConfig: DynamicConfig = {
 const fakeDynamicConfigPromises = [Promise.resolve(fakeDynamicConfig)];
 
 describe('Gtag wrapping functions', () => {
+  afterEach(() => {
+    removeGtagScripts();
+  });
+
   it('getOrCreateDataLayer is able to create a new data layer if none exists', () => {
     delete window['dataLayer'];
     expect(getOrCreateDataLayer('dataLayer')).to.deep.equal([]);
@@ -57,14 +62,24 @@ describe('Gtag wrapping functions', () => {
   });
 
   it('insertScriptIfNeeded inserts script tag', () => {
-    expect(findGtagScriptOnPage()).to.be.null;
-    insertScriptTag('customDataLayerName', fakeMeasurementId);
-    const scriptTag = findGtagScriptOnPage();
+    const customDataLayerName = 'customDataLayerName';
+    expect(findGtagScriptOnPage(customDataLayerName)).to.be.null;
+    insertScriptTag(customDataLayerName, fakeMeasurementId);
+    const scriptTag = findGtagScriptOnPage(customDataLayerName);
     expect(scriptTag).to.not.be.null;
     expect(scriptTag!.src).to.contain(`l=customDataLayerName`);
     expect(scriptTag!.src).to.contain(`id=${fakeMeasurementId}`);
   });
 
+  // The test above essentially already touches this functionality but it is still valuable
+  it('findGtagScriptOnPage returns gtag instance with matching data layer name', () => {
+    const defaultDataLayerName = 'dataLayer';
+    insertScriptTag(defaultDataLayerName, fakeMeasurementId);
+    const scriptTag = findGtagScriptOnPage(defaultDataLayerName);
+    expect(scriptTag!.src).to.contain(`l=${defaultDataLayerName}`);
+    expect(findGtagScriptOnPage('NON_EXISTENT_DATA_LAYER_ID')).to.be.null;
+  });
+
   describe('wrapOrCreateGtag() when user has not previously inserted a gtag script tag on this page', () => {
     afterEach(() => {
       delete window['gtag'];

packages/analytics/src/helpers.ts

@@ -318,12 +318,19 @@ export function wrapOrCreateGtag(
 }
 
 /**
- * Returns first script tag in DOM matching our gtag url pattern.
+ * Returns the script tag in the DOM matching both the gtag url pattern
+ * and the provided data layer name.
  */
-export function findGtagScriptOnPage(): HTMLScriptElement | null {
+export function findGtagScriptOnPage(
+  dataLayerName: string
+): HTMLScriptElement | null {
   const scriptTags = window.document.getElementsByTagName('script');
   for (const tag of Object.values(scriptTags)) {
-    if (tag.src && tag.src.includes(GTAG_URL)) {
+    if (
+      tag.src &&
+      tag.src.includes(GTAG_URL) &&
+      tag.src.includes(dataLayerName)
+    ) {
       return tag;
     }
   }

packages/analytics/src/index.test.ts

@@ -26,7 +26,7 @@ import {
 import { FirebaseApp } from '@firebase/app';
 import { GtagCommand } from './constants';
 import { findGtagScriptOnPage } from './helpers';
-import { removeGtagScript } from '../testing/gtag-script-util';
+import { removeGtagScripts } from '../testing/gtag-script-util';
 import { Deferred } from '@firebase/util';
 import { AnalyticsError } from './errors';
 import { logEvent } from './api';
@@ -150,7 +150,7 @@ describe('FirebaseAnalytics instance tests', () => {
     after(() => {
       delete window['gtag'];
       delete window['dataLayer'];
-      removeGtagScript();
+      removeGtagScripts();
       fetchStub.restore();
       clock.restore();
       idbOpenStub.restore();
@@ -208,7 +208,7 @@ describe('FirebaseAnalytics instance tests', () => {
     afterEach(() => {
       delete window['gtag'];
       delete window['dataLayer'];
-      removeGtagScript();
+      removeGtagScripts();
       fetchStub.restore();
       clock.restore();
       warnStub.restore();
@@ -304,7 +304,7 @@ describe('FirebaseAnalytics instance tests', () => {
     after(() => {
       delete window[customGtagName];
       delete window[customDataLayerName];
-      removeGtagScript();
+      removeGtagScripts();
       fetchStub.restore();
       clock.restore();
       idbOpenStub.restore();
@@ -349,13 +349,13 @@ describe('FirebaseAnalytics instance tests', () => {
       // Successfully resolves fake IDB open request.
       fakeRequest.onsuccess();
       await initializationPromisesMap[fakeAppParams.appId];
-      expect(findGtagScriptOnPage()).to.not.be.null;
+      expect(findGtagScriptOnPage('dataLayer')).to.not.be.null;
       expect(typeof window['gtag']).to.equal('function');
       expect(Array.isArray(window['dataLayer'])).to.be.true;
 
       delete window['gtag'];
       delete window['dataLayer'];
-      removeGtagScript();
+      removeGtagScripts();
       fetchStub.restore();
       idbOpenStub.restore();
     });

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

@@ -28,7 +28,7 @@ import { DynamicConfig } from './types';
 import { FirebaseApp } from '@firebase/app';
 import { Deferred } from '@firebase/util';
 import { _FirebaseInstallationsInternal } from '@firebase/installations';
-import { removeGtagScript } from '../testing/gtag-script-util';
+import { removeGtagScripts } from '../testing/gtag-script-util';
 import { setDefaultEventParameters } from './api';
 import {
   defaultConsentSettingsForInit,
@@ -68,7 +68,7 @@ describe('initializeAnalytics()', () => {
   });
   afterEach(() => {
     fetchStub.restore();
-    removeGtagScript();
+    removeGtagScripts();
   });
   it('gets FID and measurement ID and calls gtag config with them', async () => {
     stubFetch();

packages/analytics/src/initialize-analytics.ts

@@ -119,8 +119,9 @@ export async function _initializeAnalytics(
     fidPromise
   ]);
 
-  // Detect if user has already put the gtag <script> tag on this page.
-  if (!findGtagScriptOnPage()) {
+  // Detect if user has already put the gtag <script> tag on this page with the passed in
+  // data layer name.
+  if (!findGtagScriptOnPage(dataLayerName)) {
     insertScriptTag(dataLayerName, dynamicConfig.measurementId);
   }
 

packages/analytics/testing/gtag-script-util.ts

@@ -16,7 +16,7 @@
  */
 import { GTAG_URL } from '../src/constants';
 
-export function removeGtagScript(): void {
+export function removeGtagScripts(): void {
   const scriptTags = window.document.getElementsByTagName('script');
   for (const tag of Object.values(scriptTags)) {
     if (tag.src) {