fix getAuth for non browser entry points (#4519)

Author: Feiyang1

packages-exp/auth-exp/index.cordova.ts

@@ -22,7 +22,7 @@
  * just use index.ts
  */
 
-import { FirebaseApp } from '@firebase/app-exp';
+import { FirebaseApp, _getProvider } from '@firebase/app-exp';
 import { Auth } from './src/model/public_types';
 import { indexedDBLocalPersistence } from './src/platform_browser/persistence/indexed_db';
 
@@ -49,6 +49,12 @@ export {
 import { cordovaPopupRedirectResolver } from './src/platform_cordova/popup_redirect/popup_redirect';
 
 export function getAuth(app: FirebaseApp): Auth {
+  const provider = _getProvider(app, 'auth-exp');
+
+  if (provider.isInitialized()) {
+    return provider.getImmediate();
+  }
+
   return initializeAuth(app, {
     persistence: indexedDBLocalPersistence,
     popupRedirectResolver: cordovaPopupRedirectResolver

packages-exp/auth-exp/index.node.ts

@@ -24,7 +24,7 @@
 
 import * as fetchImpl from 'node-fetch';
 
-import { FirebaseApp } from '@firebase/app-exp';
+import { FirebaseApp, _getProvider } from '@firebase/app-exp';
 import { Auth } from './src/model/public_types';
 
 import { initializeAuth } from './src';
@@ -43,6 +43,12 @@ FetchProvider.initialize(
 export * from './src';
 
 export function getAuth(app: FirebaseApp): Auth {
+  const provider = _getProvider(app, 'auth-exp');
+
+  if (provider.isInitialized()) {
+    return provider.getImmediate();
+  }
+
   return initializeAuth(app);
 }
 

packages-exp/auth-exp/index.rn.ts

@@ -24,7 +24,7 @@
 
 import { AsyncStorage } from 'react-native';
 
-import { FirebaseApp } from '@firebase/app-exp';
+import { FirebaseApp, _getProvider } from '@firebase/app-exp';
 import { Auth } from './src/model/public_types';
 
 import { initializeAuth } from './src';
@@ -40,6 +40,12 @@ export const reactNativeLocalPersistence = getReactNativePersistence(
 );
 
 export function getAuth(app: FirebaseApp): Auth {
+  const provider = _getProvider(app, 'auth-exp');
+
+  if (provider.isInitialized()) {
+    return provider.getImmediate();
+  }
+
   return initializeAuth(app, {
     persistence: reactNativeLocalPersistence
   });