fix(app): fix issue with FirebaseApp extending INTERNAL

src/app/firebase_app.ts

@@ -246,6 +246,18 @@ class FirebaseAppImpl implements FirebaseApp {
               private firebase_: FirebaseNamespace) {
     this.name_ = name;
     this.options_ = deepCopy<FirebaseOptions>(options);
+    this.INTERNAL = {
+      'getUid': () => null,
+      'getToken': () => LocalPromise.resolve(null),
+      'addAuthTokenListener': (callback: (token: string|null) => void) => {
+        tokenListeners.push(callback);
+        // Make sure callback is called, asynchronously, in the absence of the auth module
+        setTimeout(() => callback(null), 0);
+      },
+      'removeAuthTokenListener': (callback) => {
+        tokenListeners = tokenListeners.filter(listener => listener !== callback);
+      },
+    };
   }
 
   get name(): string {
@@ -321,7 +333,7 @@ class FirebaseAppImpl implements FirebaseApp {
    */
   private extendApp(props: {[name: string]: any}): void {
     // Copy the object onto the FirebaseAppImpl prototype
-    deepExtend(FirebaseAppImpl.prototype, props);
+    deepExtend(this, props);
 
     /**
      * If the app has overwritten the addAuthTokenListener stub, forward
@@ -351,19 +363,6 @@ class FirebaseAppImpl implements FirebaseApp {
   }
 };
 
-FirebaseAppImpl.prototype.INTERNAL = {
-  'getUid': () => null,
-  'getToken': () => LocalPromise.resolve(null),
-  'addAuthTokenListener': (callback: (token: string|null) => void) => {
-    tokenListeners.push(callback);
-    // Make sure callback is called, asynchronously, in the absence of the auth module
-    setTimeout(() => callback(null), 0);
-  },
-  'removeAuthTokenListener': (callback) => {
-    tokenListeners = tokenListeners.filter(listener => listener !== callback);
-  },
-}
-
 // Prevent dead-code elimination of these methods w/o invalid property
 // copying.
 FirebaseAppImpl.prototype.name &&
@@ -603,4 +602,4 @@ let errors: {[code: string]: string} = {
       'Firebase App instance.'
 };
 
-let appErrors = new ErrorFactory<AppError>('app', 'Firebase', errors);
+let appErrors = new ErrorFactory<AppError>('app', 'Firebase', errors);

tests/app/unit/firebase_app.test.ts

@@ -294,6 +294,41 @@ describe("Firebase App Class", () => {
     const service = (firebase.app() as any).testService();
   });
 
+  it(`Should extend INTERNAL per app instance`, () => {
+    let counter: number = 0;
+    firebase.INTERNAL.registerService(
+      'test',
+      (app: FirebaseApp, extendApp: any) => {
+        const service = new TestService(app);
+        (service as any).token = 'tokenFor' + counter++;
+        extendApp({
+          'INTERNAL': {
+            getToken: () => {
+              return Promise.resolve({
+                accessToken: (service as any).token,
+              });
+            },
+          },
+        }); 
+        return service;
+      });
+    // Initialize 2 apps and their corresponding services.
+    const app = firebase.initializeApp({});
+    (app as any).test();
+    const app2 = firebase.initializeApp({}, 'app2');
+    (app2 as any).test();
+    // Confirm extended INTERNAL getToken resolve with the corresponding
+    // service's value.
+    return app.INTERNAL.getToken()
+      .then(token => {
+        assert.equal('tokenFor0', token.accessToken);
+        return app2.INTERNAL.getToken();
+      })
+      .then(token => {
+        assert.equal('tokenFor1', token.accessToken);
+      });
+  });
+
   describe("Check for bad app names", () => {
     let tests = ["", 123, false, null];
     for (let data of tests) {