Add auth registration

Author: cynthiajoan

packages/firebase_ai/firebase_ai/lib/src/firebase_ai.dart

@@ -69,6 +69,7 @@ class FirebaseAI extends FirebasePluginPlatform {
   }) {
     app ??= Firebase.app();
     appCheck ??= app.getService<FirebaseAppCheck>();
+    auth ??= app.getService<FirebaseAuth>();
     var instanceKey = '${app.name}::vertexai::$location';
 
     if (_cachedInstances.containsKey(instanceKey)) {
@@ -102,6 +103,7 @@ class FirebaseAI extends FirebasePluginPlatform {
   }) {
     app ??= Firebase.app();
     appCheck ??= app.getService<FirebaseAppCheck>();
+    auth ??= app.getService<FirebaseAuth>();
     var instanceKey = '${app.name}::googleai';
 
     if (_cachedInstances.containsKey(instanceKey)) {

packages/firebase_ai/firebase_ai/test/firebase_vertexai_test.dart

@@ -14,6 +14,7 @@
 
 import 'package:firebase_ai/firebase_ai.dart';
 import 'package:firebase_app_check/firebase_app_check.dart';
+import 'package:firebase_auth/firebase_auth.dart';
 import 'package:firebase_core/firebase_core.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -28,6 +29,7 @@ void main() {
   late FirebaseApp customApp;
   late FirebaseApp limitTokenApp;
   late FirebaseAppCheck customAppCheck;
+  late FirebaseAuth customAuth;
   late FirebaseAppCheck limitTokenAppCheck;
 
   group('FirebaseAI Tests', () {
@@ -47,6 +49,7 @@ void main() {
       appCheck = FirebaseAppCheck.instance;
       customAppCheck = FirebaseAppCheck.instanceFor(app: customApp);
       limitTokenAppCheck = FirebaseAppCheck.instanceFor(app: limitTokenApp);
+      customAuth = FirebaseAuth.instanceFor(app: customApp);
     });
 
     test('Singleton behavior', () {
@@ -98,11 +101,18 @@ void main() {
 
     test('Instance creation with auto-injected AppCheck', () {
       final vertexAI = FirebaseAI.vertexAI(app: customApp);
-      
+
       expect(vertexAI.app, equals(customApp));
       expect(vertexAI.appCheck, equals(customAppCheck));
     });
 
+    test('Instance creation with auto-injected Auth', () {
+      final vertexAI = FirebaseAI.vertexAI(app: customApp);
+
+      expect(vertexAI.app, equals(customApp));
+      expect(vertexAI.auth, equals(customAuth));
+    });
+
     test('generativeModel creation with Grounding tools', () {
       final ai = FirebaseAI.googleAI();
 

packages/firebase_auth/firebase_auth/lib/src/firebase_auth.dart

@@ -45,7 +45,9 @@ class FirebaseAuth extends FirebasePluginPlatform {
     required FirebaseApp app,
   }) {
     return _firebaseAuthInstances.putIfAbsent(app.name, () {
-      return FirebaseAuth._(app: app);
+      final instance = FirebaseAuth._(app: app);
+      app.registerService<FirebaseAuth>(instance);
+      return instance;
     });
   }