Firebase Auth snippets (#6)

* adds snippets for testing firebase auth

Co-authored-by: Eric Windmill <[email protected]>

Author: ericwindmill

packages/firebase_snippets_app/lib/main.dart

@@ -14,6 +14,7 @@
 
 // [START set_up_environment]
 import 'package:cloud_firestore/cloud_firestore.dart';
+import 'package:firebase_auth/firebase_auth.dart';
 import 'package:firebase_core/firebase_core.dart';
 import 'package:firebase_remote_config/firebase_remote_config.dart';
 // [END set_up_environment]
@@ -25,9 +26,7 @@ import 'package:flutter/material.dart';
 import 'firebase_options.dart';
 
 void main() async {
-  // TODO: special-case -- be sure to document
-// [START get_firestore_instance]
-
+  // [START get_firestore_instance]
   /// In the Firebase documentation, the code should look like the following example
   /// In this snippets app, we're using the FlutterFire CLI to generate FirebaseOptions
   ///```dart
@@ -41,17 +40,14 @@ void main() async {
   /// );
   /// final firestore = FirebaseFirestore.instance;
   /// ```
-
-// [END get_firestore_instance]
+  // [END get_firestore_instance]
 
   WidgetsFlutterBinding.ensureInitialized();
   await Firebase.initializeApp(
     options: DefaultFirebaseOptions.currentPlatform,
   );
 
   final db = FirebaseFirestore.instance;
-  // TODO: special-case -- be sure to document
-
   // [START access_data_offline_configure_offline_persistence]
   final settings = db.settings.copyWith(persistenceEnabled: true);
   // [END access_data_offline_configure_offline_persistence]
@@ -66,6 +62,12 @@ void main() async {
   FirebaseRemoteConfig firebaseRemoteConfig = FirebaseRemoteConfig.instance;
   // [END get_started_get_singleton_object]
 
+  if (kIsWeb) {
+    // [START auth_persistingAuthState]
+    await FirebaseAuth.instance.setPersistence(Persistence.NONE);
+    // [END auth_persistingAuthState]
+  }
+
   if (!kReleaseMode) db.useFirestoreEmulator('localhost', 8080);
 
   runApp(