fix(auth, web): currentUser is now populated right at the start of the application without needing to wait for authStateChange (#10028)

* feat: add new init function for auth

* feat: add new init function for auth

* feat: add new init function for auth

* fix(auth, web): fix formatting

* feat: change naming

* feat: fix tests

* feat: add new init function for auth

Author: Lyokone

packages/firebase_auth/firebase_auth_web/lib/firebase_auth_web.dart

@@ -89,7 +89,9 @@ class FirebaseAuthWeb extends FirebaseAuthPlatform {
 
   /// Called by PluginRegistry to register this plugin for Flutter Web
   static void registerWith(Registrar registrar) {
-    FirebaseCoreWeb.registerService('auth');
+    FirebaseCoreWeb.registerService('auth', () async {
+      await FirebaseAuthWeb.instance.delegate.onWaitInitState();
+    });
     FirebaseAuthPlatform.instance = FirebaseAuthWeb.instance;
     PhoneMultiFactorGeneratorPlatform.instance = PhoneMultiFactorGeneratorWeb();
     RecaptchaVerifierFactoryPlatform.instance =

packages/firebase_auth/firebase_auth_web/lib/src/interop/auth.dart

@@ -362,6 +362,28 @@ class Auth extends JsObjectWrapper<auth_interop.AuthJsImpl> {
 
   auth_interop.AuthSettings get settings => jsObject.settings;
 
+  User? _initUser;
+
+  /// On web we need to wait for the first onAuthStateChanged event to fire
+  /// in order to be sure that the currentUser is set.
+  /// To preserve behavior on web and mobile we store the initial user
+  /// in `_initUser` and add it manually to the `_changeController`.
+  Future<void> onWaitInitState() async {
+    final completer = Completer();
+    final nextWrapper = allowInterop((auth_interop.UserJsImpl? user) {
+      _initUser = User.getInstance(user);
+      completer.complete();
+    });
+
+    final errorWrapper = allowInterop((e) => _changeController!.addError(e));
+
+    final unsubscribe = jsObject.onAuthStateChanged(nextWrapper, errorWrapper);
+
+    await completer.future;
+
+    unsubscribe();
+  }
+
   Func0? _onAuthUnsubscribe;
   // TODO(rrousselGit): fix memory leak – the controller isn't closed even in onCancel
   // ignore: close_sinks
@@ -397,6 +419,8 @@ class Auth extends JsObjectWrapper<auth_interop.AuthJsImpl> {
         onCancel: stopListen,
         sync: true,
       );
+
+      _changeController!.add(_initUser);
     }
     return _changeController!.stream;
   }

packages/firebase_core/firebase_core_web/lib/src/firebase_core_web.dart

@@ -14,23 +14,44 @@ class FirebaseWebService {
   /// property allows overriding of web naming to Flutterfire plugin naming.
   String? override;
 
+  /// Function to call to ensure the Firebase Service is initalized.
+  /// Usually used to ensure that the Web SDK match the behavior
+  /// of native SDKs.
+  EnsurePluginInitialized ensurePluginInitialized;
+
   /// Creates a new [FirebaseWebService].
-  FirebaseWebService._(this.name, [this.override]);
+  FirebaseWebService._(
+    this.name, {
+    this.override,
+    this.ensurePluginInitialized,
+  });
 }
 
+typedef EnsurePluginInitialized = Future<void> Function()?;
+
 /// The entry point for accessing Firebase.
 ///
 /// You can get an instance by calling [FirebaseCore.instance].
 class FirebaseCoreWeb extends FirebasePlatform {
   static Map<String, FirebaseWebService> _services = {
-    'core': FirebaseWebService._('app', 'core'),
-    'app-check': FirebaseWebService._('app-check', 'app_check'),
-    'remote-config': FirebaseWebService._('remote-config', 'remote_config'),
+    'core': FirebaseWebService._('app', override: 'core'),
+    'app-check': FirebaseWebService._('app-check', override: 'app_check'),
+    'remote-config':
+        FirebaseWebService._('remote-config', override: 'remote_config'),
   };
 
   /// Internally registers a Firebase Service to be initialized.
-  static void registerService(String service) {
-    _services.putIfAbsent(service, () => FirebaseWebService._(service));
+  static void registerService(
+    String service, [
+    EnsurePluginInitialized? ensurePluginInitialized,
+  ]) {
+    _services.putIfAbsent(
+      service,
+      () => FirebaseWebService._(
+        service,
+        ensurePluginInitialized: ensurePluginInitialized,
+      ),
+    );
   }
 
   /// Registers that [FirebaseCoreWeb] is the platform implementation.
@@ -251,6 +272,18 @@ class FirebaseCoreWeb extends FirebasePlatform {
       }
     }
 
+    await Future.wait(
+      _services.values.map((service) {
+        final ensureInitializedFunction = service.ensurePluginInitialized;
+
+        if (ensureInitializedFunction == null) {
+          return Future.value();
+        }
+
+        return ensureInitializedFunction();
+      }),
+    );
+
     return _createFromJsApp(app!);
   }
 

packages/firebase_ui_auth/example/lib/main.dart

@@ -5,19 +5,18 @@
 import 'package:firebase_auth/firebase_auth.dart'
     hide PhoneAuthProvider, EmailAuthProvider;
 import 'package:firebase_core/firebase_core.dart';
-import 'package:flutter/material.dart';
 import 'package:firebase_ui_auth/firebase_ui_auth.dart';
 import 'package:firebase_ui_localizations/firebase_ui_localizations.dart';
 import 'package:firebase_ui_oauth_apple/firebase_ui_oauth_apple.dart';
 import 'package:firebase_ui_oauth_facebook/firebase_ui_oauth_facebook.dart';
 import 'package:firebase_ui_oauth_google/firebase_ui_oauth_google.dart';
 import 'package:firebase_ui_oauth_twitter/firebase_ui_oauth_twitter.dart';
+import 'package:flutter/material.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 
-import 'firebase_options.dart';
-
 import 'config.dart';
 import 'decorations.dart';
+import 'firebase_options.dart';
 
 final actionCodeSettings = ActionCodeSettings(
   url: 'https://flutterfire-e2e-tests.firebaseapp.com',