[google_sign_in_web] Fix race condition on init.

packages/google_sign_in/google_sign_in_web/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.8.3
+
+* Fix initialization error that causes https://github.com/flutter/flutter/issues/48527
+* Throw a PlatformException when there's an initialization problem (like wrong server-side config).
+
 ## 0.8.2+1
 
 * Add a non-op Android implementation to avoid a flaky Gradle issue.

packages/google_sign_in/google_sign_in_web/lib/google_sign_in_web.dart

@@ -5,14 +5,13 @@
 import 'dart:async';
 import 'dart:html' as html;
 
+import 'package:flutter/services.dart';
 import 'package:google_sign_in_platform_interface/google_sign_in_platform_interface.dart';
 import 'package:flutter_web_plugins/flutter_web_plugins.dart';
 import 'package:js/js.dart';
 import 'package:meta/meta.dart';
 
 import 'src/generated/gapiauth2.dart' as auth2;
-// TODO: Remove once this lands https://github.com/dart-lang/language/issues/671
-import 'src/generated/gapiauth2.dart' show GoogleAuthExtensions;
 import 'src/load_gapi.dart' as gapi;
 import 'src/utils.dart' show gapiUserToPluginUserData;
 
@@ -39,14 +38,15 @@ class GoogleSignInPlugin extends GoogleSignInPlatform {
   }
 
   Future<void> _isGapiInitialized;
+  Future<void> _isAuthInitialized = Completer<void>().future;
 
   /// This is only exposed for testing. It shouldn't be accessed by users of the
   /// plugin as it could break at any point.
   @visibleForTesting
-  Future<void> get initialized => _isGapiInitialized;
+  Future<void> get initialized =>
+      Future.wait([_isGapiInitialized, _isAuthInitialized]);
 
   String _autoDetectedClientId;
-  FutureOr<auth2.GoogleUser> _lastSeenUser;
 
   /// Factory method that initializes the plugin with [GoogleSignInPlatform].
   static void registerWith(Registrar registrar) {
@@ -72,7 +72,7 @@ class GoogleSignInPlugin extends GoogleSignInPlatform {
         'Check https://developers.google.com/identity/protocols/googlescopes '
         'for a list of valid OAuth 2.0 scopes.');
 
-    await initialized;
+    await _isGapiInitialized;
 
     final auth2.GoogleAuth auth = auth2.init(auth2.ClientConfig(
       hosted_domain: hostedDomain,
@@ -81,19 +81,25 @@ class GoogleSignInPlugin extends GoogleSignInPlatform {
       client_id: appClientId,
     ));
 
-    // Subscribe to changes in the auth instance returned by init,
-    // and cache the _lastSeenUser as we get notified of new values.
-    final Completer<auth2.GoogleUser> initUserCompleter =
-        Completer<auth2.GoogleUser>();
-
-    auth.currentUser.listen(allowInterop((auth2.GoogleUser nextUser) {
-      if (!initUserCompleter.isCompleted) {
-        initUserCompleter.complete(nextUser);
-      } else {
-        _lastSeenUser = nextUser;
-      }
+    Completer<void> isAuthInitialized = Completer<void>();
+    _isAuthInitialized = isAuthInitialized.future;
+
+    auth.then(allowInterop((auth2.GoogleAuth initializedAuth) {
+      // onSuccess
+
+      // TODO: https://github.com/flutter/flutter/issues/48528
+      // This plugin doesn't notify the app of external changes to the
+      // state of the authentication, i.e: if you logout elsewhere...
+
+      isAuthInitialized.complete();
+    }), allowInterop((dynamic reason) {
+      // onError
+      throw (PlatformException(
+        code: 'google_sign_in',
+        message: reason.error,
+        details: reason.details,
+      ));
     }));
-    _lastSeenUser = initUserCompleter.future;
 
     return null;
   }
@@ -102,7 +108,8 @@ class GoogleSignInPlugin extends GoogleSignInPlatform {
   Future<GoogleSignInUserData> signInSilently() async {
     await initialized;
 
-    return gapiUserToPluginUserData(await _lastSeenUser);
+    return gapiUserToPluginUserData(
+        await auth2.getAuthInstance().currentUser.get());
   }
 
   @override
@@ -154,7 +161,6 @@ class GoogleSignInPlugin extends GoogleSignInPlatform {
   Future<void> clearAuthCache({String token}) async {
     await initialized;
 
-    _lastSeenUser = null;
     return auth2.getAuthInstance().disconnect();
   }
 }

packages/google_sign_in/google_sign_in_web/pubspec.yaml

@@ -2,7 +2,7 @@ name: google_sign_in_web
 description: Flutter plugin for Google Sign-In, a secure authentication system
   for signing in with a Google account on Android, iOS and Web.
 homepage: https://github.com/flutter/plugins/tree/master/packages/google_sign_in/google_sign_in_web
-version: 0.8.2+1
+version: 0.8.3
 
 flutter:
   plugin:

packages/google_sign_in/google_sign_in_web/test/auth2_test.dart

@@ -27,9 +27,8 @@ void main() {
 
   GoogleSignInPlugin plugin;
 
-  setUp(() async {
+  setUp(() {
     plugin = GoogleSignInPlugin();
-    await plugin.initialized;
   });
 
   test('Init requires clientId', () async {
@@ -47,12 +46,13 @@ void main() {
   });
 
   group('Successful .init, then', () {
-    setUp(() {
-      plugin.init(
+    setUp(() async {
+      await plugin.init(
         hostedDomain: 'foo',
         scopes: <String>['some', 'scope'],
         clientId: '1234',
       );
+      await plugin.initialized;
     });
 
     test('signInSilently', () async {

packages/google_sign_in/google_sign_in_web/test/gapi_load_test.dart

@@ -7,14 +7,16 @@
 import 'dart:html' as html;
 
 import 'package:flutter_test/flutter_test.dart';
+import 'package:google_sign_in_platform_interface/google_sign_in_platform_interface.dart';
 import 'package:google_sign_in_web/google_sign_in_web.dart';
 import 'gapi_mocks/gapi_mocks.dart' as gapi_mocks;
 import 'utils.dart';
 
 void main() {
-  gapiUrl = toBase64Url(gapi_mocks.gapiInitSuccess());
+  gapiUrl = toBase64Url(gapi_mocks.auth2InitSuccess(GoogleSignInUserData()));
 
-  test('Plugin is initialized after GAPI fully loads', () async {
+  test('Plugin is initialized after GAPI fully loads and init is called',
+      () async {
     expect(
       html.querySelector('script[src^="data:"]'),
       isNull,
@@ -26,6 +28,12 @@ void main() {
       isNotNull,
       reason: 'Mock script should be injected',
     );
+    expect(
+      plugin.initialized,
+      doesNotComplete,
+      reason: 'The plugin should only complete the future after calling .init',
+    );
+    await plugin.init(hostedDomain: '', clientId: '');
     await plugin.initialized;
     expect(
       plugin.initialized,

packages/google_sign_in/google_sign_in_web/test/gapi_mocks/gapi_mocks.dart

@@ -10,5 +10,4 @@ import 'src/gapi.dart';
 import 'src/google_user.dart';
 import 'src/test_iife.dart';
 
-part 'src/gapi_load.dart';
 part 'src/auth2_init.dart';

packages/google_sign_in/google_sign_in_web/test/gapi_mocks/src/auth2_init.dart

@@ -13,6 +13,11 @@ var mockUser = ${googleUser(userData)};
 function GapiAuth2() {}
 GapiAuth2.prototype.init = function (initOptions) {
   return {
+    then: (onSuccess, onError) => {
+      window.setTimeout(() => {
+        onSuccess(window.gapi.auth2);
+      }, 30);
+    },
     currentUser: {
       listen: (cb) => {
         window.setTimeout(() => {