Firebase Auth linkWithGoogleCredential is broken since about 0.6.2+1

[BerndWessels]

Steps to Reproduce

await linkWithGoogleCredential gets stuck - this used to work up to 0.5.20

In the example below it never reaches log step ---------------------- 4, BUT is also doesn't catch any exception.

  final FirebaseAuth _auth = FirebaseAuth.instance;
  final GoogleSignIn _googleSignIn = GoogleSignIn();

    GoogleSignInAuthentication googleAuth;
    try {
      print("---------------------- 1");
      final GoogleSignInAccount googleUser = await _googleSignIn.signIn();
      print("---------------------- 2");
      googleAuth = await googleUser.authentication;
      print("---------------------- 3");
      final FirebaseUser user = await _auth.linkWithGoogleCredential(
        accessToken: googleAuth.accessToken,
        idToken: googleAuth.idToken,
      );
      print("---------------------- 4");
    } catch (err) {
      print("---------------------- 5");
      print(err);
    }

Logs

  # Firebase
  firebase_auth: ^0.6.6
  firebase_core: ^0.2.5+1
  firebase_dynamic_links: ^0.1.0+1
  cloud_firestore: ^0.8.2+3

  # Social login providers
  flutter_facebook_login: ^1.1.1
  google_sign_in: ^3.2.4

[√] Flutter (Channel stable, v1.0.0, on Microsoft Windows [Version 10.0.17134.407], locale en-NZ)
    • Flutter version 1.0.0 at C:\Users\b\git\flutter
    • Framework revision 5391447fae (12 days ago), 2018-11-29 19:41:26 -0800
    • Engine revision 7375a0f414
    • Dart version 2.1.0 (build 2.1.0-dev.9.4 f9ebf21297)

[√] Android toolchain - develop for Android devices (Android SDK 28.0.3)
    • Android SDK at C:\Users\b\AppData\Local\Android\sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-28, build-tools 28.0.3
    • ANDROID_HOME = C:\Users\b\AppData\Local\Android\sdk
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1136-b06)
    • All Android licenses accepted.

[√] Android Studio (version 3.2)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin version 31.1.1
    • Dart plugin version 181.5656
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1136-b06)

[√] IntelliJ IDEA Community Edition (version 2017.3)
    • IntelliJ at C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2017.3
    • Flutter plugin version 19.1
    • Dart plugin version 173.3727.108

[√] Connected device (1 available)
    • Nexus 6P • ENU7N15A27004986 • android-arm64 • Android 8.1.0 (API 27)

• No issues found!

buildscript {
    ext.kotlin_version = '1.3.11'
    repositories {
        google()
        jcenter()
        maven {
            url 'https://maven.fabric.io/public'
        }
        maven {
            url 'https://dl.bintray.com/android/android-tools'
        }
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:3.2.1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'com.google.gms:google-services:4.2.0' // Google Services plugin
    }
}

[BerndWessels]

OK, here seems to be the problem:

linkWithGoogleCredential does not work if another firebase account is already linked to the google account.

Unfortunately there is no exception thrown, it is just stuck in the await which is a big problem for the program flow.

How do we get to into this situation - easy:

1. user starts app and gets an anonymous firebase user created

2. user signs in with his google account
   2.1. anonymous firebase user gets linked with the google account

3. user signs out later
   3.1. the app creates another anonymous user for the signed out user
   3.2. the old google user is still in firebase and linked to the google account

4. now the user decides to sign in with his google account again
   4.1. linkWithGoogleCredential fails/get stuck because the google account is already linked to the old firebase user account

This is a pretty common scenario in a lot of apps - is there a workaround or can fix linkWithGoogleCredential so that it will not get stuck and either succeed or at least throw an exception?

[BerndWessels]

One more common scenario that is also broken by this bug is cross device app access.

Basically a user has the same app on multiple of his devices. He wants to sign on with his google account on all of these devices to the same app.

It will succeed on the first device but on all other devices linkWithGoogleCredential will fail as described.

@zoechi I believe this is a really serious issue and needs actually some firebase auth redesign or at least rethink - because I can't see a workaround without allowing the same social user linked to multiple firebase users.

[thevzurd]

Eagerly waiting for a workaround. I am facing a similar issue here.

I also tried to used the 'AuthCredential' and GoogleAuthProvider classes mention in the example code, but those classes does not exist in the 'package:firebase_auth/firebase_auth.dart', even though I am using the latest package.

[ksheremet]

Rolling back to 0.5.20 didn't help me. Looking at a similar issue invertase/react-native-firebase#1701 it is most likely a problem in one of the Java dependencies.

Workaround: adding the following to android/app/build.gradle in dependencies section helped:

dependencies {
    // something that's already there...
    implementation 'com.google.firebase:firebase-auth:16.0.5'
}

A long-term fix is to update version in firebase_auth plugin itself.

[MarcinusX]

Had the same issue. It seems to be fixed in version 0.8.0 as I cannot reproduce it anymore :)

[zoechi]

@BerndWessels can you still reproduce with 0.8.0?

[BerndWessels]

@zoechi @MarcinusX still badly broken :(

I've upgraded to

  # Firebase
  firebase_auth: 0.8.0+1
  firebase_core: 0.3.0
  firebase_dynamic_links: ^0.1.0+1
  cloud_firestore: 0.9.0

  # Social login providers
  flutter_facebook_login: ^1.1.1
  google_sign_in: ^3.2.4

to do so I had to go through all this pain

after upgrading the code has changed to linkWithCredential:

  final FirebaseAuth _auth = FirebaseAuth.instance;
  final GoogleSignIn _googleSignIn = GoogleSignIn();

    GoogleSignInAuthentication googleAuth;
    try {
      print("---------------------- 1");
      final GoogleSignInAccount googleUser = await _googleSignIn.signIn();
      print("---------------------- 2");
      googleAuth = await googleUser.authentication;
      final credential = GoogleAuthProvider.getCredential(idToken: googleAuth.idToken, accessToken: googleAuth.accessToken);
      print("---------------------- 3");
      final FirebaseUser user = await _auth.linkWithCredential(credential);
      print("---------------------- 4");
    } catch (err) {
      print("---------------------- 5");
      print(err);
    }

Now we get this error:

E/MethodChannel#plugins.flutter.io/firebase_auth(23208): Failed to handle method call
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): java.lang.IllegalArgumentException: Given String is empty or null
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at com.google.android.gms.common.internal.Preconditions.checkNotEmpty(Unknown Source:5)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at com.google.firebase.auth.EmailAuthProvider.getCredential(Unknown Source:2)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at io.flutter.plugins.firebaseauth.FirebaseAuthPlugin.handleLinkWithEmailAndPassword(FirebaseAuthPlugin.java:272)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at io.flutter.plugins.firebaseauth.FirebaseAuthPlugin.onMethodCall(FirebaseAuthPlugin.java:122)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:200)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at io.flutter.view.FlutterNativeView.handlePlatformMessage(FlutterNativeView.java:163)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at android.os.MessageQueue.nativePollOnce(Native Method)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at android.os.MessageQueue.next(MessageQueue.java:325)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at android.os.Looper.loop(Looper.java:142)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at android.app.ActivityThread.main(ActivityThread.java:6494)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at java.lang.reflect.Method.invoke(Native Method)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
E/MethodChannel#plugins.flutter.io/firebase_auth(23208): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
I/flutter (23208): ---------------------- 5
I/flutter (23208): PlatformException(error, Given String is empty or null, null)

I'm starting to doubt that firebase is mature enough for production, or am I just to stupid to see what is going on?