[CRASH + DISCUSSION] Should we request Twitter email transparently?

While working on another PR, I came across this crash:

12-03 12:05:15.217 16688-16688/com.firebase.uidemo E/AndroidRuntime: FATAL EXCEPTION: main
                                                                     Process: com.firebase.uidemo, PID: 16688
                                                                     java.lang.IllegalArgumentException: Given String is empty or null
                                                                         at com.google.android.gms.common.internal.zzac.zzdv(Unknown Source)
                                                                         at com.google.firebase.auth.FirebaseAuth.fetchProvidersForEmail(Unknown Source)
                                                                         at com.firebase.ui.auth.ui.idp.CredentialSignInHandler.onComplete(CredentialSignInHandler.java:73)
                                                                         at com.google.android.gms.tasks.zzc$1.run(Unknown Source)
                                                                         at android.os.Handler.handleCallback(Handler.java:751)
                                                                         at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                         at android.os.Looper.loop(Looper.java:154)
                                                                         at android.app.ActivityThread.main(ActivityThread.java:6088)
                                                                         at java.lang.reflect.Method.invoke(Native Method)
                                                                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

It’s caused by this line of code and occurs if a user has an existing account and there is a FirebaseAuthUserCollisionException.

To solve this problem, there are two solutions:

1. Check for a null email in CredentialSignInHandler and fail the sign in if the email is null.
2. Use TwitterAuthClient#requestEmail to show the request email activity.

I prefer solution 2 because we are being more transparent about requesting a user’s email, but it requires more steps and a Twitter user might not have an email: https://docs.fabric.io/android/twitter/log-in-with-twitter.html#request-user-email-address

@samtstern @amandle What should we do?

[SUPERCILEX]

@cutiko You’re totally fine, that’s why FirebaseUI has public issues! 😄

In my case the problem happened when the email was requested for Twitter but the email was already in use. Initially the login was done using google and then later using Twitter, the email is the same in both.

@samtstern Hopefully my comment and the above will help you understand why we need the email. Adding the null check in CredentialSignInHandler fixes the crash for Twitter users without an email, but we still need the email before the user is signed to perform linking for Twitter users with an email.

@cutiko Yes, the plan is to force you guys to request the email permission (or at least if you don’t neither account linking nor Smart Lock will work).

The fix should be out by FirebaseUI v1.1.0! 🎉

[samtstern]

A fix for this issue has been released in version 1.1.0