[FIREBASE_AUTH] Apple Sign in with firebase

[dheerajsarwaiya]

Is your feature request related to a problem? Please describe.
Apple do not approve IOS app without sign in with apple option. I use firebase auth for google sign in. But i dont see any option for Apple Sign in. Right now i am using git "https://github.com/zariweyo/flutterfire.git". But this git is getting old and I am unable to use any of your latest updates because that still do not support apple sign in.

Describe the solution you'd like
The best solution should be the same as Google Sign In. If not then whatever is available in the above git. Please merge the same to your latest update.

Additional context
firebase_auth:
git:
url: https://github.com/zariweyo/flutterfire.git
path: packages/firebase_auth/firebase_auth
ref: develop

[awhitford]

Go to your Firebase Console, open your Project, choose Authentication, and click on the Sign-in method tab. You need to enable the Apple provider.

[Navil]

Go to your Firebase Console, open your Project, choose Authentication, and click on the Sign-in method tab. You need to enable the Apple provider.

Flutter does however not provide a frontend solution to sign in with Apple credentials.

[cbenhagen]

@dheerajsarwaiya the changes in the repo you mentioned were merged with #1526.

[addie9000]

Seems to lack of capability to handle linkWithCredential.
Because Sign in with Apple does not permit to use the same credential twice, we need to get new credential if 'ERROR_CREDENTIAL_ALREADY_IN_USE' occured when linkWithCredential, by using error.userInfo[FIRAuthErrorUserInfoUpdatedCredentialKey].
Otherwise stuck with 'ERROR_MISSING_OR_INVALID_NONCE' error.
However I can't find the way to get error.userInfo[FIRAuthErrorUserInfoUpdatedCredentialKey].

Ref: firebase/firebase-ios-sdk#4434 (comment)

This problem is originaly mentioned #2253

[xster]

The package readme also needs documentation updates for the iOS section to specifically mention the steps needed to enable Apple as a provider for firebase auth.

[addie9000]

@Salakar
I believe there is not only documentation issue but also lack of feature.
The label should be type:missing-feature.

Or should we re-open #2253 and treat #2048 (comment) as specific issue other than general 'Apple Sign in with firebase' issue?

[Salakar]

@addie9000 it was my understanding that this is already possible using the apple_signin_plugin along with the OAuth provider - https://github.com/FirebaseExtended/flutterfire/blob/master/packages/firebase_auth/firebase_auth/lib/src/auth_provider/oauth_auth_provider.dart

Is this not the case?

Documentation label added for the purpose of documenting an example of integrating the two.

[addie9000]

@Salakar
Partially yes.
However linkWithCredential does not work with existing user as mentioned #2253 and my comment.
And more specific issue #2253 is closed and suggested to discuss about the issue here.

[Salakar]

@addie9000 ah ok that makes more sense - am I right in assuming then that it's just the information on the error (specifically the FIRAuthErrorUserInfoUpdatedCredentialKey data) that needs exposing to Dart?

We're tracking all these 'error' issues on #1456 - we'll be looking at parsing native error messages & codes and bubbling these up to the Dart layer in a consistent cross-platform format, including associated error information such as this one.