credentialFromError returns NULL after upgrade to Alpha SDK

[awinogrodzki]

[REQUIRED] Describe your environment

• Operating System version: macOS Catalina 10.15.6
• Browser version: Chrome 88.0.4324.96
• Firebase SDK version: 0.900.11
• Firebase Product: auth (auth, database, storage, etc)

[REQUIRED] Describe the problem

Steps to reproduce:

FacebookAuthProvider.credentialFromError returns null when trying to link anonymous user with an external provider, after moving to modular version of SDK.

The same applies to GoogleAuthProvider

Relevant Code:

The code with the previous version of SDK is working fine:

    const provider = new FacebookAuthProvider();
    provider.setCustomParameters({
      display: 'popup',
    });
    const firebaseUser = firebaseApp.auth().currentUser;

    if (firebaseUser && firebaseUser.isAnonymous) {
      try {
        const result = await firebaseUser.linkWithPopup(provider);
        return mapFirebaseResponseToUser(result.user!);
      } catch (error) {
        if (isCredentialAlreadyInUseError(error)) {
          await firebaseUser.delete();

          const result = await firebaseApp.auth().signInWithCredential(
            error.credential // <------ The credential here is correct
          );

          return mapFirebaseResponseToUser(result.user!);
        }

        throw error;
      }
    }

The code using Alpha SDK, null error credential:

    const provider = new FacebookAuthProvider();
    provider.setCustomParameters({
      display: 'popup',
    });
    const firebaseUser = getAuth(firebaseApp).currentUser;

    if (firebaseUser && firebaseUser.isAnonymous) {
      try {
        const result = await linkWithPopup(
          firebaseUser,
          provider, 
          browserPopupRedirectResolver
        );

        return mapFirebaseResponseToUser(result.user!);
      } catch (error) {
        if (isCredentialAlreadyInUseError(error)) {
          const credential = FacebookAuthProvider.credentialFromError(error); <!-- the credential here is null

          await firebaseUser.delete();

          const result = await signInWithCredential(
            getAuth(firebaseApp),
            credential!
          );
          return mapFirebaseResponseToUser(result.user!);
        }

        throw error;
      }
    }

[sam-gc]

Hi @awinogrodzki, thanks for the super clear before/after samples! This is indeed a bug, thanks for raising it. I should have a PR out shortly

[sam-gc]

The linked PR fixes this issue and should be included in the next release. Thanks again for trying out the Alpha and for the detailed repro steps!