Reauthenticate user who is signed in with Facebook

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I am using Flutter to create a mobile application. I am using Firebase for authentication. My user logs in with Facebook. The user should reauthenticate him/her self when deleting the account. The documentation talks about reauthentication using email and password like this:

// Create a credential
EmailAuthCredential credential = EmailAuthProvider.credential(email: email, password: password);

// Reauthenticate
await FirebaseAuth.instance.currentUser.reauthenticateWithCredential(credential);

Since the user does not have an email and password but rather he is logged in with Facebook, I should reauthenticate the user with Facebook. I searched the documentation for this but I had no luck.

Could some one be kind and tell me how to do that.

I tried to log the user in with Facebook (even though he is already logged in) but was not successful. Her is what I tried:

FacebookLoginResult result = await FacebookLogin().logIn(permissions: [
  FacebookPermission.publicProfile,
  FacebookPermission.email,
]);

switch (result.status) {
  case FacebookLoginStatus.success:
    FacebookAccessToken? accessToken = result.accessToken;
    if (accessToken == null) {
      return null;
    }

    UserCredential userCredential = await _auth.signInWithCredential(
      FacebookAuthProvider.credential(accessToken.token),
    );
    return userCredential;

  case FacebookLoginStatus.cancel:
    throw FirebaseAuthException(
      code: 'ERROR_FACEBOOK_LOGIN_FAILED',
      message: result.error?.developerMessage,
    );
  default:
    throw UnimplementedError();
}

await FirebaseAuth.instance.currentUser?.reauthenticateWithCredential(
  userCredential!.credential!,
);