Facebook support for email_in_user_when_upgrading (firebase#408)

* Facebook support for email_in_user_when_upgrading Adds support for Facebook when autolinking an exisiting user to a new federated user (Google). * Addresses comments

Author: protocol86

FirebaseAuthUI/FUIAuth.m

@@ -295,22 +295,29 @@ - (void)signInWithEmailHint:(NSString *)emailHint
 
  [self.auth fetchProvidersForEmail:emailHint completion:^(NSArray<NSString *> *_Nullable providers,
  NSError *_Nullable error) {
- NSString *federatedProviderID = [self federatedAuthProviderFromProviders:providers];
- // Google case
- if ([federatedProviderID isEqualToString:FIRGoogleAuthProviderID]) {
- id<FUIAuthProvider> googleProviderUI;
+ if (error) {
+ completion(nil, error);
+ return;
+ }
+ NSString *existingFederatedProviderID = [self federatedAuthProviderFromProviders:providers];
+ // Set of providers which can be auto-linked
+ NSSet *supportedProviders =
+ [NSSet setWithObjects:FIRGoogleAuthProviderID, FIRFacebookAuthProviderID, nil];
+ if ([supportedProviders containsObject:existingFederatedProviderID]) {
+ id<FUIAuthProvider> authProviderUI;
+ // Retrieve the FUIAuthProvider instance from FUIAuth for the existing provider ID.
  for (id<FUIAuthProvider> provider in self.providers) {
- if ([provider.providerID isEqualToString:FIRGoogleAuthProviderID]) {
- googleProviderUI = provider;
+ if ([provider.providerID isEqualToString:existingFederatedProviderID]) {
+ authProviderUI = provider;
  break;
  }
  }
- [googleProviderUI signOut];
- [googleProviderUI signInWithDefaultValue:emailHint
-  presentingViewController:presentingViewController
-  completion:^(FIRAuthCredential *_Nullable credential,
-  NSError *_Nullable error,
-  FIRAuthResultCallback _Nullable result) {
+ [authProviderUI signOut];
+ [authProviderUI signInWithDefaultValue:emailHint
+ presentingViewController:presentingViewController
+ completion:^(FIRAuthCredential *_Nullable credential,
+ NSError *_Nullable error,
+ FIRAuthResultCallback _Nullable result) {
  if (error) {
  completion(nil, error);
  return;

FirebaseGoogleAuthUI/FUIGoogleAuth.m

@@ -55,6 +55,11 @@ @implementation FUIGoogleAuth {
  @brief The callback which should be invoked when the sign in flow completes (or is cancelled.)
  */
  FIRAuthProviderSignInCompletionBlock _pendingSignInCallback;
+
+ /** @var _email
+ @brief The email address associated with this account.
+ */
+ NSString *_email;
 }
 
 - (instancetype)init {
@@ -140,6 +145,10 @@ - (BOOL)handleOpenURL:(NSURL *)URL sourceApplication:(NSString *)sourceApplicati
  return [signIn handleURL:URL sourceApplication:sourceApplication annotation:nil];
 }
 
+- (NSString *)email {
+ return _email;
+}
+
 #pragma mark - GIDSignInDelegate methods
 
 - (void)signIn:(GIDSignIn *)signIn
@@ -158,6 +167,7 @@ - (void)signIn:(GIDSignIn *)signIn
  }
  return;
  }
+ _email = user.profile.email;
  UIActivityIndicatorView *activityView =
  [FUIAuthBaseViewController addActivityIndicator:_presentingViewController.view];
  [activityView startAnimating];