Addresses comments

Addresses comments
Minor enhances
Fixes bug where wrong error is returned

Author: protocol86

FirebaseAuthUI/FUIAuth.h

@@ -190,10 +190,11 @@ __attribute__((deprecated("Instead use authUI:didSignInWithAuthDataResult:error:
  */
 @property(nonatomic, copy, nullable) NSURL *TOSURL;
 
-/** @property autoUpgradeAnonymousUsers
+/** @property shouldAutoUpgradeAnonymousUsers
     @brief Whether to enable auto upgrading of anonymous accounts, defaults to NO.
  */
-@property(nonatomic, assign, getter=isAutoUpgradeAnonymousUsers) BOOL autoUpgradeAnonymousUsers;
+@property(nonatomic, assign, getter=shouldAutoUpgradeAnonymousUsers) BOOL
+    shouldAutoUpgradeAnonymousUsers;
 
 /** @property delegate
     @brief A delegate that receives callbacks or provides custom UI for @c FUIAuth.

FirebaseAuthUI/FUIAuth.m

@@ -191,7 +191,7 @@ - (void)signInWithProviderUI:(id<FUIAuthProvider>)providerUI
     };
 
     // Check for the presence of an anonymous user and whether automatic upgrade is enabled.
-    if (_auth.currentUser.isAnonymous && [FUIAuth defaultAuthUI].autoUpgradeAnonymousUsers) {
+    if (_auth.currentUser.isAnonymous && [FUIAuth defaultAuthUI].shouldAutoUpgradeAnonymousUsers) {
       [_auth.currentUser
           linkAndRetrieveDataWithCredential:credential
                                  completion:^(FIRAuthDataResult *_Nullable authResult,
@@ -212,8 +212,8 @@ - (void)signInWithProviderUI:(id<FUIAuthProvider>)providerUI
             mergeError = [NSError errorWithDomain:FUIAuthErrorDomain
                                              code:FUIAuthErrorCodeMergeConflict
                                          userInfo:userInfo];
-            result(nil, error);
-            completeSignInBlock(authResult, error);
+            result(nil, mergeError);
+            completeSignInBlock(authResult, mergeError);
           } else {
             if (!isAuthPickerShown || error.code != FUIAuthErrorCodeUserCancelledSignIn) {
               [self invokeResultCallbackWithAuthDataResult:nil error:error];

samples/objc/FirebaseUI-demo-objc/Samples/Auth/FUIAuthViewController.m

@@ -229,7 +229,7 @@ - (IBAction)onAuthUIDelegateChanged:(UISwitch *)sender {
 
 - (IBAction)onAuthorization:(id)sender {
   if (!_auth.currentUser || _auth.currentUser.isAnonymous) {
-    FUIAuth.defaultAuthUI.autoUpgradeAnonymousUsers = YES;
+    FUIAuth.defaultAuthUI.shouldAutoUpgradeAnonymousUsers = YES;
     _authUI.providers = [self getListOfIDPs];
     _authUI.signInWithEmailHidden = ![self isEmailEnabled];
 
@@ -266,7 +266,7 @@ - (void)authUI:(FUIAuth *)authUI
       FIRAuthCredential *credential = error.userInfo[FUIAuthCredentialKey];
       NSString *anonymousUserID = authUI.auth.currentUser.uid;
       NSString *messsage = [NSString stringWithFormat:@"A merge conflict occurred. The old user ID "
-          "was: %@. You are now sig in with the following credential type: %@", anonymousUserID,
+          "was: %@. You are now signed in with the following credential type: %@", anonymousUserID,
           [credential.provider uppercaseString]];
       [self showAlertWithTitlte:@"Merge Conflict" message:messsage];
       NSLog(@"%@", messsage);