Automatic anonymous user upgrade (#481)

 Adds anonymous user upgrade through several commits.

Author: protocol86

FirebaseAuthUI/FUIAuth.h

@@ -201,6 +201,12 @@ __attribute__((deprecated("Instead use authUI:didSignInWithAuthDataResult:error:
  */
 @property(nonatomic, copy, nullable) NSURL *TOSURL;
 
+/** @property shouldAutoUpgradeAnonymousUsers
+    @brief Whether to enable auto upgrading of anonymous accounts, defaults to NO.
+ */
+@property(nonatomic, assign, getter=shouldAutoUpgradeAnonymousUsers) BOOL
+    shouldAutoUpgradeAnonymousUsers;
+
 /** @property privacyPolicyURL
     @brief The URL of your app's Privacy Policy. If not nil, a privacy policy notice is
         displayed on the initial sign-in screen and potentially the phone number auth and

FirebaseAuthUI/FUIAuth.m

@@ -242,20 +242,61 @@ + (void)showAlertWithTitle:(nullable NSString *)title
   [presentingViewController presentViewController:alertController animated:YES completion:nil];
 }
 
++ (void)showAlertWithTitle:(nullable NSString *)title
+                   message:(NSString *)message
+               actionTitle:(NSString *)actionTitle
+  presentingViewController:(UIViewController *)presentingViewController
+             actionHandler:(FUIAuthAlertActionHandler)actionHandler
+             cancelHandler:(FUIAuthAlertActionHandler)cancelHandler {
+  UIAlertController *alertController =
+      [UIAlertController alertControllerWithTitle:title
+                                          message:message
+                                   preferredStyle:UIAlertControllerStyleAlert];
+  UIAlertAction *okAction =
+      [UIAlertAction actionWithTitle:actionTitle
+                               style:UIAlertActionStyleDefault
+                             handler:^(UIAlertAction *_Nonnull action) {
+        actionHandler();
+      }];
+  [alertController addAction:okAction];
+  UIAlertAction *cancelAction =
+      [UIAlertAction actionWithTitle:FUILocalizedString(kStr_Cancel)
+                               style:UIAlertActionStyleCancel
+                               handler:^(UIAlertAction * _Nonnull action) {
+        cancelHandler();
+      }];
+  [alertController addAction:cancelAction];
+  [presentingViewController presentViewController:alertController animated:YES completion:nil];
+}
+
 + (void)showSignInAlertWithEmail:(NSString *)email
                         provider:(id<FUIAuthProvider>)provider
         presentingViewController:(UIViewController *)presentingViewController
                    signinHandler:(FUIAuthAlertActionHandler)signinHandler
                    cancelHandler:(FUIAuthAlertActionHandler)cancelHandler {
+  [self showSignInAlertWithEmail:email
+               providerShortName:provider.shortName
+             providerSignInLabel:provider.signInLabel
+        presentingViewController:presentingViewController
+                   signinHandler:signinHandler
+                   cancelHandler:cancelHandler];
+}
+
++ (void)showSignInAlertWithEmail:(NSString *)email
+               providerShortName:(NSString *)providerShortName
+             providerSignInLabel:(NSString *)providerSignInLabel
+        presentingViewController:(UIViewController *)presentingViewController
+                   signinHandler:(FUIAuthAlertActionHandler)signinHandler
+                   cancelHandler:(FUIAuthAlertActionHandler)cancelHandler {
   NSString *message =
       [NSString stringWithFormat:FUILocalizedString(kStr_ProviderUsedPreviouslyMessage),
-          email, provider.shortName];
+          email, providerShortName];
   UIAlertController *alertController =
       [UIAlertController alertControllerWithTitle:FUILocalizedString(kStr_ExistingAccountTitle)
                                           message:message
                                    preferredStyle:UIAlertControllerStyleAlert];
   UIAlertAction *signInAction =
-      [UIAlertAction actionWithTitle:provider.signInLabel
+      [UIAlertAction actionWithTitle:providerSignInLabel
                                style:UIAlertActionStyleDefault
                              handler:^(UIAlertAction *_Nonnull action) {
         signinHandler();

FirebaseAuthUI/FUIAuthBaseViewController.m

@@ -56,6 +56,51 @@ NS_ASSUME_NONNULL_BEGIN
                  actionTitle:(NSString *)actionTitle
     presentingViewController:(UIViewController *)presentingViewController;
 
+/** @fn showAlertWithTitle:message:actionTitle:presentingViewController:
+    @brief Displays an alert view with given title, message and action title  on top of the
+        specified view controller.
+    @param title The title of the alert.
+    @param message The message of the alert.
+    @param actionTitle The title of the action button.
+    @param actionHandler The block to execute if the action button is tapped.
+    @param cancelHandler The block to execute if the cancel button is tapped.
+    @param presentingViewController The controller which shows alert.
+ */
++ (void)showAlertWithTitle:(nullable NSString *)title
+                   message:(NSString *)message
+               actionTitle:(NSString *)actionTitle
+  presentingViewController:(UIViewController *)presentingViewController
+             actionHandler:(FUIAuthAlertActionHandler)actionHandler
+             cancelHandler:(FUIAuthAlertActionHandler)cancelHandler;
+
+/** @fn showSignInAlertWithEmail:provider:handler:
+    @brief Displays an alert to conform with user whether she wants to proceed with the provider.
+    @param email The email address to sign in with.
+    @param provider The identity provider to sign in with.
+    @param signinHandler Handler for the sign in action of the alert.
+    @param cancelHandler Handler for the cancel action of the alert.
+ */
++ (void)showSignInAlertWithEmail:(NSString *)email
+                        provider:(id<FUIAuthProvider>)provider
+        presentingViewController:(UIViewController *)presentingViewController
+                   signinHandler:(FUIAuthAlertActionHandler)signinHandler
+                   cancelHandler:(FUIAuthAlertActionHandler)cancelHandler;
+
+/** @fn showSignInAlertWithEmail:providerShortName:providerSignInLabel:handler:
+    @brief Displays an alert to conform with user whether she wants to proceed with the provider.
+    @param email The email address to sign in with.
+    @param providerShortName The name of the provider as displayed in the sign-in alert message.
+    @param providerSignInLabel The name of the provider as displayed in the sign-in alert button.
+    @param signinHandler Handler for the sign in action of the alert.
+    @param cancelHandler Handler for the cancel action of the alert.
+ */
++ (void)showSignInAlertWithEmail:(NSString *)email
+               providerShortName:(NSString *)providerShortName
+             providerSignInLabel:(NSString *)providerSignInLabel
+        presentingViewController:(UIViewController *)presentingViewController
+                   signinHandler:(FUIAuthAlertActionHandler)signinHandler
+                   cancelHandler:(FUIAuthAlertActionHandler)cancelHandler;
+
 /** @fn pushViewController:
     @brief Push the view controller to the navigation controller of the current view controller
         with animation. The pushed view controller will have a fixed "Back" title for back button.

FirebaseAuthUI/FUIAuthBaseViewController_Internal.h

@@ -36,6 +36,13 @@ NS_ASSUME_NONNULL_BEGIN
  */
 + (NSError *)userCancelledSignInError;
 
+/** @fn userCancelledSignIn
+    @brief Constructs an @c NSError with the @c FUIAuthErrorCodeMergeConflict code.
+    @param userInfo The userInfo dictionary to add to the NSError object.
+    @return The merge conflict error.
+ */
++ (NSError *)mergeConflictErrorWithUserInfo:(NSDictionary *)userInfo;
+
 /** @fn providerErrorWithUnderlyingError:providerID:
     @brief Constructs an @c NSError with the @c FUIAuthErrorCodeProviderError code and a populated
         @c NSUnderlyingErrorKey and @c FUIAuthErrorUserInfoProviderIDKey in the

FirebaseAuthUI/FUIAuthErrorUtils.h

@@ -26,6 +26,10 @@ + (NSError *)userCancelledSignInError {
   return [self errorWithCode:FUIAuthErrorCodeUserCancelledSignIn userInfo:nil];
 }
 
++ (NSError *)mergeConflictErrorWithUserInfo:(NSDictionary *)userInfo {
+  return [self errorWithCode:FUIAuthErrorCodeMergeConflict userInfo:userInfo];
+}
+
 + (NSError *)providerErrorWithUnderlyingError:(NSError *)underlyingError
                                    providerID:(NSString *)providerID {
   return [self errorWithCode:FUIAuthErrorCodeProviderError

FirebaseAuthUI/FUIAuthErrorUtils.m

@@ -28,6 +28,12 @@ extern NSString *const FUIAuthErrorDomain;
  */
 extern NSString *const FUIAuthErrorUserInfoProviderIDKey;
 
+/** @bar FUIAuthCredentialKey
+    @brief The key used to obtain the credential stored within the userInfo dictionary of the
+        error, if availalble.
+ */
+extern NSString *const FUIAuthCredentialKey;
+
 /** @var FUIAuthErrorCode
     @brief Error codes used by FUIAuth.
  */
@@ -50,6 +56,13 @@ typedef NS_ENUM(NSUInteger, FUIAuthErrorCode) {
           key @c FUIAuthErrorUserInfoProviderIDKey).
    */
   FUIAuthErrorCodeCantFindProvider = 3,
+
+  /** @var FUIAuthErrorCodeMergeConflict
+      @brief Indicates that a merge conflict occurred while trying to automatically upgrade an
+          anonymous user. The non-anonymous credential can be obtained from the userInfo dictionary
+          of the corresponding NSError using the @c FUIAuthCredentialKey.
+   */
+  FUIAuthErrorCodeMergeConflict = 4,
 };
 
 NS_ASSUME_NONNULL_END

FirebaseAuthUI/FUIAuthErrors.h

@@ -19,3 +19,5 @@
 NSString *const FUIAuthErrorDomain = @"FUIAuthErrorDomain";
 
 NSString *const FUIAuthErrorUserInfoProviderIDKey = @"FUIAuthErrorUserInfoProviderIDKey";
+
+NSString *const FUIAuthCredentialKey = @"FUIAuthCredentialKey";

FirebaseAuthUI/FUIAuthErrors.m

@@ -124,10 +124,15 @@ __attribute__((deprecated("This is deprecated API and will be removed in a futur
 @optional;
 
 /** @property idToken
-    @brief User Id Token obtained during sign in. Not all providers can return, thus it's optional
+    @brief User Id Token obtained during sign in. Not all providers can return, thus it's optional.
  */
 @property(nonatomic, copy, readonly) NSString *idToken;
 
+/** @fn email
+    @brief The email address associated with this provider, if any.
+ */
+- (NSString *)email;
+
 /** @fn handleOpenURL:
     @brief May be used to help complete a sign-in flow which requires a callback from Safari.
     @param URL The URL which may be handled by the auth provider if an URL is expected.

FirebaseAuthUI/FUIAuthProvider.h

@@ -14,14 +14,16 @@
 //  limitations under the License.
 //
 
-#import "FUIPasswordSignInViewController.h"
+#import "FUIPasswordSignInViewController_Internal.h"
 
 #import <FirebaseAuth/FirebaseAuth.h>
 #import "FUIAuthBaseViewController_Internal.h"
+#import "FUIAuthErrorUtils.h"
 #import "FUIAuthStrings.h"
 #import "FUIAuthTableViewCell.h"
 #import "FUIAuthUtils.h"
 #import "FUIAuth_Internal.h"
+#import "FUIAuthErrors.h"
 #import "FUIPasswordRecoveryViewController.h"
 
 /** @var kCellReuseIdentifier
@@ -78,6 +80,10 @@ - (instancetype)initWithNibName:(nullable NSString *)nibNameOrNil
     _email = [email copy];
 
     self.title = FUILocalizedString(kStr_SignInTitle);
+    __weak FUIPasswordSignInViewController *weakself = self;
+    _onDismissCallback = ^(FIRAuthDataResult *authResult, NSError *error){
+      [weakself.authUI invokeResultCallbackWithAuthDataResult:authResult error:error];
+    };
   }
   return self;
 }
@@ -127,35 +133,61 @@ - (void)signInWithDefaultValue:(NSString *)email andPassword:(NSString *)passwor
   }
 
   [self incrementActivity];
-
   FIRAuthCredential *credential =
       [FIREmailAuthProvider credentialWithEmail:email password:password];
-  [self.auth signInAndRetrieveDataWithCredential:credential
-                                      completion:^(FIRAuthDataResult *_Nullable authResult,
-                                                   NSError *_Nullable error) {
-    [self decrementActivity];
-
-    if (error) {
-      switch (error.code) {
-        case FIRAuthErrorCodeWrongPassword:
-          [self showAlertWithMessage:FUILocalizedString(kStr_WrongPasswordError)];
-          return;
-        case FIRAuthErrorCodeUserNotFound:
-          [self showAlertWithMessage:FUILocalizedString(kStr_UserNotFoundError)];
-          return;
-        case FIRAuthErrorCodeUserDisabled:
-          [self showAlertWithMessage:FUILocalizedString(kStr_AccountDisabledError)];
-          return;
-        case FIRAuthErrorCodeTooManyRequests:
-          [self showAlertWithMessage:FUILocalizedString(kStr_SignInTooManyTimesError)];
+
+    void (^completeSignInBlock)(FIRAuthDataResult *, NSError *) = ^(FIRAuthDataResult *authResult,
+                                                                    NSError *error) {
+      [self decrementActivity];
+
+      if (error) {
+        switch (error.code) {
+          case FIRAuthErrorCodeWrongPassword:
+            [self showAlertWithMessage:FUILocalizedString(kStr_WrongPasswordError)];
+            return;
+          case FIRAuthErrorCodeUserNotFound:
+            [self showAlertWithMessage:FUILocalizedString(kStr_UserNotFoundError)];
+            return;
+          case FIRAuthErrorCodeUserDisabled:
+            [self showAlertWithMessage:FUILocalizedString(kStr_AccountDisabledError)];
+            return;
+          case FIRAuthErrorCodeTooManyRequests:
+            [self showAlertWithMessage:FUILocalizedString(kStr_SignInTooManyTimesError)];
+            return;
+        }
+      }
+      [self.navigationController dismissViewControllerAnimated:YES completion:^{
+        if (self->_onDismissCallback) {
+          self->_onDismissCallback(authResult, error);
+        }
+      }];
+    };
+
+  // Check for the presence of an anonymous user and whether automatic upgrade is enabled.
+  if (self.auth.currentUser.isAnonymous &&
+    [FUIAuth defaultAuthUI].shouldAutoUpgradeAnonymousUsers) {
+
+    [self.auth.currentUser
+        linkAndRetrieveDataWithCredential:credential
+                               completion:^(FIRAuthDataResult *_Nullable authResult,
+                                            NSError *_Nullable error) {
+      if (error) {
+        if (error.code == FIRAuthErrorCodeEmailAlreadyInUse) {
+          NSDictionary *userInfo = @{ FUIAuthCredentialKey : credential };
+          NSError *mergeError = [FUIAuthErrorUtils mergeConflictErrorWithUserInfo:userInfo];
+          [self.navigationController dismissViewControllerAnimated:YES completion:^{
+            [self.authUI invokeResultCallbackWithAuthDataResult:authResult error:mergeError];
+          }];
           return;
+        }
+        completeSignInBlock(nil, error);
+        return;
       }
-    }
-    
-    [self dismissNavigationControllerAnimated:YES completion:^{
-      [self.authUI invokeResultCallbackWithAuthDataResult:authResult error:error];
+      completeSignInBlock(authResult, nil);
     }];
-  }];
+  } else {
+    [self.auth signInAndRetrieveDataWithCredential:credential completion:completeSignInBlock];
+  }
 }
 
 - (void)signIn {