feat: anonymous account upgrade with error handling

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/AuthServiceError.swift

@@ -1,31 +1,45 @@
 
+import FirebaseAuth
 import SwiftUI
 
+public struct AccountMergeConflictContext: LocalizedError {
+  public let credential: AuthCredential
+  public let underlyingError: Error
+  public let message: String
+
+  public var errorDescription: String? {
+    return message
+  }
+}
+
 public enum AuthServiceError: LocalizedError {
-  case invalidEmailLink
+  case invalidEmailLink(String)
   case notConfiguredProvider(String)
   case clientIdNotFound(String)
-  case notConfiguredActionCodeSettings
+  case notConfiguredActionCodeSettings(String)
   case reauthenticationRequired(String)
   case invalidCredentials(String)
   case signInFailed(underlying: Error)
+  case accountMergeConflict(context: AccountMergeConflictContext)
 
   public var errorDescription: String? {
     switch self {
-    case .invalidEmailLink:
-      return "Invalid sign in link. Most likely, the link you used has expired. Try signing in again."
+    case let .invalidEmailLink(description):
+      return description
     case let .notConfiguredProvider(description):
       return description
     case let .clientIdNotFound(description):
       return description
-    case .notConfiguredActionCodeSettings:
-      return "ActionCodeSettings has not been configured for `AuthConfiguration.emailLinkSignInActionCodeSettings`"
+    case let .notConfiguredActionCodeSettings(description):
+      return description
     case let .reauthenticationRequired(description):
       return description
     case let .invalidCredentials(description):
       return description
     case let .signInFailed(underlying: error):
       return "Failed to sign in: \(error.localizedDescription)"
+    case let .accountMergeConflict(context):
+      return context.errorDescription
     }
   }
 }

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/Services/AuthService.swift

@@ -124,7 +124,9 @@ public final class AuthService {
     guard let actionCodeSettings = configuration
       .emailLinkSignInActionCodeSettings else {
       throw AuthServiceError
-        .notConfiguredActionCodeSettings
+        .notConfiguredActionCodeSettings(
+          "ActionCodeSettings has not been configured for `AuthConfiguration.emailLinkSignInActionCodeSettings`"
+        )
     }
     return actionCodeSettings
   }
@@ -141,6 +143,10 @@ public final class AuthService {
     errorMessage = ""
   }
 
+  public var shouldHandleAnonymousUpgrade: Bool {
+    currentUser?.isAnonymous == true && configuration.shouldAutoUpgradeAnonymousUsers
+  }
+
   public func signOut() async throws {
     do {
       try await auth.signOut()
@@ -167,21 +173,37 @@ public final class AuthService {
     }
   }
 
+  public func handleAutoUpgradeAnonymousUser(credentials credentials: AuthCredential) async throws {
+    do {
+      try await currentUser?.link(with: credentials)
+    } catch let error as NSError {
+      if error.code == AuthErrorCode.emailAlreadyInUse.rawValue {
+        let context = AccountMergeConflictContext(
+          credential: credentials,
+          underlyingError: error,
+          message: "Unable to merge accounts. Use the credential in the context to resolve the conflict."
+        )
+        throw AuthServiceError.accountMergeConflict(context: context)
+      }
+      throw error
+    }
+  }
+
   public func signIn(credentials credentials: AuthCredential) async throws {
     authenticationState = .authenticating
-    if currentUser?.isAnonymous == true, configuration.shouldAutoUpgradeAnonymousUsers {
-      try await linkAccounts(credentials: credentials)
-    } else {
-      do {
+    do {
+      if shouldHandleAnonymousUpgrade {
+        try await handleAutoUpgradeAnonymousUser(credentials: credentials)
+      } else {
         try await auth.signIn(with: credentials)
-        updateAuthenticationState()
-      } catch {
-        authenticationState = .unauthenticated
-        errorMessage = string.localizedErrorMessage(
-          for: error
-        )
-        throw error
       }
+      updateAuthenticationState()
+    } catch {
+      authenticationState = .unauthenticated
+      errorMessage = string.localizedErrorMessage(
+        for: error
+      )
+      throw error
     }
   }
 
@@ -231,7 +253,12 @@ public extension AuthService {
     authenticationState = .authenticating
 
     do {
-      try await auth.createUser(withEmail: email, password: password)
+      if shouldHandleAnonymousUpgrade {
+        let credential = EmailAuthProvider.credential(withEmail: email, password: password)
+        try await handleAutoUpgradeAnonymousUser(credentials: credential)
+      } else {
+        try await auth.createUser(withEmail: email, password: password)
+      }
       updateAuthenticationState()
     } catch {
       authenticationState = .unauthenticated
@@ -259,7 +286,7 @@ public extension AuthService {
 public extension AuthService {
   func sendEmailSignInLink(to email: String) async throws {
     do {
-      let actionCodeSettings = try safeActionCodeSettings()
+      let actionCodeSettings = try updateActionCodeSettings()
       try await auth.sendSignInLink(
         toEmail: email,
         actionCodeSettings: actionCodeSettings
@@ -275,11 +302,27 @@ public extension AuthService {
   func handleSignInLink(url url: URL) async throws {
     do {
       guard let email = emailLink else {
-        throw AuthServiceError.invalidEmailLink
+        throw AuthServiceError
+          .invalidEmailLink("email address is missing from app storage. Is this the same device?")
       }
       let link = url.absoluteString
+      guard let continueUrl = CommonUtils.getQueryParamValue(from: link, paramName: "continueUrl")
+      else {
+        throw AuthServiceError
+          .invalidEmailLink("`continueUrl` parameter is missing from the email link URL")
+      }
+
       if auth.isSignIn(withEmailLink: link) {
-        let result = try await auth.signIn(withEmail: email, link: link)
+        let anonymousUserID = CommonUtils.getQueryParamValue(
+          from: continueUrl,
+          paramName: "ui_auid"
+        )
+        if shouldHandleAnonymousUpgrade, anonymousUserID == currentUser?.uid {
+          let credential = EmailAuthProvider.credential(withEmail: email, link: link)
+          try await handleAutoUpgradeAnonymousUser(credentials: credential)
+        } else {
+          let result = try await auth.signIn(withEmail: email, link: link)
+        }
         updateAuthenticationState()
         emailLink = nil
       }
@@ -290,6 +333,33 @@ public extension AuthService {
       throw error
     }
   }
+
+  private func updateActionCodeSettings() throws -> ActionCodeSettings {
+    let actionCodeSettings = try safeActionCodeSettings()
+    guard var urlComponents = URLComponents(string: actionCodeSettings.url!.absoluteString) else {
+      throw AuthServiceError
+        .notConfiguredActionCodeSettings(
+          "ActionCodeSettings.url has not been configured for `AuthConfiguration.emailLinkSignInActionCodeSettings`"
+        )
+    }
+
+    var queryItems: [URLQueryItem] = []
+
+    if shouldHandleAnonymousUpgrade {
+      if let currentUser = currentUser {
+        let anonymousUID = currentUser.uid
+        let auidItem = URLQueryItem(name: "ui_auid", value: anonymousUID)
+        queryItems.append(auidItem)
+      }
+    }
+
+    urlComponents.queryItems = queryItems
+    if let finalURL = urlComponents.url {
+      actionCodeSettings.url = finalURL
+    }
+
+    return actionCodeSettings
+  }
 }
 
 // MARK: - Google Sign In

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/Utils/CommonUtils.swift

@@ -46,4 +46,12 @@ public class CommonUtils {
     }
     return hash.map { String(format: "%02x", $0) }.joined()
   }
+
+  public static func getQueryParamValue(from urlString: String, paramName: String) -> String? {
+    guard let urlComponents = URLComponents(string: urlString) else {
+      return nil
+    }
+
+    return urlComponents.queryItems?.first(where: { $0.name == paramName })?.value
+  }
 }

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/Views/EmailAuthView.swift

@@ -125,7 +125,7 @@ extension EmailAuthView: View {
       .frame(maxWidth: .infinity)
       .buttonStyle(.borderedProminent)
       Button(action: {
-        authService.authView = .passwordRecovery
+        authService.authView = .emailLink
       }) {
         Text("Prefer Email link sign-in?")
       }

samples/swiftui/FirebaseSwiftUIExample/FirebaseSwiftUIExample/FirebaseSwiftUIExampleApp.swift

@@ -78,7 +78,7 @@ struct ContentView: View {
   let authService: AuthService
 
   init() {
-    // Auth.auth().signInAnonymously()
+    Auth.auth().signInAnonymously()
 
     let actionCodeSettings = ActionCodeSettings()
     actionCodeSettings.handleCodeInApp = true