example of ViewBuilder issue

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/Services/AuthService.swift

@@ -1,9 +1,11 @@
 @preconcurrency import FirebaseAuth
 import SwiftUI
 
-public protocol ExternalAuthProvider {
-  var id: String { get } 
+public protocol ExternalAuthProvider: Identifiable {
+  var id: String { get }
+  associatedtype ButtonType: View
   @MainActor func authButton() -> AnyView
+  @MainActor var authButtonView: Self.ButtonType { get }
 }
 
 public protocol GoogleProviderProtocol: ExternalAuthProvider {
@@ -65,15 +67,9 @@ private final class AuthListenerManager {
 @MainActor
 @Observable
 public final class AuthService {
-  public init(configuration: AuthConfiguration = AuthConfiguration(), auth: Auth = Auth.auth(),
-              googleProvider: (any GoogleProviderProtocol)? = nil,
-              facebookProvider: (any FacebookProviderProtocol)? = nil,
-              phoneAuthProvider: (any PhoneAuthProviderProtocol)? = nil) {
+  public init(configuration: AuthConfiguration = AuthConfiguration(), auth: Auth = Auth.auth()) {
     self.auth = auth
     self.configuration = configuration
-    self.googleProvider = googleProvider
-    self.facebookProvider = facebookProvider
-    self.phoneAuthProvider = phoneAuthProvider
     string = StringUtils(bundle: configuration.customStringsBundle ?? Bundle.module)
     listenerManager = AuthListenerManager(auth: auth, authEnvironment: self)
   }
@@ -96,19 +92,13 @@ public final class AuthService {
   private var listenerManager: AuthListenerManager?
   private var signedInCredential: AuthCredential?
 
-  private var providers: [ExternalAuthProvider] = []
-  public func register(provider: ExternalAuthProvider) {
+  private var providers: [any ExternalAuthProvider] = []
+  public func register(provider: any ExternalAuthProvider) {
     providers.append(provider)
   }
 
-  public func renderButtons(spacing: CGFloat = 16) -> AnyView {
-    AnyView(
-      VStack(spacing: spacing) {
-        ForEach(providers, id: \.id) { provider in
-          provider.authButton()
-        }
-      }
-    )
+  var availableProviders: [any ExternalAuthProvider] {
+    return providers
   }
 
   private var safeGoogleProvider: any GoogleProviderProtocol {

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/Views/AuthPickerView.swift

@@ -28,7 +28,8 @@ extension AuthPickerView: View {
         Text(authService.authenticationFlow == .login ? "Login" : "Sign up")
         VStack { Divider() }
         EmailAuthView()
-        authService.renderButtons()
+        // Xcode compiler exception: Type 'any ExternalAuthProvider' cannot conform to 'ExternalAuthProvider'
+        RenderButtonsView(providers: authService.availableProviders)
         VStack { Divider() }
         HStack {
           Text(authService

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/Views/RenderButtonsView.swift

@@ -0,0 +1,25 @@
+//
+//  RenderButtonsView.swift
+//  FirebaseUI
+//
+//  Created by Russell Wheatley on 08/05/2025.
+//
+import SwiftUI
+
+struct RenderButtonsView<Provider: ExternalAuthProvider>: View {
+  var providers: [Provider] = []
+
+  public func renderButtonViews(spacing: CGFloat = 16) -> some View {
+    VStack(spacing: spacing) {
+      ForEach(providers, id: \.id) { provider in
+        provider.authButtonView
+      }
+    }
+  }
+
+  var body: some View {
+    VStack {
+      renderButtonViews()
+    }
+  }
+}

FirebaseSwiftUI/FirebaseFacebookSwiftUI/Sources/Services/AuthService+Facebook.swift

@@ -11,6 +11,7 @@ public extension AuthService {
   @discardableResult
   func withFacebookSignIn(scopes scopes: [String]? = nil) -> AuthService {
     facebookProvider = FacebookProviderSwift(scopes: scopes)
+    register(provider: facebookProvider!)
     return self
   }
 }

FirebaseSwiftUI/FirebaseFacebookSwiftUI/Sources/Services/FacebookProviderSwift.swift

@@ -35,11 +35,15 @@ public class FacebookProviderSwift: FacebookProviderProtocol {
     rawNonce = CommonUtils.randomNonce()
     shaNonce = CommonUtils.sha256Hash(of: rawNonce)
   }
-  
+
   @MainActor public func authButton() -> AnyView {
     AnyView(SignInWithFacebookButton())
   }
 
+  @MainActor public var authButtonView: some View {
+    SignInWithFacebookButton()
+  }
+
   @MainActor public func signInWithFacebook(isLimitedLogin: Bool) async throws -> AuthCredential {
     let trackingStatus = ATTrackingManager.trackingAuthorizationStatus
     let tracking: LoginTracking = trackingStatus != .authorized ? .limited :

FirebaseSwiftUI/FirebaseGoogleSwiftUI/Sources/Services/GoogleProviderSwift.swift

@@ -34,6 +34,14 @@ public class GoogleProviderSwift: @preconcurrency GoogleProviderProtocol {
     })
   }
 
+  @MainActor public var authButtonView: some View {
+    GoogleSignInButton {
+      Task {
+        try await self.signInWithGoogle(clientID: self.clientID)
+      }
+    }
+  }
+
   @MainActor public func signInWithGoogle(clientID: String) async throws -> AuthCredential {
     guard let presentingViewController = await (UIApplication.shared.connectedScenes
       .first as? UIWindowScene)?.windows.first?.rootViewController else {

FirebaseSwiftUI/FirebasePhoneAuthSwiftUI/Sources/Services/PhoneAuthProviderSwift.swift

@@ -7,11 +7,15 @@ public typealias VerificationID = String
 public class PhoneAuthProviderSwift: @preconcurrency PhoneAuthProviderProtocol {
   public let id: String = "phone"
   public init() {}
-  
+
   @MainActor public func authButton() -> AnyView {
     AnyView(Text("phone button TODO"))
   }
 
+  @MainActor public var authButtonView: some View {
+    Text("phone button TODO")
+  }
+
   @MainActor public func verifyPhoneNumber(phoneNumber: String) async throws -> VerificationID {
     return try await withCheckedThrowingContinuation { continuation in
       PhoneAuthProvider.provider()

samples/swiftui/FirebaseSwiftUIExample/FirebaseSwiftUIExample/FirebaseSwiftUIExampleApp.swift

@@ -91,12 +91,9 @@ struct ContentView: View {
       shouldAutoUpgradeAnonymousUsers: true,
       emailLinkSignInActionCodeSettings: actionCodeSettings
     )
-    let facebookProvider = FacebookProviderSwift()
-    let phoneAuthProvider = PhoneAuthProviderSwift()
+
     authService = AuthService(
-      configuration: configuration,
-      facebookProvider: facebookProvider,
-      phoneAuthProvider: phoneAuthProvider
+      configuration: configuration
     )
     // Transition to this api
     .withGoogleSignIn()