example of ViewBuilder issue

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/Services/AuthService.swift

@@ -1,11 +1,11 @@
 @preconcurrency import FirebaseAuth
 import SwiftUI
 
-public protocol ExternalAuthProvider {
+public protocol ExternalAuthProvider: Identifiable {
   var id: String { get }
   associatedtype ButtonType: View
-  @MainActor @ViewBuilder func authButtonView() -> ButtonType
   @MainActor func authButton() -> AnyView
+  @MainActor var authButtonView: Self.ButtonType { get }
 }
 
 public protocol GoogleProviderProtocol: ExternalAuthProvider {
@@ -97,35 +97,10 @@ public final class AuthService {
     providers.append(provider)
   }
 
-  public func renderButtons(spacing: CGFloat = 16) -> AnyView {
-    AnyView(
-      VStack(spacing: spacing) {
-        ForEach(providers, id: \.id) { provider in
-          provider.authButton()
-        }
-      }
-    )
-  }
-
-  @ViewBuilder
-  public var googleButton: some View {
-    if googleProvider != nil {
-      // For purpose of demonstration
-      // This produces "Type 'any View' cannot conform to 'View'"
-      googleProvider!.authButtonView()
-    } else {
-      EmptyView()
-    }
+  var availableProviders: [any ExternalAuthProvider] {
+    return providers
   }
 
-//  public func renderButtonViews(spacing: CGFloat = 16) -> some View {
-//    VStack(spacing: spacing) {
-//      ForEach(providers, id: \.id) { provider in
-//        provider.authButtonView()
-//      }
-//    }
-//  }
-
   private var safeGoogleProvider: any GoogleProviderProtocol {
     get throws {
       guard let provider = googleProvider else {

FirebaseSwiftUI/FirebaseAuthSwiftUI/Sources/Views/AuthPickerView.swift

@@ -28,7 +28,8 @@ extension AuthPickerView: View {
         Text(authService.authenticationFlow == .login ? "Login" : "Sign up")
         VStack { Divider() }
         EmailAuthView()
-
+        // 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

@@ -40,7 +40,7 @@ public class FacebookProviderSwift: FacebookProviderProtocol {
     AnyView(SignInWithFacebookButton())
   }
 
-  @MainActor @ViewBuilder public func authButtonView() -> some View {
+  @MainActor public var authButtonView: some View {
     SignInWithFacebookButton()
   }
 

FirebaseSwiftUI/FirebaseGoogleSwiftUI/Sources/Services/GoogleProviderSwift.swift

@@ -34,7 +34,7 @@ public class GoogleProviderSwift: @preconcurrency GoogleProviderProtocol {
     })
   }
 
-  @MainActor @ViewBuilder public func authButtonView() -> some View {
+  @MainActor public var authButtonView: some View {
     GoogleSignInButton {
       Task {
         try await self.signInWithGoogle(clientID: self.clientID)

FirebaseSwiftUI/FirebasePhoneAuthSwiftUI/Sources/Services/PhoneAuthProviderSwift.swift

@@ -12,7 +12,7 @@ public class PhoneAuthProviderSwift: @preconcurrency PhoneAuthProviderProtocol {
     AnyView(Text("phone button TODO"))
   }
 
-  @MainActor @ViewBuilder public func authButtonView() -> some View {
+  @MainActor public var authButtonView: some View {
     Text("phone button TODO")
   }