Simplifies sign-in with  integration by providing an Environment-driven action similar to `openWindow` and others.

Sign in with Apple.swift

import SwiftUI
import AuthenticationServices

public struct SignInWithAppleAction: Sendable {
    public func callAsFunction() async throws -> ASAuthorization {
        try await Coordinator().perform()
    }
}

public extension EnvironmentValues {
    /// Sign in with Apple using modern concurrency and Swift error handling
    @Entry var signInWithApple: SignInWithAppleAction = .init()
}

private extension SignInWithAppleAction {
    final class Coordinator: NSObject, ASAuthorizationControllerDelegate, Sendable {
        private var continuation: CheckedContinuation<ASAuthorization, Error>?

        func perform() async throws -> ASAuthorization {
            try await withCheckedThrowingContinuation { continuation in
                let provider = ASAuthorizationAppleIDProvider()
                let request = provider.createRequest()
                request.requestedScopes = [.email]

                let controller = ASAuthorizationController(authorizationRequests: [request])
                controller.delegate = self

                DispatchQueue.global(qos: .utility).async {
                    controller.performRequests()
                }

                self.continuation = continuation
            }
        }

        func authorizationController(
            controller: ASAuthorizationController,
            didCompleteWithAuthorization authorization: ASAuthorization
        ) {
            continuation?.resume(returning: authorization)
        }

        func authorizationController(controller: ASAuthorizationController, didCompleteWithError error: any Error) {
            continuation?.resume(throwing: error)
        }
    }
}

extension ASAuthorizationController: @retroactive @unchecked Sendable {}

Example

@Environment(\.signInWithApple) private var signIn

var body: some View {
    Button("Sign in with Apple") {
        Task {
            do {
                let auth = try await signIn()
                print(auth)
            } catch {
                print(error)
            }
        }
    }
}