fix: use ASWebAuthenticationSession for log in

Sources/NextcloudKitUI/Views/Login/LoginFlowModel.swift

@@ -2,6 +2,7 @@
 // SPDX-FileCopyrightText: 2026 Milen Pivchev
 // SPDX-License-Identifier: GPL-3.0-or-later
 
+import AuthenticationServices
 #if os(iOS)
 import CodeScanner
 #endif
@@ -40,8 +41,8 @@ final class LoginFlowModel: QRCodeParsing, URLSanitizing {
     /// State toggle for presenting the error alert.
     var isPresentingAlert = false
 
-    /// State toggle for presenting the web view.
-    var isPresentingWebView = false
+    /// State toggle for presenting the login page in the system browser.
+    var isPresentingLoginPage = false
 
     /// The login address acquired from the server through the login flow API.
     var loginAddress: URL?
@@ -87,7 +88,7 @@ final class LoginFlowModel: QRCodeParsing, URLSanitizing {
                 startPolling(token: token, endpoint: endpoint)
 
                 loginAddress = login
-                isPresentingWebView = true
+                isPresentingLoginPage = true
             } catch {
                 endLogin(error)
             }
@@ -124,21 +125,36 @@ final class LoginFlowModel: QRCodeParsing, URLSanitizing {
         }
     }
 
+    func presentLoginPage(_ url: URL, using session: WebAuthenticationSession) async {
+        do {
+            _ = try await session.authenticate(using: url, callbackURLScheme: "nc", preferredBrowserSession: .ephemeral)
+        } catch {
+            // Already handled when the login completed or was cancelled.
+            guard isPresentingLoginPage else { return }
+
+            if let error = error as? ASWebAuthenticationSessionError, error.code == .canceledLogin {
+                cancel()
+            } else {
+                endLogin(error)
+            }
+        }
+    }
+
     private func complete(host: URL, name: String, password: String) {
         pollingTask = nil
         isActive = false
-        isPresentingWebView = false
+        isPresentingLoginPage = false
         addAccount(host, name, password)
     }
 
     ///
-    /// Stop polling. Called when the web view is dismissed, regardless of the reason.
+    /// Stop polling. Called when the login page is closed, regardless of the reason.
     ///
     func cancel() {
         pollingTask?.cancel()
         pollingTask = nil
         isActive = false
-        isPresentingWebView = false
+        isPresentingLoginPage = false
     }
 
     private func endLogin(_ error: Error?) {

Sources/NextcloudKitUI/Views/Login/ServerAddressView.swift

@@ -2,6 +2,7 @@
 // SPDX-FileCopyrightText: 2025 Iva Horn
 // SPDX-License-Identifier: GPL-3.0-or-later
 
+import AuthenticationServices
 import SwiftUI
 
 ///
@@ -18,7 +19,6 @@
 public struct ServerAddressView: View {
     let brandImage: Image
     var sharedAccounts: [SharedAccount]
-    let userAgent: String?
 
     ///
     /// Create a new server address view.
@@ -27,21 +27,21 @@
     ///     - backgroundColor: The main theme color the view should use. Foreground color will be adapted automatically based on this.
     ///     - brandImage: The image to display on top of the server address view. Falls back to an SF Symbol placeholder in case of `nil`.
     ///     - sharedAccounts: Any shared accounts from the app group being available for selection and faster login.
-    ///     - userAgent: An optional user agent string to override the one used by ``WKWebView``.
+    ///     - userAgent: An optional user agent for server requests.
     ///     - addAccount: see ``AddAccountHandler``.
     ///
     public init(backgroundColor: Binding<Color>, brandImage: Image, sharedAccounts: [SharedAccount], userAgent: String? = nil, addAccount: @escaping AddAccountHandler) {
         self._backgroundColor = backgroundColor
         self.brandImage = brandImage
         self.sharedAccounts = sharedAccounts
-        self.userAgent = userAgent
         self._model = State(initialValue: LoginFlowModel(userAgent: userAgent, addAccount: addAccount))
     }
 
     // MARK: - Environment
 
     @Environment(\.horizontalSizeClass) var horizontalSizeClass
     @Environment(\.verticalSizeClass) var verticalSizeClass
+    @Environment(\.webAuthenticationSession) private var webAuthenticationSession
 
     // MARK: - Bindings
 
@@ -161,7 +161,12 @@
             .safeAreaPadding(.all)
         }
         .ignoresSafeArea()
-        .webSheet(initialURL: $model.loginAddress, isPresented: $model.isPresentingWebView, userAgent: userAgent, onDismiss: { model.cancel() })
+        .task(id: model.isPresentingLoginPage) {
+            // Clearing the flag cancels this task, which closes the browser sheet.
+            guard model.isPresentingLoginPage, let loginAddress = model.loginAddress else { return }
+
+            await model.presentLoginPage(loginAddress, using: webAuthenticationSession)
+        }
         .alert(String(localized: "Login Failed", bundle: .module, comment: "Alert title"), isPresented: $model.isPresentingAlert) {
             Button(role: .cancel) {
                 model.errorMessage = nil
@@ -176,7 +181,7 @@
 
 #if DEBUG
 
 // swiftlint:disable force_unwrapping
 
 #Preview("Without Shared Accounts") {
     let backgroundColor: Binding<Color> = .constant(.accentColor)

Sources/NextcloudKitUI/Views/Login/WebView.swift

@@ -16,17 +16,13 @@
 /// All of the web view session data is not persistent.
 ///
 public struct WebView: ViewRepresentable {
-    ///
-    /// This must be a binding to support presentation inside sheets.
-    /// The way this view gets created and updated inside a sheet has a race condition with sheet presentation.
-    /// A sheet might be displayed before a passed in state variable might have been set.
-    ///
-    @Binding var initialURL: URL?
+    /// Loaded once when the web view is created, so SwiftUI updates don't reload the page.
+    let initialURL: URL?
 
     let userAgent: String?
 
-    public init(initialURL: Binding<URL?>, userAgent: String? = nil) {
-        self._initialURL = initialURL
+    public init(initialURL: URL?, userAgent: String? = nil) {
+        self.initialURL = initialURL
         self.userAgent = userAgent
     }
 
@@ -41,17 +37,11 @@
             webView.customUserAgent = userAgent
         }
 
-        return webView
-    }
-
-    func updateView(_ webView: WKWebView, context: Context) {
-
-        guard let initialURL = initialURL else {
-            return
+        if let initialURL {
+            webView.load(URLRequest(url: initialURL))
         }
 
-        let request = URLRequest(url: initialURL)
-        webView.load(request)
+        return webView
     }
 
     // MARK: - macOS
@@ -62,9 +52,7 @@
         makeView()
     }
 
-    public func updateNSView(_ webView: WKWebView, context: Context) {
-        updateView(webView, context: context)
-    }
+    public func updateNSView(_ webView: WKWebView, context: Context) {}
 
     // MARK: - iOS
 
@@ -74,14 +62,12 @@
         makeView()
     }
 
-    public func updateUIView(_ webView: WKWebView, context: Context) {
-        updateView(webView, context: context)
-    }
+    public func updateUIView(_ webView: WKWebView, context: Context) {}
 
     #endif
 }
 
 #Preview {
     // swiftlint:disable force_unwrapping
-    WebView(initialURL: .constant(URL(string: "http://localhost:8080")!), userAgent: nil)
+    WebView(initialURL: URL(string: "http://localhost:8080")!, userAgent: nil)
 }