Add foundation for presenting authorization flow without a window or view controller

Package.swift

@@ -64,22 +64,33 @@ let package = Package(
             path: "Source/AppAuthTV",
             publicHeadersPath: ""
         ),
+        .target(
+            name: "TestHelpers",
+            dependencies: ["AppAuthCore"],
+            path: "UnitTests/Helpers",
+            publicHeadersPath: ""
+        ),
         .testTarget(
             name: "AppAuthCoreTests",
-            dependencies: ["AppAuthCore"],
-            path: "UnitTests",
-            exclude: ["OIDSwiftTests.swift", "AppAuthTV"]
+            dependencies: ["AppAuthCore", "TestHelpers"],
+            path: "UnitTests/AppAuthCore",
+            exclude: ["OIDSwiftTests.swift"]
+        ),
+        .testTarget(
+            name: "AppAuthTests",
+            dependencies: ["AppAuth", "TestHelpers"],
+            path: "UnitTests/AppAuth"
         ),
         .testTarget(
             name: "AppAuthCoreSwiftTests",
             dependencies: ["AppAuthCore"],
-            path: "UnitTests",
+            path: "UnitTests/AppAuthCore",
             sources: ["OIDSwiftTests.swift"]
         ),
         .testTarget(
             name: "AppAuthTVTests",
             dependencies: ["AppAuthTV"],
             path: "UnitTests/AppAuthTV"
-        ),
+        )
     ]
 )

Source/AppAuth/iOS/OIDAuthorizationService+IOS.h

@@ -60,6 +60,32 @@ NS_ASSUME_NONNULL_BEGIN
      prefersEphemeralSession:(BOOL)prefersEphemeralSession
                     callback:(OIDAuthorizationCallback)callback API_AVAILABLE(ios(13));
 
+/*! @brief Perform an authorization flow using the @c ASWebAuthenticationSession optionally using an
+        emphemeral browser session that shares no cookies or data with the normal browser session.
+    @param request The authorization request.
+    @param callback The method called when the request has completed or failed.
+    @return A @c OIDExternalUserAgentSession instance which will terminate when it
+        receives a @c OIDExternalUserAgentSession.cancel message, or after processing a
+        @c OIDExternalUserAgentSession.resumeExternalUserAgentFlowWithURL: message.
+ */
++ (id<OIDExternalUserAgentSession>)presentAuthorizationRequest:(OIDAuthorizationRequest *)request
+                                                      callback:(OIDAuthorizationCallback)callback;
+
+/*! @brief Perform an authorization flow using the @c ASWebAuthenticationSession optionally using an
+        emphemeral browser session that shares no cookies or data with the normal browser session.
+    @param request The authorization request.
+    @param prefersEphemeralSession Whether the caller prefers to use a private authentication
+        session. See @c ASWebAuthenticationSession.prefersEphemeralWebBrowserSession for more.
+    @param callback The method called when the request has completed or failed.
+    @return A @c OIDExternalUserAgentSession instance which will terminate when it
+        receives a @c OIDExternalUserAgentSession.cancel message, or after processing a
+        @c OIDExternalUserAgentSession.resumeExternalUserAgentFlowWithURL: message.
+ */
++ (id<OIDExternalUserAgentSession>)presentAuthorizationRequest:(OIDAuthorizationRequest *)request
+                                       prefersEphemeralSession:(BOOL)prefersEphemeralSession
+                                                      callback:(OIDAuthorizationCallback)callback
+    API_AVAILABLE(ios(13));
+
 @end
 
 NS_ASSUME_NONNULL_END

Source/AppAuth/iOS/OIDAuthorizationService+IOS.m

@@ -57,6 +57,46 @@ @implementation OIDAuthorizationService (IOS)
   return [self presentAuthorizationRequest:request externalUserAgent:externalUserAgent callback:callback];
 }
 
++ (id<OIDExternalUserAgentSession>)presentAuthorizationRequest:(OIDAuthorizationRequest *)request
+                                                      callback:(OIDAuthorizationCallback)callback {
+  return [self presentAuthorizationRequest:request
+        prefersEphemeralSessionIfAvailable:NO
+                                  callback:callback];
+}
+
++ (id<OIDExternalUserAgentSession>)presentAuthorizationRequest:(OIDAuthorizationRequest *)request
+                                       prefersEphemeralSession:(BOOL)prefersEphemeralSession
+                                                      callback:(OIDAuthorizationCallback)callback {
+  return [self presentAuthorizationRequest:request
+        prefersEphemeralSessionIfAvailable:prefersEphemeralSession
+                                  callback:callback];
+}
+
++ (id<OIDExternalUserAgentSession>)presentAuthorizationRequest:(OIDAuthorizationRequest *)request
+                            prefersEphemeralSessionIfAvailable:(BOOL)prefersEphemeralSession
+                                                      callback:(OIDAuthorizationCallback)callback {
+  id<OIDExternalUserAgent> externalUserAgent;
+
+  if (@available(iOS 13, *)) {
+#if TARGET_OS_MACCATALYST
+    externalUserAgent = [[OIDExternalUserAgentCatalyst alloc]
+                            initWithPrefersEphemeralSession:prefersEphemeralSession];
+#else // TARGET_OS_MACCATALYST
+    externalUserAgent = [[OIDExternalUserAgentIOS alloc]
+                            initWithPrefersEphemeralSession:prefersEphemeralSession];
+#endif // TARGET_OS_MACCATALYST
+  } else {
+#if TARGET_OS_MACCATALYST
+    externalUserAgent = [[OIDExternalUserAgentCatalyst alloc] init];
+#else // TARGET_OS_MACCATALYST
+    externalUserAgent = [[OIDExternalUserAgentIOS alloc] init];
+#endif // TARGET_OS_MACCATALYST
+  }
+  return [self presentAuthorizationRequest:request
+                         externalUserAgent:externalUserAgent
+                                  callback:callback];
+}
+
 @end
 
 NS_ASSUME_NONNULL_END

Source/AppAuth/iOS/OIDExternalUserAgentCatalyst.h

@@ -32,18 +32,27 @@ NS_ASSUME_NONNULL_BEGIN
 API_AVAILABLE(macCatalyst(13)) API_UNAVAILABLE(ios)
 @interface OIDExternalUserAgentCatalyst : NSObject<OIDExternalUserAgent>
 
-/*! @internal
-    @brief Unavailable. Please use @c initWithPresentingViewController:
+/*! @brief Create an external user-agent.
+    @discussion The specific authentication UI used depends on the iOS version and accessibility
+        options. iOS 8 uses the system browser, iOS 9-10 use @c SFSafariViewController, iOS 11 uses
+        @c SFAuthenticationSession (unless Guided Access is on which does not work) or uses
+        @c SFSafariViewController, and iOS 12+ uses @c ASWebAuthenticationSession (unless Guided
+        Access is on).
  */
-- (nonnull instancetype)init NS_UNAVAILABLE;
+- (nonnull instancetype)init;
 
-/*! @brief The designated initializer.
+/*! @brief Create an external user-agent which optionally uses a private authentication session.
+    @param prefersEphemeralSession Whether the caller prefers to use a private authentication
+        session. See @c ASWebAuthenticationSession.prefersEphemeralWebBrowserSession for more.
+ */
+- (nullable instancetype)initWithPrefersEphemeralSession:(BOOL)prefersEphemeralSession;
+
+/*! @brief Create an external user-agent with a presenting view controller.
     @param presentingViewController The view controller from which to present the
         \SFSafariViewController.
  */
 - (nullable instancetype)initWithPresentingViewController:
-    (UIViewController *)presentingViewController
-    NS_DESIGNATED_INITIALIZER;
+    (UIViewController *)presentingViewController;
 
 /*! @brief Create an external user-agent which optionally uses a private authentication session.
     @param presentingViewController The view controller from which to present the browser.

Source/AppAuth/iOS/OIDExternalUserAgentCatalyst.m

@@ -45,9 +45,22 @@ @implementation OIDExternalUserAgentCatalyst {
   ASWebAuthenticationSession *_webAuthenticationVC;
 }
 
+- (nonnull instancetype)init {
+  self = [super init];
+  return self;
+}
+
+- (nullable instancetype)initWithPrefersEphemeralSession:(BOOL)prefersEphemeralSession {
+  self = [self init];
+  if (self) {
+    _prefersEphemeralSession = prefersEphemeralSession;
+  }
+  return self;
+}
+
 - (nullable instancetype)initWithPresentingViewController:
     (UIViewController *)presentingViewController {
-  self = [super init];
+  self = [self init];
   if (self) {
     _presentingViewController = presentingViewController;
   }
@@ -71,6 +84,38 @@ - (BOOL)presentExternalUserAgentRequest:(id<OIDExternalUserAgentRequest>)request
     return NO;
   }
 
+  if (!_presentingViewController) {
+    // Find presentingViewController
+    if (@available(iOS 13.0, *)) {
+      NSSet<UIWindowScene *> *scenes =
+          (NSSet<UIWindowScene *> *)[UIApplication sharedApplication].connectedScenes;
+
+      NSMutableArray<UIWindow *> *windows = [NSMutableArray array];
+
+      for (UIWindowScene *scene in scenes) {
+        [windows addObjectsFromArray:scene.windows];
+      }
+
+      for (UIWindow *window in windows) {
+        if (window.isKeyWindow) { // False if calling before window appears
+          UIWindow *keyWindow = window;
+          _presentingViewController = keyWindow.rootViewController;
+          break;
+        }
+      }
+    } else {
+      // ≤ iOS 12.X
+      NSArray<UIWindow *> *windows = UIApplication.sharedApplication.windows;
+      NSPredicate *keyWindowPredicate = [NSPredicate predicateWithFormat:@"keyWindow == YES"];
+      UIWindow *keyWindow = [windows filteredArrayUsingPredicate:keyWindowPredicate].firstObject;
+      _presentingViewController = keyWindow.rootViewController;
+    }
+    if (!_presentingViewController) {
+      // Unable to find a presentingViewController; perhaps because no window is key and visible
+      return NO;
+    }
+  }
+
   _externalUserAgentFlowInProgress = YES;
   _session = session;
   BOOL openedUserAgent = NO;

Source/AppAuth/iOS/OIDExternalUserAgentIOS.h

@@ -34,21 +34,25 @@ NS_ASSUME_NONNULL_BEGIN
 API_UNAVAILABLE(macCatalyst)
 @interface OIDExternalUserAgentIOS : NSObject<OIDExternalUserAgent>
 
-- (nullable instancetype)init API_AVAILABLE(ios(11))
-    __deprecated_msg("This method will not work on iOS 13, use "
-                     "initWithPresentingViewController:presentingViewController");
+/*! @brief Create an external user-agent.
+    @discussion The specific authentication UI used depends on the iOS version and accessibility
+        options. iOS 8 uses the system browser, iOS 9-10 use @c SFSafariViewController, iOS 11 uses
+        @c SFAuthenticationSession (unless Guided Access is on which does not work) or uses
+        @c SFSafariViewController, and iOS 12+ uses @c ASWebAuthenticationSession (unless Guided
+        Access is on).
+ */
+- (nullable instancetype)init;
 
-/*! @brief The designated initializer.
+/*! @brief Create an external user-agent with the presenting view controller.
     @param presentingViewController The view controller from which to present the authentication UI.
     @discussion The specific authentication UI used depends on the iOS version and accessibility
         options. iOS 8 uses the system browser, iOS 9-10 use @c SFSafariViewController, iOS 11 uses
-        @c SFAuthenticationSession
-        (unless Guided Access is on which does not work) or uses @c SFSafariViewController, and iOS
-        12+ uses @c ASWebAuthenticationSession (unless Guided Access is on).
+        @c SFAuthenticationSession (unless Guided Access is on which does not work) or uses
+        @c SFSafariViewController, and iOS 12+ uses @c ASWebAuthenticationSession (unless Guided
+        Access is on).
  */
 - (nullable instancetype)initWithPresentingViewController:
-    (UIViewController *)presentingViewController
-    NS_DESIGNATED_INITIALIZER;
+    (UIViewController *)presentingViewController;
 
 /*! @brief Create an external user-agent which optionally uses a private authentication session.
     @param presentingViewController The view controller from which to present the browser.
@@ -62,6 +66,15 @@ API_UNAVAILABLE(macCatalyst)
                                   prefersEphemeralSession:(BOOL)prefersEphemeralSession
     API_AVAILABLE(ios(13));
 
+/*! @brief Create an external user-agent which optionally uses a private authentication session.
+    @param prefersEphemeralSession Whether the caller prefers to use a private authentication
+        session. See @c ASWebAuthenticationSession.prefersEphemeralWebBrowserSession for more.
+    @discussion Authentication is performed with @c ASWebAuthenticationSession (unless Guided Access
+        is on), setting the ephemerality based on the argument.
+ */
+- (nullable instancetype)initWithPrefersEphemeralSession:(BOOL)prefersEphemeralSession
+    API_AVAILABLE(ios(13));
+
 @end
 
 NS_ASSUME_NONNULL_END

Source/AppAuth/iOS/OIDExternalUserAgentIOS.m

@@ -56,21 +56,22 @@ @implementation OIDExternalUserAgentIOS {
 }
 
 - (nullable instancetype)init {
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wnonnull"
-  return [self initWithPresentingViewController:nil];
-#pragma clang diagnostic pop
+  self = [super init];
+  return self;
+}
+
+- (nullable instancetype)initWithPrefersEphemeralSession:(BOOL)prefersEphemeralSession {
+  self = [self init];
+  if (self) {
+    _prefersEphemeralSession = prefersEphemeralSession;
+  }
+  return self;
 }
 
 - (nullable instancetype)initWithPresentingViewController:
     (UIViewController *)presentingViewController {
-  self = [super init];
+  self = [self init];
   if (self) {
-#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 130000
-    NSAssert(presentingViewController != nil,
-             @"presentingViewController cannot be nil on iOS 13");
-#endif // __IPHONE_OS_VERSION_MAX_ALLOWED >= 130000
-
     _presentingViewController = presentingViewController;
   }
   return self;
@@ -93,6 +94,38 @@ - (BOOL)presentExternalUserAgentRequest:(id<OIDExternalUserAgentRequest>)request
     return NO;
   }
 
+  if (!_presentingViewController) {
+    // Find presentingViewController
+    if (@available(iOS 13.0, *)) {
+      NSSet<UIWindowScene *> *scenes =
+          (NSSet<UIWindowScene *> *)[UIApplication sharedApplication].connectedScenes;
+
+      NSMutableArray<UIWindow *> *windows = [NSMutableArray array];
+
+      for (UIWindowScene *scene in scenes) {
+        [windows addObjectsFromArray:scene.windows];
+      }
+
+      for (UIWindow *window in windows) {
+        if (window.isKeyWindow) { // False if calling before window appears
+          UIWindow *keyWindow = window;
+          _presentingViewController = keyWindow.rootViewController;
+          break;
+        }
+      }
+    } else {
+      // ≤ iOS 12.X
+      NSArray<UIWindow *> *windows = UIApplication.sharedApplication.windows;
+      NSPredicate *keyWindowPredicate = [NSPredicate predicateWithFormat:@"keyWindow == YES"];
+      UIWindow *keyWindow = [windows filteredArrayUsingPredicate:keyWindowPredicate].firstObject;
+      _presentingViewController = keyWindow.rootViewController;
+    }
+    if (!_presentingViewController) {
+      // Unable to find a presentingViewController; perhaps because no window is key and visible
+      return NO;
+    }
+  }
+
   _externalUserAgentFlowInProgress = YES;
   _session = session;
   BOOL openedUserAgent = NO;

UnitTests/AppAuth/OIDExternUserAgentTests.m

@@ -0,0 +1,60 @@
+/*! @file OIDExternalUserAgentTests.m
+   @brief AppAuth iOS SDK
+   @copyright
+       Copyright 2023 The AppAuth Authors. All Rights Reserved.
+   @copydetails
+       Licensed under the Apache License, Version 2.0 (the "License");
+       you may not use this file except in compliance with the License.
+       You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+       Unless required by applicable law or agreed to in writing, software
+       distributed under the License is distributed on an "AS IS" BASIS,
+       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+       See the License for the specific language governing permissions and
+       limitations under the License.
+*/
+
+#import <TargetConditionals.h>
+
+#import <XCTest/XCTest.h>
+
+#if SWIFT_PACKAGE
+@import AppAuth;
+@import TestHelpers;
+#else
+#import "Source/AppAuth/iOS/OIDExternalUserAgentCatalyst.h"
+#import "Source/AppAuth/iOS/OIDExternalUserAgentIOS.h"
+#import "Source/AppAuthCore/OIDError.h"
+#import "UnitTests/TestHelpers/OIDAuthorizationRequest+TestHelper.h"
+#endif
+
+@interface OIDExternalUserAgentTests : XCTestCase
+
+@end
+
+@implementation OIDExternalUserAgentTests
+
+- (void)testThatPresentExternalUserAgentRequestReturnsNoWhenMissingPresentingViewController {
+  id<OIDExternalUserAgent> userAgent;
+
+#if TARGET_OS_MACCATALYST
+  userAgent = [[OIDExternalUserAgentCatalyst alloc] init];
+#elif TARGET_OS_IOS
+  userAgent = [[OIDExternalUserAgentIOS alloc] init];
+#endif
+
+  OIDAuthorizationRequest *authRequest = [OIDAuthorizationRequest testInstance];
+  [OIDAuthorizationService
+      presentAuthorizationRequest:authRequest
+      externalUserAgent:userAgent
+      callback:^(OIDAuthorizationResponse * _Nullable authorizationResponse,
+                 NSError * _Nullable error) {
+    XCTAssertNotNil(error);
+    XCTAssertEqual(error.code, OIDErrorCodeSafariOpenError);
+    XCTAssertEqualObjects(error.localizedDescription, @"Unable to open Safari.");
+  }];
+}
+
+@end