[Foundation] Improve cookie storage a bit in NSUrlSessionHandler. Fixes #23950.

src/Foundation/NSUrlSessionHandler.cs

@@ -399,27 +399,42 @@ public CookieContainer? CookieContainer {
 			}
 		}
 
+		/// <summary>Enable or disable the use of cookies.</summary>
+		/// <remarks>
+		///   <para>
+		///       For default and background sessions, the shared cookie storage (<see cref="NSHttpCookieStorage.SharedStorage" /> will be used.
+		///       This shared cookie storage will persist beyond app restarts; to clear the cookies call <c>NSHttpCookieStorage.SharedStorage.RemoveCookiesSinceDate(NSDate.DistantPast)</c>.
+		///       To use a custom cookie storage, use a custom <see cref="NSUrlSessionConfiguration" />, set the <see cref="NSUrlSessionConfiguration.HttpCookieStorage" /> property, and then pass in the custom session configuration when creating the <see cref="NSUrlSessionHandler(NSUrlSessionConfiguration)" />.
+		///   </para>
+		///   <para>Ephemeral sessions have by default a private cookie storage area. This private cookie storage area can't be recreated, which means that if the use of cookies is disabled, then it can't be re-enabled.</para>
+		/// </remarks>
 		public bool UseCookies {
 			get {
 				return session.Configuration.HttpCookieStorage is not null;
 			}
 			set {
 				EnsureModifiability ();
-				if (sessionType == NSUrlSessionConfiguration.SessionConfigurationType.Ephemeral)
-					throw new InvalidOperationException ("Cannot set the use of cookies in Ephemeral sessions.");
+
+				// first check if anything changed
+				if (value == UseCookies)
+					return;
+
 				// we have to consider the following table of cases:
-				// 1. Value is set to true and cookie storage is not null -> we do nothing
+				// 1. Value is set to true and cookie storage is not null -> we do nothing (already handled above)
 				// 2. Value is set to true and cookie storage is null -> we create/set the storage.
 				// 3. Value is false and cookie container is not null -> we clear the cookie storage
-				// 4. Value is false and cookie container is null -> we do nothing
+				// 4. Value is false and cookie container is null -> we do nothing (already handled above)
 				var oldSession = session;
 				var configuration = session.Configuration;
 				if (value && configuration.HttpCookieStorage is null) {
 					// create storage because the user wants to use it. Things are not that easy, we have to 
 					// consider the following:
 					// 1. Default Session -> uses sharedHTTPCookieStorage
 					// 2. Background Session -> uses sharedHTTPCookieStorage
-					// 3. Ephemeral Session -> no allowed. apple does not provide a way to access to the private implementation of the storage class :/
+					// 3. Ephemeral Session -> we can't create an instance of a private cookie storage. Note that ephemeral sessions have a private cookie storage by default, so this can only happen if the developer disables cookies, and then re-enables them.
+					if (sessionType == NSUrlSessionConfiguration.SessionConfigurationType.Ephemeral)
+						throw new InvalidOperationException ("Can't re-enable the use of cookies in Ephemeral sessions.");
+
 					configuration.HttpCookieStorage = NSHttpCookieStorage.SharedStorage;
 				}
 				if (!value && configuration.HttpCookieStorage is not null) {

tests/monotouch-test/System.Net.Http/MessageHandlers.cs

@@ -64,9 +64,22 @@ public void DnsFailure (Type handlerType)
 			Assert.IsInstanceOf (typeof (HttpRequestException), ex, "Exception");
 		}
 
-		// ensure that we do get the same cookies as the managed handler
+		// ensure that we do get the same cookies as the managed handler for the default session
 		[Test]
 		public void TestNSUrlSessionHandlerCookies ()
+		{
+			TestNSUrlSessionHandlerCookiesImpl (new NSUrlSessionHandler ());
+		}
+
+		// ensure that we do get the same cookies as the managed handler for ephemeral sessions
+		[Test]
+		public void TestNSUrlSessionEphemeralHandlerCookies ()
+		{
+			using var ephemeralConfig = NSUrlSessionConfiguration.EphemeralSessionConfiguration;
+			TestNSUrlSessionHandlerCookiesImpl (new NSUrlSessionHandler (ephemeralConfig));
+		}
+
+		void TestNSUrlSessionHandlerCookiesImpl (NSUrlSessionHandler nativeHandler)
 		{
 			var managedCookieResult = false;
 			var nativeCookieResult = false;
@@ -82,13 +95,12 @@ public void TestNSUrlSessionHandlerCookies ()
 				var managedResponse = await managedClient.GetAsync (url);
 				managedCookieResult = managedResponse.Headers.TryGetValues ("Set-Cookie", out managedCookies);
 
-				var nativeHandler = new NSUrlSessionHandler () {
-					AllowAutoRedirect = false,
-				};
 				nativeHandler.AllowAutoRedirect = true;
 				var nativeClient = new HttpClient (nativeHandler);
 				var nativeResponse = await nativeClient.GetAsync (url);
 				nativeCookieResult = nativeResponse.Headers.TryGetValues ("Set-Cookie", out nativeCookies);
+
+				Assert.That (nativeHandler.UseCookies, Is.EqualTo (true), "UseCookies");
 			}, out var ex);
 
 			if (!completed || !managedCookieResult || !nativeCookieResult)
@@ -106,6 +118,18 @@ public void TestNSUrlSessionHandlerCookies ()
 		// ensure that we can use a cookie container to set the cookies for a url
 		[Test]
 		public void TestNSUrlSessionHandlerCookieContainer ()
+		{
+			TestNSUrlSessionHandlerCookieContainerImpl (new NSUrlSessionHandler ());
+		}
+
+		[Test]
+		public void TestNSUrlSessionEphemeralHandlerCookieContainer ()
+		{
+			using var ephemeralConfig = NSUrlSessionConfiguration.EphemeralSessionConfiguration;
+			TestNSUrlSessionHandlerCookieContainerImpl (new NSUrlSessionHandler (ephemeralConfig));
+		}
+
+		void TestNSUrlSessionHandlerCookieContainerImpl (NSUrlSessionHandler nativeHandler)
 		{
 			var url = NetworkResources.Httpbin.CookiesUrl;
 			var cookie = new Cookie ("cookie", "chocolate-chip");
@@ -124,10 +148,8 @@ public void TestNSUrlSessionHandlerCookieContainer ()
 				var managedResponse = await managedClient.GetAsync (url);
 				managedCookieResult = await managedResponse.Content.ReadAsStringAsync ();
 
-				var nativeHandler = new NSUrlSessionHandler () {
-					AllowAutoRedirect = true,
-					CookieContainer = cookieContainer,
-				};
+				nativeHandler.AllowAutoRedirect = true;
+				nativeHandler.CookieContainer = cookieContainer;
 				var nativeClient = new HttpClient (nativeHandler);
 				var nativeResponse = await nativeClient.GetAsync (url);
 				nativeCookieResult = await nativeResponse.Content.ReadAsStringAsync ();
@@ -255,14 +277,25 @@ public void TestNSUrlSessionDefaultDisableCookiesWithManagedContainer ()
 		[Test]
 		public void TestNSUrlSessionEphemeralDisabledCookies ()
 		{
-			// assert we do throw an exception with ephmeral configs.
-			using (var config = NSUrlSessionConfiguration.EphemeralSessionConfiguration) {
-				Assert.True (config.SessionType == NSUrlSessionConfiguration.SessionConfigurationType.Ephemeral, "Session type.");
-				var nativeHandler = new NSUrlSessionHandler (config);
-				Assert.Throws<InvalidOperationException> (() => {
-					nativeHandler.UseCookies = false;
-				});
-			}
+			// assert that we can't re-enable cookies for ephemeral sessions
+			using var config = NSUrlSessionConfiguration.EphemeralSessionConfiguration;
+			Assert.That (config.SessionType, Is.EqualTo (NSUrlSessionConfiguration.SessionConfigurationType.Ephemeral), "Session type.");
+			var nativeHandler = new NSUrlSessionHandler (config);
+			Assert.That (nativeHandler.UseCookies, Is.EqualTo (true), "UseCookies #1");
+			nativeHandler.UseCookies = true;
+			Assert.That (nativeHandler.UseCookies, Is.EqualTo (true), "UseCookies #2");
+			nativeHandler.UseCookies = false;
+			Assert.That (nativeHandler.UseCookies, Is.EqualTo (false), "UseCookies #3");
+			nativeHandler.UseCookies = false;
+			Assert.That (nativeHandler.UseCookies, Is.EqualTo (false), "UseCookies #4");
+			Assert.Throws<InvalidOperationException> (() => {
+				nativeHandler.UseCookies = true;
+			}, "UseCookies #5");
+			Assert.That (nativeHandler.UseCookies, Is.EqualTo (false), "UseCookies #6");
+			Assert.Throws<InvalidOperationException> (() => {
+				nativeHandler.UseCookies = true;
+			}, "UseCookies #7");
+			Assert.That (nativeHandler.UseCookies, Is.EqualTo (false), "UseCookies #8");
 		}
 
 		[Test]