Add work-around for iCloud responses to ENABLE QRESYNC

Fixes issue #1871

MailKit/Net/Imap/ImapClient.cs

@@ -380,9 +380,18 @@ bool TryQueueEnableQuickResyncCommand (CancellationToken cancellationToken, out
 			return true;
 		}
 
-		static void ProcessEnableResponse (ImapCommand ic)
+		void ProcessEnableResponse (ImapCommand ic)
 		{
 			ic.ThrowIfNotOk ("ENABLE");
+
+			if (engine.QuirksMode == ImapQuirksMode.iCloud) {
+				// Note: iCloud's response to the `ENABLE QRESYNC CONDSTORE` command does not include an untagged response
+				// notifying us that QRESYNC or CONDSTORE have been enabled. Instead, if we get a tagged OK response, we
+				// assume that these features were enabled successfully.
+				//
+				// See https://github.com/jstedfast/MailKit/issues/1871 for details.
+				engine.QResyncEnabled = true;
+			}
 		}
 
 		/// <summary>

UnitTests/Net/Imap/ImapClientTests.cs

@@ -71,6 +71,16 @@ public class ImapClientTests
 			ImapCapabilities.ESearch | ImapCapabilities.Compress | ImapCapabilities.Enable | ImapCapabilities.ListExtended |
 			ImapCapabilities.ListStatus | ImapCapabilities.Move | ImapCapabilities.UTF8Accept | ImapCapabilities.XList |
 			ImapCapabilities.GMailExt1 | ImapCapabilities.LiteralMinus | ImapCapabilities.AppendLimit;
+		static readonly ImapCapabilities ICloudInitialCapabilities = ImapCapabilities.IMAP4 | ImapCapabilities.IMAP4rev1 |
+			ImapCapabilities.Status | ImapCapabilities.SaslIR;
+		static readonly ImapCapabilities ICloudAuthenticatedCapabilities = ImapCapabilities.IMAP4 | ImapCapabilities.IMAP4rev1 |
+			ImapCapabilities.Status | ImapCapabilities.CondStore | ImapCapabilities.Enable | ImapCapabilities.QuickResync |
+			ImapCapabilities.Quota | ImapCapabilities.Namespace | ImapCapabilities.UidPlus | ImapCapabilities.Children |
+			ImapCapabilities.Binary | ImapCapabilities.Unselect | ImapCapabilities.Sort | ImapCapabilities.Catenate |
+			ImapCapabilities.Language | ImapCapabilities.ESearch | ImapCapabilities.ESort | ImapCapabilities.Thread |
+			ImapCapabilities.Context | ImapCapabilities.Within | ImapCapabilities.SaslIR | ImapCapabilities.SearchResults |
+			ImapCapabilities.Metadata | ImapCapabilities.Id | ImapCapabilities.Annotate | ImapCapabilities.MultiSearch |
+			ImapCapabilities.Idle | ImapCapabilities.ListStatus;
 		static readonly ImapCapabilities IMAP4rev2CoreCapabilities = ImapCapabilities.IMAP4rev2 | ImapCapabilities.Status |
 			ImapCapabilities.Namespace | ImapCapabilities.Unselect | ImapCapabilities.UidPlus | ImapCapabilities.ESearch |
 			ImapCapabilities.SearchResults | ImapCapabilities.Enable | ImapCapabilities.Idle | ImapCapabilities.SaslIR | ImapCapabilities.ListExtended |
@@ -3564,6 +3574,8 @@ public void TestEnableQuickResync ()
 
 				client.EnableQuickResync ();
 
+				Assert.That (client.Inbox.Supports (FolderFeature.QuickResync), Is.True, "Expected the INBOX to support QRESYNC");
+
 				// ENABLE QRESYNC a second time should no-op.
 				client.EnableQuickResync ();
 
@@ -3606,6 +3618,100 @@ public async Task TestEnableQuickResyncAsync ()
 
 				await client.EnableQuickResyncAsync ();
 
+				Assert.That (client.Inbox.Supports (FolderFeature.QuickResync), Is.True, "Expected the INBOX to support QRESYNC");
+
+				// ENABLE QRESYNC a second time should no-op.
+				await client.EnableQuickResyncAsync ();
+
+				await client.DisconnectAsync (false);
+			}
+		}
+
+		static List<ImapReplayCommand> CreateEnableQuickResynciCloudCommands ()
+		{
+			return new List<ImapReplayCommand> {
+				new ImapReplayCommand ("", "icloud.greeting.txt"),
+				new ImapReplayCommand ("A00000000 AUTHENTICATE PLAIN AHVzZXJuYW1lAHBhc3N3b3Jk\r\n", "icloud.authenticate-plain.txt"),
+				new ImapReplayCommand ("A00000001 CAPABILITY\r\n", "icloud.capability.txt"),
+				new ImapReplayCommand ("A00000002 NAMESPACE\r\n", "icloud.namespace.txt"),
+				new ImapReplayCommand ("A00000003 LIST \"\" \"INBOX\"\r\n", "icloud.list-inbox.txt"),
+				new ImapReplayCommand ("A00000004 ENABLE QRESYNC CONDSTORE\r\n", "icloud.enable-qresync.txt"),
+			};
+		}
+
+		[Test]
+		public void TestEnableQuickResynciCloud ()
+		{
+			var commands = CreateEnableQuickResynciCloudCommands ();
+
+			using (var client = new ImapClient () { TagPrefix = 'A' }) {
+				try {
+					client.Connect (new ImapReplayStream (commands, false), "localhost", 143, SecureSocketOptions.None);
+				} catch (Exception ex) {
+					Assert.Fail ($"Did not expect an exception in Connect: {ex}");
+				}
+
+				Assert.That (client.Capabilities, Is.EqualTo (ICloudInitialCapabilities));
+				Assert.That (client.AuthenticationMechanisms, Has.Count.EqualTo (4));
+				Assert.That (client.AuthenticationMechanisms, Does.Contain ("ATOKEN"), "Expected SASL ATOKEN auth mechanism");
+				Assert.That (client.AuthenticationMechanisms, Does.Contain ("PLAIN"), "Expected SASL PLAIN auth mechanism");
+				Assert.That (client.AuthenticationMechanisms, Does.Contain ("ATOKEN2"), "Expected SASL ATOKEN2 auth mechanism");
+				Assert.That (client.AuthenticationMechanisms, Does.Contain ("XOAUTH2"), "Expected SASL XOAUTH2 auth mechanism");
+
+				try {
+					client.Authenticate ("username", "password");
+				} catch (Exception ex) {
+					Assert.Fail ($"Did not expect an exception in Authenticate: {ex}");
+				}
+
+				Assert.That (client.Capabilities, Is.EqualTo (ICloudAuthenticatedCapabilities));
+				Assert.That (client.ThreadingAlgorithms, Does.Contain (ThreadingAlgorithm.OrderedSubject), "Expected THREAD=ORDEREDSUBJECT");
+				Assert.That (client.ThreadingAlgorithms, Does.Contain (ThreadingAlgorithm.References), "Expected THREAD=REFERENCES");
+
+				client.EnableQuickResync ();
+
+				Assert.That (client.Inbox.Supports (FolderFeature.QuickResync), Is.True, "Expected the INBOX to support QRESYNC");
+
+				// ENABLE QRESYNC a second time should no-op.
+				client.EnableQuickResync ();
+
+				client.Disconnect (false);
+			}
+		}
+
+		[Test]
+		public async Task TestEnableQuickResynciCloudAsync ()
+		{
+			var commands = CreateEnableQuickResynciCloudCommands ();
+
+			using (var client = new ImapClient () { TagPrefix = 'A' }) {
+				try {
+					await client.ConnectAsync (new ImapReplayStream (commands, true), "localhost", 143, SecureSocketOptions.None);
+				} catch (Exception ex) {
+					Assert.Fail ($"Did not expect an exception in Connect: {ex}");
+				}
+
+				Assert.That (client.Capabilities, Is.EqualTo (ICloudInitialCapabilities));
+				Assert.That (client.AuthenticationMechanisms, Has.Count.EqualTo (4));
+				Assert.That (client.AuthenticationMechanisms, Does.Contain ("ATOKEN"), "Expected SASL ATOKEN auth mechanism");
+				Assert.That (client.AuthenticationMechanisms, Does.Contain ("PLAIN"), "Expected SASL PLAIN auth mechanism");
+				Assert.That (client.AuthenticationMechanisms, Does.Contain ("ATOKEN2"), "Expected SASL ATOKEN2 auth mechanism");
+				Assert.That (client.AuthenticationMechanisms, Does.Contain ("XOAUTH2"), "Expected SASL XOAUTH2 auth mechanism");
+
+				try {
+					await client.AuthenticateAsync ("username", "password");
+				} catch (Exception ex) {
+					Assert.Fail ($"Did not expect an exception in Authenticate: {ex}");
+				}
+
+				Assert.That (client.Capabilities, Is.EqualTo (ICloudAuthenticatedCapabilities));
+				Assert.That (client.ThreadingAlgorithms, Does.Contain (ThreadingAlgorithm.OrderedSubject), "Expected THREAD=ORDEREDSUBJECT");
+				Assert.That (client.ThreadingAlgorithms, Does.Contain (ThreadingAlgorithm.References), "Expected THREAD=REFERENCES");
+
+				await client.EnableQuickResyncAsync ();
+
+				Assert.That (client.Inbox.Supports (FolderFeature.QuickResync), Is.True, "Expected the INBOX to support QRESYNC");
+
 				// ENABLE QRESYNC a second time should no-op.
 				await client.EnableQuickResyncAsync ();
 

UnitTests/Net/Imap/Resources/icloud/authenticate-plain.txt

@@ -0,0 +1 @@
+A######## OK user username authenticated

UnitTests/Net/Imap/Resources/icloud/capability.txt

@@ -0,0 +1,2 @@
+* CAPABILITY XAPPLEPUSHSERVICE IMAP4 IMAP4rev1 CONDSTORE ENABLE QRESYNC QUOTA XAPPLELITERAL NAMESPACE UIDPLUS CHILDREN BINARY UNSELECT SORT CATENATE URLAUTH LANGUAGE ESEARCH ESORT THREAD=ORDEREDSUBJECT THREAD=REFERENCES CONTEXT=SEARCH CONTEXT=SORT WITHIN SASL-IR SEARCHRES METADATA ID XMSEARCH X-SUN-SORT ANNOTATE-EXPERIMENT-1 X-UNAUTHENTICATE X-SUN-IMAP XUM1 MULTISEARCH IDLE X-APPLE-REMOTE-LINKS LIST-STATUS
+A######## OK Completed

UnitTests/Net/Imap/Resources/icloud/enable-qresync.txt

@@ -0,0 +1 @@
+A######## OK ENABLE completed

UnitTests/Net/Imap/Resources/icloud/greeting.txt

@@ -1 +1 @@
-* OK [CAPABILITY XAPPLEPUSHSERVICE IMAP4 IMAP4rev1 SASL-IR AUTH=ATOKEN AUTH=PLAIN] (2313B20-3ff771b405ab) pv50p00im-tygg10010601.me.com
+* OK [CAPABILITY XAPPLEPUSHSERVICE IMAP4 IMAP4rev1 SASL-IR AUTH=ATOKEN AUTH=PLAIN AUTH=ATOKEN2 AUTH=XOAUTH2] (2428B47-26126cfe23cd) p00-iscream-f9f7bf749-qjr87

UnitTests/Net/Imap/Resources/icloud/list-inbox.txt

@@ -0,0 +1,2 @@
+* LIST (\Noinferiors) "/" "INBOX"
+A######## OK LIST completed (took 0 ms)

UnitTests/Net/Imap/Resources/icloud/namespace.txt

@@ -0,0 +1,2 @@
+* NAMESPACE (("" "/")) NIL NIL
+A######## OK NAMESPACE completed (took 0 ms)