ClientMessageQueueInterceptor continues with subscription processing. (#1685)

* ClientMessageQueueInterceptor continues with subscription processing.

* Update readme

---------

Co-authored-by: Christian <6939810+chkr1011@users.noreply.github.com>

.github/workflows/ReleaseNotes.md

@@ -13,4 +13,5 @@
 * [Server] Added a new API method which allows reading a single retained message without the need to processing the entire set of retained messages (#1659).
 * [Server] Added a new event (InterceptingClientEnqueueAsync) which allows intercepting when an application message is enqueued for a client (#1648).
 * [Server] Fixed race condition when handling connections which leads to stopped message transfers (#1677, thanks to @RazvanEmilR).
+* [Server] Fixed not delivered packets to other sessions if the _InterceptingClientEnqueueEvent_ is used and accepting the packet is denied (#1685, thanks to @RossHNPC).
 * [Server] Added missing user properties to subscribe and unsubscribe interceptor (#1702).

Source/MQTTnet.Tests/Server/Publishing_Tests.cs

@@ -105,5 +105,42 @@ namespace MQTTnet.Tests.Server
                 receivedMessages.AssertReceivedCountEquals(1);
             }
         }
+
+        [TestMethod]
+        public async Task Intercept_Client_Enqueue_Multiple_Clients_Subscribed_Messages_Are_Filtered()
+        {
+            using (var testEnvironment = CreateTestEnvironment())
+            {
+                var server = await testEnvironment.StartServer();
+
+                var sender = await testEnvironment.ConnectClient();
+
+                var receiverOne = await testEnvironment.ConnectClient(o => o.WithClientId("One"));
+                await receiverOne.SubscribeAsync("A");
+                var receivedMessagesOne = testEnvironment.CreateApplicationMessageHandler(receiverOne);
+
+                var receiverTwo = await testEnvironment.ConnectClient(o => o.WithClientId("Two"));
+                await receiverTwo.SubscribeAsync("A");
+                var receivedMessagesTwo = testEnvironment.CreateApplicationMessageHandler(receiverTwo);
+
+                var receiverThree = await testEnvironment.ConnectClient(o => o.WithClientId("Three"));
+                await receiverThree.SubscribeAsync("A");
+                var receivedMessagesThree = testEnvironment.CreateApplicationMessageHandler(receiverThree);
+
+                server.InterceptingClientEnqueueAsync += e =>
+                {
+                    if (e.ReceiverClientId.Contains("Two")) e.AcceptEnqueue = false;
+                    return CompletedTask.Instance;
+                };
+
+                await sender.PublishStringAsync("A", "Payload", MqttQualityOfServiceLevel.AtLeastOnce);
+
+                await LongTestDelay();
+
+                receivedMessagesOne.AssertReceivedCountEquals(1);
+                receivedMessagesTwo.AssertReceivedCountEquals(0);
+                receivedMessagesThree.AssertReceivedCountEquals(1);
+            }
+        }
     }
 }

Source/MQTTnet/Server/Internal/MqttClientSessionsManager.cs

@@ -207,9 +207,8 @@ namespace MQTTnet.Server
 
                             if (!eventArgs.AcceptEnqueue)
                             {
-                                // There will be no reason string and use properties because in this case the clients will
+                                // Continue checking the other subscriptions
-                                // not receive a packet at all.
+                                continue;
-                                return new DispatchApplicationMessageResult(reasonCode, eventArgs.CloseSenderConnection, null, null);
                             }
                         }