Fix wrong QoS when using MqttClientMessageQueueInterceptor #978

Source/MQTTnet/Server/MqttClientConnection.cs

@@ -397,17 +397,13 @@ namespace MQTTnet.Server
                     // Set the retain flag to true according to [MQTT-3.3.1-8] and [MQTT-3.3.1-9].
                     publishPacket.Retain = queuedApplicationMessage.IsRetainedMessage;
 
-                    if (publishPacket.QualityOfServiceLevel > 0)
-                    {
-                        publishPacket.PacketIdentifier = _packetIdentifierProvider.GetNextPacketIdentifier();
-                    }
-
                     if (_serverOptions.ClientMessageQueueInterceptor != null)
                     {
                         var context = new MqttClientMessageQueueInterceptorContext(
                             queuedApplicationMessage.SenderClientId,
                             ClientId,
-                            queuedApplicationMessage.ApplicationMessage);
+                            queuedApplicationMessage.ApplicationMessage,
+                            queuedApplicationMessage.SubscriptionQualityOfServiceLevel);
 
                         if (_serverOptions.ClientMessageQueueInterceptor != null)
                         {
@@ -421,7 +417,12 @@ namespace MQTTnet.Server
 
                         publishPacket.Topic = context.ApplicationMessage.Topic;
                         publishPacket.Payload = context.ApplicationMessage.Payload;
-                        publishPacket.QualityOfServiceLevel = context.ApplicationMessage.QualityOfServiceLevel;
+                        publishPacket.QualityOfServiceLevel = context.SubscriptionQualityOfServiceLevel;
+                    }
+
+                    if (publishPacket.QualityOfServiceLevel > 0)
+                    {
+                        publishPacket.PacketIdentifier = _packetIdentifierProvider.GetNextPacketIdentifier();
                     }
 
                     if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)

Tests/MQTTnet.Core.Tests/Server_Tests.cs

@@ -1452,5 +1452,31 @@ namespace MQTTnet.Tests
             }
         }
 
+        [TestMethod]
+        public async Task Intercept_ClientMessageQueue_Different_QoS_Of_Subscription_And_Message()
+        {
+            const string topic = "a";
+
+            using (var testEnvironment = new TestEnvironment(TestContext))
+            {
+                await testEnvironment.StartServerAsync(new MqttServerOptionsBuilder()
+                    .WithClientMessageQueueInterceptor(c => { })); // Interceptor does nothing but has to be present.
+
+                bool receivedMessage = false;
+                var client = await testEnvironment.ConnectClientAsync();
+                client.UseApplicationMessageReceivedHandler(c =>
+                {
+                    receivedMessage = true;
+                });
+
+                await client.SubscribeAsync(topic, MqttQualityOfServiceLevel.AtLeastOnce);
+
+                await client.PublishAsync(new MqttApplicationMessage{ Topic = topic, QualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce });
+
+                await Task.Delay(500);
+
+                Assert.IsTrue(receivedMessage);
+            }
+        }
     }
 }