Conventional topic configuration is correctly applied w/ MQTT. Closes…

src/Transports/MQTT/Wolverine.MQTT.Tests/Bugs/Bug_1634_not_using_default_serializer_correctly.cs

@@ -0,0 +1,47 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Shouldly;
+using Wolverine.MQTT.Internals;
+using Wolverine.Runtime.Serialization;
+using Wolverine.Tracking;
+
+namespace Wolverine.MQTT.Tests.Bugs;
+
+public class Bug_1634_not_using_default_serializer_correctly
+{
+    [Fact]
+    public async Task try_it_out()
+    {
+        using var host = await Host.CreateDefaultBuilder()
+            .UseWolverine(opts =>
+            {
+                // cfg.PublishMessagesToMqttTopic((Event e) => e.Id).DefaultSerializer(new Serializer());
+                opts.PublishMessagesToMqttTopic((Event e) => e.Id);
+
+                opts.UseMqttWithLocalBroker()
+                    .ConfigureSenders(sub => sub.DefaultSerializer(new Serializer()));
+            }).StartAsync();
+
+        var runtime = host.GetRuntime();
+        var topic = runtime.Options.Transports.GetOrCreate<MqttTransport>().Topics["One"];
+
+        // This would have been done by creating a sender anyway
+        topic.Compile(runtime);
+        topic.DefaultSerializer.ShouldBeOfType<Serializer>();
+    }
+}
+
+public record Event(string Id);
+
+public class Serializer : IMessageSerializer
+{
+    public byte[] Write(Envelope envelope) => throw new NotImplementedException();
+
+    public object ReadFromData(Type messageType, Envelope envelope) => throw new NotImplementedException();
+
+    public object ReadFromData(byte[] data) => throw new NotImplementedException();
+
+    public byte[] WriteMessage(object message) => throw new NotImplementedException();
+
+    public string ContentType => "text/plain";
+}

src/Transports/MQTT/Wolverine.MQTT/MqttTopic.cs

@@ -11,7 +11,7 @@
 
 namespace Wolverine.MQTT;
 
-public class MqttTopic : Endpoint, ISender
+public class MqttTopic : Endpoint, ISender, ITopicEndpoint
 {
     public const string WolverineTopicsName = "wolverine/topics";
 
@@ -44,6 +44,8 @@ public override bool AutoStartSendingAgent()
 
     public override async ValueTask<IListener> BuildListenerAsync(IWolverineRuntime runtime, IReceiver receiver)
     {
+        Compile(runtime);
+
         _cancellation = runtime.Cancellation;
 
         MessageTypeName = MessageType?.ToMessageTypeName();
@@ -60,6 +62,7 @@ public override async ValueTask<IListener> BuildListenerAsync(IWolverineRuntime
 
     protected override ISender CreateSender(IWolverineRuntime runtime)
     {
+        Compile(runtime);
         return this;
     }
 

src/Transports/MQTT/Wolverine.MQTT/MqttTransportExpression.cs

@@ -1,6 +1,7 @@
 using JasperFx.Core.Reflection;
 using Wolverine.Configuration;
 using Wolverine.MQTT.Internals;
+using Wolverine.Runtime;
 
 namespace Wolverine.MQTT;
 
@@ -59,7 +60,7 @@ public MqttTransportExpression ConfigureSenders(Action<MqttSubscriberConfigurati
                 return;
             }
 
-            if (!e.Subscriptions.Any())
+            if (!e.Subscriptions.Any() && e is not ITopicEndpoint)
             {
                 return;
             }

src/Wolverine/Runtime/ITopicEndpoint.cs

@@ -0,0 +1,10 @@
+namespace Wolverine.Runtime;
+
+/// <summary>
+/// Marker interface that just tells Wolverine this endpoint
+/// is a topic for brokers that support topic-based routing.
+///
+/// Tells Wolverine that this endpoint *might* have subscriptions
+/// later
+/// </summary>
+public interface ITopicEndpoint;