Fix CloudEvents fallback and message aliases

src/Testing/CoreTests/Runtime/Handlers/HandlerGraphTests.cs

@@ -56,6 +56,27 @@ public async Task register_message_type()
         type.ShouldBe(typeof(DummyMessage));
     }
 
+    [Fact]
+    public async Task register_message_type_with_multiple_aliases()
+    {
+        using var host = await Host.CreateDefaultBuilder()
+            .UseWolverine(opts =>
+            {
+                opts.RegisterMessageType(typeof(DummyMessage), "custom-alias-1");
+                opts.RegisterMessageType(typeof(DummyMessage), "custom-alias-2");
+            }).StartAsync();
+
+        var graph = host.Services.GetRequiredService<HandlerGraph>();
+
+        graph.TryFindMessageType(typeof(DummyMessage).ToMessageTypeName(), out _).ShouldBeFalse();
+
+        graph.TryFindMessageType("custom-alias-1", out var firstType).ShouldBeTrue();
+        firstType.ShouldBe(typeof(DummyMessage));
+
+        graph.TryFindMessageType("custom-alias-2", out var secondType).ShouldBeTrue();
+        secondType.ShouldBe(typeof(DummyMessage));
+    }
+
     [Fact]
     public async Task register_message_types_with_same_alias_throws_invalid_operation_exception()
     {

src/Testing/CoreTests/Runtime/Interop/CloudEventsMapper_unknown_type_tests.cs

@@ -1,6 +1,8 @@
+using System.Text;
 using System.Text.Json;
 using Wolverine.Runtime.Handlers;
 using Wolverine.Runtime.Interop;
+using Wolverine.Util;
 using Xunit;
 
 namespace CoreTests.Runtime.Interop;
@@ -14,6 +16,8 @@ public CloudEventsMapper_unknown_type_tests()
     {
         _handlers = new HandlerGraph();
         _handlers.RegisterMessageType(typeof(ApproveOrder), "com.dapr.event.sent");
+        _handlers.RegisterMessageType(typeof(MultiAliasApproveOrder), "data.updated.v1");
+        _handlers.RegisterMessageType(typeof(MultiAliasApproveOrder), "data.updated.v2");
 
         var options = new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase };
         _mapper = new CloudEventsMapper(_handlers, options);
@@ -79,4 +83,53 @@ public void should_overwrite_raw_type_with_resolved_type_on_success()
         envelope.MessageType.ShouldNotBeNull();
         envelope.Message.ShouldBeOfType<ApproveOrder>();
     }
+
+    [Fact]
+    public void should_fall_back_to_original_message_type_when_cloudevent_type_is_unknown()
+    {
+        var json = """
+        {
+          "data": { "orderId": 1 },
+          "id": "5929aaac-a5e2-4ca1-859c-edfe73f11565",
+          "specversion": "1.0",
+          "type": "some.unknown.event.v1",
+          "source": "test"
+        }
+        """;
+
+        var envelope = new Envelope
+        {
+            Data = Encoding.UTF8.GetBytes(json),
+            MessageType = typeof(FallbackApproveOrder).ToMessageTypeName()
+        };
+
+        var message = _mapper.ReadFromData(typeof(FallbackApproveOrder), envelope);
+
+        message.ShouldBeOfType<FallbackApproveOrder>().OrderId.ShouldBe(1);
+        envelope.Message.ShouldBeSameAs(message);
+        envelope.MessageType.ShouldBe(typeof(FallbackApproveOrder).ToMessageTypeName());
+    }
+
+    [Fact]
+    public void should_resolve_second_registered_alias_for_same_message_type()
+    {
+        var json = """
+        {
+          "data": { "orderId": 2 },
+          "id": "5929aaac-a5e2-4ca1-859c-edfe73f11565",
+          "specversion": "1.0",
+          "type": "data.updated.v2",
+          "source": "test"
+        }
+        """;
+
+        var envelope = new Envelope();
+        _mapper.MapIncoming(envelope, json);
+
+        envelope.Message.ShouldBeOfType<MultiAliasApproveOrder>().OrderId.ShouldBe(2);
+        envelope.MessageType.ShouldNotBe("data.updated.v2");
+    }
 }
+
+public record FallbackApproveOrder(int OrderId);
+public record MultiAliasApproveOrder(int OrderId);

src/Wolverine/Runtime/Handlers/HandlerGraph.cs

@@ -617,18 +617,13 @@ public void RegisterMessageType(Type messageType)
 
     public void RegisterMessageType(Type messageType, string messageAlias)
     {
-        if (_messageTypes.TryFind(messageAlias, out var type))
-        {
-            throw new InvalidOperationException($"Cannot register type {type} with alias {messageAlias} because alias is already used");
-        }
-
-        if (_replyTypes.Contains(messageType))
-        {
-            return;
-        }
-
         lock (_messageTypesLock)
         {
+            if (_messageTypes.TryFind(messageAlias, out var type))
+            {
+                throw new InvalidOperationException($"Cannot register type {type} with alias {messageAlias} because alias is already used");
+            }
+
             _messageTypes = _messageTypes.AddOrUpdate(messageAlias, messageType);
             _replyTypes = _replyTypes.Add(messageType);
         }

src/Wolverine/Runtime/Interop/CloudEventsMapper.cs

@@ -109,6 +109,11 @@ public void MapIncoming(Envelope envelope, string json)
     }
 
     public void MapIncoming(Envelope envelope, JsonNode? node)
+    {
+        mapIncoming(envelope, node, fallbackType: null);
+    }
+
+    private void mapIncoming(Envelope envelope, JsonNode? node, Type? fallbackType)
     {
         if (node == null) return;
 
@@ -122,7 +127,7 @@ public void MapIncoming(Envelope envelope, JsonNode? node)
             }
             else if (message.GetValueKind() == JsonValueKind.Object)
             {
-                MapIncoming(envelope, node["Message"]);
+                mapIncoming(envelope, node["Message"], fallbackType);
                 return;
             }
         }
@@ -165,16 +170,22 @@ public void MapIncoming(Envelope envelope, JsonNode? node)
             // If resolution fails, the raw type survives for dead-letter persistence.
             envelope.MessageType = cloudEventType;
 
-            if (_handlers.TryFindMessageType(cloudEventType, out var messageType))
+            // Resolve: try CloudEvent type alias first, then fall back to caller-provided
+            // type (e.g. from DefaultIncomingMessage<T> via ReadFromData)
+            var resolvedType = _handlers.TryFindMessageType(cloudEventType, out var messageType)
+                ? messageType
+                : fallbackType;
+
+            if (resolvedType != null)
             {
                 var data = node!["data"];
                 if (data != null)
                 {
-                    envelope.Message = data.Deserialize(messageType, _options);
+                    envelope.Message = data.Deserialize(resolvedType, _options);
                 }
 
                 // Overwrite with the canonical Wolverine message type name
-                envelope.MessageType = messageType.ToMessageTypeName();
+                envelope.MessageType = resolvedType.ToMessageTypeName();
             }
             else
             {
@@ -205,7 +216,7 @@ public byte[] Write(Envelope envelope)
     public object ReadFromData(Type messageType, Envelope envelope)
     {
         var node = JsonNode.Parse(envelope.Data);
-        MapIncoming(envelope, node);
+        mapIncoming(envelope, node, fallbackType: messageType);
 
         return envelope.Message!;
     }