The SignalR triggered function return value not working

[Y-Sindo]

The SignalR Microsoft.Azure.WebJobs.Host.Triggers.ITriggerData.ReturnValueProvider.SetValueAsync(object value, CancellationToken cancellationToken) is always invoked with parameter value=null for isolated worker. This means the return value of SignalR triggered function without output binding annotated is not working at all. However, it works in the in-process model and the isolated process model of HTTP trigger.

[Function("Broadcast")]
public async Task<NewMessage> Broadcast(
[SignalRTrigger(nameof(Functions), "messages", "broadcast", "message")] SignalRInvocationContext invocationContext, string message)
{
    return new NewMessage(invocationContext, "this is returned from function");
}

The Worker.Extensions.Http` trigger is quite simple that has nothing to do with the return value handling. Need more investigation on what makes the difference. Any insight would be appreciated.

[fabiocav]

@Y-Sindo has this been validated for the other OOP languages as well?

The first step here would be to validate that your return value is being assigned as expected and defined in the metadata with the appropriate $return name.

Is the example above all we'd need in order to repro your issue? If possible, having that in a repo we can simply clone would make this process easier.

Thanks!

[Y-Sindo]

@fabiocav The node worker also doesn't work. It seems like a common problem in isolated workers. However, I don't know how to declare the $return name to use the return value of a trigger instead of an output binding. I have tried as follows but the functions cannot even start normally.

{
  "disabled": false,
  "bindings": [
    {
      "type": "signalRTrigger",
      "name": "invocation",
      "hubName": "SignalRTest",
      "category": "messages",
      "event": "SendMessage",
      "parameterNames": ["message"],
      "direction": "in"
    },
    {
      "type": "signalRTrigger",
      "name": "$return",
      "hubName": "SignalRTest",
      "category": "messages",
      "event": "SendMessage",
      "parameterNames": ["message"],
      "direction": "out"
    }
  ]
}

The first step here would be to validate that your return value is being assigned as expected and defined in the metadata with the appropriate $return name.

I'm not sure what the return value is. Is the $return name used as follows? The functions.metadata seems like the functions.json in node worker, but in my understanding, we don't need functions.json in dotnet isolated worker. Or is it something our extensions developer needs to declare somewhere?

azure-functions-dotnet-worker/test/SdkE2ETests/Contents/functions.metadata

Lines 22 to 26 in 1c9b7e0

	{
	"name": "$return",
	"type": "http",
	"direction": "Out"
	}

[Y-Sindo]

I have added a repo to repro the issue. The reproducing steps are a little bit complicated. Please see https://github.com/Y-Sindo/DotnetIsolated-SignalRTrigger/blob/main/README.md for details. Thanks.