Returning ServiceBusMessage doesn't work correctly

When returning a ServiceBusMessage, the message posted contains incorrect information.

[Function(nameof(Run))]
[ServiceBusOutput("audit", Connection = "AzureServiceBus")]
public async Task<ServiceBusMessage> Run([ServiceBusTrigger("Notifications", Connection = "AzureServiceBus")] ServiceBusReceivedMessage message)
{
    // removed for brevity 

    return new ServiceBusMessage(rawMessage);
}

For an incoming message

The returned message body is

1 - missing original header 2 - incorrect body 3 - incorrect content type

Expected:

1 - the original header (EventType) is found 2 - original body 3 - correct content type

[SeanFeldman]

I’d probably want to still present the client approach as an option to consider when discussing the single message return in guidance

+1 on that.

Also, I’d suggest showing the sample how to handle the incoming message from middleware. Much of the boilerplate code could be moved from functions into middleware (related to issue #1824) when implementing some sort of custom framework on top of SB-triggered functions.

[SeanFeldman]

I could imagine simplifying the hypothetical: what if the function can just get the ServiceBusSender and then call .SendMessageAsync(msg)?

This might be more effective as the clients could be cached based on the connection and entity those are requested for.

With all that said, receiving a ServiceBusReceivedMessage and returning from function a ServiceBusMessage would be extremely simple and powerful. And would satisfy a lot of scenarios where an incoming message is generating an outgoing message. For multiple messages, I’d agree that a client is a better approach (IAsyncCollector in In-Proc SDK was a bit of a weird API). But for a single returned message, there’s a value in considering returning just a ServiceBusMessage w/o the need for a client or sender.