MqttRpcClient.ExecuteRpcAsync no longer works if MqttClient already has a message receive handler

Describe the bug

After updating from 3.0.12 to 3.0.14, MqttRpcClient.ExecuteRpcAsync no longer works properly if underlying MqttClient has its own MqttApplicationMessageReceivedHandler.

RpcAwareApplicationMessageReceivedHandler looks like it was changed to return immediately after OriginalHandler instead of also calling MqttRpcClient’s handler.

Which project is your bug related to?

• MQTTnet.Extensions.Rpc

To Reproduce

Steps to reproduce the behavior:

1. Using version MQTTnet ‘3.0.14’
2. Create a MqttClient or ManagedMqttClient
3. Add ApplicationMessageReceivedHandler handler to the client
4. Create a MqttRpcClient using this same client
5. Run ‘ExecuteRpcAsync’
6. MqttClient message received handler is called
7. MqttRpcClient message handler is skipped
8. ExecuteRpcAsync fails

Expected behavior

• MqttRpcClient.ExecuteRpcAsync should work if using a MqttClient or ManagedMqttClient that already has its own message receive handler.
• Verified that RPC_Tests only work because the MqttRpcClient is using a response MqttClient without its own ApplicationMessageReceivedHandler so they do not exercise the OriginalHandler condition.

Screenshots

Bug appears to have been introduced with this change from awaits to returns…

Proposed Fix: ExecuteRpcAsynce works properly again by simply removing the immediate return after calling OriginalHandler

.

public Task HandleApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs eventArgs)
{
    if (OriginalHandler != null)
    {
        OriginalHandler.HandleApplicationMessageReceivedAsync(eventArgs);
    }

    return _handleReceivedApplicationMessageAsync(eventArgs);
}

[chkr1011]

@BrianG500 In my opinion the issue is that both handlers must be called in order to work correctly. Currently only one is called and the method returns. I fixed this in master. Now both handlers are invoked properly. Please let me know if this fixes your issue.

[chkr1011]

I will close this because it is fixed in 3.0.15-rc2.