WithoutThrowOnNonSuccessfulConnectResponse

[ramonsmits]

The log shows:

Client will now throw an MqttConnectingFailedException. This is obsolete and will be removed in the future. Consider setting ThrowOnNonSuccessfulResponseFromServer=False in client options.

The thing is... I don't have any exceptions in my code :)

So I started browsing the code and found:

https://github.com/dotnet/MQTTnet/blob/v4.2.1.781/Source/MQTTnet/Client/MqttClient.cs#L455-L467

Which resulted in the following PR as that warning should only logged when actually throwing the exception:

• Only logging "Client will now throw an _MqttConnectingFailedException_." warning when actually throwing the exception #1801

However, the documentation isn't making any mention of this and its a bit unclear how to actually deal with server errors.

In code it states:

This is no feature. It is basically a backward compatibility option and should be removed in the future.
The client should not throw any exception if the transport layer connection was successful and the server
did send a proper ACK packet with a non success response.

How should I deal with the result?

I can do something like the following to just suppress the warning and just move the throwing of the exception:

mqttClientOptions.WithoutThrowOnNonSuccessfulConnectResponse();

var result = await mqttClient.ConnectAsync(mqttClientOptions.Build());

if (result.ResultCode != MqttClientConnectResultCode.Success)
    throw new($"Expected `Success` but was `{result.ResultCode}`");

But... based on the code comment it seems it is expected a different type of handling and I'm interested to learn what is expected from a user.