QoS::AtMostOnce not handled properly when encoding/decoding a publish packet

[vincentdephily]

Mqttrs always expects a PacketIdentifier to be present, but the spec explains that the field is only present in PUBLISH Packets where the QoS level is 1 or 2.

The symptoms are missing two initial bytes of payload when decoding an AtMostOnce publish packet, a panic when trying to encode a publish packet with pid=None, corrupted payload when read by conforming clients, etc.

I'll try to send a PR.

[00imvj00]

awesome, thank you.

[vincentdephily]

Thanks for the fix, sorry for never following up with a PR: priorities shifted and holidays happened. I'll get back to QoS soon and hopefully stress-test this.

[00imvj00]

It is ok. :) and thank you for finding issues.

[vincentdephily]

Sorry, not sure how I missed that, but only from_buffer() was fixed, leaving to_buffer() with the same bug. It should be possible to encode a Publish packet without a PacketIdentifier, if the QoS is 0.

[vincentdephily]

I've got the fix, just working on a more comprehensive test.