MQTT 5.0 cannot subscribe: Cannot parse topic

[miqmago]

I'm trying to use MQTT 5.0 but I'm always getting the same error: Cannot parse topic

        client.connect({
            clientId: activeInterface.mac_address.replace(/:/ig, '').toUpperCase(),
            username: 'bla',
            password: 'bla',
            protocolId: 'MQTT',
            protocolVersion: 5,
        });

        client.on('connack', () => {
            console.log('client connected... sending subscribe');
            client.subscribe({
                messageId: 0,
                subscriptions: [{
                    topic: 'whatever',
                    qos: 0,
                    nl: false, // no Local MQTT 5.0 flag
                    rap: true, // Retain as Published MQTT 5.0 flag
                    rh: 1, // Retain Handling MQTT 5.0
                }],
            });
        });

I've add this line in parser.js:466 for debugging:

console.log(length, end, this._list.length, this.packet.length, this._list.toString('utf8'));

It always fails (whatever topic I place):

2167 2172 13 13 '\u0000\u0000\u0000\bwhatever\u0000'
client error Error: Cannot parse topic
    at Parser._parseSubscribe (/node_modules/mqtt-connection/node_modules/mqtt-packet/parser.js:304:48)
    at Parser._parsePayload (/node_modules/mqtt-connection/node_modules/mqtt-packet/parser.js:99:14)
    at Parser.parse (/node_modules/mqtt-connection/node_modules/mqtt-packet/parser.js:39:41)
    at DestroyableTransform.process [as _transform] (/node_modules/mqtt-connection/lib/parseStream.js:14:17)
    at DestroyableTransform.Transform._read (/node_modules/through2/node_modules/readable-stream/lib/_stream_transform.js:184:10)
    at DestroyableTransform.Transform._write (/node_modules/through2/node_modules/readable-stream/lib/_stream_transform.js:172:83)
    at doWrite (/node_modules/through2/node_modules/readable-stream/lib/_stream_writable.js:428:64)
    at writeOrBuffer (/node_modules/through2/node_modules/readable-stream/lib/_stream_writable.js:417:5)
    at DestroyableTransform.Writable.write (/node_modules/through2/node_modules/readable-stream/lib/_stream_writable.js:334:11)
    at Socket.ondata (_stream_readable.js:639:20)

If I switch to MQTT lower version it works perfectly...

[miqmago]

If I place a console.log at _parseNum parser.js:499 it seems that _pos is one byte misfit:

  console.log(this._list._bufs);
  console.log(this._list._bufs.map(b => b.toString()), this._pos, result);

[ <Buffer 00 00 00 08 77 68 61 74 65 76 65 72 00> ]
[ '\u0000\u0000\u0000\bwhatever\u0000' ] 3 2167

00 08 = 8 (= 'whatever'.length)
08 77 = 2167

[miqmago]

Seems a problem of options:
When the packet is receiving connack, it calls setOptions with connectPacket. I don't see a way to return protocol version from server in connack, or the connack from client is not getting original options or assigning original options to packet. That way, protocolVersion is being lost.

I've ended by overriding options manually, doing this:

    mqttConnection.on('connack', this.conAck.bind(this));

    conAck(resp) {
        this.mqttConnection.setOptions({
            protocolVersion: 5,
        });
        this.mqttConnection.subscribe({
            messageId: 1,
            subscriptions: [{
                topic: 'whatever',
                qos: 0,
                nl: false, // no Local MQTT 5.0 flag
                rap: true, // Retain as Published MQTT 5.0 flag
                rh: 1, // Retain Handling MQTT 5.0
            }],
        });
    }

[miqmago]

Problem reported at mqttjs/mqtt-packet#50