Race condition on connect to wildcard topics

[ x ] Bug exists Release Version 1.2.5 ( Master Branch)
[ x ] Bug exists in MQTTv3 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)
[ x ] Bug exists in MQTTv5 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)

In the class:

https://github.com/eclipse/paho.mqtt.java/blob/master/org.eclipse.paho.client.mqttv3/src/main/java/org/eclipse/paho/client/mqttv3/internal/CommsCallback.java

within run() function, the lines:

                MqttPublish message = null;
                synchronized (messageQueue) {
                    if (!messageQueue.isEmpty()) {
                        // Note, there is a window on connect where a publish
                        // could arrive before we've
                        // finished the connect logic.
                        message = (MqttPublish) messageQueue.elementAt(0);

                        messageQueue.removeElementAt(0);
                    }
                }
                if (null != message) {
                    handleMessage(message);
                }

seemingly try to handle situation when messages arrive and are added to messageQueue before the "connect logic" is finished (as stated in the comment).

The handling takes the message and just re-publishes it (by means of the handleMessage method). This is fine for subscriptions to fully qualified topics. However, for wildcard topics this mechanism must fail and an exception is thrown at org.eclipse.paho.client.mqttv3.MqttTopic.validate(MqttTopic.java:226), correctly saying, it is not allowed to publish to wildcard topics.

I think, the code should block until connect() is done and then continue with any other logic.

Comments also mention this in https://github.com/eclipse/paho.mqtt.java/issues/340 . However, this thread is super old and originally not related. To this one.

eclipse-paho / paho.mqtt.java

Race condition on connect to wildcard topics #817