MMQTTException vs partial reads on read timeout

[vladak]

The common use case of the library is as follows (adapted from https://github.com/adafruit/Adafruit_CircuitPython_MiniMQTT/issues/163#issue-1689131569):

while True:
    temperature = dps310.temperature
    mqtt_client.publish("foo", temperature)

    try:
        mqtt_client.loop()
    except (MMQTTException) as e:
        print("MQTTException: \n", e)
        time.sleep(300)
        continue

The documentation of the MMQTTException does not give any advice as to what to do if the exception is raised. Usually, the safest thing would be to reconnect() on the exception, notably because as indicated on https://github.com/adafruit/Adafruit_CircuitPython_MiniMQTT/issues/175#issuecomment-1902251442 the message data could be partially read and lost when the exception is raised which would result in garbage on the next read.

There are two choices:

• easy: augment the MMQTTException docstring
• more difficult: to allow for the graceful handling of the read timeout, the buffer should be kept around so that message reassembly can be performed