Retained topics sometimes removed, found solution

[H4nsie]

I noticed when sometimes data is missing in de VW app (don't know why, but see screenshot attached; available km range and available % fuel is not displayed in the app when this happens), it is also directly missing in the raw jason, and then WeConnect-mqtt removes the topic from the broker. (My home-automation sets the values then to zero, causing problems in my sensors/scripts, I'd rather prefer retaining the old topics and values, and wait a few hours for data available again at the VW's server.)

A retained topic is removed from a broker by publishing the topic with the retain-flag and a null ('') payload. WeConnect-mqtt does this on line 544, by sending this command to the broker. I've commented out this command:

544c544
<             self.publish(topic=f'{self.prefix}{element.getGlobalAddress()}', qos=1, retain=True, payload='')
---
>             #self.publish(topic=f'{self.prefix}{element.getGlobalAddress()}', qos=1, retain=True, payload='')

Now topics are always retained. Perhaps you could make this configurable with a parameter? (--alwaysretain)?

I've tested a few days and the number of topics stay the same on my broker. Now I can confirm it working for the VW California 6.1 camper, with mosquitto version 2.0.11, Domoticz 2024.7 using domoticz-mqttmapper-plugin