Add workaround for long keys= in mqtt-publisher

[ondras12345]

This fixes #3084 (but I would prefer to see a better solution, this feels like an ugly workaround).

[petterreinholdtsen]

[Ondřej Sluka]

This fixes #3084 (but I would prefer to see a better solution, this feels like an ugly workaround).

I agree, but it seem like an elegant solution to a ugly problem. Note there is a behaviour change in the code, if the same key is specified several times. I believe using key={}, duplicates would be removed, with key=[] they will show up several times instead. Perhaps duplicate removal should be added? Also, is there a warning somewhere if the .ini file contain lines longer than 255 characters? I guess there should be a popup letting the user know that it is going to fail...

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-- Happy hacking Petter Reinholdtsen

[ondras12345]

Previously, the initialization of keys with an empty dict would be unused as keys was reassigned with a new list:

linuxcnc/src/hal/user_comps/mqtt-publisher.py

Line 150 in 69feb3b

keys = extra.split('=')[1].split(',')

There should be no change in behavior regarding duplicates with my patch.

That being said, it might be a good idea to use a set instead of a list to drop duplicates (but that introduces a change in behavior).

The only warning I encountered was this:

warning: Missing pin halui.mist.is-o not sent to MQTT

It comes from the mqtt-publisher process and was only printed to my terminal. It might also happen that the list of keys will get cropped at the position of a comma. In that case, there would be no warning whatsoever.

[andypugh]

I rebased this on 2.9 and committed as 317595e
And, then in master I committed what I think is a more elegant fix: 9eb94c3

I left in the ability to specify multiple keys= sections.