Update to add MQTT(PlugIn.Helper) publish support (issue #39)

[jcassel]

Update to add MQTT(PlugIn.Helper) publish support for last known weight value.

I have to be honest, I did not have a load cell to test this on. So the only value for the last known weight was "Error" but I did not change any of the functional code for the PlugIn.. I simply added the hook to the MQTT PlugIn and then setup a Publish to it if it was found. I did thoroughly test the MQTT Sections. If you think it should be sending some other value or if you think I need to add some additional checks around the value of "lastknownweight" let me know, I will make an update.

[techman83]

Only one minor question! I would like to keep the format related changes in a separate commit at the very least, but preferably a separate PR. But the project really could use porting to Black, and really appreciate this contribution.

Overall looks great, I'll try and do a sanity check at some point today. If it goes well, I'll cut a release!

[techman83]

I'll need to do some further debugging, I do get it seeing that mqtt is available

2023-08-11 10:01:23,640 - octoprint.plugins.filament_scale - INFO - do send weight
2023-08-11 10:01:23,641 - octoprint.plugins.filament_scale - INFO - baseTopic:octoPrint/

and the mqtt plugin is publishing

octoPrint/mqtt connected
octoPrint/progress/printing {"location": "", "path": "", "progress": 0, "_timestamp": 1691744473}
octoPrint/progress/slicing {"slicer": "", "source_location": "", "source_path": "", "destination_location": "", "destination_path": "", "progress": 0, "_timestamp": 1691744473}

But I'm not getting any weights show up. Though just need to rule out an issue with the load cell!

[jcassel]

This is what I get from a more or less default MQTT setup.

I ordered a loadcell and board. It might be here today.

[jcassel]

I was looking at this again.. Just noted that I reused the timer t for the new MQTT method. I am making an update. I also looked harder in my shop and found a good load cell and board. I have it hooked up. Let me work this a little and I will update later today I hope.

[jcassel]

OK, with the last commit, I think it is all worked out. I should not have submitted the changes without having tested it fully. Including hooking up a load cell. Lessons learned. Anyway I have connected a load cell and done a full test. Seems to be good now. Issue was mostly the Timer reuse but also had found a conversion need for the value int to str.

Hope this tests out well for you as well.

[techman83]

@jcassel - I combined your commits into #41 if you'd like to take a look. I noticed that it didn't show the correct weight. I originally ported the existing library from python2 -> python3, and it has a few quirks as a result.

Things I fixed/changed over in my PR

• lastknownweight only gets updated when the web fronted is loaded, so weight wouldn't change if the UI wasn't open
• lastknownweight is the raw value, I've implemented a python version of what happens in the frontend to get the filament weight
• I simplified the methods a little
• Fixed up the commit messages

If you would like to give it a once over, I'll get a release out the door!