[Homematic] Fix "Channel not found for Datapoint" errors

[Flole998]

Issue described and tested in https://community.openhab.org/t/homematic-binding-channel-not-found-for-datapoint-errors-for-definitely-existing-channels/26209/113

Fixes: #11214
Signed-off-by: Flole flole@flole.de

[Flole998]

@FStolte @gerrieg @mdicke2s Can anybody review please?

[openhab-bot]

This pull request has been mentioned on openHAB Community. There might be relevant details there:

https://community.openhab.org/t/homematic-binding-channel-not-found-for-datapoint-errors-for-definitely-existing-channels/26209/134

[maniac103]

What still irks me about this is that this change is just a workaround for what should be a bug elsewhere. Did you try adding some breakpoints in ThingFactory or BaseThingHandlerFactory to check the state of the ThingType at thing creation time?
AFAICT, the flow is

• inbox contains thing UID and thing type UID
• inbox calls ThingFactory.createThing(), passing thing UID, thing type UID, and bridge UID
• ThingFactory.createThing() tries to lookup a ThingHandlerFactory based on the thing type UID; if this fails, no thing is created
• ThingFactory.craeteThing() calls createThing() in the found factory (here, it's HomematicThingHandlerFactory)
• HomematicThingHandlerFactory.createThing (or rather the base class implementation in BaseThingHandlerFactory) looks up the ThingType by the thing type UID via ThingTypeRegistry, which in turn looks through all registered ThingTypeProviders. In our case, HomematicThingTypeProviderImpl should match. If no ThingType can be found, no thing is created.
• ThingFactory.createThing is called, passing in the found ThingType, which in turn calls ThingFactoryHelper.createChannels
• ThingFactoryHelper.createChannels loops over thingType.getChannelDefinitions(), calling ThingFactoryHelper.createChannel for each one, which in turn calls ThingFactoryHelper.createChannelBuilder
• That one looks up a ChannelType from the channel type UID in the channel definition using a call to ChannelTypeRegistry.getChannelType()
• That one looks through all ChannelTypeProviders (here: HomematicChannelTypeProviderImpl) for a matching channel type
• EDIT: HomematicChannelTypeProviderImpl should return the channel type which was added at HomematicTypeGeneratorImpl.generate() time

AFAICT, the only case where a thing can be created without channels is if the channel type lookup fails, so it would be great if you could verify this actually being the case (maybe start by overriding and adding some debug statements to HomematicThingHandlerFactory.createThing() and HomematicChannelTypeProviderImpl.getChannelType()). If it is, we need to check what's off in channel type registration. Unfortunately it's hard to follow git history due to the code being moved between repositories several times.

[Flole998]

The reason this is necessary is, that (at least) when using text based config it could happen that things are created before the bridge is online or the thing type has been populated with the channels. In that case an empty thing type is used and the thing is missing the channels as when a thing type is updated the things that use it aren't automatically. So this will add the channels in that case.

[maniac103]

So this essentially means that createThing() is called before generate() is called, right?

[Flole998]

Yes iirc that was the issue. I also tried to re-create (basically reload) the thing if the channels are empty and that created the channels as well (but caused other issues).

If you ask me the current attempt is a wrong approach anyways as there's another Limit: If there are multiple versions of the same device with different channels it will cause issues. It would be better to request the channels for each thing and populate them on initialization.

[Flole998]

@maniac103 I just fixed the 2 things you commented.

[fwolter]

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[openhab-bot]

This pull request has been mentioned on openHAB Community. There might be relevant details there:

https://community.openhab.org/t/homematic-binding-channel-not-found-for-datapoint-errors-for-definitely-existing-channels/26209/136