Migrate to generic discovery method

[balloob]

The only thing that has changed… is everything.

@kellerza introduced a generic load platform discovery mechanism for the Entity Component a couple of releases ago. This makes our existing hardcoded platform discovery obsolete so this PR removes it.

This is my first pass at it. I bet I made some mistakes…

[kellerza]

Going through it it looks good. Even added a tox test for load_platform. I never got to it and must say not sure I understand the mock calls yet.

I was wondering if load_platform should not rather be in homeassistant.util or homeassistant.helper?

When I started out discovery through discovery: in the config and all this "discovery" which is actually just a way of loading platforms from components was quite confusing. Even some of the component help on the websites adds to this confusion.

Some used discover, some not (but seems like you got them all here now) and overall its more uniform.

The fact that EntityComponent, which is part of the core, is dependant on a homeassistant.component.discovery feels wrong. homeassistant.components adds functionality, but core functionality should not be dependant on homeassistant.components in my view

[balloob]

You are so right. I will be moving all the discovery things to a discovery helper. The discovery component will solely exist to interface with netdisco and forward discoveries to the correct component/platform.

[kellerza]

Great, if you can please add qwikswitch.py import this should be good. Did a search its the only component that uses it atm.

[kellerza]

One extra bit that would be nice is a way to pass objects around, I know you said you only want it serializable on the event bus.

I add the below code to some of my custom components (qwikswitch is only used since it can be imported, custom components not) and it then gives me a global variable -- there might be a better way?

But with this custom component also have a way to pass objects around. (and so do some/lots of other components, without keeping their own globals)

def push_obj(obj):
    import homeassistant.components.qwikswitch as qwikswitch
    if qwikswitch.QSUSB is None:
        qwikswitch.QSUSB = {}
    oid = id(obj)
    qwikswitch.QSUSB[oid] = obj
    return oid

def pop_obj(id):
    import homeassistant.components.qwikswitch as qwikswitch
    return qwikswitch.QSUSB.pop(id)

I also based this on a weakref dictionary once, but could not find that code now. I think weakref mght be important, but not sure how solid my logic is there

[balloob]

All events on the eventbus have to be serializable because they are also being sent over MQTT and HTTP.

[kellerza]

So the bit of code above still allows it to be serializable, since you only send the oid

-The component push_obj and sends the oid in the params (all serializable)
-The platform receives the params with oid and uses the oid to pop_obj

[balloob]

Sorry, did not read your full comment because I was also watching a series 💃

I don't want to push objects over the event bus. Instead we should add some sort of global accessible objects to the hass instance. (captured in this pivotal story)

[kellerza]

farcy is always vigilant 👓 , even when you're watching series 😄