Set icons for sensors that are in units of degrees

[sdague]

This also updates the icon rotation direction based on the degrees
direction, which means that something like a wind sensor will have an
icon which is in a representative direction.

[mention-bot]

@sdague, thanks for your PR! By analyzing the history of the files in this pull request, we identified @balloob, @armills and @robbiet480 to be potential reviewers.

[sdague]

This is mostly a concept patch to figure out if going down this direction is something that's worth while. Please let me know what you think.

[emlove]

You can use device_class as the semantic selector for this behavior. (This is a new feature going out with 0.39.) The first step would be a PR to add device_class support to the sensor component to replace these icon exceptions. See home-assistant/core#5881 as an example. You could then maybe use navigation, or a new device class for the rotation.

[sdague]

@armills yeh, I could see putting device_class into the sensors infrastructure and selecting on that. Sensors are the things I'm most interested in right now, and I think that actually semantically calling things:

"temperature"
"humidity"
"wind:speed"
"wind:gust"
"wind:direction"
"barometer"
"light:brightness"
"light:uv"

possibly others. Honestly, if there was a good existing taxonomy would just want to reuse that. That could push a lot of the guessing based on units out of the JS and do this more semantic approach.

[emlove]

Yep, this is exactly what device_class is for. I don't think we currently have a well defined list of possible classes, but that's what device_class will add. The specific names used will have to be hashed out in the PR. We don't need to come up with a complete list all at once, but once we add a class we should expect it to never change.

[MartinHjelmare]

I've been looking at refactoring the unit system in HA to be more coherent. Point is that a device type or attribute type should have the same unit all over HA. Another point with this is the possiblity to group entities and attributes by type and not by unit of measure. This is important eg when logging data into a db like influxdb. The device_class concept will work nicely in that plan. I think using the device_class to look up unit and icon for an entity is the way to go.

[balloob]

I like using the device_class.

[sdague]

Ok, how should I go about standardizing device_class? Issue tracking on the main home-assistant side, then start looking at the taxonomy there?

[balloob]

I think that we should do like we did for binary sensor - grow as we go:

• Pick a platform, add device classes to it.
• Add support for device class in frontend
• Repeat.

[balloob]

Going to close this PR as it's gone stale. The idea is still good, let's hope someone starts on it.