Add area sensor device class and unit conversions

[mikey0000]

Background

Several integrations are reporting area mowed or vacuumed, but lack the functionality to have the area converted according to the user's configured unit system. Integrations are currently mostly using AREA_SQUARE_METER (which has no conversion to US Customary).

Proposal

Add an area sensor device class with support for unit conversion between US customary area measurements as well as metric area units

The following units should be supported:

SQUARE_METERS = "m²"
SQUARE_CENTIMETERS = "cm²"
SQUARE_KILOMETERS = "km²"
SQUARE_MILLIMETERS = "mm²"
SQUARE_INCHES = "in²"
SQUARE_FEET = "ft²"
SQUARE_YARDS = "yd²"
SQUARE_MILES = "mi²"
ACRES = "ac"
HECTARES = "ha"

Draft PR for reference: home-assistant/core#123563

Integrations which can benefit from the proposal

Currently there are the following integrations making use of AREA_SQUARE_METER
mammotion (HACS robot lawn mower)/me
ecovacs
bloomsky
rituals_perfume_genie
roborock
romy
roomba
smartthings
xiaomi_miio

[emontnemery]

Please make the proposal more concrete:

• Which area units will be supported
• We'll also need a new sensor device class, please update the proposal with that

[mikey0000]

Updated, please advise if there is anything I've missed.

[emontnemery]

Thanks a lot! I did some adjustment of the formatting.

[emontnemery]

The proposal has been approved in the core architectural meeting ✅

[frenck]

Done in home-assistant/core#123563

[make-all]

Perhaps there should be a checklist to ensure documentation is updated and announcements made about architectural changes that introduce deprecation warnings. Since the release of 2024.12 my issue tracker has been flooded with reports from users because HA is telling them to report a "bug" in my integration, but there is no mention of this in either the developer documentation, the user documentation or the developer blog (there is a one liner in the release notes, but it does not cover the scope of what has changed).

[mikey0000]

Seems the dev blog for it was not mergex
home-assistant/developers.home-assistant#2448

[mikey0000]

I'd missed an important comment and will address it so it can be merged