nixos/home-assistant: Imperial unit system deprecated, cannot set new option

[NullCub3]

Nixpkgs version

• Unstable (25.05)

Describe the bug

Setting services.home-assistant.config.homeassistant.unit_system to imperial causes the following error to be shown inside of home assistant:

The imperial unit system is deprecated
Warning ⸱ Reported by Home Assistant Core Integration
The imperial unit system is deprecated and your system is currently using us customary. Please update your configuration to use the us customary unit system and reload the core configuration to fix this issue.

The correct value to use is us_customary but setting the option to that throws an error while trying to build the config:

error: A definition for option `services.home-assistant.config.homeassistant.unit_system' is not of type `null or one of "metric", "imperial"'. Definition values:
       - In `/nix/store/bc3d7zgqpx1g9vhjf0mi95ajy2kvjc7y-source/nixosModules/home-assistant.nix': "us_customary"

Steps to reproduce

1. Set services.home-assistant.config.homeassistant.unit_system to imperial
2. Warning about deprecation
3. Set services.home-assistant.config.homeassistant.unit_system to us_customary
4. Get error building configuration

Expected behaviour

Setting unit_system to us_customary should not throw an error

Screenshots

Relevant log output

No response

Additional context

home-assistant/core#130979
https://www.home-assistant.io/integrations/homeassistant/#unit_system

I am running nixos-24.11 for my main system but using the home-assistant package and module from nixos-unstable (As described in the wiki)

System metadata

• system: "x86_64-linux"
• host os: Linux 6.6.71, NixOS, 24.11 (Vicuna), 24.11pre-git
• multi-user?: yes
• sandbox: yes
• version: nix-env (Lix, like Nix) 2.91.1 System type: x86_64-linux Additional system types: i686-linux, x86_64-v1-linux, x86_64-v2-linux Features: gc, signed-caches System configuration file: /etc/nix/nix.conf User configuration files: /home/nullcube/.config/nix/nix.conf:/etc/xdg/nix/nix.conf:/home/nullcube/.nix-profile/etc/xdg/nix/nix.conf:/nix/profile/etc/xdg/nix/nix.conf:/home/nullcube/.local/state/nix/profile/etc/xdg/nix/nix.conf:/etc/profiles/per-user/nullcube/etc/xdg/nix/nix.conf:/nix/var/nix/profiles/default/etc/xdg/nix/nix.conf:/run/current-system/sw/etc/xdg/nix/nix.conf Store directory: /nix/store State directory: /nix/var/nix Data directory: /nix/store/6dxshp2qaas92v7d36baf7y95q0v98dn-lix-2.91.1/share
• nixpkgs: /nix/store/zd5dgszslv09jzybcpf25gpl12s6r2d9-source

Notify maintainers

@Mic92 @fabaff @mweinelt

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[SigmaSquadron]

Looks like all this needs is a tiny change in the assertion, so I'm marking this as a good first issue.

This is the line that needs to be changed:

nixpkgs/nixos/modules/services/home-automation/home-assistant.nix

Line 276 in 635e887

type = types.nullOr (types.enum [ "metric" "imperial" ]);