nixfiles/modules/features.nix

# Feature-flag option declarations shared by every NixOS host (imported via
# baseModules in flake.nix). Declaring the flags here -- rather than inside the
# module that implements them -- means a host can read or set a flag without
# importing the (often large) implementation module. In particular,
# features.swayDesktop.enable is read by modules/users.nix on every host, but a
# headless host (e.g. the Pi) must be able to leave it at its default without
# pulling in modules/sway.nix. The implementation lives in modules/sway.nix,
# gated on this flag.
{ lib, ... }:
{
  options.features.swayDesktop.enable = lib.mkEnableOption "the Sway desktop";
}