nixos-config/modules/nixos/_private/state/default.nix

{ lib, ... }:

{
  imports = [
    ./paths.nix
    ./ports.nix
  ];

  # We can basically dump everything that is supposed to hold values for the
  # entire system. This entry module should contain NOTHING ELSE!
  options.state = lib.mkOption {
    type = lib.types.submodule {
      freeformType = with lib.types; attrsOf anything;
      default = { };
    };
    default = { };
    description = ''
      A set of values referring to the system state for use in other parts of
      the NixOS system. Useful for consistent values and referring to a single
      source of truth for different parts (e.g., services, program) of the
      system.
    '';
    example = lib.literalExpression ''
      {
        services = {
          postgresql.directory = "/var/lib/postgresql";
          backup.ignoreDirectories = [
            "node_modules"
            ".direnv"
          ];
        };
      }
    '';
  };
}