nixpkgs/pkgs/top-level/config.nix

# This file defines the structure of the `config` nixpkgs option.

{ lib, ... }:

with lib;

let

  mkMassRebuild = args: mkOption (builtins.removeAttrs args [ "feature" ] // {
    type = args.type or (types.uniq types.bool);
    default = args.default or false;
    description = (args.description or ''
      Whether to ${args.feature} while building nixpkgs packages.
    '') + ''
      Changing the default may cause a mass rebuild.
    '';
  });

  options = {

    /* Internal stuff */

    warnings = mkOption {
      type = types.listOf types.str;
      default = [];
      internal = true;
    };

    /* Config options */

    doCheckByDefault = mkMassRebuild {
      feature = "run <literal>checkPhase</literal> by default";
    };

    allowAliases = mkOption {
      type = types.bool;
      default = true;
      description = ''
        Whether to expose old attribute names for compatibility.

        The recommended setting is to enable this, as it
        improves backward compatibity, easing updates.

        The only reason to disable aliases is for continuous
        integration purposes. For instance, Nixpkgs should
        not depend on aliases in its internal code. Projects
        that aren't Nixpkgs should be cautious of instantly
        removing all usages of aliases, as migrating too soon
        can break compatibility with the stable Nixpkgs releases.
      '';
    };

  };

in {

  inherit options;

}