dream2nix/lib/types/default.nix

{
  lib,
  dream2nix,
  specialArgs,
  ...
}: let
  t = lib.types;
in rec {
  derivation = t.oneOf [t.str t.path t.package];

  # A stricter submodule type that prevents derivations from being
  # detected as modules by accident. (derivations are attrs as well as modules)
  drvPart = let
    type = t.submoduleWith {
      modules = [dream2nix.modules.dream2nix.core];
      inherit specialArgs;
    };
  in
    type
    // {
      # Ensure that derivations are never detected as modules by accident.
      check = val: type.check val && (val.type or null != "derivation");
    };

  # polymorphic type, that can either represent a derivation or a drv-part.
  # The stricter`drvPart` type is needed to prevent derivations being
  #   classified as modules by accident.
  # This is important because derivations cannot be merged with drv-parts.
  drvPartOrPackage = t.either derivation drvPart;
}