lib.options.mkPackageOptionMD

The following is the current implementation of this function.

mkPackageOption =
    pkgs: name:
    {
      nullable ? false,
      default ? name,
      example ? null,
      extraDescription ? "",
      pkgsText ? "pkgs",
    }:
    let
      name' = if isList name then last name else name;
      default' = toList default;
      defaultText = showAttrPath default';
      defaultValue = attrByPath default' (throw "${defaultText} cannot be found in ${pkgsText}") pkgs;
      defaults =
        if default != null then
          {
            default = defaultValue;
            defaultText = literalExpression "${pkgsText}.${defaultText}";
          }
        else
          optionalAttrs nullable {
            default = null;
          };
    in
    mkOption (
      defaults
      // {
        description =
          "The ${name'} package to use." + (if extraDescription == "" then "" else " ") + extraDescription;
        type = with lib.types; (if nullable then nullOr else lib.id) package;
      }
      // optionalAttrs (example != null) {
        example = literalExpression (
          if isList example then "${pkgsText}.${showAttrPath example}" else example
        );
      }
    );