lib.options.mkPackageOptionMD

The following is the current implementation of this function.

mkPackageOption =
    # Package set (an instantiation of nixpkgs such as pkgs in modules or another package set)
    pkgs:
      # Name for the package, shown in option description
      name:
      {
        # Whether the package can be null, for example to disable installing a package altogether (defaults to false)
        nullable ? false,
        # The attribute path where the default package is located (may be omitted, in which case it is copied from `name`)
        default ? name,
        # A string or an attribute path to use as an example (may be omitted)
        example ? null,
        # Additional text to include in the option description (may be omitted)
        extraDescription ? "",
        # Representation of the package set passed as pkgs (defaults to `"pkgs"`)
        pkgsText ? "pkgs"
      }:
      let
        name' = if isList name then last name else name;
        default' = if isList default then default else [ default ];
        defaultText = concatStringsSep "." 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}." + concatStringsSep "." example else example);
      });