{ lib, ... }@flakeArg:
let
  inherit (builtins)
    isAttrs
    isBool
    isList
    isNull
    isString
    typeOf
    ;
  inherit (lib.strings) optionalString;
in
{

  conditionalString =
    cond:
    optionalString (
      if isNull cond then
        false
      else if isBool cond then
        cond
      else if isString cond then
        cond != ""
      else if isList cond then
        cond != [ ]
      else if isAttrs cond then
        cond.enable or (cond != { })
      else
        throw "unexpected type of condition ${typeOf cond}"
    );

}