1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
{ lib, config, ... }: let inherit (lib) types; in { options = { fun = lib.mkOption { type = types.functionTo types.str; }; result = lib.mkOption { type = types.str; default = config.fun 0; }; }; config.fun = input: input + 1; }