{
  lib,
  ...
}:
let
  # Every .nix file below a directory. Paths containing "/_" are skipped,
  # which is how work-in-progress modules stay out of the import tree.
  listModules =
    directory:
    lib.filter (
      path:
      let
        string = toString path;
      in
      lib.hasSuffix ".nix" string && !(lib.hasInfix "/_" string)
    ) (lib.filesystem.listFilesRecursive directory);
in
{
  inherit listModules;
}