pkgs:
with pkgs.lib; let
  inherit (pkgs) buildEnv callPackage writeTextDir;

  importAll = { root, exclude ? [] }:

    # adapted from http://chriswarbo.net/projects/nixos/useful_hacks.html
    let
      basename = removeSuffix ".nix";

      isMatch = name: type: (hasSuffix ".nix" name || type == "directory")
                         && ! elem name (map basename exclude);

      entry = name: _: {
        name = basename name;
        value = import (root + "/${name}");
      };
    in
      mapAttrs' entry (filterAttrs isMatch (readDir root))

in {
  shenvs = let
    build = name: { paths, enter ? null }: buildEnv {
      name = "shenv-${name}";
      paths = (optional (enter != null) (writeTextDir "lib/shenv/enter" enter))
            ++ paths;
    };
  in mapAttrs (name: shenv: build name (shenv pkgs)) (importAll {
    root = ../shenvs;
    exclude = [ "config" ];
  });
}