let
  pkgs = import <unstable> { }; # pin the channel to ensure reproducibility!
in
pkgs.haskellPackages.developPackage {
  root = ./.;
  modifier = drv:
    pkgs.haskell.lib.addBuildTools drv (with pkgs.haskellPackages;
      [ cabal-install
        ghcid
        ghc
        haskell-language-server
        zlib
        cabal-plan
      ]);
}