mkShell: use extendMkDerivation

{

  lib,

  stdenv,

  buildEnv,

}:

# A special kind of derivation that is only meant to be consumed by the

# nix-shell.

lib.extendMkDerivation {

  constructDrv = stdenv.mkDerivation;

  excludeDrvArgNames = [

    "packages"

    "inputsFrom"

  ];

  extendDrvArgs =

    _finalAttrs:

    {

      name ? "nix-shell",

      # a list of packages to add to the shell environment

      packages ? [ ],

      # propagate all the inputs from the given derivations

      inputsFrom ? [ ],

  buildInputs ? [ ],

  nativeBuildInputs ? [ ],

  propagatedBuildInputs ? [ ],

  propagatedNativeBuildInputs ? [ ],

      ...

    }@attrs:

    let

          # 3. filter out of the result everything that's in `inputsFrom` itself

          # this leaves actual dependencies of the derivations in `inputsFrom`, but never the derivations themselves

          (lib.subtractLists inputsFrom (lib.flatten (lib.catAttrs name inputsFrom)));

  rest = removeAttrs attrs [

    "name"

    "packages"

    "inputsFrom"

    "buildInputs"

    "nativeBuildInputs"

    "propagatedBuildInputs"

    "propagatedNativeBuildInputs"

    "shellHook"

  ];

    in

stdenv.mkDerivation (

    {

      inherit name;

        lib.catAttrs "shellHook" (lib.reverseList inputsFrom ++ [ attrs ])

      );

    phases = [ "buildPhase" ];

      phases = attrs.phases or [ "buildPhase" ];

    buildPhase = ''

      buildPhase =

        attrs.buildPhase or ''

          { echo "------------------------------------------------------------";

            echo " WARNING: the existence of this path is not guaranteed.";

            echo " It is an internal implementation detail for pkgs.mkShell.";

          } >> "$out"

        '';

    preferLocalBuild = true;

      preferLocalBuild = attrs.preferLocalBuild or true;

    };

}

  // rest

)