A .nix file for building whatever version of purescript you want from the github releases

purescript.nix

{ env, pkgs, ghc }:
let
  pname = "purescript";
  pversion = "0.10.3";
  url = "https://github.com/purescript/purescript/archive/v${pversion}.tar.gz";
  sha256 = "46c3f695ccc6e7be3cb2afe1ea9586eafdf51a04f1d40fe7240def0d8693ca68";

in env.mkDerivation rec {
  name = pname;
  version = pversion;

  src = pkgs.fetchurl {
    url = url;
    sha256 = sha256;
    name = pname;
  };

  buildInputs = [ pkgs.stack
                  pkgs.haskell.compiler."${ghc}"
                  pkgs.ncurses5
                  pkgs.zlib
                  pkgs.haskell.packages."${ghc}".alex
                  pkgs.haskell.packages."${ghc}".happy
                ];

  # copied from generic-stack-builder.nix in the nixpkgs repository
  # workaround for https://ghc.haskell.org/trac/ghc/ticket/11042
  LD_LIBRARY_PATH = pkgs.stdenv.lib.makeLibraryPath (buildInputs);

  buildCommand = ''
    export HOME=/tmp/stack

    tar -xf $src
    cd purescript-0.10.3
    mkdir -p $out

    stack build --system-ghc --local-bin-path=$out/bin --copy-bins
  '';
}

shell.nix

let
  pkgs = import <nixpkgs> {};
  stdenv = pkgs.stdenv;
  purescript = pkgs.callPackage ./nix-deps/purescript.nix { env = pkgs.stdenv;
                                                            pkgs = pkgs;
                                                            ghc = "ghc7103";
                                                          };
in stdenv.mkDerivation {
  name =
  ...
}

I'm sure there is a better way to do this, but the purescript.nix file above is my solution to needing to get a particular version of purescript that is not actually in the nixpkgs mainline. I set it up with the intent that shell.nix for my project would include the purescript derivation. I also explicitly specify /tmp/stack as a way to cache stack build results so that I didn't have to rebuild the world on every single invocation of this script. I find this an acceptable compromise, at least for now, because stack does a reasonable job of handling build artifacts.