fetch-cabal.nix

# use it like this: (import ./fetch-cabal pkgs pkgs.haskellPackages).fetchZip "url" "sha256" "subfolder in archive"

pkgs: haskellPackages:
let
  srcPackage = src: folder:
    pkgs.runCommand "src-package"
      {
        inherit src;
        buildInputs = [ pkgs.cabal2nix ];
      }
      ''
        mkdir -p $out
        cp -r $src/${folder}/* $out
        cd $out
        cabal2nix . > package.nix
      '';

  fetch = src: folder: haskellPackages.callPackage "${srcPackage src folder}/package.nix" {};
in {
  inherit fetch;

  fromGit = url: rev: sha256: fetch (pkgs.fetchgit {
    inherit url rev sha256;
  });
  fromZip = url: sha256: fetch (pkgs.fetchzip {
    inherit url sha256;
  });
}