core/pkgs/build-support/fetchbower/default.nix

{
  stdenvNoCC,
  lib,
  bower2nix,
  cacert,
}:
let
  bowerVersion =
    version:
    let
      components = lib.splitString "#" version;
      hash = lib.last components;
      ver = if builtins.length components == 1 then (cleanName version) else hash;
    in
    ver;

  cleanName =
    name:
    lib.replaceStrings
      [
        "/"
        ":"
      ]
      [
        "-"
        "-"
      ]
      name;

  fetchbower =
    name: version: target: outputHash:
    stdenvNoCC.mkDerivation {
      name = "${cleanName name}-${bowerVersion version}";
      buildCommand = ''
        fetch-bower --quiet --out=$PWD/out "${name}" "${target}" "${version}"
        # In some cases, the result of fetchBower is different depending
        # on the output directory (e.g. if the bower package contains
        # symlinks). So use a local output directory before copying to
        # $out.
        cp -R out $out
      '';
      outputHashMode = "recursive";
      outputHashAlgo = "sha256";
      inherit outputHash;
      nativeBuildInputs = [
        bower2nix
        cacert
      ];
    };

in
fetchbower