Add an overlay for node packages with coffeescript

overlay.nix

@@ -6,6 +6,9 @@ let
   override = rec {
     # These packages will hide packages in the top level nixpkgs
     swift = self.callPackage ./pkgs/swift { };
+
+    # Add our additional node packages
+    nodePackages = super.nodePackages // self.callPackage ./pkgs/node-packages { };
   };
 in {
   replitPackages = rec {

pkgs/node-packages/default.nix

@@ -0,0 +1,20 @@
+# This file has been generated by node2nix 1.9.0. Do not edit!
+
+{ pkgs ? import <nixpkgs> {
+    inherit system;
+  }
+, system ? builtins.currentSystem
+, nodejs ? pkgs."nodejs-12_x"
+}:
+
+let
+  nodeEnv = import ./node-env.nix {
+    inherit (pkgs) stdenv lib python2 runCommand writeTextFile;
+    inherit pkgs nodejs;
+    libtool = if pkgs.stdenv.isDarwin then pkgs.darwin.cctools else null;
+  };
+in
+import ./node-packages.nix {
+  inherit (pkgs) fetchurl nix-gitignore stdenv lib fetchgit;
+  inherit nodeEnv;
+}

pkgs/node-packages/generate.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+nix-shell -p nodePackages.node2nix --run 'node2nix -i node-packages.json'
+nix-shell -p nixpkgs-fmt --run 'nixpkgs-fmt .'
+