Packaging/Ruby

Ruby projects are generally packaged with bundix. This guide will show how to package a ruby project

Building BeEF

$ git clone https://github.com/beefproject/beef/

Create shell.nix with all dependencies

we create a shell.nix in the project directory:

with import <nixpkgs> {};
stdenv.mkDerivation {
  name = "env";
  buildInputs = [
    ruby.devEnv
    git
    sqlite
    libpcap
    postgresql
    libxml2
    libxslt
    pkg-config
    bundix
    gnumake
  ];
}

Build Gemfile.lock and gemset.nix

$ nix-shell
$ bundle install      # generates Gemfile.lock
$ bundix              # generates gemset.nix

Build default.nix

This will be the package configuration:

{ stdenv, bundlerEnv, ruby }:
let
  # the magic which will include gemset.nix
  gems = bundlerEnv {
    name = "beef-env";
    inherit ruby;
    gemdir  = ./.;
  };
in stdenv.mkDerivation {
  name = "beef";
  src = ./.;
  buildInputs = [gems ruby];
  installPhase = ''
    mkdir -p $out/{bin,share/beef}
    cp -r * $out/share/beef
    bin=$out/bin/beef
# we are using bundle exec to start in the bundled environment
    cat > $bin <<EOF
#!/bin/sh -e
exec ${gems}/bin/bundle exec ${ruby}/bin/ruby $i "\$@"
EOF
    chmod +x $bin
  '';
}

Build the package

$ nix-build -E '((import <nixpkgs> {}).callPackage (import ./default.nix) { })' --keep-failed
....
do_sqlite3 build FAILED!

Our Problem is that do_sqlite3 wants to build native extensions and requires sqlite as dependency. There are two ways to solve this issue:

1. add a global override to your nixpkgs
2. set the gemConfig for the bundleEnv manually

Adding a global override for a gem

We edit: <nixpkgs/pkgs/development/ruby-modules/gem-config/default.nix:

{
   ...
   do_sqlite3 = attrs: {
     buildInputs = [ sqlite ];
   };
   ...
}

After this change we build the package again.

Defining groups

Sophisticated applications use groups to organize their gems like development, test and production. bundlerEnv only makes the default group available in the environment, that is all gems which are not in a group. To make other groups available, they need to be provided as an array. Don't forget to include the default group.

Example:

  gems = pkgs.bundlerEnv {
    name = "exampleApp";
    inherit ruby;
    gemfile = ./Gemfile;
    lockfile = ./Gemfile.lock;
    gemset = ./gemset.nix;
    groups = [ "default" "production" "development" "test" ];
  };

set the local gemConfig

TODO: also merge with the defaultGemConfig somehow

Using Bundler 2

Bundler 2 comes included with Ruby, so instead of importing ruby.devEnv import Ruby and Bundix separately.