<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-language-ruby"> <title>Ruby</title> <para> There currently is support to bundle applications that are packaged as Ruby gems. The utility "bundix" allows you to write a <filename>Gemfile</filename>, let bundler create a <filename>Gemfile.lock</filename>, and then convert this into a nix expression that contains all Gem dependencies automatically. </para> <para> For example, to package sensu, we did: </para> <screen> <![CDATA[$ cd pkgs/servers/monitoring $ mkdir sensu $ cd sensu $ cat > Gemfile source 'https://rubygems.org' gem 'sensu' $ $(nix-build '<nixpkgs>' -A bundix --no-out-link)/bin/bundix --magic $ cat > default.nix { lib, bundlerEnv, ruby }: bundlerEnv rec { name = "sensu-${version}"; version = (import gemset).sensu.version; inherit ruby; # expects Gemfile, Gemfile.lock and gemset.nix in the same directory gemdir = ./.; meta = with lib; { description = "A monitoring framework that aims to be simple, malleable, and scalable"; homepage = "http://sensuapp.org/"; license = with licenses; mit; maintainers = with maintainers; [ theuni ]; platforms = platforms.unix; }; }]]> </screen> <para> Please check in the <filename>Gemfile</filename>, <filename>Gemfile.lock</filename> and the <filename>gemset.nix</filename> so future updates can be run easily. </para> <para> Updating Ruby packages can then be done like this: </para> <screen> <![CDATA[$ cd pkgs/servers/monitoring/sensu $ nix-shell -p bundler --run 'bundle lock --update' $ nix-shell -p bundix --run 'bundix' ]]> </screen> <para> For tools written in Ruby - i.e. where the desire is to install a package and then execute e.g. <command>rake</command> at the command line, there is an alternative builder called <literal>bundlerApp</literal>. Set up the <filename>gemset.nix</filename> the same way, and then, for example: </para> <screen> <![CDATA[{ lib, bundlerApp }: bundlerApp { pname = "corundum"; gemdir = ./.; exes = [ "corundum-skel" ]; meta = with lib; { description = "Tool and libraries for maintaining Ruby gems."; homepage = "https://github.com/nyarly/corundum"; license = licenses.mit; maintainers = [ maintainers.nyarly ]; platforms = platforms.unix; }; }]]> </screen> <para> The chief advantage of <literal>bundlerApp</literal> over <literal>bundlerEnv</literal> is the executables introduced in the environment are precisely those selected in the <literal>exes</literal> list, as opposed to <literal>bundlerEnv</literal> which adds all the executables made available by gems in the gemset, which can mean e.g. <command>rspec</command> or <command>rake</command> in unpredictable versions available from various packages. </para> <para> Resulting derivations for both builders also have two helpful attributes, <literal>env</literal> and <literal>wrappedRuby</literal>. The first one allows one to quickly drop into <command>nix-shell</command> with the specified environment present. E.g. <command>nix-shell -A sensu.env</command> would give you an environment with Ruby preset so it has all the libraries necessary for <literal>sensu</literal> in its paths. The second one can be used to make derivations from custom Ruby scripts which have <filename>Gemfile</filename>s with their dependencies specified. It is a derivation with <command>ruby</command> wrapped so it can find all the needed dependencies. For example, to make a derivation <literal>my-script</literal> for a <filename>my-script.rb</filename> (which should be placed in <filename>bin</filename>) you should run <command>bundix</command> as specified above and then use <literal>bundlerEnv</literal> like this: </para> <programlisting> <![CDATA[let env = bundlerEnv { name = "my-script-env"; inherit ruby; gemfile = ./Gemfile; lockfile = ./Gemfile.lock; gemset = ./gemset.nix; }; in stdenv.mkDerivation { name = "my-script"; buildInputs = [ env.wrappedRuby ]; script = ./my-script.rb; buildCommand = '' install -D -m755 $script $out/bin/my-script patchShebangs $out/bin/my-script ''; }]]> </programlisting> </section>