tjh.dev
1<section xmlns="http://docbook.org/ns/docbook"
2 xmlns:xlink="http://www.w3.org/1999/xlink"
3 xml:id="sec-language-ruby">
4 <title>Ruby</title>
5
6 <para>
7 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.
8 </para>
9
10 <para>
11 For example, to package sensu, we did:
12 </para>
13
14<screen>
15<prompt>$ </prompt>cd pkgs/servers/monitoring
16<prompt>$ </prompt>mkdir sensu
17<prompt>$ </prompt>cd sensu
18<prompt>$ </prompt>cat > Gemfile
19source 'https://rubygems.org'
20gem 'sensu'
21<prompt>$ </prompt>$(nix-build '<nixpkgs>' -A bundix --no-out-link)/bin/bundix --magic
22<prompt>$ </prompt>cat > default.nix
23{ lib, bundlerEnv, ruby }:
24
25bundlerEnv rec {
26 name = "sensu-${version}";
27
28 version = (import gemset).sensu.version;
29 inherit ruby;
30 # expects Gemfile, Gemfile.lock and gemset.nix in the same directory
31 gemdir = ./.;
32
33 meta = with lib; {
34 description = "A monitoring framework that aims to be simple, malleable, and scalable";
35 homepage = "http://sensuapp.org/";
36 license = with licenses; mit;
37 maintainers = with maintainers; [ theuni ];
38 platforms = platforms.unix;
39 };
40}
41</screen>
42
43 <para>
44 Please check in the <filename>Gemfile</filename>, <filename>Gemfile.lock</filename> and the <filename>gemset.nix</filename> so future updates can be run easily.
45 </para>
46
47 <para>
48 Updating Ruby packages can then be done like this:
49 </para>
50
51<screen>
52<prompt>$ </prompt>cd pkgs/servers/monitoring/sensu
53<prompt>$ </prompt>nix-shell -p bundler --run 'bundle lock --update'
54<prompt>$ </prompt>nix-shell -p bundix --run 'bundix'
55</screen>
56
57 <para>
58 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:
59 </para>
60
61<programlisting>
62<![CDATA[{ lib, bundlerApp }:
63
64bundlerApp {
65 pname = "corundum";
66 gemdir = ./.;
67 exes = [ "corundum-skel" ];
68
69 meta = with lib; {
70 description = "Tool and libraries for maintaining Ruby gems.";
71 homepage = "https://github.com/nyarly/corundum";
72 license = licenses.mit;
73 maintainers = [ maintainers.nyarly ];
74 platforms = platforms.unix;
75 };
76}]]>
77</programlisting>
78
79 <para>
80 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.
81 </para>
82
83 <para>
84 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:
85 </para>
86
87<programlisting>
88<![CDATA[let env = bundlerEnv {
89 name = "my-script-env";
90
91 inherit ruby;
92 gemfile = ./Gemfile;
93 lockfile = ./Gemfile.lock;
94 gemset = ./gemset.nix;
95};
96
97in stdenv.mkDerivation {
98 name = "my-script";
99 buildInputs = [ env.wrappedRuby ];
100 script = ./my-script.rb;
101 buildCommand = ''
102 install -D -m755 $script $out/bin/my-script
103 patchShebangs $out/bin/my-script
104 '';
105}]]>
106</programlisting>
107</section>