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1 | -*- mode: org; coding: utf-8; -*- |
2 | ||
08ba7ff3 | 3 | #+TITLE: Hacking GNU Guix and Its Incredible Distro |
450ccdc3 | 4 | |
5ff3c4b8 | 5 | Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org> |
84dbbc76 | 6 | Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org> |
5ff3c4b8 | 7 | Copyright © 2014 Pierre-Antoine Rault <par@rigelk.eu> |
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8 | |
9 | Copying and distribution of this file, with or without modification, | |
10 | are permitted in any medium without royalty provided the copyright | |
11 | notice and this notice are preserved. | |
12 | ||
13 | ||
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14 | * Building from Git |
15 | ||
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16 | When building Guix from a checkout, the following packages are required in |
17 | addition to those mentioned in the installation instructions: | |
18 | ||
19 | - [[http://www.gnu.org/software/autoconf/][GNU Autoconf]] | |
20 | - [[http://www.gnu.org/software/automake/][GNU Automake]] | |
21 | - [[http://www.gnu.org/software/gettext/][GNU Gettext]] | |
22 | - [[http://www.graphviz.org/][Graphviz]] | |
23 | ||
24 | Run ‘./bootstrap’ to download the Nix daemon source code and to generate the | |
25 | build system infrastructure using autoconf. It reports an error if an | |
26 | inappropriate version of the above packages is being used. | |
27 | ||
25ed6edb | 28 | If you get an error like this one: |
84dbbc76 | 29 | |
25ed6edb | 30 | configure.ac:46: error: possibly undefined macro: PKG_CHECK_MODULES |
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31 | |
32 | it probably means that Autoconf couldn’t find ‘pkg.m4’, which is provided by | |
33 | pkg-config. Make sure that ‘pkg.m4’ is available. For instance, if you | |
34 | installed Automake in ‘/usr/local’, it wouldn’t look for ‘.m4’ files in | |
35 | ‘/usr/share’. So you have to invoke the following command in that case | |
36 | ||
37 | $ export ACLOCAL_PATH=/usr/share/aclocal | |
38 | ||
39 | See “info '(automake) Macro Search Path'” for more information. | |
40 | ||
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41 | Then, run ‘./configure’ as usual. |
42 | ||
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43 | Finally, you have to invoke ‘make check’ to run tests. If anything fails, |
44 | take a look at “info '(guix) Installation'” or send a message to | |
8b2d9e5d | 45 | <guix-devel@gnu.org>. |
84dbbc76 | 46 | |
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47 | * Running Guix before it is installed |
48 | ||
49 | Command-line tools can be used even if you have not run "make install". | |
50 | To do that, prefix each command with ‘./pre-inst-env’, as in: | |
51 | ||
9bf3c1a7 | 52 | ./pre-inst-env guix build --help |
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53 | |
54 | Similarly, for a Guile session using the Guix modules: | |
55 | ||
56 | ./pre-inst-env guile -c '(use-modules (guix utils)) (pk (%current-system))' | |
57 | ||
58 | The ‘pre-inst-env’ script sets up all the environment variables | |
59 | necessary to support this. | |
60 | ||
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61 | * The Perfect Setup |
62 | ||
63 | The Perfect Setup to hack on Guix is basically the perfect setup used | |
64 | for Guile hacking (info "(guile) Using Guile in Emacs"). First, you | |
65 | need more than an editor, you need [[http://www.gnu.org/software/emacs][Emacs]], empowered by the wonderful | |
66 | [[http://nongnu.org/geiser/][Geiser]]. | |
67 | ||
68 | Geiser allows for interactive and incremental development from within | |
69 | Emacs: code compilation and evaluation from within buffers, access to | |
70 | on-line documentation (docstrings), context-sensitive completion, M-. to | |
71 | jump to an object definition, a REPL to try out your code, and more. | |
72 | ||
73 | To actually edit the code, Emacs already has a neat Scheme mode. But in | |
74 | addition to that, you must not miss [[http://www.emacswiki.org/emacs/ParEdit][Paredit]]. It provides facilities to | |
75 | directly operate on the syntax tree, such as raising an s-expression or | |
76 | wrapping it, swallowing or rejecting the following s-expression, etc. | |
77 | ||
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78 | * Submitting Patches |
79 | ||
80 | Development is done using the Git distributed version control system. Thus, | |
81 | access to the repository is not strictly necessary. We welcome contributions | |
82 | in the form of patches as produced by ‘git format-patch’ sent to | |
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83 | guix-devel@gnu.org. Please write commit logs in the [[http://www.gnu.org/prep/standards/html_node/Change-Logs.html#Change-Logs][GNU ChangeLog |
84 | format]]; you can check the commit history for examples. | |
85 | ||
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86 | Before submitting a patch that adds or modifies a package definition, please |
87 | run ‘guix lint PACKAGE’, where PACKAGE is the name of the new or modified | |
88 | package, and fix any errors it reports. In addition, please make sure the | |
89 | package builds on your platform, using ‘guix build’. You may also want to | |
90 | check that dependent package (if applicable) are not affected by the change; | |
91 | ‘guix refresh --list-dependent PACKAGE’ will help you do that. | |
92 | ||
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93 | When posting a patch to the mailing list, use "[PATCH] ..." as a subject. You |
94 | may use your email client or the ‘git send-mail’ command. | |
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95 | |
96 | As you become a regular contributor, you may find it convenient to have write | |
97 | access to the repository (see below.) | |
98 | ||
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99 | * Coding Style |
100 | ||
101 | In general our code follows the [[info:standards][GNU Coding Standards]] (GCS). However, the GCS | |
102 | do not say much about Scheme, so here are some additional rules. | |
103 | ||
104 | ** Programming Paradigm | |
105 | ||
106 | Scheme code in Guix is written in a purely functional style. One exception is | |
107 | code that involves input/output, and procedures that implement low-level | |
108 | concepts, such as the ‘memoize’ procedure. | |
109 | ||
110 | ** Modules | |
111 | ||
112 | Guile modules that are meant to be used on the builder side must live in the | |
113 | (guix build …) name space. They must not refer to other Guix or GNU modules. | |
114 | However, it is OK for a “host-side” module to use a build-side module. | |
115 | ||
116 | Modules that deal with the broader GNU system should be in the (gnu …) name | |
117 | space rather than (guix …). | |
118 | ||
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119 | ** Data Types and Pattern Matching |
120 | ||
121 | The tendency in classical Lisp is to use lists to represent everything, and | |
122 | then to browse them “by hand” using ‘car’, ‘cdr’, ‘cadr’, and co. There are | |
123 | several problems with that style, notably the fact that it is hard to read, | |
124 | error-prone, and a hindrance to proper type error reports. | |
125 | ||
126 | Guix code should define appropriate data types (for instance, using | |
127 | ‘define-record-type*’) rather than abuse lists. In addition, it should use | |
128 | pattern matching, via Guile’s (ice-9 match) module, especially when matching | |
129 | lists. | |
130 | ||
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131 | ** Formatting Code |
132 | ||
133 | When writing Scheme code, we follow common wisdom among Scheme programmers. | |
134 | In general, we follow the [[http://mumble.net/~campbell/scheme/style.txt][Riastradh's Lisp Style Rules]]. This document happens | |
135 | to describe the conventions mostly used in Guile’s code too. It is very | |
136 | thoughtful and well written, so please do read it. | |
137 | ||
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138 | Some special forms introduced in Guix, such as the ‘substitute*’ macro, have |
139 | special indentation rules. These are defined in the .dir-locals.el file, | |
140 | which Emacs automatically uses. If you do not use Emacs, please make sure to | |
141 | let your editor know the rules. | |
142 | ||
143 | We require all top-level procedures to carry a docstring. This requirement | |
144 | can be relaxed for simple private procedures in the (guix build …) name space, | |
145 | though. | |
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146 | |
147 | Procedures should not have more than four positional parameters. Use keyword | |
148 | parameters for procedures that take more than four parameters. | |
149 | ||
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150 | * Commit Access |
151 | ||
152 | For frequent contributors, having write access to the repository is | |
153 | convenient. When you deem it necessary, feel free to ask for it on the | |
154 | mailing list. When you get commit access, please make sure to follow the | |
2d2ad989 | 155 | policy below (discussions of the policy can take place on guix-devel@gnu.org.) |
9bf3c1a7 | 156 | |
2d2ad989 | 157 | Non-trivial patches should always be posted to guix-devel@gnu.org (trivial |
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158 | patches include fixing typos, etc.) |
159 | ||
160 | For patches that just add a new package, and a simple one, it’s OK to commit, | |
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161 | if you’re confident (which means you successfully built it in a chroot setup, |
162 | and have done a reasonable copyright and license auditing.) Likewise for | |
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163 | package upgrades, except upgrades that trigger a lot of rebuilds (for example, |
164 | upgrading GnuTLS or GLib.) We have a mailing list for commit notifications | |
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165 | (guix-commits@gnu.org), so people can notice. Before pushing your changes, |
166 | make sure to run ‘git pull --rebase’. | |
9bf3c1a7 | 167 | |
2d2ad989 | 168 | For anything else, please post to guix-devel@gnu.org and leave time for a |
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169 | review, without committing anything. If you didn’t receive any reply |
170 | after two weeks, and if you’re confident, it’s OK to commit. | |
171 | ||
172 | That last part is subject to being adjusted, allowing individuals to commit | |
173 | directly on non-controversial changes on parts they’re familiar with. |