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  1. @node Contributing
  2. @chapter Contributing
  3. This project is a cooperative effort, and we need your help to make it
  4. grow! Please get in touch with us on @email{guix-devel@@gnu.org} and
  5. @code{#guix} on the Freenode IRC network. We welcome ideas, bug
  6. reports, patches, and anything that may be helpful to the project. We
  7. particularly welcome help on packaging (@pxref{Packaging Guidelines}).
  8. @cindex code of conduct, of contributors
  9. @cindex contributor covenant
  10. We want to provide a warm, friendly, and harassment-free environment, so
  11. that anyone can contribute to the best of their abilities. To this end
  12. our project uses a ``Contributor Covenant'', which was adapted from
  13. @url{http://contributor-covenant.org/}. You can find a local version in
  14. the @file{CODE-OF-CONDUCT} file in the source tree.
  15. Contributors are not required to use their legal name in patches and
  16. on-line communication; they can use any name or pseudonym of their
  17. choice.
  18. @menu
  19. * Building from Git:: The latest and greatest.
  20. * Running Guix Before It Is Installed:: Hacker tricks.
  21. * The Perfect Setup:: The right tools.
  22. * Coding Style:: Hygiene of the contributor.
  23. * Submitting Patches:: Share your work.
  24. @end menu
  25. @node Building from Git
  26. @section Building from Git
  27. If you want to hack Guix itself, it is recommended to use the latest
  28. version from the Git repository. When building Guix from a checkout,
  29. the following packages are required in addition to those mentioned in
  30. the installation instructions (@pxref{Requirements}).
  31. @itemize
  32. @item @url{http://gnu.org/software/autoconf/, GNU Autoconf};
  33. @item @url{http://gnu.org/software/automake/, GNU Automake};
  34. @item @url{http://gnu.org/software/gettext/, GNU Gettext};
  35. @item @url{http://gnu.org/software/texinfo/, GNU Texinfo};
  36. @item @url{http://www.graphviz.org/, Graphviz};
  37. @item @url{http://www.gnu.org/software/help2man/, GNU Help2man (optional)}.
  38. @end itemize
  39. The easiest way to set up a development environment for Guix is, of
  40. course, by using Guix! The following command starts a new shell where
  41. all the dependencies and appropriate environment variables are set up to
  42. hack on Guix:
  43. @example
  44. guix environment guix
  45. @end example
  46. @xref{Invoking guix environment}, for more information on that command.
  47. Extra dependencies can be added with @option{--ad-hoc}:
  48. @example
  49. guix environment guix --ad-hoc help2man git strace
  50. @end example
  51. Run @command{./bootstrap} to generate the build system infrastructure
  52. using Autoconf and Automake. If you get an error like this one:
  53. @example
  54. configure.ac:46: error: possibly undefined macro: PKG_CHECK_MODULES
  55. @end example
  56. @noindent
  57. it probably means that Autoconf couldn’t find @file{pkg.m4}, which is
  58. provided by pkg-config. Make sure that @file{pkg.m4} is available. The
  59. same holds for the @file{guile.m4} set of macros provided by Guile. For
  60. instance, if you installed Automake in @file{/usr/local}, it wouldn’t
  61. look for @file{.m4} files in @file{/usr/share}. In that case, you have
  62. to invoke the following command:
  63. @example
  64. export ACLOCAL_PATH=/usr/share/aclocal
  65. @end example
  66. @xref{Macro Search Path,,, automake, The GNU Automake Manual}, for
  67. more information.
  68. Then, run @command{./configure} as usual. Make sure to pass
  69. @code{--localstatedir=@var{directory}} where @var{directory} is the
  70. @code{localstatedir} value used by your current installation (@pxref{The
  71. Store}, for information about this).
  72. Finally, you have to invoke @code{make check} to run tests
  73. (@pxref{Running the Test Suite}). If anything
  74. fails, take a look at installation instructions (@pxref{Installation})
  75. or send a message to the @email{guix-devel@@gnu.org, mailing list}.
  76. @node Running Guix Before It Is Installed
  77. @section Running Guix Before It Is Installed
  78. In order to keep a sane working environment, you will find it useful to
  79. test the changes made in your local source tree checkout without
  80. actually installing them. So that you can distinguish between your
  81. ``end-user'' hat and your ``motley'' costume.
  82. To that end, all the command-line tools can be used even if you have not
  83. run @code{make install}. To do that, prefix each command with
  84. @command{./pre-inst-env} (the @file{pre-inst-env} script lives in the
  85. top build tree of Guix), as in:
  86. @example
  87. $ sudo ./pre-inst-env guix-daemon --build-users-group=guixbuild
  88. $ ./pre-inst-env guix build hello
  89. @end example
  90. @noindent
  91. Similarly, for a Guile session using the Guix modules:
  92. @example
  93. $ ./pre-inst-env guile -c '(use-modules (guix utils)) (pk (%current-system))'
  94. ;;; ("x86_64-linux")
  95. @end example
  96. @noindent
  97. @cindex REPL
  98. @cindex read-eval-print loop
  99. @dots{} and for a REPL (@pxref{Using Guile Interactively,,, guile, Guile
  100. Reference Manual}):
  101. @example
  102. $ ./pre-inst-env guile
  103. scheme@@(guile-user)> ,use(guix)
  104. scheme@@(guile-user)> ,use(gnu)
  105. scheme@@(guile-user)> (define snakes
  106. (fold-packages
  107. (lambda (package lst)
  108. (if (string-prefix? "python"
  109. (package-name package))
  110. (cons package lst)
  111. lst))
  112. '()))
  113. scheme@@(guile-user)> (length snakes)
  114. $1 = 361
  115. @end example
  116. The @command{pre-inst-env} script sets up all the environment variables
  117. necessary to support this, including @env{PATH} and @env{GUILE_LOAD_PATH}.
  118. Note that @command{./pre-inst-env guix pull} does @emph{not} upgrade the
  119. local source tree; it simply updates the @file{~/.config/guix/latest}
  120. symlink (@pxref{Invoking guix pull}). Run @command{git pull} instead if
  121. you want to upgrade your local source tree.@footnote{If you would like
  122. to set up @command{guix} to use your Git checkout, you can point the
  123. @file{~/.config/guix/latest} symlink to your Git checkout directory.
  124. If you are the sole user of your system, you may also consider pointing
  125. the @file{/root/.config/guix/latest} symlink to point to
  126. @file{~/.config/guix/latest}; this way it will always use the same
  127. @command{guix} as your user does.}
  128. @node The Perfect Setup
  129. @section The Perfect Setup
  130. The Perfect Setup to hack on Guix is basically the perfect setup used
  131. for Guile hacking (@pxref{Using Guile in Emacs,,, guile, Guile Reference
  132. Manual}). First, you need more than an editor, you need
  133. @url{http://www.gnu.org/software/emacs, Emacs}, empowered by the
  134. wonderful @url{http://nongnu.org/geiser/, Geiser}.
  135. Geiser allows for interactive and incremental development from within
  136. Emacs: code compilation and evaluation from within buffers, access to
  137. on-line documentation (docstrings), context-sensitive completion,
  138. @kbd{M-.} to jump to an object definition, a REPL to try out your code,
  139. and more (@pxref{Introduction,,, geiser, Geiser User Manual}). For
  140. convenient Guix development, make sure to augment Guile’s load path so
  141. that it finds source files from your checkout:
  142. @lisp
  143. ;; @r{Assuming the Guix checkout is in ~/src/guix.}
  144. (with-eval-after-load 'geiser-guile
  145. (add-to-list 'geiser-guile-load-path "~/src/guix"))
  146. @end lisp
  147. To actually edit the code, Emacs already has a neat Scheme mode. But in
  148. addition to that, you must not miss
  149. @url{http://www.emacswiki.org/emacs/ParEdit, Paredit}. It provides
  150. facilities to directly operate on the syntax tree, such as raising an
  151. s-expression or wrapping it, swallowing or rejecting the following
  152. s-expression, etc.
  153. @node Coding Style
  154. @section Coding Style
  155. In general our code follows the GNU Coding Standards (@pxref{Top,,,
  156. standards, GNU Coding Standards}). However, they do not say much about
  157. Scheme, so here are some additional rules.
  158. @menu
  159. * Programming Paradigm:: How to compose your elements.
  160. * Modules:: Where to store your code?
  161. * Data Types and Pattern Matching:: Implementing data structures.
  162. * Formatting Code:: Writing conventions.
  163. @end menu
  164. @node Programming Paradigm
  165. @subsection Programming Paradigm
  166. Scheme code in Guix is written in a purely functional style. One
  167. exception is code that involves input/output, and procedures that
  168. implement low-level concepts, such as the @code{memoize} procedure.
  169. @node Modules
  170. @subsection Modules
  171. Guile modules that are meant to be used on the builder side must live in
  172. the @code{(guix build @dots{})} name space. They must not refer to
  173. other Guix or GNU modules. However, it is OK for a ``host-side'' module
  174. to use a build-side module.
  175. Modules that deal with the broader GNU system should be in the
  176. @code{(gnu @dots{})} name space rather than @code{(guix @dots{})}.
  177. @node Data Types and Pattern Matching
  178. @subsection Data Types and Pattern Matching
  179. The tendency in classical Lisp is to use lists to represent everything,
  180. and then to browse them ``by hand'' using @code{car}, @code{cdr},
  181. @code{cadr}, and co. There are several problems with that style,
  182. notably the fact that it is hard to read, error-prone, and a hindrance
  183. to proper type error reports.
  184. Guix code should define appropriate data types (for instance, using
  185. @code{define-record-type*}) rather than abuse lists. In addition, it
  186. should use pattern matching, via Guile’s @code{(ice-9 match)} module,
  187. especially when matching lists.
  188. @node Formatting Code
  189. @subsection Formatting Code
  190. When writing Scheme code, we follow common wisdom among Scheme
  191. programmers. In general, we follow the
  192. @url{http://mumble.net/~campbell/scheme/style.txt, Riastradh's Lisp
  193. Style Rules}. This document happens to describe the conventions mostly
  194. used in Guile’s code too. It is very thoughtful and well written, so
  195. please do read it.
  196. Some special forms introduced in Guix, such as the @code{substitute*}
  197. macro, have special indentation rules. These are defined in the
  198. @file{.dir-locals.el} file, which Emacs automatically uses. If you do
  199. not use Emacs, please make sure to let your editor know the rules.
  200. We require all top-level procedures to carry a docstring. This
  201. requirement can be relaxed for simple private procedures in the
  202. @code{(guix build @dots{})} name space, though.
  203. Procedures should not have more than four positional parameters. Use
  204. keyword parameters for procedures that take more than four parameters.
  205. @node Submitting Patches
  206. @section Submitting Patches
  207. Development is done using the Git distributed version control system.
  208. Thus, access to the repository is not strictly necessary. We welcome
  209. contributions in the form of patches as produced by @code{git
  210. format-patch} sent to the @email{guix-devel@@gnu.org, mailing list}.
  211. Please write commit logs in the ChangeLog format (@pxref{Change Logs,,,
  212. standards, GNU Coding Standards}); you can check the commit history for
  213. examples.
  214. Before submitting a patch that adds or modifies a package definition,
  215. please run through this check list:
  216. @enumerate
  217. @item
  218. Take some time to provide an adequate synopsis and description for the
  219. package. @xref{Synopses and Descriptions}, for some guidelines.
  220. @item
  221. Run @code{guix lint @var{package}}, where @var{package} is the
  222. name of the new or modified package, and fix any errors it reports
  223. (@pxref{Invoking guix lint}).
  224. @item
  225. Make sure the package builds on your platform, using @code{guix build
  226. @var{package}}.
  227. @item
  228. @cindex bundling
  229. Make sure the package does not use bundled copies of software already
  230. available as separate packages.
  231. Sometimes, packages include copies of the source code of their
  232. dependencies as a convenience for users. However, as a distribution, we
  233. want to make sure that such packages end up using the copy we already
  234. have in the distribution, if there is one. This improves resource usage
  235. (the dependency is built and stored only once), and allows the
  236. distribution to make transverse changes such as applying security
  237. updates for a given software package in a single place and have them
  238. affect the whole system---something that bundled copies prevent.
  239. @item
  240. Take a look at the profile reported by @command{guix size}
  241. (@pxref{Invoking guix size}). This will allow you to notice references
  242. to other packages unwillingly retained. It may also help determine
  243. whether to split the package (@pxref{Packages with Multiple Outputs}),
  244. and which optional dependencies should be used.
  245. @item
  246. For important changes, check that dependent package (if applicable) are
  247. not affected by the change; @code{guix refresh --list-dependent
  248. @var{package}} will help you do that (@pxref{Invoking guix refresh}).
  249. Packages with roughly 100 dependents or more usually have to be
  250. committed to a separate branch. That branch can then be built
  251. separately by our build farm, and later merged into @code{master} once
  252. everything has been successfully built. This allows us to fix issues
  253. before they hit users, and to reduce the window during which pre-built
  254. binaries are not available.
  255. @item
  256. @cindex determinism, of build processes
  257. @cindex reproducible builds, checking
  258. Check whether the package's build process is deterministic. This
  259. typically means checking whether an independent build of the package
  260. yields the exact same result that you obtained, bit for bit.
  261. A simple way to do that is by building the same package several times in
  262. a row on your machine (@pxref{Invoking guix build}):
  263. @example
  264. guix build --rounds=2 my-package
  265. @end example
  266. This is enough to catch a class of common non-determinism issues, such
  267. as timestamps or randomly-generated output in the build result.
  268. Another option is to use @command{guix challenge} (@pxref{Invoking guix
  269. challenge}). You may run it once the package has been committed and
  270. built by @code{hydra.gnu.org} to check whether it obtains the same
  271. result as you did. Better yet: Find another machine that can build it
  272. and run @command{guix publish}. Since the remote build machine is
  273. likely different from yours, this can catch non-determinism issues
  274. related to the hardware---e.g., use of different instruction set
  275. extensions---or to the operating system kernel---e.g., reliance on
  276. @code{uname} or @file{/proc} files.
  277. @item
  278. When writing documentation, please use gender-neutral wording when
  279. referring to people, such as
  280. @uref{https://en.wikipedia.org/wiki/Singular_they, singular
  281. ``they''@comma{} ``their''@comma{} ``them''}, and so forth.
  282. @item
  283. Verify that your patch contains only one set of related changes.
  284. Bundling unrelated changes together makes reviewing harder and slower.
  285. Examples of unrelated changes include the addition of several packages,
  286. or a package update along with fixes to that package.
  287. @end enumerate
  288. When posting a patch to the mailing list, use @samp{[PATCH] @dots{}} as
  289. a subject. You may use your email client or the @command{git
  290. send-email} command. We prefer to get patches in plain text messages,
  291. either inline or as MIME attachments. You are advised to pay attention if
  292. your email client changes anything like line breaks or indentation which
  293. could potentially break the patches.