@node Contributing @chapter Contributing This project is a cooperative effort, and we need your help to make it grow! Please get in touch with us on @email{guix-devel@@gnu.org} and @code{#guix} on the Freenode IRC network. We welcome ideas, bug reports, patches, and anything that may be helpful to the project. We particularly welcome help on packaging (@pxref{Packaging Guidelines}). @cindex code of conduct, of contributors @cindex contributor covenant We want to provide a warm, friendly, and harassment-free environment, so that anyone can contribute to the best of their abilities. To this end our project uses a ``Contributor Covenant'', which was adapted from @url{http://contributor-covenant.org/}. You can find a local version in the @file{CODE-OF-CONDUCT} file in the source tree. Contributors are not required to use their legal name in patches and on-line communication; they can use any name or pseudonym of their choice. @menu * Building from Git:: The latest and greatest. * Running Guix Before It Is Installed:: Hacker tricks. * The Perfect Setup:: The right tools. * Packaging Guidelines:: Growing the distribution. * Coding Style:: Hygiene of the contributor. * Submitting Patches:: Share your work. @end menu @node Building from Git @section Building from Git If you want to hack Guix itself, it is recommended to use the latest version from the Git repository: @example git clone https://git.savannah.gnu.org/git/guix.git @end example When building Guix from a checkout, the following packages are required in addition to those mentioned in the installation instructions (@pxref{Requirements}). @itemize @item @url{http://gnu.org/software/autoconf/, GNU Autoconf}; @item @url{http://gnu.org/software/automake/, GNU Automake}; @item @url{http://gnu.org/software/gettext/, GNU Gettext}; @item @url{http://gnu.org/software/texinfo/, GNU Texinfo}; @item @url{http://www.graphviz.org/, Graphviz}; @item @url{http://www.gnu.org/software/help2man/, GNU Help2man (optional)}. @end itemize The easiest way to set up a development environment for Guix is, of course, by using Guix! The following command starts a new shell where all the dependencies and appropriate environment variables are set up to hack on Guix: @example guix environment guix @end example @xref{Invoking guix environment}, for more information on that command. Extra dependencies can be added with @option{--ad-hoc}: @example guix environment guix --ad-hoc help2man git strace @end example Run @command{./bootstrap} to generate the build system infrastructure using Autoconf and Automake. If you get an error like this one: @example configure.ac:46: error: possibly undefined macro: PKG_CHECK_MODULES @end example @noindent it probably means that Autoconf couldn’t find @file{pkg.m4}, which is provided by pkg-config. Make sure that @file{pkg.m4} is available. The same holds for the @file{guile.m4} set of macros provided by Guile. For instance, if you installed Automake in @file{/usr/local}, it wouldn’t look for @file{.m4} files in @file{/usr/share}. In that case, you have to invoke the following command: @example export ACLOCAL_PATH=/usr/share/aclocal @end example @xref{Macro Search Path,,, automake, The GNU Automake Manual}, for more information. Then, run @command{./configure} as usual. Make sure to pass @code{--localstatedir=@var{directory}} where @var{directory} is the @code{localstatedir} value used by your current installation (@pxref{The Store}, for information about this). Finally, you have to invoke @code{make check} to run tests (@pxref{Running the Test Suite}). If anything fails, take a look at installation instructions (@pxref{Installation}) or send a message to the @email{guix-devel@@gnu.org, mailing list}. @node Running Guix Before It Is Installed @section Running Guix Before It Is Installed In order to keep a sane working environment, you will find it useful to test the changes made in your local source tree checkout without actually installing them. So that you can distinguish between your ``end-user'' hat and your ``motley'' costume. To that end, all the command-line tools can be used even if you have not run @code{make install}. To do that, you first need to have an environment with all the dependencies available (@pxref{Building from Git}), and then simply prefix each command with @command{./pre-inst-env} (the @file{pre-inst-env} script lives in the top build tree of Guix; it is generated by @command{./configure}), as in@footnote{The @option{-E} flag to @command{sudo} guarantees that @code{GUILE_LOAD_PATH} is correctly set such that @command{guix-daemon} and the tools it uses can find the Guile modules they need.}: @example $ sudo -E ./pre-inst-env guix-daemon --build-users-group=guixbuild $ ./pre-inst-env guix build hello @end example @noindent Similarly, for a Guile session using the Guix modules: @example $ ./pre-inst-env guile -c '(use-modules (guix utils)) (pk (%current-system))' ;;; ("x86_64-linux") @end example @noindent @cindex REPL @cindex read-eval-print loop @dots{} and for a REPL (@pxref{Using Guile Interactively,,, guile, Guile Reference Manual}): @example $ ./pre-inst-env guile scheme@@(guile-user)> ,use(guix) scheme@@(guile-user)> ,use(gnu) scheme@@(guile-user)> (define snakes (fold-packages (lambda (package lst) (if (string-prefix? "python" (package-name package)) (cons package lst) lst)) '())) scheme@@(guile-user)> (length snakes) $1 = 361 @end example The @command{pre-inst-env} script sets up all the environment variables necessary to support this, including @env{PATH} and @env{GUILE_LOAD_PATH}. Note that @command{./pre-inst-env guix pull} does @emph{not} upgrade the local source tree; it simply updates the @file{~/.config/guix/current} symlink (@pxref{Invoking guix pull}). Run @command{git pull} instead if you want to upgrade your local source tree. @node The Perfect Setup @section The Perfect Setup The Perfect Setup to hack on Guix is basically the perfect setup used for Guile hacking (@pxref{Using Guile in Emacs,,, guile, Guile Reference Manual}). First, you need more than an editor, you need @url{http://www.gnu.org/software/emacs, Emacs}, empowered by the wonderful @url{http://nongnu.org/geiser/, Geiser}. To set that up, run: @example guix package -i emacs guile emacs-geiser @end example Geiser allows for interactive and incremental development from within Emacs: code compilation and evaluation from within buffers, access to on-line documentation (docstrings), context-sensitive completion, @kbd{M-.} to jump to an object definition, a REPL to try out your code, and more (@pxref{Introduction,,, geiser, Geiser User Manual}). For convenient Guix development, make sure to augment Guile’s load path so that it finds source files from your checkout: @lisp ;; @r{Assuming the Guix checkout is in ~/src/guix.} (with-eval-after-load 'geiser-guile (add-to-list 'geiser-guile-load-path "~/src/guix")) @end lisp To actually edit the code, Emacs already has a neat Scheme mode. But in addition to that, you must not miss @url{http://www.emacswiki.org/emacs/ParEdit, Paredit}. It provides facilities to directly operate on the syntax tree, such as raising an s-expression or wrapping it, swallowing or rejecting the following s-expression, etc. @cindex code snippets @cindex templates @cindex reducing boilerplate We also provide templates for common git commit messages and package definitions in the @file{etc/snippets} directory. These templates can be used with @url{http://joaotavora.github.io/yasnippet/, YASnippet} to expand short trigger strings to interactive text snippets. You may want to add the snippets directory to the @var{yas-snippet-dirs} variable in Emacs. @lisp ;; @r{Assuming the Guix checkout is in ~/src/guix.} (with-eval-after-load 'yasnippet (add-to-list 'yas-snippet-dirs "~/src/guix/etc/snippets")) @end lisp The commit message snippets depend on @url{https://magit.vc/, Magit} to display staged files. When editing a commit message type @code{add} followed by @kbd{TAB} to insert a commit message template for adding a package; type @code{update} followed by @kbd{TAB} to insert a template for updating a package; type @code{https} followed by @kbd{TAB} to insert a template for changing the home page URI of a package to HTTPS. The main snippet for @code{scheme-mode} is triggered by typing @code{package...} followed by @kbd{TAB}. This snippet also inserts the trigger string @code{origin...}, which can be expanded further. The @code{origin} snippet in turn may insert other trigger strings ending on @code{...}, which also can be expanded further. @node Packaging Guidelines @section Packaging Guidelines @cindex packages, creating The GNU distribution is nascent and may well lack some of your favorite packages. This section describes how you can help make the distribution grow. Free software packages are usually distributed in the form of @dfn{source code tarballs}---typically @file{tar.gz} files that contain all the source files. Adding a package to the distribution means essentially two things: adding a @dfn{recipe} that describes how to build the package, including a list of other packages required to build it, and adding @dfn{package metadata} along with that recipe, such as a description and licensing information. In Guix all this information is embodied in @dfn{package definitions}. Package definitions provide a high-level view of the package. They are written using the syntax of the Scheme programming language; in fact, for each package we define a variable bound to the package definition, and export that variable from a module (@pxref{Package Modules}). However, in-depth Scheme knowledge is @emph{not} a prerequisite for creating packages. For more information on package definitions, @pxref{Defining Packages}. Once a package definition is in place, stored in a file in the Guix source tree, it can be tested using the @command{guix build} command (@pxref{Invoking guix build}). For example, assuming the new package is called @code{gnew}, you may run this command from the Guix build tree (@pxref{Running Guix Before It Is Installed}): @example ./pre-inst-env guix build gnew --keep-failed @end example Using @code{--keep-failed} makes it easier to debug build failures since it provides access to the failed build tree. Another useful command-line option when debugging is @code{--log-file}, to access the build log. If the package is unknown to the @command{guix} command, it may be that the source file contains a syntax error, or lacks a @code{define-public} clause to export the package variable. To figure it out, you may load the module from Guile to get more information about the actual error: @example ./pre-inst-env guile -c '(use-modules (gnu packages gnew))' @end example Once your package builds correctly, please send us a patch (@pxref{Submitting Patches}). Well, if you need help, we will be happy to help you too. Once the patch is committed in the Guix repository, the new package automatically gets built on the supported platforms by @url{http://hydra.gnu.org/jobset/gnu/master, our continuous integration system}. @cindex substituter Users can obtain the new package definition simply by running @command{guix pull} (@pxref{Invoking guix pull}). When @code{@value{SUBSTITUTE-SERVER}} is done building the package, installing the package automatically downloads binaries from there (@pxref{Substitutes}). The only place where human intervention is needed is to review and apply the patch. @menu * Software Freedom:: What may go into the distribution. * Package Naming:: What's in a name? * Version Numbers:: When the name is not enough. * Synopses and Descriptions:: Helping users find the right package. * Python Modules:: A touch of British comedy. * Perl Modules:: Little pearls. * Java Packages:: Coffee break. * Fonts:: Fond of fonts. @end menu @node Software Freedom @subsection Software Freedom @c Adapted from http://www.gnu.org/philosophy/philosophy.html. @cindex free software The GNU operating system has been developed so that users can have freedom in their computing. GNU is @dfn{free software}, meaning that users have the @url{http://www.gnu.org/philosophy/free-sw.html,four essential freedoms}: to run the program, to study and change the program in source code form, to redistribute exact copies, and to distribute modified versions. Packages found in the GNU distribution provide only software that conveys these four freedoms. In addition, the GNU distribution follow the @url{http://www.gnu.org/distros/free-system-distribution-guidelines.html,free software distribution guidelines}. Among other things, these guidelines reject non-free firmware, recommendations of non-free software, and discuss ways to deal with trademarks and patents. Some otherwise free upstream package sources contain a small and optional subset that violates the above guidelines, for instance because this subset is itself non-free code. When that happens, the offending items are removed with appropriate patches or code snippets in the @code{origin} form of the package (@pxref{Defining Packages}). This way, @code{guix build --source} returns the ``freed'' source rather than the unmodified upstream source. @node Package Naming @subsection Package Naming @cindex package name A package has actually two names associated with it: First, there is the name of the @emph{Scheme variable}, the one following @code{define-public}. By this name, the package can be made known in the Scheme code, for instance as input to another package. Second, there is the string in the @code{name} field of a package definition. This name is used by package management commands such as @command{guix package} and @command{guix build}. Both are usually the same and correspond to the lowercase conversion of the project name chosen upstream, with underscores replaced with hyphens. For instance, GNUnet is available as @code{gnunet}, and SDL_net as @code{sdl-net}. We do not add @code{lib} prefixes for library packages, unless these are already part of the official project name. But @pxref{Python Modules} and @ref{Perl Modules} for special rules concerning modules for the Python and Perl languages. Font package names are handled differently, @pxref{Fonts}. @node Version Numbers @subsection Version Numbers @cindex package version We usually package only the latest version of a given free software project. But sometimes, for instance for incompatible library versions, two (or more) versions of the same package are needed. These require different Scheme variable names. We use the name as defined in @ref{Package Naming} for the most recent version; previous versions use the same name, suffixed by @code{-} and the smallest prefix of the version number that may distinguish the two versions. The name inside the package definition is the same for all versions of a package and does not contain any version number. For instance, the versions 2.24.20 and 3.9.12 of GTK+ may be packaged as follows: @example (define-public gtk+ (package (name "gtk+") (version "3.9.12") ...)) (define-public gtk+-2 (package (name "gtk+") (version "2.24.20") ...)) @end example If we also wanted GTK+ 3.8.2, this would be packaged as @example (define-public gtk+-3.8 (package (name "gtk+") (version "3.8.2") ...)) @end example @c See <https://lists.gnu.org/archive/html/guix-devel/2016-01/msg00425.html>, @c for a discussion of what follows. @cindex version number, for VCS snapshots Occasionally, we package snapshots of upstream's version control system (VCS) instead of formal releases. This should remain exceptional, because it is up to upstream developers to clarify what the stable release is. Yet, it is sometimes necessary. So, what should we put in the @code{version} field? Clearly, we need to make the commit identifier of the VCS snapshot visible in the version string, but we also need to make sure that the version string is monotonically increasing so that @command{guix package --upgrade} can determine which version is newer. Since commit identifiers, notably with Git, are not monotonically increasing, we add a revision number that we increase each time we upgrade to a newer snapshot. The resulting version string looks like this: @example 2.0.11-3.cabba9e ^ ^ ^ | | `-- upstream commit ID | | | `--- Guix package revision | latest upstream version @end example It is a good idea to strip commit identifiers in the @code{version} field to, say, 7 digits. It avoids an aesthetic annoyance (assuming aesthetics have a role to play here) as well as problems related to OS limits such as the maximum shebang length (127 bytes for the Linux kernel.) It is best to use the full commit identifiers in @code{origin}s, though, to avoid ambiguities. A typical package definition may look like this: @example (define my-package (let ((commit "c3f29bc928d5900971f65965feaae59e1272a3f7") (revision "1")) ;Guix package revision (package (version (git-version "0.9" revision commit)) (source (origin (method git-fetch) (uri (git-reference (url "git://example.org/my-package.git") (commit commit))) (sha256 (base32 "1mbikn@dots{}")) (file-name (git-file-name name version)))) ;; @dots{} ))) @end example @node Synopses and Descriptions @subsection Synopses and Descriptions @cindex package description @cindex package synopsis As we have seen before, each package in GNU@tie{}Guix includes a synopsis and a description (@pxref{Defining Packages}). Synopses and descriptions are important: They are what @command{guix package --search} searches, and a crucial piece of information to help users determine whether a given package suits their needs. Consequently, packagers should pay attention to what goes into them. Synopses must start with a capital letter and must not end with a period. They must not start with ``a'' or ``the'', which usually does not bring anything; for instance, prefer ``File-frobbing tool'' over ``A tool that frobs files''. The synopsis should say what the package is---e.g., ``Core GNU utilities (file, text, shell)''---or what it is used for---e.g., the synopsis for GNU@tie{}grep is ``Print lines matching a pattern''. Keep in mind that the synopsis must be meaningful for a very wide audience. For example, ``Manipulate alignments in the SAM format'' might make sense for a seasoned bioinformatics researcher, but might be fairly unhelpful or even misleading to a non-specialized audience. It is a good idea to come up with a synopsis that gives an idea of the application domain of the package. In this example, this might give something like ``Manipulate nucleotide sequence alignments'', which hopefully gives the user a better idea of whether this is what they are looking for. Descriptions should take between five and ten lines. Use full sentences, and avoid using acronyms without first introducing them. Please avoid marketing phrases such as ``world-leading'', ``industrial-strength'', and ``next-generation'', and avoid superlatives like ``the most advanced''---they are not helpful to users looking for a package and may even sound suspicious. Instead, try to be factual, mentioning use cases and features. @cindex Texinfo markup, in package descriptions Descriptions can include Texinfo markup, which is useful to introduce ornaments such as @code{@@code} or @code{@@dfn}, bullet lists, or hyperlinks (@pxref{Overview,,, texinfo, GNU Texinfo}). However you should be careful when using some characters for example @samp{@@} and curly braces which are the basic special characters in Texinfo (@pxref{Special Characters,,, texinfo, GNU Texinfo}). User interfaces such as @command{guix package --show} take care of rendering it appropriately. Synopses and descriptions are translated by volunteers @uref{http://translationproject.org/domain/guix-packages.html, at the Translation Project} so that as many users as possible can read them in their native language. User interfaces search them and display them in the language specified by the current locale. To allow @command{xgettext} to extract them as translatable strings, synopses and descriptions @emph{must be literal strings}. This means that you cannot use @code{string-append} or @code{format} to construct these strings: @lisp (package ;; @dots{} (synopsis "This is translatable") (description (string-append "This is " "*not*" " translatable."))) @end lisp Translation is a lot of work so, as a packager, please pay even more attention to your synopses and descriptions as every change may entail additional work for translators. In order to help them, it is possible to make recommendations or instructions visible to them by inserting special comments like this (@pxref{xgettext Invocation,,, gettext, GNU Gettext}): @example ;; TRANSLATORS: "X11 resize-and-rotate" should not be translated. (description "ARandR is designed to provide a simple visual front end for the X11 resize-and-rotate (RandR) extension. @dots{}") @end example @node Python Modules @subsection Python Modules @cindex python We currently package Python 2 and Python 3, under the Scheme variable names @code{python-2} and @code{python} as explained in @ref{Version Numbers}. To avoid confusion and naming clashes with other programming languages, it seems desirable that the name of a package for a Python module contains the word @code{python}. Some modules are compatible with only one version of Python, others with both. If the package Foo compiles only with Python 3, we name it @code{python-foo}; if it compiles only with Python 2, we name it @code{python2-foo}. If it is compatible with both versions, we create two packages with the corresponding names. If a project already contains the word @code{python}, we drop this; for instance, the module python-dateutil is packaged under the names @code{python-dateutil} and @code{python2-dateutil}. If the project name starts with @code{py} (e.g.@: @code{pytz}), we keep it and prefix it as described above. @subsubsection Specifying Dependencies @cindex inputs, for Python packages Dependency information for Python packages is usually available in the package source tree, with varying degrees of accuracy: in the @file{setup.py} file, in @file{requirements.txt}, or in @file{tox.ini}. Your mission, when writing a recipe for a Python package, is to map these dependencies to the appropriate type of ``input'' (@pxref{package Reference, inputs}). Although the @code{pypi} importer normally does a good job (@pxref{Invoking guix import}), you may want to check the following check list to determine which dependency goes where. @itemize @item We currently package Python 2 with @code{setuptools} and @code{pip} installed like Python 3.4 has per default. Thus you don't need to specify either of these as an input. @command{guix lint} will warn you if you do. @item Python dependencies required at run time go into @code{propagated-inputs}. They are typically defined with the @code{install_requires} keyword in @file{setup.py}, or in the @file{requirements.txt} file. @item Python packages required only at build time---e.g., those listed with the @code{setup_requires} keyword in @file{setup.py}---or only for testing---e.g., those in @code{tests_require}---go into @code{native-inputs}. The rationale is that (1) they do not need to be propagated because they are not needed at run time, and (2) in a cross-compilation context, it's the ``native'' input that we'd want. Examples are the @code{pytest}, @code{mock}, and @code{nose} test frameworks. Of course if any of these packages is also required at run-time, it needs to go to @code{propagated-inputs}. @item Anything that does not fall in the previous categories goes to @code{inputs}, for example programs or C libraries required for building Python packages containing C extensions. @item If a Python package has optional dependencies (@code{extras_require}), it is up to you to decide whether to add them or not, based on their usefulness/overhead ratio (@pxref{Submitting Patches, @command{guix size}}). @end itemize @node Perl Modules @subsection Perl Modules @cindex perl Perl programs standing for themselves are named as any other package, using the lowercase upstream name. For Perl packages containing a single class, we use the lowercase class name, replace all occurrences of @code{::} by dashes and prepend the prefix @code{perl-}. So the class @code{XML::Parser} becomes @code{perl-xml-parser}. Modules containing several classes keep their lowercase upstream name and are also prepended by @code{perl-}. Such modules tend to have the word @code{perl} somewhere in their name, which gets dropped in favor of the prefix. For instance, @code{libwww-perl} becomes @code{perl-libwww}. @node Java Packages @subsection Java Packages @cindex java Java programs standing for themselves are named as any other package, using the lowercase upstream name. To avoid confusion and naming clashes with other programming languages, it is desirable that the name of a package for a Java package is prefixed with @code{java-}. If a project already contains the word @code{java}, we drop this; for instance, the package @code{ngsjava} is packaged under the name @code{java-ngs}. For Java packages containing a single class or a small class hierarchy, we use the lowercase class name, replace all occurrences of @code{.} by dashes and prepend the prefix @code{java-}. So the class @code{apache.commons.cli} becomes package @code{java-apache-commons-cli}. @node Fonts @subsection Fonts @cindex fonts For fonts that are in general not installed by a user for typesetting purposes, or that are distributed as part of a larger software package, we rely on the general packaging rules for software; for instance, this applies to the fonts delivered as part of the X.Org system or fonts that are part of TeX Live. To make it easier for a user to search for fonts, names for other packages containing only fonts are constructed as follows, independently of the upstream package name. The name of a package containing only one font family starts with @code{font-}; it is followed by the foundry name and a dash @code{-} if the foundry is known, and the font family name, in which spaces are replaced by dashes (and as usual, all upper case letters are transformed to lower case). For example, the Gentium font family by SIL is packaged under the name @code{font-sil-gentium}. For a package containing several font families, the name of the collection is used in the place of the font family name. For instance, the Liberation fonts consist of three families, Liberation Sans, Liberation Serif and Liberation Mono. These could be packaged separately under the names @code{font-liberation-sans} and so on; but as they are distributed together under a common name, we prefer to package them together as @code{font-liberation}. In the case where several formats of the same font family or font collection are packaged separately, a short form of the format, prepended by a dash, is added to the package name. We use @code{-ttf} for TrueType fonts, @code{-otf} for OpenType fonts and @code{-type1} for PostScript Type 1 fonts. @node Coding Style @section Coding Style In general our code follows the GNU Coding Standards (@pxref{Top,,, standards, GNU Coding Standards}). However, they do not say much about Scheme, so here are some additional rules. @menu * Programming Paradigm:: How to compose your elements. * Modules:: Where to store your code? * Data Types and Pattern Matching:: Implementing data structures. * Formatting Code:: Writing conventions. @end menu @node Programming Paradigm @subsection Programming Paradigm Scheme code in Guix is written in a purely functional style. One exception is code that involves input/output, and procedures that implement low-level concepts, such as the @code{memoize} procedure. @node Modules @subsection Modules Guile modules that are meant to be used on the builder side must live in the @code{(guix build @dots{})} name space. They must not refer to other Guix or GNU modules. However, it is OK for a ``host-side'' module to use a build-side module. Modules that deal with the broader GNU system should be in the @code{(gnu @dots{})} name space rather than @code{(guix @dots{})}. @node Data Types and Pattern Matching @subsection Data Types and Pattern Matching The tendency in classical Lisp is to use lists to represent everything, and then to browse them ``by hand'' using @code{car}, @code{cdr}, @code{cadr}, and co. There are several problems with that style, notably the fact that it is hard to read, error-prone, and a hindrance to proper type error reports. Guix code should define appropriate data types (for instance, using @code{define-record-type*}) rather than abuse lists. In addition, it should use pattern matching, via Guile’s @code{(ice-9 match)} module, especially when matching lists. @node Formatting Code @subsection Formatting Code @cindex formatting code @cindex coding style When writing Scheme code, we follow common wisdom among Scheme programmers. In general, we follow the @url{http://mumble.net/~campbell/scheme/style.txt, Riastradh's Lisp Style Rules}. This document happens to describe the conventions mostly used in Guile’s code too. It is very thoughtful and well written, so please do read it. Some special forms introduced in Guix, such as the @code{substitute*} macro, have special indentation rules. These are defined in the @file{.dir-locals.el} file, which Emacs automatically uses. Also note that Emacs-Guix provides @code{guix-devel-mode} mode that indents and highlights Guix code properly (@pxref{Development,,, emacs-guix, The Emacs-Guix Reference Manual}). @cindex indentation, of code @cindex formatting, of code If you do not use Emacs, please make sure to let your editor knows these rules. To automatically indent a package definition, you can also run: @example ./etc/indent-code.el gnu/packages/@var{file}.scm @var{package} @end example @noindent This automatically indents the definition of @var{package} in @file{gnu/packages/@var{file}.scm} by running Emacs in batch mode. To indent a whole file, omit the second argument: @example ./etc/indent-code.el gnu/services/@var{file}.scm @end example @cindex Vim, Scheme code editing If you are editing code with Vim, we recommend that you run @code{:set autoindent} so that your code is automatically indented as you type. Additionally, @uref{https://www.vim.org/scripts/script.php?script_id=3998, @code{paredit.vim}} may help you deal with all these parentheses. We require all top-level procedures to carry a docstring. This requirement can be relaxed for simple private procedures in the @code{(guix build @dots{})} name space, though. Procedures should not have more than four positional parameters. Use keyword parameters for procedures that take more than four parameters. @node Submitting Patches @section Submitting Patches Development is done using the Git distributed version control system. Thus, access to the repository is not strictly necessary. We welcome contributions in the form of patches as produced by @code{git format-patch} sent to the @email{guix-patches@@gnu.org} mailing list. This mailing list is backed by a Debbugs instance accessible at @uref{https://bugs.gnu.org/guix-patches}, which allows us to keep track of submissions. Each message sent to that mailing list gets a new tracking number assigned; people can then follow up on the submission by sending email to @code{@var{NNN}@@debbugs.gnu.org}, where @var{NNN} is the tracking number (@pxref{Sending a Patch Series}). Please write commit logs in the ChangeLog format (@pxref{Change Logs,,, standards, GNU Coding Standards}); you can check the commit history for examples. Before submitting a patch that adds or modifies a package definition, please run through this check list: @enumerate @item If the authors of the packaged software provide a cryptographic signature for the release tarball, make an effort to verify the authenticity of the archive. For a detached GPG signature file this would be done with the @code{gpg --verify} command. @item Take some time to provide an adequate synopsis and description for the package. @xref{Synopses and Descriptions}, for some guidelines. @item Run @code{guix lint @var{package}}, where @var{package} is the name of the new or modified package, and fix any errors it reports (@pxref{Invoking guix lint}). @item Make sure the package builds on your platform, using @code{guix build @var{package}}. @item We recommend you also try building the package on other supported platforms. As you may not have access to actual hardware platforms, we recommend using the @code{qemu-binfmt-service-type} to emulate them. In order to enable it, add the following service to the list of services in your @code{operating-system} configuration: @example (service qemu-binfmt-service-type (qemu-binfmt-configuration (platforms (lookup-qemu-platforms "arm" "aarch64" "ppc" "mips64el")) (guix-support? #t))) @end example Then reconfigure your system. You can then build packages for different platforms by specifying the @code{--system} option. For example, to build the "hello" package for the armhf, aarch64, powerpc, or mips64 architectures, you would run the following commands, respectively: @example guix build --system=armhf-linux --rounds=2 hello guix build --system=aarch64-linux --rounds=2 hello guix build --system=powerpc-linux --rounds=2 hello guix build --system=mips64el-linux --rounds=2 hello @end example @item @cindex bundling Make sure the package does not use bundled copies of software already available as separate packages. Sometimes, packages include copies of the source code of their dependencies as a convenience for users. However, as a distribution, we want to make sure that such packages end up using the copy we already have in the distribution, if there is one. This improves resource usage (the dependency is built and stored only once), and allows the distribution to make transverse changes such as applying security updates for a given software package in a single place and have them affect the whole system---something that bundled copies prevent. @item Take a look at the profile reported by @command{guix size} (@pxref{Invoking guix size}). This will allow you to notice references to other packages unwillingly retained. It may also help determine whether to split the package (@pxref{Packages with Multiple Outputs}), and which optional dependencies should be used. In particular, avoid adding @code{texlive} as a dependency: because of its extreme size, use @code{texlive-tiny} or @code{texlive-union} instead. @item For important changes, check that dependent package (if applicable) are not affected by the change; @code{guix refresh --list-dependent @var{package}} will help you do that (@pxref{Invoking guix refresh}). @c See <https://lists.gnu.org/archive/html/guix-devel/2016-10/msg00933.html>. @cindex branching strategy @cindex rebuild scheduling strategy Depending on the number of dependent packages and thus the amount of rebuilding induced, commits go to different branches, along these lines: @table @asis @item 300 dependent packages or less @code{master} branch (non-disruptive changes). @item between 300 and 1,200 dependent packages @code{staging} branch (non-disruptive changes). This branch is intended to be merged in @code{master} every 3 weeks or so. Topical changes (e.g., an update of the GNOME stack) can instead go to a specific branch (say, @code{gnome-updates}). @item more than 1,200 dependent packages @code{core-updates} branch (may include major and potentially disruptive changes). This branch is intended to be merged in @code{master} every 2.5 months or so. @end table All these branches are @uref{https://hydra.gnu.org/project/gnu, tracked by our build farm} and merged into @code{master} once everything has been successfully built. This allows us to fix issues before they hit users, and to reduce the window during which pre-built binaries are not available. Generally, branches other than @code{master} are considered @emph{frozen} if there has been a recent evaluation, or there is a corresponding @code{-next} branch. Please ask on the mailing list or IRC if unsure where to place a patch. @c TODO: It would be good with badges on the website that tracks these @c branches. Or maybe even a status page. @item @cindex determinism, of build processes @cindex reproducible builds, checking Check whether the package's build process is deterministic. This typically means checking whether an independent build of the package yields the exact same result that you obtained, bit for bit. A simple way to do that is by building the same package several times in a row on your machine (@pxref{Invoking guix build}): @example guix build --rounds=2 my-package @end example This is enough to catch a class of common non-determinism issues, such as timestamps or randomly-generated output in the build result. Another option is to use @command{guix challenge} (@pxref{Invoking guix challenge}). You may run it once the package has been committed and built by @code{@value{SUBSTITUTE-SERVER}} to check whether it obtains the same result as you did. Better yet: Find another machine that can build it and run @command{guix publish}. Since the remote build machine is likely different from yours, this can catch non-determinism issues related to the hardware---e.g., use of different instruction set extensions---or to the operating system kernel---e.g., reliance on @code{uname} or @file{/proc} files. @item When writing documentation, please use gender-neutral wording when referring to people, such as @uref{https://en.wikipedia.org/wiki/Singular_they, singular ``they''@comma{} ``their''@comma{} ``them''}, and so forth. @item Verify that your patch contains only one set of related changes. Bundling unrelated changes together makes reviewing harder and slower. Examples of unrelated changes include the addition of several packages, or a package update along with fixes to that package. @item Please follow our code formatting rules, possibly running the @command{etc/indent-code.el} script to do that automatically for you (@pxref{Formatting Code}). @item When possible, use mirrors in the source URL (@pxref{Invoking guix download}). Use reliable URLs, not generated ones. For instance, GitHub archives are not necessarily identical from one generation to the next, so in this case it's often better to clone the repository. Don't use the @command{name} field in the URL: it is not very useful and if the name changes, the URL will probably be wrong. @end enumerate When posting a patch to the mailing list, use @samp{[PATCH] @dots{}} as a subject. You may use your email client or the @command{git send-email} command (@pxref{Sending a Patch Series}). We prefer to get patches in plain text messages, either inline or as MIME attachments. You are advised to pay attention if your email client changes anything like line breaks or indentation which could potentially break the patches. When a bug is resolved, please close the thread by sending an email to @email{@var{NNN}-done@@debbugs.gnu.org}. @unnumberedsubsec Sending a Patch Series @anchor{Sending a Patch Series} @cindex patch series @cindex @code{git send-email} @cindex @code{git-send-email} When sending a patch series (e.g., using @code{git send-email}), please first send one message to @email{guix-patches@@gnu.org}, and then send subsequent patches to @email{@var{NNN}@@debbugs.gnu.org} to make sure they are kept together. See @uref{https://debbugs.gnu.org/Advanced.html, the Debbugs documentation} for more information. @c Debbugs bug: https://debbugs.gnu.org/db/15/15361.html