guix/doc/contributing.texi

@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 Libera Chat 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{https://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
* Requirements::                Software needed to build and run Guix.
* Building from Git::           The latest and greatest.
* Running the Test Suite::      Testing Guix.
* Running Guix Before It Is Installed::  Hacker tricks.
* The Perfect Setup::           The right tools.
* Alternative Setups::          Other possible tools that do the job.
* Source Tree Structure::       Source code guided tour.
* Packaging Guidelines::        Growing the distribution.
* Coding Style::                Hygiene of the contributor.
* Submitting Patches::          Share your work.
* Tracking Bugs and Changes::   Keeping it all organized.
* Commit Access::               Pushing to the official repository.
* Reviewing the Work of Others::  Some guidelines for sharing reviews.
* Updating the Guix Package::   Updating the Guix package definition.
* Writing Documentation::       Improving documentation in GNU Guix.
* Translating Guix::            Make Guix speak your native language.
@end menu

@node Requirements
@section Requirements

You can easily hack on Guix itself using Guix and Git, which we use for
version control (@pxref{Building from Git}).

But when packaging Guix for foreign distros or when bootstrapping on
systems without Guix, and if you decide to not just trust and install
our readily made binary (@pxref{Binary Installation}), you can download
a release version of our reproducible source tarball and read on.

This section lists requirements when building Guix from source.  The
build procedure for Guix is the same as for other GNU software, and is
not covered here.  Please see the files @file{README} and @file{INSTALL}
in the Guix source tree for additional details.

@cindex official website
GNU Guix is available for download from its website at
@url{https://www.gnu.org/software/guix/}.

GNU Guix depends on the following packages:

@itemize
@item @url{https://gnu.org/software/guile/, GNU Guile}, version 3.0.x,
version 3.0.3 or later;
@item @url{https://notabug.org/cwebber/guile-gcrypt, Guile-Gcrypt}, version
0.1.0 or later;
@item
@uref{https://gitlab.com/gnutls/guile/, Guile-GnuTLS} (@pxref{Guile
Preparations, how to install the GnuTLS bindings for Guile,,
gnutls-guile, GnuTLS-Guile})@footnote{The Guile bindings to
@uref{https://gnutls.org/, GnuTLS} were distributed as part of GnuTLS
until version 3.7.8 included.};
@item
@uref{https://notabug.org/guile-sqlite3/guile-sqlite3, Guile-SQLite3}, version 0.1.0
or later;
@item @uref{https://notabug.org/guile-zlib/guile-zlib, Guile-zlib},
version 0.1.0 or later;
@item @uref{https://notabug.org/guile-lzlib/guile-lzlib, Guile-lzlib};
@item @uref{https://www.nongnu.org/guile-avahi/, Guile-Avahi};
@item
@uref{https://gitlab.com/guile-git/guile-git, Guile-Git}, version 0.5.0
or later;
@item @uref{https://git-scm.com, Git} (yes, both!);
@item @uref{https://savannah.nongnu.org/projects/guile-json/, Guile-JSON}
4.3.0 or later;
@item @url{https://www.gnu.org/software/make/, GNU Make}.
@end itemize

The following dependencies are optional:

@itemize
@item
@c Note: We need at least 0.13.0 for #:nodelay.
Support for build offloading (@pxref{Daemon Offload Setup}) and
@command{guix copy} (@pxref{Invoking guix copy}) depends on
@uref{https://github.com/artyom-poptsov/guile-ssh, Guile-SSH},
version 0.13.0 or later.

@item
@uref{https://notabug.org/guile-zstd/guile-zstd, Guile-zstd}, for zstd
compression and decompression in @command{guix publish} and for
substitutes (@pxref{Invoking guix publish}).

@item
@uref{https://ngyro.com/software/guile-semver.html, Guile-Semver} for
the @code{crate} importer (@pxref{Invoking guix import}).

@item
@uref{https://www.nongnu.org/guile-lib/doc/ref/htmlprag/, Guile-Lib} for
the @code{go} importer (@pxref{Invoking guix import}) and for some of
the ``updaters'' (@pxref{Invoking guix refresh}).

@item
When @url{http://www.bzip.org, libbz2} is available,
@command{guix-daemon} can use it to compress build logs.
@end itemize

Unless @option{--disable-daemon} was passed to @command{configure}, the
following packages are also needed:

@itemize
@item @url{https://gnupg.org/, GNU libgcrypt};
@item @url{https://sqlite.org, SQLite 3};
@item @url{https://gcc.gnu.org, GCC's g++}, with support for the
C++11 standard.
@end itemize

@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

@cindex authentication, of a Guix checkout
How do you ensure that you obtained a genuine copy of the repository?
To do that, run @command{guix git authenticate}, passing it the commit
and OpenPGP fingerprint of the @dfn{channel introduction}
(@pxref{Invoking guix git authenticate}):

@c The commit and fingerprint below must match those of the channel
@c introduction in '%default-channels'.
@example
git fetch origin keyring:keyring
guix git authenticate 9edb3f66fd807b096b48283debdcddccfea34bad \
  "BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 54FA"
@end example

@noindent
This command completes with exit code zero on success; it prints an
error message and exits with a non-zero code otherwise.

As you can see, there is a chicken-and-egg problem: you first need to
have Guix installed.  Typically you would install Guix System
(@pxref{System Installation}) or Guix on top of another distro
(@pxref{Binary Installation}); in either case, you would verify the
OpenPGP signature on the installation medium.  This ``bootstraps'' the
trust chain.

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 shell -D guix -CPW
@end example

or even, from within a Git worktree for Guix:

@example
guix shell -CPW
@end example

If @option{-C} (short for @option{--container}) is not supported on your
system, try @command{--pure} instead of @option{-CPW}.
@xref{Invoking guix shell}, for more information on that command.

If you are unable to use Guix when building Guix from a checkout, the
following are the required packages in addition to those mentioned in the
installation instructions (@pxref{Requirements}).

@itemize
@item @url{https://gnu.org/software/autoconf/, GNU Autoconf};
@item @url{https://gnu.org/software/automake/, GNU Automake};
@item @url{https://gnu.org/software/gettext/, GNU Gettext};
@item @url{https://gnu.org/software/texinfo/, GNU Texinfo};
@item @url{https://www.graphviz.org/, Graphviz};
@item @url{https://www.gnu.org/software/help2man/, GNU Help2man (optional)}.
@end itemize

On Guix, extra dependencies can be added by instead running @command{guix
shell}:

@example
guix shell -D guix help2man git strace --pure
@end example

From there you can generate the build system infrastructure
using Autoconf and Automake:

@example
./bootstrap
@end example

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.

@cindex state directory
@cindex localstatedir
@cindex system configuration directory
@cindex sysconfdir
Then, run:

@example
./configure
@end example

@noindent
... where @file{/var} is the normal @code{localstatedir} value
(@pxref{The Store}, for information about this) and @file{/etc} is the
normal @code{sysconfdir} value.  Note that you will probably not run
@command{make install} at the end (you don't have to) but it's still
important to pass the right @code{localstatedir} and @code{sysconfdir}
values, which get recorded in the @code{(guix config)} Guile module.

Finally, you can build Guix and, if you feel so inclined, run the tests
(@pxref{Running the Test Suite}):

@example
make
make check
@end example

@noindent
If anything fails, take a look at installation instructions
(@pxref{Installation}) or send a message to the
@email{guix-devel@@gnu.org, mailing list}.

From there on, you can authenticate all the commits included in your
checkout by running:

@example
guix git authenticate \
  9edb3f66fd807b096b48283debdcddccfea34bad \
  "BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 54FA"
@end example

The first run takes a couple of minutes, but subsequent runs are faster.
On subsequent runs, you can run the command without any arguments since
the @dfn{introduction} (the commit ID and OpenPGP fingerprints above)
will have been recorded@footnote{This requires a recent version of Guix,
from May 2024 or more recent.}:

@example
guix git authenticate
@end example

When your configuration for your local Git repository doesn't match
the default one, you can provide the reference for the @code{keyring}
branch @i{via} the @option{-k} option.  The following
example assumes that you have a Git remote called @samp{myremote}
pointing to the official repository:

@example
guix git authenticate \
  -k myremote/keyring \
  9edb3f66fd807b096b48283debdcddccfea34bad \
  "BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 54FA"
@end example

@xref{Invoking guix git authenticate}, for more information on this
command.

@quotation Note
By default, hooks are installed such that @command{guix git
authenticate} is invoked anytime you run @command{git pull} or
@command{git push}.
@end quotation

After updating the repository, @command{make} might fail with an error
similar to the following example:

@example
error: failed to load 'gnu/packages/linux.scm':
ice-9/eval.scm:293:34: In procedure abi-check: #<record-type <origin>>: record ABI mismatch; recompilation needed
@end example

This means that one of the record types that Guix defines (in this
example, the @code{origin} record) has changed, and all of guix needs
to be recompiled to take that change into account.  To do so, run
@command{make clean-go} followed by @command{make}.

Should @command{make} fail with an Automake error message after
updating, you need to repeat the steps outlined in this section,
commencing with @command{./bootstrap}.

@node Running the Test Suite
@section Running the Test Suite

@cindex test suite
After a successful @command{configure} and @code{make} run, it is a good
idea to run the test suite.  It can help catch issues with the setup or
environment, or bugs in Guix itself---and really, reporting test
failures is a good way to help improve the software.  To run the test
suite, type:

@example
make check
@end example

Test cases can run in parallel: you can use the @code{-j} option of
GNU@tie{}make to speed things up.  The first run may take a few minutes
on a recent machine; subsequent runs will be faster because the store
that is created for test purposes will already have various things in
cache.

It is also possible to run a subset of the tests by defining the
@code{TESTS} makefile variable as in this example:

@example
make check TESTS="tests/store.scm tests/cpio.scm"
@end example

By default, tests results are displayed at a file level.  In order to
see the details of every individual test cases, it is possible to define
the @code{SCM_LOG_DRIVER_FLAGS} makefile variable as in this example:

@example
make check TESTS="tests/base64.scm" SCM_LOG_DRIVER_FLAGS="--brief=no"
@end example

The underlying SRFI 64 custom Automake test driver used for the 'check'
test suite (located at @file{build-aux/test-driver.scm}) also allows
selecting which test cases to run at a finer level, via its
@option{--select} and @option{--exclude} options.  Here's an example, to
run all the test cases from the @file{tests/packages.scm} test file
whose names start with ``transaction-upgrade-entry'':

@example
export SCM_LOG_DRIVER_FLAGS="--select=^transaction-upgrade-entry"
make check TESTS="tests/packages.scm"
@end example

Those wishing to inspect the results of failed tests directly from the
command line can add the @option{--errors-only=yes} option to the
@code{SCM_LOG_DRIVER_FLAGS} makefile variable and set the @code{VERBOSE}
Automake makefile variable, as in:

@example
make check SCM_LOG_DRIVER_FLAGS="--brief=no --errors-only=yes" VERBOSE=1
@end example

The @option{--show-duration=yes} option can be used to print the
duration of the individual test cases, when used in combination with
@option{--brief=no}:

@example
make check SCM_LOG_DRIVER_FLAGS="--brief=no --show-duration=yes"
@end example

@xref{Parallel Test Harness,,,automake,GNU Automake} for more
information about the Automake Parallel Test Harness.

Upon failure, please email @email{bug-guix@@gnu.org} and attach the
@file{test-suite.log} file.  Please specify the Guix version being used
as well as version numbers of the dependencies (@pxref{Requirements}) in
your message.

Guix also comes with a whole-system test suite that tests complete
Guix System instances.  It can only run on systems where
Guix is already installed, using:

@example
make check-system
@end example

@noindent
or, again, by defining @code{TESTS} to select a subset of tests to run:

@example
make check-system TESTS="basic mcron"
@end example

These system tests are defined in the @code{(gnu tests @dots{})}
modules.  They work by running the operating systems under test with
lightweight instrumentation in a virtual machine (VM).  They can be
computationally intensive or rather cheap, depending on whether
substitutes are available for their dependencies (@pxref{Substitutes}).
Some of them require a lot of storage space to hold VM images.

Again in case of test failures, please send @email{bug-guix@@gnu.org}
all the details.

@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;
@pxref{Building from Git} to generate it).  As an example, here is how you
would build the @code{hello} package as defined in your working tree (this
assumes @command{guix-daemon} is already running on your system; it's OK if
it's a different version):

@example
$ ./pre-inst-env guix build hello
@end example

@noindent
Similarly, an example 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 Guix Interactively}):

@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

If you are hacking on the daemon and its supporting code or if
@command{guix-daemon} is not already running on your system, you can
launch it straight from the build tree@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
@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.

Sometimes, especially if you have recently updated your repository,
running @command{./pre-inst-env} will print a message similar to the
following example:

@example
;;; note: source file /home/user/projects/guix/guix/progress.scm
;;;       newer than compiled /home/user/projects/guix/guix/progress.go
@end example

This is only a note and you can safely ignore it.  You can get rid of
the message by running @command{make -j4}.  Until you do, Guile will run
slightly slower because it will interpret the code instead of using
prepared Guile object (@file{.go}) files.

You can run @command{make} automatically as you work using
@command{watchexec} from the @code{watchexec} package.  For example,
to build again each time you update a package file, run
@samp{watchexec -w gnu/packages -- make -j4}.

@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{https://www.gnu.org/software/emacs, Emacs}, empowered by the
wonderful @url{https://nongnu.org/geiser/, Geiser}.  To set that up, run:

@example
guix install emacs guile emacs-geiser emacs-geiser-guile
@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}).  If you
allow Emacs to load the @file{.dir-locals.el} file at the root of the
project checkout, it will cause Geiser to automatically add the local
Guix sources to the Guile load path.

To actually edit the code, Emacs already has a neat Scheme mode.  But in
addition to that, you must not miss
@url{https://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 to expand short trigger strings to interactive text snippets. If
you use @url{https://joaotavora.github.io/yasnippet/, YASnippet}, you
may want to add the @file{etc/snippets/yas} snippets directory to the
@var{yas-snippet-dirs} variable.  If you use
@url{https://github.com/minad/tempel/, Tempel}, you may want to add the
@file{etc/snippets/tempel/*} path to the @var{tempel-path} variable in
Emacs.

@lisp
;; @r{Assuming the Guix checkout is in ~/src/guix.}
;; @r{Yasnippet configuration}
(with-eval-after-load 'yasnippet
  (add-to-list 'yas-snippet-dirs "~/src/guix/etc/snippets/yas"))
;; @r{Tempel configuration}
(with-eval-after-load 'tempel
   ;; Ensure tempel-path is a list -- it may also be a string.
   (unless (listp 'tempel-path)
     (setq tempel-path (list tempel-path)))
   (add-to-list 'tempel-path "~/src/guix/etc/snippets/tempel/*"))
@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.

@cindex insert or update copyright
@cindex @code{M-x guix-copyright}
@cindex @code{M-x copyright-update}
We additionally provide insertion and automatic update of a copyright in
@file{etc/copyright.el}.  You may want to set your full name, mail, and
load a file.

@lisp
(setq user-full-name "Alice Doe")
(setq user-mail-address "alice@@mail.org")
;; @r{Assuming the Guix checkout is in ~/src/guix.}
(load-file "~/src/guix/etc/copyright.el")
@end lisp

To insert a copyright at the current line invoke @code{M-x guix-copyright}.

To update a copyright you need to specify a @code{copyright-names-regexp}.

@lisp
(setq copyright-names-regexp
      (format "%s <%s>" user-full-name user-mail-address))
@end lisp

You can check if your copyright is up to date by evaluating @code{M-x
copyright-update}.  If you want to do it automatically after each buffer
save then add @code{(add-hook 'after-save-hook 'copyright-update)} in
Emacs.

@node Viewing Bugs within Emacs
@subsection Viewing Bugs within Emacs

Emacs has a nice minor mode called @code{bug-reference}, which, when
combined with @samp{emacs-debbugs} (the Emacs package), can be used to
open links such as @samp{<https://bugs.gnu.org/58697>} or
@samp{<https://issues.guix.gnu.org/58697>} as bug report buffers.  From
there you can easily consult the email thread via the Gnus interface,
reply or modify the bug status, all without leaving the comfort of
Emacs!  Below is a sample configuration to add to your @file{~/.emacs}
configuration file:

@lisp
;;; Bug references.
(require 'bug-reference)
(add-hook 'prog-mode-hook #'bug-reference-prog-mode)
(add-hook 'gnus-mode-hook #'bug-reference-mode)
(add-hook 'erc-mode-hook #'bug-reference-mode)
(add-hook 'gnus-summary-mode-hook #'bug-reference-mode)
(add-hook 'gnus-article-mode-hook #'bug-reference-mode)

;;; This extends the default expression (the top-most, first expression
;;; provided to 'or') to also match URLs such as
;;; <https://issues.guix.gnu.org/58697> or <https://bugs.gnu.org/58697>.
;;; It is also extended to detect "Fixes: #NNNNN" git trailers.
(setq bug-reference-bug-regexp
      (rx (group (or (seq word-boundary
                          (or (seq (char "Bb") "ug"
                                   (zero-or-one " ")
                                   (zero-or-one "#"))
                              (seq (char "Pp") "atch"
                                   (zero-or-one " ")
                                   "#")
                              (seq (char "Ff") "ixes"
                                   (zero-or-one ":")
                                   (zero-or-one " ") "#")
                              (seq "RFE"
                                   (zero-or-one " ") "#")
                              (seq "PR "
                                   (one-or-more (char "a-z+-")) "/"))
                          (group (one-or-more (char "0-9"))
                                 (zero-or-one
                                  (seq "#" (one-or-more
                                            (char "0-9"))))))
                     (seq (? "<") "https://bugs.gnu.org/"
                          (group-n 2 (one-or-more (char "0-9")))
                          (? ">"))
                     (seq (? "<") "https://issues.guix.gnu.org/"
                          (? "issue/")
                          (group-n 2 (one-or-more (char "0-9")))
                          (? ">"))))))
(setq bug-reference-url-format "https://issues.guix.gnu.org/%s")

(require 'debbugs)
(require 'debbugs-browse)
(add-hook 'bug-reference-mode-hook #'debbugs-browse-mode)
(add-hook 'bug-reference-prog-mode-hook #'debbugs-browse-mode)

;; The following allows Emacs Debbugs user to open the issue directly within
;; Emacs.
(setq debbugs-browse-url-regexp
      (rx line-start
          "http" (zero-or-one "s") "://"
          (or "debbugs" "issues.guix" "bugs")
          ".gnu.org" (one-or-more "/")
          (group (zero-or-one "cgi/bugreport.cgi?bug="))
          (group-n 3 (one-or-more digit))
          line-end))

;; Change the default when run as 'M-x debbugs-gnu'.
(setq debbugs-gnu-default-packages '("guix" "guix-patches"))

;; Show feature requests.
(setq debbugs-gnu-default-severities
 '("serious" "important" "normal" "minor" "wishlist"))
@end lisp

For more information, refer to @ref{Bug Reference,,, emacs, The GNU
Emacs Manual} and @ref{Minor Mode,,, debbugs-ug, The Debbugs User
Guide}.

@node Alternative Setups
@section Alternative Setups

Alternative setups than Emacs may let you work on Guix with a
similar development experience and they might work better with the
tools you currently use or help you make the transition to Emacs.

The options listed below only provide the alternatives to the Emacs
based setup, which is the most widely used in the Guix community. If
you want to really understand how is the perfect setup for Guix
development supposed to work, we encourage you to read the section
before this regardless the editor you choose to use.

@menu
* Guile Studio::                First step in your transition to Emacs.
* Vim and NeoVim::              When you are evil to the root.
@end menu

@node Guile Studio
@subsection Guile Studio

Guile Studio is a pre-configured Emacs with mostly everything you need
to start hacking in Guile. If you are not familiar with Emacs it makes
the transition easier for you.

@example
guix install guile-studio
@end example

Guile Studio comes with Geiser preinstalled and prepared for action.

@node Vim and NeoVim
@subsection Vim and NeoVim


Vim (and NeoVim) are also packaged in Guix, just in case you decided
to go for the evil path.

@example
guix install vim
@end example

If you want to enjoy a similar development experience to that in the perfect
setup, you should install several plugins to configure the editor. Vim (and
NeoVim) have the equivalent to Paredit,
@uref{https://www.vim.org/scripts/script.php?script_id=3998,
@code{paredit.vim}}, that will help you with the structural editing of Scheme
files (the support for very large files is not great, though).

@example
guix install vim-paredit
@end example

We also recommend that you run @code{:set autoindent} so that your code is
automatically indented as you type.

For the interaction with Git,
@uref{https://www.vim.org/scripts/script.php?script_id=2975,
@code{fugitive.vim}} is the most commonly used plugin:

@example
guix install vim-fugitive
@end example

And of course if you want to interact with Guix directly from inside of
vim, using the built-in terminal emulator, we have our very own
@code{guix.vim} package!

@example
guix install vim-guix-vim
@end example

In NeoVim you can even make a similar setup to Geiser using
@url{https://conjure.fun/, Conjure} that lets you connect to a running Guile
process and inject your code there live (sadly it's not packaged in Guix yet).


@node Source Tree Structure
@section Source Tree Structure

@cindex structure, of the source tree
If you're willing to contribute to Guix beyond packages, or if you'd
like to learn how it all fits together, this section provides a guided
tour in the code base that you may find useful.

Overall, the Guix source tree contains almost exclusively Guile
@dfn{modules}, each of which can be seen as an independent library
(@pxref{Modules,,, guile, GNU Guile Reference Manual}).

The following table gives an overview of the main directories and what
they contain.  Remember that in Guile, each module name is derived from
its file name---e.g., the module in file @file{guix/packages.scm} is
called @code{(guix packages)}.

@table @file
@item guix
This is the location of core Guix mechanisms.  To illustrate what is
meant by ``core'', here are a few examples, starting from low-level
tools and going towards higher-level tools:

@table @code
@item (guix store)
Connecting to and interacting with the build daemon (@pxref{The Store}).
@item (guix derivations)
Creating derivations (@pxref{Derivations}).
@item (guix gexps)
Writing G-expressions (@pxref{G-Expressions}).
@item (guix packages)
Defining packages and origins (@pxref{package Reference}).
@item (guix download)
@itemx (guix git-download)
The @code{url-fetch} and @code{git-fetch} origin download methods
(@pxref{origin Reference}).
@item (guix swh)
Fetching source code from the
@uref{https://archive.softwareheritage.org,Software Heritage archive}.
@item (guix search-paths)
Implementing search paths (@pxref{Search Paths}).
@item (guix build-system)
The build system interface (@pxref{Build Systems}).
@item (guix profiles)
Implementing profiles.
@end table

@cindex build system, directory structure
@item guix/build-system
This directory contains specific build system implementations
(@pxref{Build Systems}), such as:

@table @code
@item (guix build-system gnu)
the GNU build system;
@item (guix build-system cmake)
the CMake build system;
@item (guix build-system pyproject)
The Python ``pyproject'' build system.
@end table

@item guix/build
This contains code generally used on the ``build side''
(@pxref{G-Expressions, strata of code}).  This includes code used to
build packages or other operating system components, as well as
utilities:

@table @code
@item (guix build utils)
Utilities for package definitions and more (@pxref{Build Utilities}).
@item (guix build gnu-build-system)
@itemx (guix build cmake-build-system)
@itemx (guix build pyproject-build-system)
Implementation of build systems, and in particular definition of their
build phases (@pxref{Build Phases}).
@item (guix build syscalls)
Interface to the C library and to Linux system calls.
@end table

@cindex command-line tools, as Guile modules
@cindex command modules
@item guix/scripts
This contains modules corresponding to @command{guix} sub-commands.  For
example, the @code{(guix scripts shell)} module exports the
@code{guix-shell} procedure, which directly corresponds to the
@command{guix shell} command (@pxref{Invoking guix shell}).

@cindex importer modules
@item guix/import
This contains supporting code for the importers and updaters
(@pxref{Invoking guix import}, and @pxref{Invoking guix refresh}).  For
example, @code{(guix import pypi)} defines the interface to PyPI, which
is used by the @code{guix import pypi} command.
@end table

The directories we have seen so far all live under @file{guix/}.  The
other important place is the @file{gnu/} directory, which contains
primarily package definitions as well as libraries and tools for Guix
System (@pxref{System Configuration}) and Guix Home (@pxref{Home
Configuration}), all of which build upon functionality provided by
@code{(guix @dots{})} modules@footnote{For this reason, @code{(guix
@dots{})} modules must generally not depend on @code{(gnu @dots{})}
modules, with notable exceptions: @code{(guix build-system @dots{})}
modules may look up packages at run time---e.g., @code{(guix
build-system cmake)} needs to access the @code{cmake} variable at run
time---, @code{(guix scripts @dots{})} often rely on @code{(gnu @dots{})}
modules, and the same goes for some of the @code{(guix import @dots{})}
modules.}.

@table @file
@cindex package modules
@item gnu/packages
This is by far the most crowded directory of the source tree: it
contains @dfn{package modules} that export package definitions
(@pxref{Package Modules}).  A few examples:

@table @code
@item (gnu packages base)
Module providing ``base'' packages: @code{glibc}, @code{coreutils},
@code{grep}, etc.
@item (gnu packages guile)
Guile and core Guile packages.
@item (gnu packages linux)
The Linux-libre kernel and related packages.
@item (gnu packages python)
Python and core Python packages.
@item (gnu packages python-xyz)
Miscellaneous Python packages (we were not very creative).
@end table

In any case, you can jump to a package definition using @command{guix
edit} (@pxref{Invoking guix edit}) and view its location with
@command{guix show} (@pxref{Invoking guix package}).

@findex search-patches
@item gnu/packages/patches
This directory contains patches applied against packages and obtained
using the @code{search-patches} procedure.

@item gnu/services
This contains service definitions, primarily for Guix System
(@pxref{Services}) but some of them are adapted and reused for Guix Home
as we will see below.  Examples:

@table @code
@item (gnu services)
The service framework itself, which defines the service and service type
data types (@pxref{Service Composition}).
@item (gnu services base)
``Base'' services (@pxref{Base Services}).
@item (gnu services desktop)
``Desktop'' services (@pxref{Desktop Services}).
@item (gnu services shepherd)
Support for Shepherd services (@pxref{Shepherd Services}).
@end table

You can jump to a service definition using @command{guix system edit}
and view its location with @command{guix system search} (@pxref{Invoking
guix system}).

@item gnu/system
These are core Guix System modules, such as:

@table @code
@item (gnu system)
Defines @code{operating-system} (@pxref{operating-system Reference}).
@item (gnu system file-systems)
Defines @code{file-system} (@pxref{File Systems}).
@item (gnu system mapped-devices)
Defines @code{mapped-device} (@pxref{Mapped Devices}).
@end table

@item gnu/build
These are modules that are either used on the ``build side'' when
building operating systems or packages, or at run time by operating
systems.

@table @code
@item (gnu build accounts)
Creating @file{/etc/passwd}, @file{/etc/shadow}, etc. (@pxref{User
Accounts}).
@item (gnu build activation)
Activating an operating system at boot time or reconfiguration time.
@item (gnu build file-systems)
Searching, checking, and mounting file systems.
@item (gnu build linux-boot)
@itemx (gnu build hurd-boot)
Booting GNU/Linux and GNU/Hurd operating systems.
@item (gnu build linux-initrd)
Creating a Linux initial RAM disk (@pxref{Initial RAM Disk}).
@end table

@item gnu/home
This contains all things Guix Home (@pxref{Home Configuration});
examples:

@table @code
@item (gnu home services)
Core services such as @code{home-files-service-type}.
@item (gnu home services ssh)
SSH-related services (@pxref{Secure Shell}).
@end table

@item gnu/installer
This contains the text-mode graphical system installer (@pxref{Guided
Graphical Installation}).

@item gnu/machine
These are the @dfn{machine abstractions} used by @command{guix deploy}
(@pxref{Invoking guix deploy}).

@item gnu/tests
This contains system tests---tests that spawn virtual machines to check
that system services work as expected (@pxref{Running the Test Suite}).
@end table

Last, there's also a few directories that contain files that are
@emph{not} Guile modules:

@table @file
@item nix
This is the C++ implementation of @command{guix-daemon}, inherited from
Nix (@pxref{Invoking guix-daemon}).

@item tests
These are unit tests, each file corresponding more or less to one
module, in particular @code{(guix @dots{})} modules (@pxref{Running the
Test Suite}).

@item doc
This is the documentation in the form of Texinfo files: this manual and
the Cookbook.  @xref{Writing a Texinfo File,,, texinfo, GNU Texinfo},
for information on Texinfo markup language.

@item po
This is the location of translations of Guix itself, of package synopses
and descriptions, of the manual, and of the cookbook.  Note that
@file{.po} files that live here are pulled directly from Weblate
(@pxref{Translating Guix}).

@item etc
Miscellaneous files: shell completions, support for systemd and other
init systems, Git hooks, etc.
@end table

With all this, a fair chunk of your operating system is at your
fingertips!  Beyond @command{grep} and @command{git grep}, @pxref{The
Perfect Setup} on how to navigate code from your editor, and
@pxref{Using Guix Interactively} for information on how to use Scheme
modules interactively.  Enjoy!

@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{https://@value{SUBSTITUTE-SERVER-1}, 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-1}} 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.
* Snippets versus Phases::      Whether to use a snippet, or a build phase.
* Cyclic Module Dependencies::  Going full circle.
* Emacs Packages::              Your Elisp fix.
* Python Modules::              A touch of British comedy.
* Perl Modules::                Little pearls.
* Java Packages::               Coffee break.
* Rust Crates::                 Beware of oxidation.
* Elm Packages::                Trees of browser code
* 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{https://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{https://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 actually has 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}.

A noteworthy exception to this rule is when the project name is only a
single character, or if an older maintained project with the same name
already exists---regardless of whether it has already been packaged for
Guix.  Use common sense to make such names unambiguous and meaningful.
For example, Guix's package for the shell called ``s'' upstream is
@code{s-shell} and @emph{not} @code{s}.  Feel free to ask your fellow
hackers for inspiration.

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:

@lisp
(define-public gtk+
  (package
    (name "gtk+")
    (version "3.9.12")
    ...))
(define-public gtk+-2
  (package
    (name "gtk+")
    (version "2.24.20")
    ...))
@end lisp
If we also wanted GTK+ 3.8.2, this would be packaged as
@lisp
(define-public gtk+-3.8
  (package
    (name "gtk+")
    (version "3.8.2")
    ...))
@end lisp

@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).  There are helper functions for doing this for packages using
@code{git-fetch} or @code{hg-fetch} (see below).  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:


@lisp
(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 lisp

@deffn {Procedure} git-version @var{VERSION} @var{REVISION} @var{COMMIT}
Return the version string for packages using @code{git-fetch}.

@lisp
(git-version "0.2.3" "0" "93818c936ee7e2f1ba1b315578bde363a7d43d05")
@result{} "0.2.3-0.93818c9"
@end lisp
@end deffn

@deffn {Procedure} hg-version @var{VERSION} @var{REVISION} @var{CHANGESET}
Return the version string for packages using @code{hg-fetch}.  It works
in the same way as @code{git-version}.
@end deffn

@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 show} take care of rendering it
appropriately.

Synopses and descriptions are translated by volunteers
@uref{https://translate.fedoraproject.org/projects/guix/packages, at
Weblate} 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}):

@lisp
;; 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 lisp

@node Snippets versus Phases
@subsection Snippets versus Phases

@cindex snippets, when to use
The boundary between using an origin snippet versus a build phase to
modify the sources of a package can be elusive.  Origin snippets are
typically used to remove unwanted files such as bundled libraries,
nonfree sources, or to apply simple substitutions.  The source derived
from an origin should produce a source that can be used to build the
package on any system that the upstream package supports (i.e., act as
the corresponding source).  In particular, origin snippets must not
embed store items in the sources; such patching should rather be done
using build phases.  Refer to the @code{origin} record documentation for
more information (@pxref{origin Reference}).

@node Cyclic Module Dependencies
@subsection Cyclic Module Dependencies

While there cannot be circular dependencies between packages, Guile's
lax module loading mechanism allows circular dependencies between Guile
modules, which doesn't cause problems as long as the following
conditions are followed for two modules part of a dependency cycle:

@cindex rules to cope with circular module dependencies
@enumerate
@item
Macros are not shared between the co-dependent modules
@item
Top-level variables are only referenced in delayed (@i{thunked}) package
fields: @code{arguments}, @code{native-inputs}, @code{inputs},
@code{propagated-inputs} or @code{replacement}
@item
Procedures referencing top-level variables from another module are not
called at the top level of a module themselves.
@end enumerate

Straying away from the above rules may work while there are no
dependency cycles between modules, but given such cycles are confusing
and difficult to troubleshoot, it is best to follow the rules to avoid
introducing problems down the line.

@noindent
Here is a common trap to avoid:

@lisp
(define-public avr-binutils
  (package
    (inherit (cross-binutils "avr"))
    (name "avr-binutils")))
@end lisp

In the above example, the @code{avr-binutils} package was defined in the
module @code{(gnu packages avr)}, and the @code{cross-binutils}
procedure in @code{(gnu packages cross-base)}.  Because the
@code{inherit} field is not delayed (thunked), it is evaluated at the
top level at load time, which is problematic in the presence of module
dependency cycles.  This could be resolved by turning the package into a
procedure instead, like:

@lisp
(define (make-avr-binutils)
  (package
    (inherit (cross-binutils "avr"))
    (name "avr-binutils")))
@end lisp

Care would need to be taken to ensure the above procedure is only ever
used in a package delayed fields or within another procedure also not
called at the top level.

@node Emacs Packages
@subsection Emacs Packages

@cindex emacs, packaging
@cindex elisp, packaging
Emacs packages should preferably use the Emacs build system
(@pxref{emacs-build-system}), for uniformity and the benefits provided
by its build phases, such as the auto-generation of the autoloads file
and the byte compilation of the sources.  Because there is no
standardized way to run a test suite for Emacs packages, tests are
disabled by default.  When a test suite is available, it should be
enabled by setting the @code{#:tests?} argument to @code{#true}.  By
default, the command to run the test is @command{make check}, but any
command can be specified via the @code{#:test-command} argument.  The
@code{#:test-command} argument expects a list containing a command and
its arguments, to be invoked during the @code{check} phase.

The Elisp dependencies of Emacs packages are typically provided as
@code{propagated-inputs} when required at run time.  As for other
packages, build or test dependencies should be specified as
@code{native-inputs}.

Emacs packages sometimes depend on resources directories that should be
installed along the Elisp files.  The @code{#:include} argument can be
used for that purpose, by specifying a list of regexps to match.  The
best practice when using the @code{#:include} argument is to extend
rather than override its default value (accessible via the
@code{%default-include} variable).  As an example, a yasnippet extension
package typically include a @file{snippets} directory, which could be
copied to the installation directory using:

@lisp
#:include (cons "^snippets/" %default-include)
@end lisp

When encountering problems, it is wise to check for the presence of the
@code{Package-Requires} extension header in the package main source
file, and whether any dependencies and their versions listed therein are
satisfied.

@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 is compiled with Python 3, we name it
@code{python-foo}.  If it is compiled with Python 2, we name it
@code{python2-foo}.  Python 2 packages are being removed from the
distribution; please do no not submit any new Python 2 packages.

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.

@quotation Note
Currently there are two different build systems for Python packages in Guix:
@var{python-build-system} and @var{pyproject-build-system}.  For the
longest time, Python packages were built from an informally specified
@file{setup.py} file.  That worked amazingly well, considering Python's
success, but was difficult to build tooling around.  As a result, a host
of alternative build systems emerged and the community eventually settled on a
@url{https://peps.python.org/pep-0517/, formal standard} for specifying build
requirements.  @var{pyproject-build-system} is Guix's implementation of this
standard.  It is considered ``experimental'' in that it does not yet support
all the various PEP-517 @emph{build backends}, but you are encouraged to try
it for new Python packages and report any problems.  It will eventually be
deprecated and merged into @var{python-build-system}.
@end quotation

@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{pyproject.toml} file, the @file{setup.py} file, in
@file{requirements.txt}, or in @file{tox.ini} (the latter mostly for
test dependencies).

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 with @code{setuptools} and @code{pip}
installed per default.  This is about to change, and users are encouraged
to use @code{python-toolchain} if they want a build environment for Python.

@command{guix lint} will warn if @code{setuptools} or @code{pip} are
added as native-inputs because they are generally not necessary.

@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 under
@code{build-system.requires} in @file{pyproject.toml} or with the
@code{setup_requires} keyword in @file{setup.py}---or dependencies only
for testing---e.g., those in @code{tests_require} or @file{tox.ini}---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 Rust Crates
@subsection Rust Crates

@cindex rust
Rust programs standing for themselves are named as any other package, using the
lowercase upstream name.

To prevent namespace collisions we prefix all other Rust packages with the
@code{rust-} prefix.  The name should be changed to lowercase as appropriate and
dashes should remain in place.

In the rust ecosystem it is common for multiple incompatible versions of a
package to be used at any given time, so all package definitions should have a
versioned suffix.  The versioned suffix is the left-most non-zero digit (and
any leading zeros, of course).  This follows the ``caret'' version scheme
intended by Cargo.  Examples@: @code{rust-clap-2}, @code{rust-rand-0.6}.

Because of the difficulty in reusing rust packages as pre-compiled inputs for
other packages the Cargo build system (@pxref{Build Systems,
@code{cargo-build-system}}) presents the @code{#:cargo-inputs} and
@code{cargo-development-inputs} keywords as build system arguments.  It would be
helpful to think of these as similar to @code{propagated-inputs} and
@code{native-inputs}.  Rust @code{dependencies} and @code{build-dependencies}
should go in @code{#:cargo-inputs}, and @code{dev-dependencies} should go in
@code{#:cargo-development-inputs}.  If a Rust package links to other libraries
then the standard placement in @code{inputs} and the like should be used.

Care should be taken to ensure the correct version of dependencies are used; to
this end we try to refrain from skipping the tests or using @code{#:skip-build?}
when possible.  Of course this is not always possible, as the package may be
developed for a different Operating System, depend on features from the Nightly
Rust compiler, or the test suite may have atrophied since it was released.


@node Elm Packages
@subsection Elm Packages

@cindex Elm
Elm applications can be named like other software: their names need not
mention Elm.

Packages in the Elm sense (see @code{elm-build-system} under @ref{Build
Systems}) are required use names of the format
@var{author}@code{/}@var{project}, where both the @var{author} and the
@var{project} may contain hyphens internally, and the @var{author} sometimes
contains uppercase letters.

To form the Guix package name from the upstream name, we follow a convention
similar to Python packages (@pxref{Python Modules}), adding an @code{elm-}
prefix unless the name would already begin with @code{elm-}.

In many cases we can reconstruct an Elm package's upstream name heuristically,
but, since conversion to a Guix-style name involves a loss of information,
this is not always possible.  Care should be taken to add the
@code{'upstream-name} property when necessary so that @samp{guix import elm}
will work correctly (@pxref{Invoking guix import}). The most notable scenarios
when explicitly specifying the upstream name is necessary are:

@enumerate
@item
When the @var{author} is @code{elm} and the @var{project} contains one or more
hyphens, as with @code{elm/virtual-dom}; and

@item
When the @var{author} contains hyphens or uppercase letters, as with
@code{Elm-Canvas/raster-shapes}---unless the @var{author} is
@code{elm-explorations}, which is handled as a special case, so packages like
@code{elm-explorations/markdown} do @emph{not} need to use the
@code{'upstream-name} property.
@end enumerate

The module @code{(guix build-system elm)} provides the following utilities for
working with names and related conventions:

@deffn {Procedure} elm-package-origin @var{elm-name} @var{version} @
  @var{hash}
Returns a Git origin using the repository naming and tagging regime required
for a published Elm package with the upstream name @var{elm-name} at version
@var{version} with sha256 checksum @var{hash}.

For example:
@lisp
(package
  (name "elm-html")
  (version "1.0.0")
  (source
   (elm-package-origin
    "elm/html"
    version
    (base32 "15k1679ja57vvlpinpv06znmrxy09lbhzfkzdc89i01qa8c4gb4a")))
  ...)
@end lisp
@end deffn

@deffn {Procedure} elm->package-name @var{elm-name}
Returns the Guix-style package name for an Elm package with upstream name
@var{elm-name}.

Note that there is more than one possible @var{elm-name} for which
@code{elm->package-name} will produce a given result.
@end deffn

@deffn {Procedure} guix-package->elm-name @var{package}
Given an Elm @var{package}, returns the possibly-inferred upstream name, or
@code{#f} the upstream name is not specified via the @code{'upstream-name}
property and can not be inferred by @code{infer-elm-package-name}.
@end deffn

@deffn {Procedure} infer-elm-package-name @var{guix-name}
Given the @var{guix-name} of an Elm package, returns the inferred upstream
name, or @code{#f} if the upstream name can't be inferred.  If the result is
not @code{#f}, supplying it to @code{elm->package-name} would produce
@var{guix-name}.
@end deffn

@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
@cindex build-side modules
@cindex host-side 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.  As an example, the @code{(guix
search-paths)} module should not be imported and used by a package since
it isn't meant to be used as a ``build-side'' module.  It would also
couple the module with the package's dependency graph, which is
undesirable.

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.

@findex define-record-type*
@findex match-record
@cindex pattern matching
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 (@pxref{Pattern Matching,,, guile, GNU
Guile Reference Manual}); pattern matching for records is better done
using @code{match-record} from @code{(guix records)}, which, unlike
@code{match}, verifies field names at macro-expansion time.

When defining a new record type, keep the @dfn{record type descriptor}
(RTD) private (@pxref{Records,,, guile, GNU Guile Reference Manual}, for
more on records and RTDs).  As an example, the @code{(guix packages)}
module defines @code{<package>} as the RTD for package records but it
does not export it; instead, it exports a type predicate, a constructor,
and field accessors.  Exporting RTDs would make it harder to change the
application binary interface (because code in other modules might be
matching fields by position) and would make it trivial for users to
forge records of that type, bypassing any checks we may have in the
official constructor (such as ``field sanitizers'').

@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{https://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
./pre-inst-env guix style @var{package}
@end example

@noindent
@xref{Invoking guix style}, for more information.

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
(@pxref{Submitting patches to a project,,, git, Git User Manual}).
Contributors are encouraged to take a moment to set some Git repository
options (@pxref{Configuring Git}) first, which can improve the
readability of patches.  Seasoned Guix developers may also want to look
at the section on commit access (@pxref{Commit Access}).

This mailing list is backed by a Debbugs instance, which allows us to
keep track of submissions (@pxref{Tracking Bugs and Changes}).
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{ISSUE_NUMBER}@@debbugs.gnu.org}, where @var{ISSUE_NUMBER}
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.

You can help make the review process more efficient, and increase the
chance that your patch will be reviewed quickly, by describing the
context of your patch and the impact you expect it to have.  For
example, if your patch is fixing something that is broken, describe the
problem and how your patch fixes it.  Tell us how you have tested your
patch.  Will users of the code changed by your patch have to adjust
their workflow at all?  If so, tell us how.  In general, try to imagine
what questions a reviewer will ask, and answer those questions in
advance.

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
Run @code{guix style @var{package}} to format the new package definition
according to the project's conventions (@pxref{Invoking guix style}).

@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 @code{virtualization} service module and the
following service to the list of services in your @code{operating-system}
configuration:

@lisp
(service qemu-binfmt-service-type
 (qemu-binfmt-configuration
   (platforms (lookup-qemu-platforms "arm" "aarch64"))))
@end lisp

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 or aarch64 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
@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-updmap.cfg} procedure instead.

@item
Check that dependent packages (if applicable) are not affected by the
change; @code{guix refresh --list-dependent @var{package}} will help you
do that (@pxref{Invoking guix refresh}).

@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-1}} 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
@command{guix style} 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.

@item
Check if Guix builds (@pxref{Building from Git}) and address the
warnings, especially those about use of undefined symbols.

@item
Make sure your changes do not break Guix and simulate a @code{guix pull} with:
@example
guix pull --url=/path/to/your/checkout --profile=/tmp/guix.master
@end example

@end enumerate

When posting a patch to the mailing list, use @samp{[PATCH] @dots{}} as
a subject, if your patch is to be applied on a branch other than
@code{master}, say @code{core-updates}, specify it in the subject like
@samp{[PATCH core-updates] @dots{}}.

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.

Expect some delay when you submit your very first patch to
@email{guix-patches@@gnu.org}. You have to wait until you get an
acknowledgement with the assigned tracking number. Future acknowledgements
should not be delayed.

When a bug is resolved, please close the thread by sending an email to
@email{@var{ISSUE_NUMBER}-done@@debbugs.gnu.org}.

@menu
* Configuring Git::
* Sending a Patch Series::
* Teams::
@end menu

@node Configuring Git
@subsection Configuring Git
@cindex git configuration
@cindex @code{git format-patch}
@cindex @code{git send-email}

If you have not done so already, you may wish to set a name and email
that will be associated with your commits (@pxref{telling git your name,
, Telling Git your name, git, Git User Manual}).  If you wish to use a
different name or email just for commits in this repository, you can
use @command{git config --local}, or edit @file{.git/config} in the
repository instead of @file{~/.gitconfig}.

@cindex commit-msg hook
Other important Git configuration will automatically be configured when
building the project (@pxref{Building from Git}).  A
@file{.git/hooks/commit-msg} hook will be installed that embeds
@samp{Change-Id} Git @emph{trailers} in your commit messages for
traceability purposes.  It is important to preserve these when editing
your commit messages, particularly if a first version of your proposed
changes was already submitted for review.  If you have a
@file{commit-msg} hook of your own you would like to use with Guix, you
can place it under the @file{.git/hooks/commit-msg.d/} directory.

@node Sending a Patch Series
@subsection Sending a Patch Series
@cindex patch series
@cindex @code{git send-email}
@cindex @code{git format-patch}

@unnumberedsubsubsec Single Patches
@anchor{Single Patches}
The @command{git send-email} command is the best way to send both single
patches and patch series (@pxref{Multiple Patches}) to the Guix mailing
list.  Sending patches as email attachments may make them difficult to
review in some mail clients, and @command{git diff} does not store commit
metadata.

@quotation Note
The @command{git send-email} command is provided by the @code{send-email}
output of the @code{git} package, i.e. @code{git:send-email}.
@end quotation

The following command will create a patch email from the latest commit,
open it in your @var{EDITOR} or @var{VISUAL} for editing, and send it to
the Guix mailing list to be reviewed and merged.  Assuming you have
already configured Git according to @xref{Configuring Git}, you can
simply use:

@example
$ git send-email --annotate -1
@end example

@quotation Tip
To add a prefix to the subject of your patch, you may use the
@option{--subject-prefix} option.  The Guix project uses this to
specify that the patch is intended for a branch or repository
other than the @code{master} branch of
@url{https://git.savannah.gnu.org/cgit/guix.git}.

@example
git send-email --annotate --subject-prefix='PATCH core-updates' -1
@end example
@end quotation

The patch email contains a three-dash separator line after the commit
message.  You may ``annotate'' the patch with explanatory text by adding
it under this line.  If you do not wish to annotate the email, you may
drop the @option{--annotate} option.

If you need to send a revised patch, don't resend it like this or send
a ``fix'' patch to be applied on top of the last one; instead, use
@command{git commit --amend} or @url{https://git-rebase.io,
@command{git rebase}} to modify the commit, and use the
@email{@var{ISSUE_NUMBER}@@debbugs.gnu.org} address and the @option{-v}
flag with @command{git send-email}.

@example
$ git commit --amend
$ git send-email --annotate -v@var{REVISION} \
      --to=@var{ISSUE_NUMBER}@@debbugs.gnu.org -1
@end example

@quotation Note
Due to an apparent bug in @command{git send-email},
@option{-v @var{REVISION}} (with the space) will not work; you
@emph{must} use @option{-v@var{REVISION}}.
@end quotation

You can find out @var{ISSUE_NUMBER} either by searching on the mumi
interface at @url{https://issues.guix.gnu.org} for the name of your patch or
reading the acknowledgement email sent automatically by Debbugs in
reply to incoming bugs and patches, which contains the bug number.

@unnumberedsubsubsec Notifying Teams
@anchor{Notifying Teams}
@cindex teams
If your git checkout has been correctly configured (@pxref{Configuring
Git}), the @command{git send-email} command will automatically notify
the appropriate team members, based on the scope of your changes.  This
relies on the @file{etc/teams.scm} script, which can also be invoked
manually if you do not use the preferred @command{git send-email}
command to submit patches.  To list the available actions of the script,
you can invoke it via the @command{etc/teams.scm help} command.  For
more information regarding teams, @pxref{Teams}.

@quotation Note
On foreign distros, you might have to use @command{./pre-inst-env git
send-email} for @file{etc/teams.scm} to work.
@end quotation

@unnumberedsubsubsec Multiple Patches
@anchor{Multiple Patches}
@cindex cover letter
While @command{git send-email} alone will suffice for a single
patch, an unfortunate flaw in Debbugs means you need to be more
careful when sending multiple patches: if you send them all to the
@email{guix-patches@@gnu.org} address, a new issue will be created
for each patch!

When sending a series of patches, it's best to send a Git ``cover
letter'' first, to give reviewers an overview of the patch series.
We can create a directory called @file{outgoing} containing both
our patch series and a cover letter called @file{0000-cover-letter.patch}
with @command{git format-patch}.

@example
$ git format-patch -@var{NUMBER_COMMITS} -o outgoing \
      --cover-letter --base=auto
@end example

We can now send @emph{just} the cover letter to the
@email{guix-patches@@gnu.org} address, which will create an issue
that we can send the rest of the patches to.

@example
$ git send-email outgoing/0000-cover-letter.patch --annotate
$ rm outgoing/0000-cover-letter.patch # we don't want to resend it!
@end example

Ensure you edit the email to add an appropriate subject line and
blurb before sending it.  Note the automatically generated shortlog
and diffstat below the blurb.

Once the Debbugs mailer has replied to your cover letter email, you
can send the actual patches to the newly-created issue address.

@example
$ git send-email outgoing/*.patch --to=@var{ISSUE_NUMBER}@@debbugs.gnu.org
$ rm -rf outgoing # we don't need these anymore
@end example

Thankfully, this @command{git format-patch} dance is not necessary
to send an amended patch series, since an issue already exists for
the patchset.

@example
$ git send-email -@var{NUMBER_COMMITS} -v@var{REVISION} \
      --to=@var{ISSUE_NUMBER}@@debbugs.gnu.org
@end example

If need be, you may use @option{--cover-letter --annotate} to send
another cover letter, e.g. for explaining what's changed since the last
revision, and these changes are necessary.

@node Teams
@subsection Teams
@cindex teams

There are several teams mentoring different parts of the Guix source
code.  To list all those teams, you can run from a Guix checkout:

@example
$ ./etc/teams.scm list-teams
id: mentors
name: Mentors
description: A group of mentors who chaperone contributions by newcomers.
members:
+ Christopher Baines <mail@@cbaines.net>
+ Ricardo Wurmus <rekado@@elephly.net>
+ Mathieu Othacehe <othacehe@@gnu.org>
+ jgart <jgart@@dismail.de>
+ Ludovic Courtès <ludo@@gnu.org>
@dots{}
@end example

You can run the following command to have the @code{Mentors} team put in
CC of a patch series:

@example
$ git send-email --to=@var{ISSUE_NUMBER}@@debbugs.gnu.org \
  --header-cmd='etc/teams.scm cc-mentors-header-cmd' *.patch
@end example

The appropriate team or teams can also be inferred from the modified
files.  For instance, if you want to send the two latest commits of the
current Git repository to review, you can run:

@example
$ guix shell -D guix
[env]$ git send-email --to=@var{ISSUE_NUMBER}@@debbugs.gnu.org -2
@end example

@node Tracking Bugs and Changes
@section Tracking Bugs and Changes

This section describes how the Guix project tracks its bug reports,
patch submissions and topic branches.

@menu
* The Issue Tracker::           The official bug and patch tracker.
* Managing Patches and Branches::  How changes to Guix are managed.
* Debbugs User Interfaces::     Ways to interact with Debbugs.
* Debbugs Usertags::            Tag reports with custom labels.
* Cuirass Build Notifications::  Be alerted of any breakage via RSS feeds.
@end menu

@node The Issue Tracker
@subsection The Issue Tracker

@cindex bug reports, tracking
@cindex patch submissions, tracking
@cindex issue tracking
@cindex Debbugs, issue tracking system
Bug reports and patch submissions are currently tracked using the
Debbugs instance at @uref{https://bugs.gnu.org}.  Bug reports are filed
against the @code{guix} ``package'' (in Debbugs parlance), by sending
email to @email{bug-guix@@gnu.org}, while patch submissions are filed
against the @code{guix-patches} package by sending email to
@email{guix-patches@@gnu.org} (@pxref{Submitting Patches}).

@node Managing Patches and Branches
@subsection Managing Patches and Branches
@cindex branching strategy
@cindex rebuild scheduling strategy

Changes should be posted to @email{guix-patches@@gnu.org}.  This mailing
list fills the patch-tracking database (@pxref{The Issue Tracker}).  It
also allows patches to be picked up and tested by the quality assurance
tooling; the result of that testing eventually shows up on the dashboard
at @indicateurl{https://qa.guix.gnu.org/issue/@var{ISSUE_NUMBER}}, where
@var{ISSUE_NUMBER} is the number assigned by the issue tracker.  Leave
time for a review, without committing anything.

As an exception, some changes considered ``trivial'' or ``obvious'' may
be pushed directly to the @code{master} branch.  This includes changes
to fix typos and reverting commits that caused immediate problems.  This
is subject to being adjusted, allowing individuals to commit directly on
non-controversial changes on parts they’re familiar with.

Changes which affect more than 300 dependent packages (@pxref{Invoking
guix refresh}) should first be pushed to a topic branch other than
@code{master}; the set of changes should be consistent---e.g., ``GNOME
update'', ``NumPy update'', etc.  This allows for testing: the branch
will automatically show up at
@indicateurl{https://qa.guix.gnu.org/branch/@var{branch}}, with an
indication of its build status on various platforms.

@cindex feature branches, coordination
To help coordinate the merging of branches, you must create a new
guix-patches issue each time you create a branch (@pxref{The Issue
Tracker}).  The title of the issue requesting to merge a branch should
have the following format:

@cindex merge requests, template
@example
Request for merging "@var{name}" branch
@end example

The @url{https://qa.guix.gnu.org/, QA infrastructure} recognizes such
issues and lists the merge requests on its main page.  The following
points apply to managing these branches:

@enumerate
@item
The commits on the branch should be a combination of the patches
relevant to the branch.  Patches not related to the topic of the branch
should go elsewhere.

@item
Any changes that can be made on the master branch, should be made on the
master branch.  If a commit can be split to apply part of the changes on
master, this is good to do.

@item
It should be possible to re-create the branch by starting from master
and applying the relevant patches.

@item
Avoid merging master in to the branch.  Prefer rebasing or re-creating
the branch on top of an updated master revision.

@item
Minimise the changes on master that are missing on the branch prior to
merging the branch in to master.  This means that the state of the
branch better reflects the state of master should the branch be merged.

@item
If you don't have commit access, create the ``Request for merging''
issue and request that someone creates the branch.  Include a list of
issues/patches to include on the branch.
@end enumerate

Normally branches will be merged in a ``first come, first merged''
manner, tracked through the guix-patches issues.  If you agree on a
different order with those involved, you can track this by updating
which issues block@footnote{You can mark an issue as blocked by another
by emailing @email{control@@debbugs.gnu.org} with the following line in
the body of the email: @code{block XXXXX by YYYYY}.  Where @code{XXXXX}
is the number for the blocked issue, and @code{YYYYY} is the number for
the issue blocking it.} which other issues.  Therefore, to know which
branch is at the front of the queue, look for the oldest issue, or the
issue that isn't @dfn{blocked} by any other branch merges.  An ordered
list of branches with the open issues is available at
@url{https://qa.guix.gnu.org}.

Once a branch is at the front of the queue, wait until sufficient time
has passed for the build farms to have processed the changes, and for
the necessary testing to have happened.  For example, you can check
@indicateurl{https://qa.guix.gnu.org/branch/@var{branch}} to see
information on some builds and substitute availability.

Once the branch has been merged, the issue should be closed and the
branch deleted.

@node Debbugs User Interfaces
@subsection Debbugs User Interfaces

@subsubsection Web interface

A web interface (actually @emph{two} web interfaces!) are available to
browse issues:

@itemize
@item
@url{https://issues.guix.gnu.org} provides a pleasant
interface@footnote{The web interface at
@url{https://issues.guix.gnu.org} is powered by Mumi, a nice piece of
software written in Guile, and you can help!  See
@url{https://git.savannah.gnu.org/cgit/guix/mumi.git}.} to browse
bug reports and patches, and to participate in discussions;
@item
@url{https://bugs.gnu.org/guix} lists bug reports;
@item
@url{https://bugs.gnu.org/guix-patches} lists patch submissions.
@end itemize

To view discussions related to issue number @var{n}, go to
@indicateurl{https://issues.guix.gnu.org/@var{n}} or
@indicateurl{https://bugs.gnu.org/@var{n}}.

@subsubsection Command-line interface

Mumi also comes with a command-line interface that can be used to search
existing issues, open new issues and send patches.  You do not need to
use Emacs to use the mumi command-line client.  You interact with it
only on the command-line.

To use the mumi command-line interface, navigate to a local clone of the
Guix git repository, and drop into a shell with mumi, git and
git:send-email installed.

@example
$ cd guix
~/guix$ guix shell mumi git git:send-email
@end example

To search for issues, say all open issues about "zig", run

@example
~/guix [env]$ mumi search zig is:open

#60889 Add zig-build-system
opened on 17 Jan 17:37 Z by Ekaitz Zarraga
#61036 [PATCH 0/3] Update zig to 0.10.1
opened on 24 Jan 09:42 Z by Efraim Flashner
#39136 [PATCH] gnu: services: Add endlessh.
opened on 14 Jan 2020 21:21 by Nicol? Balzarotti
#60424 [PATCH] gnu: Add python-online-judge-tools
opened on 30 Dec 2022 07:03 by gemmaro
#45601 [PATCH 0/6] vlang 0.2 update
opened on  1 Jan 2021 19:23 by Ryan Prior
@end example

Pick an issue and make it the "current" issue.

@example
~/guix [env]$ mumi current 61036

#61036 [PATCH 0/3] Update zig to 0.10.1
opened on 24 Jan 09:42 Z by Efraim Flashner
@end example

Once an issue is the current issue, you can easily create and send
patches to it using

@example
~/guix [env]$ git format-patch origin/master
~/guix [env]$ mumi send-email foo.patch bar.patch
@end example

Note that you do not have to pass in @samp{--to} or @samp{--cc}
arguments to @command{git format-patch}.  @command{mumi send-email} will
put them in correctly when sending the patches.

To open a new issue, run

@example
~/guix [env]$ mumi new
@end example

and send patches

@example
~/guix [env]$ mumi send-email foo.patch bar.patch
@end example

@command{mumi send-email} is really a wrapper around @command{git
send-email} that automates away all the nitty-gritty of sending patches.
It uses the current issue state to automatically figure out the correct
@samp{To} address to send to, other participants to @samp{Cc}, headers
to add, etc.

Also note that, unlike @command{git send-email}, @command{mumi
send-email} works perfectly well with single and multiple patches alike.
It automates away the debbugs dance of sending the first patch, waiting
for a response from debbugs and sending the remaining patches.  It does
so by sending the first patch, polling the server for a response, and
then sending the remaining patches.  This polling can unfortunately take
a few minutes.  So, please be patient.

@subsubsection Emacs interface

If you use Emacs, you may find it more convenient to interact with
issues using @file{debbugs.el}, which you can install with:

@example
guix install emacs-debbugs
@end example

For example, to list all open issues on @code{guix-patches}, hit:

@example
@kbd{C-u} @kbd{M-x} debbugs-gnu @kbd{RET} @kbd{RET} guix-patches @kbd{RET} n y
@end example

For a more convenient (shorter) way to access both the bugs and patches
submissions, you may want to configure the
@code{debbugs-gnu-default-packages} and
@code{debbugs-gnu-default-severities} Emacs variables (@pxref{Viewing
Bugs within Emacs}).

To search for bugs, @samp{@kbd{M-x} debbugs-gnu-guix-search} can be
used.

@xref{Top,,, debbugs-ug, Debbugs User Guide}, for more information on
this nifty tool!

@node Debbugs Usertags
@subsection Debbugs Usertags

@cindex usertags, for debbugs
@cindex Debbugs usertags
Debbugs provides a feature called @dfn{usertags} that allows any user to
tag any bug with an arbitrary label.  Bugs can be searched by usertag,
so this is a handy way to organize bugs@footnote{The list of usertags is
public information, and anyone can modify any user's list of usertags,
so keep that in mind if you choose to use this feature.}.  If you use
Emacs Debbugs, the entry-point to consult existing usertags is the
@samp{C-u M-x debbugs-gnu-usertags} procedure.  To set a usertag, press
@samp{C} while consulting a bug within the *Guix-Patches* buffer opened
with @samp{C-u M-x debbugs-gnu-bugs} buffer, then select @code{usertag}
and follow the instructions.

For example, to view all the bug reports (or patches, in the case of
@code{guix-patches}) tagged with the usertag @code{powerpc64le-linux}
for the user @code{guix}, open a URL like the following in a web
browser:
@url{https://debbugs.gnu.org/cgi-bin/pkgreport.cgi?tag=powerpc64le-linux;users=guix}.

For more information on how to use usertags, please refer to the
documentation for Debbugs or the documentation for whatever tool you use
to interact with Debbugs.

In Guix, we are experimenting with usertags to keep track of
architecture-specific issues, as well as reviewed ones.  To facilitate
collaboration, all our usertags are associated with the single user
@code{guix}.  The following usertags currently exist for that user:

@table @code

@item powerpc64le-linux
The purpose of this usertag is to make it easy to find the issues that
matter most for the @code{powerpc64le-linux} system type.  Please assign
this usertag to bugs or patches that affect @code{powerpc64le-linux} but
not other system types.  In addition, you may use it to identify issues
that for some reason are particularly important for the
@code{powerpc64le-linux} system type, even if the issue affects other
system types, too.

@item reproducibility
For issues related to reproducibility.  For example, it would be
appropriate to assign this usertag to a bug report for a package that
fails to build reproducibly.

@item reviewed-looks-good
You have reviewed the series and it looks good to you (LGTM).

@end table

If you're a committer and you want to add a usertag, just start using it
with the @code{guix} user.  If the usertag proves useful to you,
consider updating this section of the manual so that others will know
what your usertag means.

@node Cuirass Build Notifications
@subsection Cuirass Build Notifications

@cindex build event notifications, RSS feed
@cindex notifications, build events
Cuirass includes @acronym{RSS, Really Simple Syndication} feeds as one
of its features (@pxref{Notifications,,,cuirass}).  Since
@url{https://ci.guix.gnu.org/, Berlin} runs an instance of Cuirass, this
feature can be used to keep track of recently broken or fixed packages
caused by changes pushed to the Guix git repository.  Any RSS client can
be used.  A good one, included with Emacs, is @xref{Gnus,,,gnus}.  To
register the feed, copy its URL, then from the main Gnus buffer,
@samp{*Group*}, do the following:

@cindex Gnus, configuration to read CI RSS feeds
@cindex RSS feeds, Gnus configuration
@example
@kbd{G R} https://ci.guix.gnu.org/events/rss/?specification=master RET
Guix CI - master RET Build events for specification master. RET
@end example

@noindent
Then, back at the @samp{*Group*} buffer, press @kbd{s} to save the newly
added RSS group.  As for any other Gnus group, you can update its
content by pressing the @kbd{g} key.  You should now receive
notifications that read like:

@example
 . [ ?: Cuirass ] Build tree-sitter-meson.aarch64-linux on master is fixed.
 . [ ?: Cuirass ] Build rust-pbkdf2.aarch64-linux on master is fixed.
 . [ ?: Cuirass ] Build rust-pbkdf2.x86_64-linux on master is fixed.
@end example

@noindent
where each RSS entry contains a link to the Cuirass build details page
of the associated build.

@node Commit Access
@section Commit Access

@cindex commit access, for developers
Everyone can contribute to Guix without having commit access
(@pxref{Submitting Patches}).  However, for frequent contributors,
having write access to the repository can be convenient.  As a rule of
thumb, a contributor should have accumulated fifty (50) reviewed commits
to be considered as a committer and have sustained their activity in the
project for at least 6 months.  This ensures enough interactions with
the contributor, which is essential for mentoring and assessing whether
they are ready to become a committer.  Commit access should not be
thought of as a ``badge of honor'' but rather as a responsibility a
contributor is willing to take to help the project.  It is expected from
all contributors, and even more so from committers, to help build
consensus and make decisions based on consensus.  By using consensus, we
are committed to finding solutions that everyone can live with.  It
implies that no decision is made against significant concerns and these
concerns are actively resolved with proposals that work for everyone.  A
contributor (which may or may not have commit access) wishing to block a
proposal bears a special responsibility for finding alternatives,
proposing ideas/code or explain the rationale for the status quo to
resolve the deadlock.  To learn what consensus decision making means and
understand its finer details, you are encouraged to read
@url{https://www.seedsforchange.org.uk/consensus}.

The following sections explain how to get commit access, how to be ready
to push commits, and the policies and community expectations for commits
pushed upstream.

@subsection Applying for Commit Access

When you deem it necessary, consider applying for commit
access by following these steps:

@enumerate
@item
Find three committers who would vouch for you.  You can view the list of
committers at
@url{https://savannah.gnu.org/project/memberlist.php?group=guix}.  Each
of them should email a statement to @email{guix-maintainers@@gnu.org} (a
private alias for the collective of maintainers), signed with their
OpenPGP key.

Committers are expected to have had some interactions with you as a
contributor and to be able to judge whether you are sufficiently
familiar with the project's practices.  It is @emph{not} a judgment on
the value of your work, so a refusal should rather be interpreted as
``let's try again later''.

@item
Send @email{guix-maintainers@@gnu.org} a message stating your intent,
listing the three committers who support your application, signed with
the OpenPGP key you will use to sign commits, and giving its fingerprint
(see below).  See @uref{https://emailselfdefense.fsf.org/en/}, for an
introduction to public-key cryptography with GnuPG.

@c See <https://sha-mbles.github.io/>.
Set up GnuPG such that it never uses the SHA1 hash algorithm for digital
signatures, which is known to be unsafe since 2019, for instance by
adding the following line to @file{~/.gnupg/gpg.conf} (@pxref{GPG
Esoteric Options,,, gnupg, The GNU Privacy Guard Manual}):

@example
digest-algo sha512
@end example

@item
Maintainers ultimately decide whether to grant you commit access,
usually following your referrals' recommendation.

@item
@cindex OpenPGP, signed commits
If and once you've been given access, please send a message to
@email{guix-devel@@gnu.org} to say so, again signed with the OpenPGP key
you will use to sign commits (do that before pushing your first commit).
That way, everyone can notice and ensure you control that OpenPGP key.

@quotation Important
Before you can push for the first time, maintainers must:

@enumerate
@item
add your OpenPGP key to the @code{keyring} branch;
@item
add your OpenPGP fingerprint to the @file{.guix-authorizations} file of
the branch(es) you will commit to.
@end enumerate
@end quotation

@item
Make sure to read the rest of this section and... profit!
@end enumerate

@quotation Note
Maintainers are happy to give commit access to people who have been
contributing for some time and have a track record---don't be shy and
don't underestimate your work!

However, note that the project is working towards a more automated patch
review and merging system, which, as a consequence, may lead us to have
fewer people with commit access to the main repository.  Stay tuned!
@end quotation

All commits that are pushed to the central repository on Savannah must
be signed with an OpenPGP key, and the public key should be uploaded to
your user account on Savannah and to public key servers, such as
@code{keys.openpgp.org}.  To configure Git to automatically sign
commits, run:

@example
git config commit.gpgsign true

# Substitute the fingerprint of your public PGP key.
git config user.signingkey CABBA6EA1DC0FF33
@end example

To check that commits are signed with correct key, use:

@example
make authenticate
@end example

To avoid accidentally pushing unsigned or signed with the wrong key
commits to Savannah, make sure to configure Git according to
@xref{Configuring Git}.

@subsection Commit Policy

If you get commit access, please make sure to follow the policy below
(discussions of the policy can take place on
@email{guix-devel@@gnu.org}).

Ensure you're aware of how the changes should be handled
(@pxref{Managing Patches and Branches}) prior to being pushed to the
repository, especially for the @code{master} branch.

If you're committing and pushing your own changes, try and wait at least
one week (two weeks for more significant changes) after you send them
for review. After this, if no one else is available to review them and
if you're confident about the changes, it's OK to commit.

When pushing a commit on behalf of somebody else, please add a
@code{Signed-off-by} line at the end of the commit log message---e.g.,
with @command{git am --signoff}.  This improves tracking of who did
what.

When adding channel news entries (@pxref{Channels, Writing Channel
News}), make sure they are well-formed by running the following command
right before pushing:

@example
make check-channel-news
@end example

@subsection Addressing Issues

Peer review (@pxref{Submitting Patches}) and tools such as
@command{guix lint} (@pxref{Invoking guix lint}) and the test suite
(@pxref{Running the Test Suite}) should catch issues before they are
pushed.  Yet, commits that ``break'' functionality might occasionally
go through.  When that happens, there are two priorities: mitigating
the impact, and understanding what happened to reduce the chance of
similar incidents in the future.  The responsibility for both these
things primarily lies with those involved, but like everything this is
a group effort.

Some issues can directly affect all users---for instance because they
make @command{guix pull} fail or break core functionality, because they
break major packages (at build time or run time), or because they
introduce known security vulnerabilities.

@cindex reverting commits
The people involved in authoring, reviewing, and pushing such
commit(s) should be at the forefront to mitigate their impact in a
timely fashion: by pushing a followup commit to fix it (if possible),
or by reverting it to leave time to come up with a proper fix, and by
communicating with other developers about the problem.

If these persons are unavailable to address the issue in time, other
committers are entitled to revert the commit(s), explaining in the
commit log and on the mailing list what the problem was, with the goal
of leaving time to the original committer, reviewer(s), and author(s)
to propose a way forward.

Once the problem has been dealt with, it is the responsibility of
those involved to make sure the situation is understood.  If you are
working to understand what happened, focus on gathering information
and avoid assigning any blame.  Do ask those involved to describe what
happened, do not ask them to explain the situation---this would
implicitly blame them, which is unhelpful.  Accountability comes from
a consensus about the problem, learning from it and improving
processes so that it's less likely to reoccur.

@subsection Commit Revocation

In order to reduce the possibility of mistakes, committers will have
their Savannah account removed from the Guix Savannah project and their
key removed from @file{.guix-authorizations} after 12 months of
inactivity; they can ask to regain commit access by emailing the
maintainers, without going through the vouching process.

Maintainers@footnote{See @uref{https://guix.gnu.org/en/about} for the
current list of maintainers.  You can email them privately at
@email{guix-maintainers@@gnu.org}.} may also revoke an individual's
commit rights, as a last resort, if cooperation with the rest of the
community has caused too much friction---even within the bounds of the
project's code of conduct (@pxref{Contributing}).  They would only do so
after public or private discussion with the individual and a clear
notice.  Examples of behavior that hinders cooperation and could lead to
such a decision include:

@itemize
@item repeated violation of the commit policy stated above;
@item repeated failure to take peer criticism into account;
@item breaching trust through a series of grave incidents.
@end itemize

When maintainers resort to such a decision, they notify developers on
@email{guix-devel@@gnu.org}; inquiries may be sent to
@email{guix-maintainers@@gnu.org}.  Depending on the situation, the
individual may still be welcome to contribute.

@subsection Helping Out

One last thing: the project keeps moving forward because committers not
only push their own awesome changes, but also offer some of their time
@emph{reviewing} and pushing other people's changes.  As a committer,
you're welcome to use your expertise and commit rights to help other
contributors, too!

@node Reviewing the Work of Others
@section Reviewing the Work of Others

Perhaps the biggest action you can do to help GNU Guix grow as a project
is to review the work contributed by others.  You do not need to be a
committer to do so; applying, reading the source, building, linting and
running other people's series and sharing your comments about your
experience will give some confidence to committers.  Basically, you must
ensure the check list found in the @ref{Submitting Patches} section has
been correctly followed.  A reviewed patch series should give the best
chances for the proposed change to be merged faster, so if a change you
would like to see merged hasn't yet been reviewed, this is the most
appropriate thing to do!

@cindex reviewing, guidelines
Review comments should be unambiguous; be as clear and explicit as you
can about what you think should be changed, ensuring the author can take
action on it.  Please try to keep the following guidelines in mind
during review:

@enumerate
@item
@emph{Be clear and explicit about changes you are suggesting}, ensuring
the author can take action on it.  In particular, it is a good idea to
explicitly ask for new revisions when you want it.

@item
@emph{Remain focused: do not change the scope of the work being
reviewed.}  For example, if the contribution touches code that follows a
pattern deemed unwieldy, it would be unfair to ask the submitter to fix
all occurrences of that pattern in the code; to put it simply, if a
problem unrelated to the patch at hand was already there, do not ask the
submitter to fix it.

@item
@emph{Ensure progress.}  As they respond to review, submitters may
submit new revisions of their changes; avoid requesting changes that you
did not request in the previous round of comments.  Overall, the
submitter should get a clear sense of progress; the number of items open
for discussion should clearly decrease over time.

@item
@emph{Aim for finalization.}  Reviewing code is time-consuming.  Your
goal as a reviewer is to put the process on a clear path towards
integration, possibly with agreed-upon changes, or rejection, with a
clear and mutually-understood reasoning.  Avoid leaving the review
process in a lingering state with no clear way out.

@item
@emph{Review is a discussion.}  The submitter's and reviewer's views on
how to achieve a particular change may not always be aligned.  To lead
the discussion, remain focused, ensure progress and aim for
finalization, spending time proportional to the stakes@footnote{The
tendency to discuss minute details at length is often referred to as
``bikeshedding'', where much time is spent discussing each one's
preference for the color of the shed at the expense of progress made on
the project to keep bikes dry.}.  As a reviewer, try hard to explain the
rationale for suggestions you make, and to understand and take into
account the submitter's motivation for doing things in a certain way.
@end enumerate

@cindex LGTM, Looks Good To Me
@cindex review tags
@cindex Reviewed-by, git trailer
When you deem the proposed change adequate and ready for inclusion
within Guix, the following well understood/codified
@samp{Reviewed-by:@tie{}Your@tie{}Name<your-email@@example.com>}
@footnote{The @samp{Reviewed-by} Git trailer is used by other projects
such as Linux, and is understood by third-party tools such as the
@samp{b4 am} sub-command, which is able to retrieve the complete
submission email thread from a public-inbox instance and add the Git
trailers found in replies to the commit patches.} line should be used to
sign off as a reviewer, meaning you have reviewed the change and that it
looks good to you:

@itemize
@item
If the @emph{whole} series (containing multiple commits) looks good to
you, reply with @samp{Reviewed-by:@tie{}Your@tie{}Name<your-email@@example.com>}
to the cover page if it has one, or to the last patch of the series
otherwise, adding another @samp{(for the whole series)} comment on the
line below to explicit this fact.

@item
If you instead want to mark a @emph{single commit} as reviewed (but not
the whole series), simply reply with
@samp{Reviewed-by:@tie{}Your@tie{}Name<your-email@@example.com>} to that
commit message.
@end itemize

If you are not a committer, you can help others find a @emph{series} you
have reviewed more easily by adding a @code{reviewed-looks-good} usertag
for the @code{guix} user (@pxref{Debbugs Usertags}).

@node Updating the Guix Package
@section Updating the Guix Package

@cindex update-guix-package, updating the guix package
It is sometimes desirable to update the @code{guix} package itself (the
package defined in @code{(gnu packages package-management)}), for
example to make new daemon features available for use by the
@code{guix-service-type} service type.  In order to simplify this task,
the following command can be used:

@example
make update-guix-package
@end example

The @code{update-guix-package} make target will use the last known
@emph{commit} corresponding to @code{HEAD} in your Guix checkout,
compute the hash of the Guix sources corresponding to that commit and
update the @code{commit}, @code{revision} and hash of the @code{guix}
package definition.

To validate that the updated @code{guix} package hashes are correct and
that it can be built successfully, the following command can be run from
the directory of your Guix checkout:

@example
./pre-inst-env guix build guix
@end example

To guard against accidentally updating the @code{guix} package to a
commit that others can't refer to, a check is made that the commit used
has already been pushed to the Savannah-hosted Guix git repository.

This check can be disabled, @emph{at your own peril}, by setting the
@code{GUIX_ALLOW_ME_TO_USE_PRIVATE_COMMIT} environment variable.  When
this variable is set, the updated package source is also added to the
store.  This is used as part of the release process of Guix.

@cindex documentation
@node Writing Documentation
@section Writing Documentation

Guix is documented using the Texinfo system.  If you are not yet
familiar with it, we accept contributions for documentation in most
formats.  That includes plain text, Markdown, Org, etc.

Documentation contributions can be sent to
@email{guix-patches@@gnu.org}.  Prepend @samp{[DOCUMENTATION]} to the
subject.

When you need to make more than a simple addition to the documentation,
we prefer that you send a proper patch as opposed to sending an email
as described above.  @xref{Submitting Patches} for more information on
how to send your patches.

To modify the documentation, you need to edit @file{doc/guix.texi} and
@file{doc/contributing.texi} (which contains this documentation
section), or @file{doc/guix-cookbook.texi} for the cookbook.  If
you compiled the Guix repository before, you will have
many more @file{.texi} files that are translations of these
documents.  Do not modify them, the translation is managed through
@uref{https://translate.fedoraproject.org/projects/guix, Weblate}.
@xref{Translating Guix} for more information.

To render documentation, you must first make sure that you ran
@command{./configure} in your source tree (@pxref{Running Guix Before
It Is Installed}).  After that you can run one of the following
commands:

@itemize
@item @samp{make doc/guix.info} to compile the Info manual.
      You can check it with @command{info doc/guix.info}.
@item @samp{make doc/guix.html} to compile the HTML version.
      You can point your browser to the relevant file in the
      @file{doc/guix.html} directory.
@item @samp{make doc/guix-cookbook.info} for the cookbook Info manual.
@item @samp{make doc/guix-cookbook.html} for the cookbook HTML version.
@end itemize

@cindex translation
@cindex l10n
@cindex i18n
@cindex native language support
@node Translating Guix
@section Translating Guix

Writing code and packages is not the only way to provide a meaningful
contribution to Guix.  Translating to a language you speak is another
example of a valuable contribution you can make.  This section is designed
to describe the translation process.  It gives you advice on how you can
get involved, what can be translated, what mistakes you should avoid and
what we can do to help you!

Guix is a big project that has multiple components that can be translated.
We coordinate the translation effort on a
@uref{https://translate.fedoraproject.org/projects/guix/,Weblate instance}
hosted by our friends at Fedora.  You will need an account to submit
translations.

Some of the software packaged in Guix also contain translations.  We do not
host a translation platform for them.  If you want to translate a package
provided by Guix, you should contact their developers or find the information
on their website.  As an example, you can find the homepage of the
@code{hello} package by typing @code{guix show hello}.  On the ``homepage''
line, you will see @url{https://www.gnu.org/software/hello/} as the homepage.

Many GNU and non-GNU packages can be translated on the
@uref{https://translationproject.org,Translation Project}.  Some projects
with multiple components have their own platform.  For instance, GNOME has
its own platform, @uref{https://l10n.gnome.org/,Damned Lies}.

Guix has five components hosted on Weblate.

@itemize
@item @code{guix} contains all the strings from the Guix software (the
      guided system installer, the package manager, etc), excluding packages.
@item @code{packages} contains the synopsis (single-sentence description
      of a package) and description (longer description) of packages in Guix.
@item @code{website} contains the official Guix website, except for
      blog posts and multimedia content.
@item @code{documentation-manual} corresponds to this manual.
@item @code{documentation-cookbook} is the component for the cookbook.
@end itemize

@subsubheading General Directions

Once you get an account, you should be able to select a component from
@uref{https://translate.fedoraproject.org/projects/guix/,the guix project},
and select a language.  If your language does not appear in the list, go
to the bottom and click on the ``Start new translation'' button.  Select
the language you want to translate to from the list, to start your new
translation.

Like lots of other free software packages, Guix uses
@uref{https://www.gnu.org/software/gettext,GNU Gettext} for its translations,
with which translatable strings are extracted from the source code to so-called
PO files.

Even though PO files are text files, changes should not be made with a text
editor but with PO editing software.  Weblate integrates PO editing
functionality.  Alternatively, translators can use any of various
free-software tools for filling in translations, of which
@uref{https://poedit.net/,Poedit} is one example, and (after logging in)
@uref{https://docs.weblate.org/en/latest/user/files.html,upload} the changed
file.  There is also a special
@uref{https://www.emacswiki.org/emacs/PoMode,PO editing mode} for users of GNU
Emacs.  Over time translators find out what software they are happy with and
what features they need.

On Weblate, you will find various links to the editor, that will show various
subsets (or all) of the strings.  Have a look around and at the
@uref{https://docs.weblate.org/en/latest/,documentation} to familiarize
yourself with the platform.

@subsubheading Translation Components

In this section, we provide more detailed guidance on the translation
process, as well as details on what you should or should not do.  When in
doubt, please contact us, we will be happy to help!

@table @asis
@item guix
Guix is written in the Guile programming language, and some strings contain
special formatting that is interpreted by Guile.  These special formatting
should be highlighted by Weblate.  They start with @code{~} followed by one
or more characters.

When printing the string, Guile replaces the special formatting symbols with
actual values.  For instance, the string @samp{ambiguous package specification
`~a'} would be substituted to contain said package specification instead of
@code{~a}.  To properly translate this string, you must keep the formatting
code in your translation, although you can place it where it makes sense in
your language.  For instance, the French translation says @samp{spécification
du paquet « ~a » ambiguë} because the adjective needs to be placed in the
end of the sentence.

If there are multiple formatting symbols, make sure to respect the order.
Guile does not know in which order you intended the string to be read, so it
will substitute the symbols in the same order as the English sentence.

As an example, you cannot translate @samp{package '~a' has been superseded by
'~a'} by @samp{'~a' superseeds package '~a'}, because the meaning would be
reversed.  If @var{foo} is superseded by @var{bar}, the translation would read
@samp{'foo' superseeds package 'bar'}.  To work around this problem, it
is possible to use more advanced formatting to select a given piece of data,
instead of following the default English order.  @xref{Formatted Output,,,
guile, GNU Guile Reference Manual}, for more information on formatting in Guile.

@item packages

Package descriptions occasionally contain Texinfo markup (@pxref{Synopses
and Descriptions}).   Texinfo markup looks like @samp{@@code@{rm -rf@}},
@samp{@@emph@{important@}}, etc.  When translating, please leave markup as is.

The characters after ``@@'' form the name of the markup, and the text between
``@{'' and ``@}'' is its content.  In general, you should not translate the
content of markup like @code{@@code}, as it contains literal code that do not
change with language.  You can translate the content of formatting markup such
as @code{@@emph}, @code{@@i}, @code{@@itemize}, @code{@@item}.  However, do
not translate the name of the markup, or it will not be recognized.  Do
not translate the word after @code{@@end}, it is the name of the markup that
is closed at this position (e.g.@: @code{@@itemize ... @@end itemize}).

@item documentation-manual and documentation-cookbook

The first step to ensure a successful translation of the manual is to find
and translate the following strings @emph{first}:

@itemize
@item @code{version.texi}: Translate this string as @code{version-xx.texi},
      where @code{xx} is your language code (the one shown in the URL on
      weblate).
@item @code{contributing.texi}: Translate this string as
      @code{contributing.xx.texi}, where @code{xx} is the same language code.
@item @code{Top}: Do not translate this string, it is important for Texinfo.
      If you translate it, the document will be empty (missing a Top node).
      Please look for it, and register @code{Top} as its translation.
@end itemize

Translating these strings first ensure we can include your translation in
the guix repository without breaking the make process or the
@command{guix pull} machinery.

The manual and the cookbook both use Texinfo.  As for @code{packages}, please
keep Texinfo markup as is.  There are more possible markup types in the manual
than in the package descriptions.  In general, do not translate the content
of @code{@@code}, @code{@@file}, @code{@@var}, @code{@@value}, etc.  You
should translate the content of formatting markup such as @code{@@emph},
@code{@@i}, etc.

The manual contains sections that can be referred to by name by @code{@@ref},
@code{@@xref} and @code{@@pxref}.  We have a mechanism in place so you do
not have to translate their content.  If you keep the English title, we will
automatically replace it with your translation of that title.  This ensures
that Texinfo will always be able to find the node. If you decide to change
the translation of the title, the references will automatically be updated
and you will not have to update them all yourself.

When translating references from the cookbook to the manual, you need to
replace the name of the manual and the name of the section.  For instance,
to translate @code{@@pxref@{Defining Packages,,, guix, GNU Guix Reference
Manual@}}, you would replace @code{Defining Packages} with the title of that
section in the translated manual @emph{only} if that title is translated.
If the title is not translated in your language yet, do not translate it here,
or the link will be broken.  Replace @code{guix} with @code{guix.xx} where
@code{xx} is your language code.  @code{GNU Guix Reference Manual} is the
text of the link.  You can translate it however you wish.

@item website

The website pages are written using SXML, an s-expression version of HTML,
the basic language of the web.  We have a process to extract translatable
strings from the source, and replace complex s-expressions with a more familiar
XML markup, where each markup is numbered.  Translators can arbitrarily change
the ordering, as in the following example.

@example
#. TRANSLATORS: Defining Packages is a section name
#. in the English (en) manual.
#: apps/base/templates/about.scm:64
msgid "Packages are <1>defined<1.1>en</1.1><1.2>Defining-Packages.html</1.2></1> as native <2>Guile</2> modules."
msgstr "Pakete werden als reine <2>Guile</2>-Module <1>definiert<1.1>de</1.1><1.2>Pakete-definieren.html</1.2></1>."
@end example

Note that you need to include the same markups.  You cannot skip any.
@end table

In case you make a mistake, the component might fail to build properly with your
language, or even make guix pull fail.  To prevent that, we have a process
in place to check the content of the files before pushing to our repository.
We will not be able to update the translation for your language in Guix, so
we will notify you (through weblate and/or by email) so you get a chance to
fix the issue.

@subsubheading Outside of Weblate

Currently, some parts of Guix cannot be translated on Weblate, help wanted!

@itemize
@item @command{guix pull} news can be translated in @file{news.scm}, but is not
      available from Weblate.  If you want to provide a translation, you
      can prepare a patch as described above, or simply send us your
      translation with the name of the news entry you translated and your
      language. @xref{Writing Channel News}, for more information about
      channel news.
@item Guix blog posts cannot currently be translated.
@item The installer script (for foreign distributions) is entirely in English.
@item Some of the libraries Guix uses cannot be translated or are translated
      outside of the Guix project.  Guile itself is not internationalized.
@item Other manuals linked from this manual or the cookbook might not be
      translated.
@end itemize

@subsubheading Conditions for Inclusion

There are no conditions for adding new translations of the @code{guix} and
@code{guix-packages} components, other than they need at least one translated
string.  New languages will be added to Guix as soon as possible.  The
files may be removed if they fall out of sync and have no more translated
strings.

Given that the web site is dedicated to new users, we want its translation
to be as complete as possible before we include it in the language menu.
For a new language to be included, it needs to reach at least 80% completion.
When a language is included, it may be removed in the future if it stays
out of sync and falls below 60% completion.

The manual and cookbook are automatically added in the default compilation
target.  Every time we synchronize translations, developers need to
recompile all the translated manuals and cookbooks.  This is useless for what
is essentially the English manual or cookbook.  Therefore, we will only
include a new language when it reaches 10% completion in the component.
When a language is included, it may be removed in the future if it stays
out of sync and falls below 5% completion.

@subsubheading Translation Infrastructure

Weblate is backed by a git repository from which it discovers new strings to
translate and pushes new and updated translations.  Normally, it would be
enough to give it commit access to our repositories.  However, we decided
to use a separate repository for two reasons.  First, we would have to give
Weblate commit access and authorize its signing key, but we do not trust it
in the same way we trust guix developers, especially since we do not manage
the instance ourselves.  Second, if translators mess something up, it can
break the generation of the website and/or guix pull for all our users,
independently of their language.

For these reasons, we use a dedicated repository to host translations, and we
synchronize it with our guix and artworks repositories after checking no issue
was introduced in the translation.

Developers can download the latest PO files from weblate in the Guix
repository by running the @command{make download-po} command.  It will
automatically download the latest files from weblate, reformat them to a
canonical form, and check they do not contain issues.  The manual needs to be
built again to check for additional issues that might crash Texinfo.

Before pushing new translation files, developers should add them to the
make machinery so the translations are actually available.  The process
differs for the various components.

@itemize
@item New po files for the @code{guix} and @code{packages} components must
      be registered by adding the new language to @file{po/guix/LINGUAS} or
      @file{po/packages/LINGUAS}.
@item New po files for the @code{documentation-manual} component must be
      registered by adding the file name to @code{DOC_PO_FILES} in
      @file{po/doc/local.mk}, the generated @file{%D%/guix.xx.texi} manual to
      @code{info_TEXINFOS} in @file{doc/local.mk} and the generated
      @file{%D%/guix.xx.texi} and @file{%D%/contributing.xx.texi} to
      @code{TRANSLATED_INFO} also in @file{doc/local.mk}.
@item New po files for the @code{documentation-cookbook} component must be
      registered by adding the file name to @code{DOC_COOKBOOK_PO_FILES} in
      @file{po/doc/local.mk}, the generated @file{%D%/guix-cookbook.xx.texi}
      manual to @code{info_TEXINFOS} in @file{doc/local.mk} and the generated
      @file{%D%/guix-cookbook.xx.texi} to @code{TRANSLATED_INFO} also
      in @file{doc/local.mk}.
@item New po files for the @code{website} component must be added to the
      @code{guix-artwork} repository, in @file{website/po/}.
      @file{website/po/LINGUAS} and @file{website/po/ietf-tags.scm} must
      be updated accordingly (see @file{website/i18n-howto.txt} for more
      information on the process).
@end itemize