build-system: Add zig-build-system.

* guix/build-system/zig.scm: New file.
* guix/build/zig-build-system.scm: New file.
* Makefile.am: Add them.
* doc/guix.texi: Document it.
* etc/snippets/yas/scheme-mode/guix-package (build-system): Add
  zig-build-system.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

Makefile.am

@@ -184,6 +184,7 @@ MODULES =					\
   guix/build-system/texlive.scm			\
   guix/build-system/tree-sitter.scm		\
   guix/build-system/trivial.scm			\
+  guix/build-system/zig.scm			\
   guix/ftp-client.scm				\
   guix/http-client.scm				\
   guix/gnupg.scm				\
@@ -270,6 +271,7 @@ MODULES =					\
   guix/build/graft.scm				\
   guix/build/bournish.scm			\
   guix/build/qt-utils.scm			\
+  guix/build/zig-build-system.scm		\
   guix/build/make-bootstrap.scm			\
   guix/search-paths.scm				\
   guix/packages.scm				\

doc/guix.texi

@@ -10219,6 +10219,27 @@ Python package is used to run the script can be specified with the
 @code{#:python} parameter.
 @end defvar
 
+@defvar zig-build-system
+This variable is exported by @code{(guix build-system zig)}.  It implements
+the build procedures for the @uref{https://ziglang.org/, Zig}
+build system (@command{zig build} command).
+
+Selecting this build system adds @code{zig} to the package inputs, in
+addition to the packages of @code{gnu-build-system}.
+
+There is no @code{configure} phase because Zig packages typically do not
+need to be configured.  The @code{#:zig-build-flags} parameter is a list of
+flags that are passed to the @code{zig} command during the build.  The
+@code{#:zig-test-flags} parameter is a list of flags that are passed to the
+@code{zig test} command during the @code{check} phase.  The default compiler
+package can be overridden with the @code{#:zig} argument.
+
+The optional @code{zig-release-type} parameter declares the type of release.
+Possible values are: @code{safe}, @code{fast}, or @code{small}. The default
+value is @code{#f}, which causes the release flag to be omitted from the
+@code{zig} command.  That results in a @code{debug} build.
+@end defvar
+
 @defvar scons-build-system
 This variable is exported by @code{(guix build-system scons)}.  It
 implements the build procedure used by the SCons software construction

etc/snippets/yas/scheme-mode/guix-package

@@ -43,8 +43,9 @@
                                           "scons-build-system"
                                           "texlive-build-system"
                                           "trivial-build-system"
-                                          "waf-build-system")})
+                                          "waf-build-system"
+                                          "zig-build-system")})
     (home-page "$4")
     (synopsis "$5")
     (description "$6")
-    (license $7)))
+    (license $7)))

guix/build-system/zig.scm

@@ -0,0 +1,124 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2023 Ekaitz Zarraga <ekaitz@elenq.tech>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix build-system zig)
+  #:use-module (guix search-paths)
+  #:use-module (guix store)
+  #:use-module (guix utils)
+  #:use-module (guix gexp)
+  #:use-module (guix monads)
+  #:use-module (guix packages)
+  #:use-module (guix build-system)
+  #:use-module (guix build-system gnu)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-26)
+  #:export (zig-build-system))
+
+
+(define (default-zig)
+  "Return the default zig package."
+  ;; Lazily resolve the binding to avoid a circular dependency.
+  (let ((zig (resolve-interface '(gnu packages zig))))
+    (module-ref zig 'zig)))
+
+(define %zig-build-system-modules
+  ;; Build-side modules imported by default.
+  `((guix build zig-build-system)
+    (guix build syscalls)
+    ,@%gnu-build-system-modules))
+
+(define* (zig-build name inputs
+                    #:key
+                    source
+                    (tests? #t)
+                    (test-target #f)
+                    (zig-build-flags ''())
+                    (zig-test-flags ''())
+                    (zig-release-type #f)
+                    (phases '%standard-phases)
+                    (outputs '("out"))
+                    (search-paths '())
+                    (system (%current-system))
+                    (guile #f)
+                    (imported-modules %zig-build-system-modules)
+                    (modules '((guix build zig-build-system)
+                               (guix build utils))))
+  "Build SOURCE using Zig, and with INPUTS."
+  (define builder
+    (with-imported-modules imported-modules
+      #~(begin
+          (use-modules #$@(sexp->gexp modules))
+          (zig-build #:name #$name
+                     #:source #+source
+                     #:system #$system
+                     #:test-target #$test-target
+                     #:zig-build-flags #$zig-build-flags
+                     #:zig-test-flags #$zig-test-flags
+                     #:zig-release-type #$zig-release-type
+                     #:tests? #$tests?
+                     #:phases #$phases
+                     #:outputs #$(outputs->gexp outputs)
+                     #:search-paths '#$(sexp->gexp
+                                        (map search-path-specification->sexp
+                                             search-paths))
+                     #:inputs #$(input-tuples->gexp inputs)))))
+
+  (mlet %store-monad ((guile (package->derivation (or guile (default-guile))
+                                                  system #:graft? #f)))
+    (gexp->derivation name builder
+                      #:system system
+                      #:guile-for-build guile)))
+
+(define* (lower name
+                #:key source inputs native-inputs outputs system target
+                (zig (default-zig))
+                #:allow-other-keys
+                #:rest arguments)
+  "Return a bag for NAME."
+
+  (define private-keywords
+    '(#:target #:zig #:inputs #:native-inputs #:outputs))
+
+  ;; TODO: support cross-compilation
+  ;; It's as simple as adding some build flags to `zig-build-flags`
+  ;; -Dtarget=aarch64-linux-musl, for example.
+  (and (not target)
+       (bag
+         (name name)
+         (system system)
+         (target target)
+         (host-inputs `(,@(if source
+                              `(("source" ,source))
+                              '())
+                        ,@inputs
+
+                        ;; Keep the standard inputs of 'gnu-build-system'
+                        ;; TODO: do we need this?
+                        ,@(standard-packages)))
+         (build-inputs `(("zig" ,zig)
+                         ,@native-inputs))
+         (outputs outputs)
+         (build zig-build)
+         (arguments (strip-keyword-arguments private-keywords arguments)))))
+
+(define zig-build-system
+  (build-system
+    (name 'zig)
+    (description
+     "Zig build system, to build Zig packages")
+    (lower lower)))

guix/build/zig-build-system.scm

@@ -0,0 +1,100 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2023 Ekaitz Zarraga <ekaitz@elenq.tech>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix build zig-build-system)
+  #:use-module ((guix build gnu-build-system) #:prefix gnu:)
+  #:use-module (guix build utils)
+  #:use-module (ice-9 popen)
+  #:use-module (ice-9 rdelim)
+  #:use-module (ice-9 ftw)
+  #:use-module (ice-9 format)
+  #:use-module (ice-9 match)
+  #:use-module (rnrs io ports)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:export (%standard-phases
+            zig-build))
+
+;; Interesting guide here:
+;; https://github.com/riverwm/river/blob/master/PACKAGING.md
+(define global-cache-dir "zig-cache")
+
+(define* (set-cc #:rest args)
+  ;; TODO: Zig needs the gcc-toolchain in order to find the libc.
+  ;;       we need to think about how to solve this in the build system
+  ;;       directly: --libc
+  (setenv "CC" "gcc"))
+
+(define* (set-zig-global-cache-dir #:rest args)
+  (setenv "ZIG_GLOBAL_CACHE_DIR" global-cache-dir))
+
+(define* (build #:key
+                zig-build-flags
+                zig-release-type       ;; "safe", "fast" or "small" empty for a
+                                       ;; debug build"
+                #:allow-other-keys)
+  "Build a given Zig package."
+
+  (setenv "DESTDIR" "out")
+  (let ((call `("zig" "build"
+                     "--prefix"             ""            ;; Don't add /usr
+                     "--prefix-lib-dir"     "lib"
+                     "--prefix-exe-dir"     "bin"
+                     "--prefix-include-dir" "include"
+                     ,@(if zig-release-type
+                         (list (string-append "-Drelease-" zig-release-type))
+                         '())
+                     ,@zig-build-flags)))
+  (format #t "running: ~s~%" call)
+  (apply invoke call)))
+
+(define* (check #:key tests?
+                zig-test-flags
+                #:allow-other-keys)
+  "Run all the tests"
+  (when tests?
+    (let ((old-destdir (getenv "DESTDIR")))
+      (setenv "DESTDIR" "test-out") ;; Avoid colisions with the build output
+      (let ((call `("zig" "build" "test"
+                    ,@zig-test-flags)))
+        (format #t "running: ~s~%" call)
+        (apply invoke call))
+      (if old-destdir
+        (setenv "DESTDIR" old-destdir)
+        (unsetenv "DESTDIR")))))
+
+(define* (install #:key inputs outputs #:allow-other-keys)
+  "Install a given Zig package."
+  (let ((out (assoc-ref outputs "out")))
+    (copy-recursively "out" out)))
+
+(define %standard-phases
+  (modify-phases gnu:%standard-phases
+    (delete 'bootstrap)
+    (delete 'configure)
+    (add-before 'build 'set-zig-global-cache-dir set-zig-global-cache-dir)
+    (add-before 'build 'set-cc set-cc)
+    (replace 'build build)
+    (replace 'check check)
+    (replace 'install install)))
+
+
+(define* (zig-build #:key inputs (phases %standard-phases)
+                      #:allow-other-keys #:rest args)
+  "Build the given Zig package, applying all of PHASES in order."
+  (apply gnu:gnu-build #:inputs inputs #:phases phases args))