build: Add ruby build system.

* guix/build-system/ruby.scm: New file.
* guix/build/ruby-build-system: New file.
* Makefile.am (MODULES): Add new files.
* doc/guix.texi (Build Systems): Document ruby-build-system.

Makefile.am

@@ -50,6 +50,7 @@ MODULES =					\
   guix/build-system/gnu.scm			\
   guix/build-system/perl.scm			\
   guix/build-system/python.scm			\
+  guix/build-system/ruby.scm			\
   guix/build-system/trivial.scm			\
   guix/ftp-client.scm				\
   guix/http-client.scm				\
@@ -64,6 +65,7 @@ MODULES =					\
   guix/build/gnu-dist.scm			\
   guix/build/perl-build-system.scm		\
   guix/build/python-build-system.scm		\
+  guix/build/ruby-build-system.scm		\
   guix/build/store-copy.scm			\
   guix/build/utils.scm				\
   guix/build/union.scm				\

doc/guix.texi

@@ -1648,6 +1648,14 @@ the @code{#:make-maker-flags} parameter.
 Which Perl package is used can be specified with @code{#:perl}.
 @end defvr
 
+@defvr {Scheme Variable} ruby-build-system
+This variable is exported by @code{(guix build-system ruby)}.  It
+implements the RubyGems build procedure used by Ruby packages, which
+involves running @code{gem build} followed by @code{gem install}.
+
+Which Ruby package is used can be specified with the @code{#:ruby}
+parameter.
+@end defvr
 
 Lastly, for packages that do not need anything as sophisticated, a
 ``trivial'' build system is provided.  It is trivial in the sense that

guix/build-system/ruby.scm

@@ -0,0 +1,108 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 David Thompson <davet@gnu.org>
+;;;
+;;; 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 ruby)
+  #:use-module (guix store)
+  #:use-module (guix utils)
+  #:use-module (guix packages)
+  #:use-module (guix derivations)
+  #:use-module (guix build-system)
+  #:use-module (guix build-system gnu)
+  #:use-module (gnu packages version-control)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-26)
+  #:export (ruby-build
+            ruby-build-system))
+
+(define (default-ruby)
+  "Return the default Ruby package."
+  ;; Lazily resolve the binding to avoid a circular dependency.
+  (let ((ruby (resolve-interface '(gnu packages ruby))))
+    (module-ref ruby 'ruby)))
+
+(define* (ruby-build store name source inputs
+                     #:key
+                     (ruby (default-ruby))
+                     (test-target "test")
+                     (tests? #t)
+                     (phases '(@ (guix build ruby-build-system)
+                                 %standard-phases))
+                     (outputs '("out"))
+                     (search-paths '())
+                     (system (%current-system))
+                     (guile #f)
+                     (imported-modules '((guix build ruby-build-system)
+                                         (guix build gnu-build-system)
+                                         (guix build utils)))
+                     (modules '((guix build ruby-build-system)
+                                (guix build utils))))
+  "Build SOURCE using RUBY and INPUTS."
+  (define ruby-search-paths
+    (append (package-native-search-paths ruby)
+            (standard-search-paths)))
+
+  (define builder
+    `(begin
+       (use-modules ,@modules)
+       (ruby-build #:name ,name
+                   #:source ,(if (derivation? source)
+                                 (derivation->output-path source)
+                                 source)
+                   #:system ,system
+                   #:test-target ,test-target
+                   #:tests? ,tests?
+                   #:phases ,phases
+                   #:outputs %outputs
+                   #:search-paths ',(map search-path-specification->sexp
+                                         (append ruby-search-paths
+                                                 search-paths))
+                   #:inputs %build-inputs)))
+
+  (define guile-for-build
+    (match guile
+      ((? package?)
+       (package-derivation store guile system))
+      ((and (? string?) (? derivation-path?))
+       guile)
+      (#f
+       (let* ((distro (resolve-interface '(gnu packages commencement)))
+              (guile  (module-ref distro 'guile-final)))
+         (package-derivation store guile system)))))
+
+  (let ((ruby (package-derivation store ruby system))
+        (git (package-derivation store git system)))
+    (build-expression->derivation store name builder
+                                  #:inputs
+                                  `(,@(if source
+                                          `(("source" ,source))
+                                          '())
+                                    ("ruby" ,ruby)
+                                    ,@inputs
+                                    ;; Keep the standard inputs of
+                                    ;; 'gnu-build-system'.
+                                    ,@(standard-inputs system))
+                                  #:system system
+                                  #:modules imported-modules
+                                  #:outputs outputs
+                                  #:guile-for-build guile-for-build)))
+
+(define ruby-build-system
+  (build-system
+   (name 'ruby)
+   (description "The standard Ruby build system")
+   (build ruby-build)))

guix/build/ruby-build-system.scm

@@ -0,0 +1,75 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 David Thompson <davet@gnu.org>
+;;;
+;;; 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 ruby-build-system)
+  #:use-module ((guix build gnu-build-system) #:prefix gnu:)
+  #:use-module (guix build utils)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:export (%standard-phases
+            ruby-build))
+
+;; Commentary:
+;;
+;; Builder-side code of the standard Ruby package build procedure.
+;;
+;; Code:
+
+(define (first-matching-file pattern)
+  "Return the first file name that matches PATTERN in the current working
+directory."
+  (match (find-files "." pattern)
+    ((file-name . _) file-name)
+    (() (error "No files matching pattern: " pattern))))
+
+(define build
+  (lambda _
+    (zero? (system* "gem" "build" (first-matching-file "\\.gemspec$")))))
+
+(define* (check #:key tests? test-target #:allow-other-keys)
+  (if tests?
+      (zero? (system* "rake" test-target))
+      #t))
+
+(define* (install #:key source inputs outputs #:allow-other-keys)
+  (let* ((ruby-version
+          (match:substring (string-match "ruby-(.*)$"
+                                         (assoc-ref inputs "ruby"))
+                           1))
+         (gem-home (string-append (assoc-ref outputs "out")
+                                  "/lib/ruby/gems/"
+                                  ruby-version)))
+    (setenv "GEM_HOME" gem-home)
+    (mkdir-p gem-home)
+    (zero? (system* "gem" "install" "--local"
+                    (first-matching-file "\\.gem$")))))
+
+(define %standard-phases
+  (alist-replace
+   'build build
+   (alist-replace
+    'install install
+    (alist-replace
+     'check check
+     (alist-delete 'configure gnu:%standard-phases)))))
+
+(define* (ruby-build #:key inputs (phases %standard-phases)
+                     #:allow-other-keys #:rest args)
+  (apply gnu:gnu-build #:inputs inputs #:phases phases args))