ruby-build-system: Error or return #t from all phases.

Previously, if the tests didn't pass, the check phase would evaluate to #f,
but the package would be built sucessfully. This changes all the phases to
raise exceptions if errors are encountered, and return #t otherwise.

This involves using invoke rather than system*, so that exceptions are raised
if the program exits with a status other than 0, and also returning #t at the
end of functions.

* gnu/build/ruby-build-system.scm (unpack): Use invoke rather than system*,
and return #t at the end.
(build, check): Use invoke rather than system*.
(install): Remove the use of "and", and rewrite the error handling to raise an
exception.
(wrap): Return #t.

guix/build/ruby-build-system.scm

@@ -52,7 +52,8 @@ directory."
 (define* (unpack #:key source #:allow-other-keys)
   "Unpack the gem SOURCE and enter the resulting directory."
   (if (gem-archive? source)
-      (and (zero? (system* "gem" "unpack" source))
+      (begin
+        (invoke "gem" "unpack" source)
         ;; The unpacked gem directory is named the same as the archive,
         ;; sans the ".gem" extension.  It is renamed to simply "gem" in an
         ;; effort to keep file names shorter to avoid UNIX-domain socket
@@ -62,8 +63,8 @@ directory."
                                                   (basename source))
                                     1)))
           (rename-file dir "gem")
-             (chdir "gem")
-             #t))
+          (chdir "gem"))
+        #t)
       ;; Use GNU unpack strategy for things that aren't gem archives.
       (gnu:unpack #:source source)))
 
@@ -104,7 +105,8 @@ generate the files list."
                   (write-char (read-char pipe) out))))
             #t)
           (lambda ()
-            (close-pipe pipe)))))))
+            (close-pipe pipe)))))
+    #t))
 
 (define* (build #:key source #:allow-other-keys)
   "Build a new gem using the gemspec from the SOURCE gem."
@@ -112,13 +114,13 @@ generate the files list."
   ;; Build a new gem from the current working directory.  This also allows any
   ;; dynamic patching done in previous phases to be present in the installed
   ;; gem.
-  (zero? (system* "gem" "build" (first-gemspec))))
+  (invoke "gem" "build" (first-gemspec)))
 
 (define* (check #:key tests? test-target #:allow-other-keys)
   "Run the gem's test suite rake task TEST-TARGET.  Skip the tests if TESTS?
 is #f."
   (if tests?
-      (zero? (system* "rake" test-target))
+      (invoke "rake" test-target)
       #t))
 
 (define* (install #:key inputs outputs (gem-flags '())
@@ -137,32 +139,30 @@ GEM-FLAGS are passed to the 'gem' invokation, if present."
                               0
                               (- (string-length gem-file-basename) 4))))
     (setenv "GEM_VENDOR" vendor-dir)
-    (and (let ((install-succeeded?
-                (zero?
+
+    (or (zero?
          (apply system* "gem" "install" gem-file
                 "--local" "--ignore-dependencies" "--vendor"
                 ;; Executables should go into /bin, not
                 ;; /lib/ruby/gems.
                 "--bindir" (string-append out "/bin")
-                        gem-flags))))
-           (or install-succeeded?
+                gem-flags))
         (begin
-                 (simple-format #t "installation failed\n")
           (let ((failed-output-dir (string-append (getcwd) "/out")))
             (mkdir failed-output-dir)
             (copy-recursively out failed-output-dir))
-                 #f)))
-         (begin
+          (error "installation failed")))
+
     ;; Remove the cached gem file as this is unnecessary and contains
     ;; timestamped files rendering builds not reproducible.
     (let ((cached-gem (string-append vendor-dir "/cache/" gem-file)))
       (log-file-deletion cached-gem)
       (delete-file cached-gem))
+
     ;; For gems with native extensions, several Makefile-related files
     ;; are created that contain timestamps or other elements making
     ;; them not reproducible.  They are unnecessary so we remove them.
-           (if (file-exists? (string-append vendor-dir "/ext"))
-               (begin
+    (when (file-exists? (string-append vendor-dir "/ext"))
       (for-each (lambda (file)
                   (log-file-deletion file)
                   (delete-file file))
@@ -172,8 +172,9 @@ GEM-FLAGS are passed to the 'gem' invokation, if present."
                  (find-files (string-append vendor-dir "/extensions")
                              "gem_make.out")
                  (find-files (string-append vendor-dir "/ext")
-                                        "Makefile")))))
-           #t))))
+                             "Makefile"))))
+
+    #t))
 
 (define* (wrap-ruby-program prog #:key (gem-clear-paths #t) #:rest vars)
   "Make a wrapper for PROG.  VARS should look like this:
@@ -301,7 +302,8 @@ extended with definitions for VARS."
                 (let ((files (list-of-files dir)))
                   (for-each (cut wrap-ruby-program <> var)
                             files)))
-              bindirs)))
+              bindirs))
+  #t)
 
 (define (log-file-deletion file)
   (display (string-append "deleting '" file "' for reproducibility\n")))