guix: emacs-utils: Add emacs-batch-script.

* guix/build/emacs-utils.scm (emacs-batch-script): New procedure.

* tests/build-emacs-utils.scm: New file.

* Makefile.am (TESTS): Add `tests/build-emacs-utils.scm'.

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

Makefile.am

@@ -472,6 +472,7 @@ SCM_TESTS =					\
   tests/boot-parameters.scm			\
   tests/bournish.scm				\
   tests/builders.scm				\
+  tests/build-emacs-utils.scm			\
   tests/build-utils.scm			\
   tests/cache.scm				\
   tests/challenge.scm				\

guix/build/emacs-utils.scm

@@ -3,6 +3,7 @@
 ;;; Copyright © 2014 Alex Kost <alezost@gmail.com>
 ;;; Copyright © 2018, 2020, 2022 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;; Copyright © 2019 Liliana Marie Prikler <liliana.prikler@gmail.com>
+;;; Copyright © 2022 Fredrik Salomonsson <plattfot@posteo.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -22,10 +23,19 @@
 (define-module (guix build emacs-utils)
   #:use-module (guix build utils)
   #:use-module (ice-9 format)
+  #:use-module (ice-9 popen)
+  #:use-module (ice-9 rdelim)
+  #:use-module (srfi srfi-34)
+  #:use-module (srfi srfi-35)
   #:export (%emacs
             emacs-batch-eval
             emacs-batch-edit-file
             emacs-batch-disable-compilation
+            emacs-batch-script
+
+            emacs-batch-error?
+            emacs-batch-error-message
+
             emacs-generate-autoloads
             emacs-byte-compile-directory
 
@@ -69,6 +79,26 @@ (define (emacs-batch-disable-compilation file)
       (add-file-local-variable 'no-byte-compile t)
       (basic-save-buffer))))
 
+(define-condition-type &emacs-batch-error &error
+  emacs-batch-error?
+  (message emacs-batch-error-message))
+
+(define (emacs-batch-script expr)
+  "Execute the Elisp code EXPR in Emacs batch mode and return output."
+  (let* ((error-pipe (pipe))
+         (port (parameterize ((current-error-port (cdr error-pipe)))
+                 (open-pipe*
+                  OPEN_READ
+                  (%emacs) "--quick" "--batch"
+                  (string-append "--eval=" (expr->string expr)))))
+         (output (read-string port))
+         (status (close-pipe port)))
+    (close-port (cdr error-pipe))
+    (unless (zero? status)
+      (raise (condition (&emacs-batch-error
+                         (message (read-string (car error-pipe)))))))
+    output))
+
 (define (emacs-generate-autoloads name directory)
   "Generate autoloads for Emacs package NAME placed in DIRECTORY."
   (let* ((file (string-append directory "/" name "-autoloads.el"))

tests/build-emacs-utils.scm

@@ -0,0 +1,43 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2022 Fredrik Salomonsson <plattfot@posteo.net>
+;;;
+;;; 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 (test build-emacs-utils)
+  #:use-module (guix tests)
+  #:use-module (guix build emacs-utils)
+  #:use-module (guix build utils)
+  #:use-module ((guix utils)
+                #:select (call-with-temporary-directory))
+  #:use-module (srfi srfi-34)
+  #:use-module (srfi srfi-64))
+
+(test-begin "build-emacs-utils")
+;; Only run the following tests if emacs is present.
+(test-skip (if (which "emacs") 0 2))
+
+(test-equal "emacs-batch-script: print foo from emacs"
+  "foo"
+  (emacs-batch-script '(princ "foo")))
+
+(test-assert "emacs-batch-script: raise &emacs-batch-error on failure"
+  (guard (c ((emacs-batch-error? c)
+             (string-contains (emacs-batch-error-message c)
+                              "Lisp error: (wrong-type-argument numberp \"three\")")))
+    (emacs-batch-script '(mapcar 'number-to-string (list 1 2 "three")))))
+
+(test-end "build-emacs-utils")