>From 9ffc27f7a076e4213ef3bee00e5cebad501685ac Mon Sep 17 00:00:00 2001
From: Alex Kost <address@hidden>
Date: Thu, 23 Jul 2015 16:16:41 +0300
Subject: [PATCH 2/2] guix build: Add 'build-package'.
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* guix/scripts/system.scm (maybe-build): Move to ...
* guix/scripts/build.scm: ...here.
  (build-package): New procedure.

Co-authored-by: Ludovic Courtès <address@hidden>
---
 guix/scripts/build.scm  | 41 ++++++++++++++++++++++++++++++++++++++++-
 guix/scripts/system.scm | 13 -------------
 2 files changed, 40 insertions(+), 14 deletions(-)

diff --git a/guix/scripts/build.scm b/guix/scripts/build.scm
index f169853..ee4a3d6 100644
--- a/guix/scripts/build.scm
+++ b/guix/scripts/build.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2012, 2013, 2014, 2015 Ludovic Courtès <address@hidden>
 ;;; Copyright © 2013 Mark H Weaver <address@hidden>
+;;; Copyright © 2015 Alex Kost <address@hidden>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -39,9 +40,47 @@
             set-build-options-from-command-line
             set-build-options-from-command-line*
             show-build-options-help
-
+            maybe-build
+            build-package
             guix-build))
 
+;; XXX This procedure does not belong this module: it is used by
+;; 'build-package' and (guix scripts system).
+(define* (maybe-build drvs
+                      #:key dry-run? use-substitutes?)
+  "Show what will/would be built, and actually build DRVS, unless DRY-RUN? is
+true."
+  (with-monad %store-monad
+    (>>= (show-what-to-build* drvs
+                              #:dry-run? dry-run?
+                              #:use-substitutes? use-substitutes?)
+         (lambda (_)
+           (if dry-run?
+               (return #f)
+               (built-derivations drvs))))))
+
+;; XXX This procedure does not belong this module, but currently there
+;; is no better place for it.  It is used by Emacs development tools
+;; ("emacs/guix-devel.el").
+(define* (build-package package
+                        #:key (use-substitutes? #t) (dry-run? #f)
+                        #:allow-other-keys
+                        #:rest build-options)
+  "Build PACKAGE using BUILD-OPTIONS.
+Show what and how will/would be built."
+  (with-store store
+    (run-with-store store
+      (mbegin %store-monad
+        (apply set-build-options*
+               #:use-substitutes? use-substitutes?
+               (strip-keyword-arguments '(#:dry-run?) build-options))
+        (mlet %store-monad ((derivation (package->derivation package)))
+          (mbegin %store-monad
+            (maybe-build (list derivation)
+                         #:use-substitutes? use-substitutes?
+                         #:dry-run? dry-run?)
+            (return (show-derivation-outputs derivation))))))))
+
 (define (register-root store paths root)
   "Register ROOT as an indirect GC root for all of PATHS."
   (let* ((root (string-append (canonicalize-path (dirname root))
diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index 45f5982..0db4953 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -298,19 +298,6 @@ it atomically, and then run OS's activation script."
     ((disk-image)
      (system-disk-image os #:disk-image-size image-size))))
 
-(define* (maybe-build drvs
-                      #:key dry-run? use-substitutes?)
-  "Show what will/would be built, and actually build DRVS, unless DRY-RUN? is
-true."
-  (with-monad %store-monad
-    (>>= (show-what-to-build* drvs
-                              #:dry-run? dry-run?
-                              #:use-substitutes? use-substitutes?)
-         (lambda (_)
-           (if dry-run?
-               (return #f)
-               (built-derivations drvs))))))
-
 (define* (perform-action action os
                          #:key grub? dry-run?
                          use-substitutes? device target
-- 
2.5.0