From c08ea55e7ec25261e4596bf6726a83c1ed056b94 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Sun, 11 Jun 2017 23:05:23 +0200
Subject: [PATCH] packages: Add 'specifications->manifest'.

* gnu/packages.scm (specifications->manifest): New procedure.
* doc/guix.texi (Invoking guix package): Change example from using
'(compose list specification->package+output)' to using
'specifications->manifest'.
---
 doc/guix.texi    |  9 ++++-----
 gnu/packages.scm | 12 +++++++++++-
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 87aaae8545..83f20c8598 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -1742,18 +1742,17 @@ of packages:
        (list guile-2.0 "debug")))
 @end example
 
-@findex specification->package+output
+@findex specifications->manifest
 In this example we have to know which modules define the @code{emacs}
 and @code{guile-2.0} variables to provide the right
 @code{use-package-modules} line, which can be cumbersome.  We can
 instead provide regular package specifications and let
-@code{specification->package-output} look up the corresponding package
+@code{specifications->manifest} look up the corresponding package
 objects, like this:
 
 @example
-(packages->manifest
- (map (compose list specification->package+output)
-      '("emacs" "guile@@2.0" "guile@@2.0:debug")))
+(specifications->manifest
+ '("emacs" "guile@@2.2" "guile@@2.2:debug"))
 @end example
 
 @item --roll-back
diff --git a/gnu/packages.scm b/gnu/packages.scm
index 57907155fb..5629061788 100644
--- a/gnu/packages.scm
+++ b/gnu/packages.scm
@@ -29,6 +29,7 @@ (define-module (gnu packages)
   #:use-module ((guix build utils)
                 #:select ((package-name->name+version
                            . hyphen-separated-name->name+version)))
+  #:autoload   (guix profiles) (packages->manifest)
   #:use-module (ice-9 vlist)
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-1)
@@ -53,7 +54,8 @@ (define-module (gnu packages)
             find-newest-available-packages
 
             specification->package
-            specification->package+output))
+            specification->package+output
+            specifications->manifest))
 
 ;;; Commentary:
 ;;;
@@ -278,3 +280,11 @@ (define* (specification->package+output spec #:optional (output "out"))
            (leave (G_ "package `~a' lacks output `~a'~%")
                   (package-full-name package)
                   sub-drv))))))
+
+(define (specifications->manifest specs)
+  "Given SPECS, a list of specifications such as \"emacs@25.2\" or
+\"guile:debug\", return a profile manifest."
+  ;; This procedure exists mostly so users of 'guix package -m' don't have to
+  ;; fiddle with multiple-value returns.
+  (packages->manifest
+   (map (compose list specification->package+output) specs)))