packages: Add 'specifications->packages'.

* gnu/packages.scm (specifications->packages): New procedure.
* guix/scripts/home/import.scm (manifest+configuration-files->code): Use it.
* tests/home-import.scm (match-home-environment-no-services)
(match-home-environment-no-services-nor-packages)
(match-home-environment-bash-service)
(match-home-environment-bash-service-with-alias): Adjust 'packages'
field accordingly.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

gnu/packages.scm

@@ -4,6 +4,7 @@
 ;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
 ;;; Copyright © 2016, 2017 Alex Kost <alezost@gmail.com>
 ;;; Copyright © 2016 Mathieu Lirzin <mthl@gnu.org>
+;;; Copyright © 2022 Antero Mejr <antero@mailbox.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -65,6 +66,7 @@
             specification->package+output
             specification->location
             specifications->manifest
+            specifications->packages
 
             package-unique-version-prefix
 
@@ -554,13 +556,20 @@ output."
                   (package-full-name package)
                   sub-drv))))))
 
+(define (specifications->packages specs)
+  "Given SPECS, a list of specifications such as \"emacs@25.2\" or
+\"guile:debug\", return a list of package/output tuples."
+  ;; This procedure exists so users of 'guix home' don't have to write out the
+  ;; (map (compose list specification->package+output)... boilerplate.
+  (map (compose list specification->package+output) specs))
+
 (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)))
+   (specifications->packages specs)))
 
 (define (package-unique-version-prefix name version)
   "Search among all the versions of package NAME that are available, and

guix/scripts/home/import.scm

@@ -3,6 +3,7 @@
 ;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
 ;;; Copyright © 2021-2022 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2022 Arjan Adriaanse <arjan@adriaan.se>
+;;; Copyright © 2022 Antero Mejr <antero@mailbox.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -170,8 +171,7 @@ user's files to CONFIGURATION-DIRECTORY; the generated sexp refers to them."
                         ,@(delete-duplicates (concatenate modules)))
 
            (home-environment
-            (packages (map (compose list specification->package+output)
-                           ,packages))
+            (packages (specifications->packages ,packages))
             (services (list ,@services)))))))))
 
 (define* (import-manifest

tests/home-import.scm

@@ -103,8 +103,8 @@ corresponding file."
      ('gnu 'services))
     ('home-environment
      ('packages
-      ('map ('compose 'list 'specification->package+output)
-            ('list "guile@2.0.9" "gcc:lib" "glibc@2.19")))
+      ('specifications->packages
+       ('list "guile@2.0.9" "gcc:lib" "glibc@2.19")))
      ('services
       ('list)))))
 
@@ -132,8 +132,7 @@ corresponding file."
      ('gnu 'services))
     ('home-environment
      ('packages
-      ('map ('compose 'list 'specification->package+output)
-            ('list)))
+      ('specifications->packages ('list)))
      ('services
       ('list)))))
 
@@ -147,8 +146,7 @@ corresponding file."
      ('gnu 'home 'services 'shells))
     ('home-environment
      ('packages
-      ('map ('compose 'list 'specification->package+output)
-            ('list)))
+      ('specifications->packages ('list)))
      ('services
       ('list ('service
               'home-bash-service-type
@@ -168,8 +166,7 @@ corresponding file."
      ('gnu 'home 'services 'shells))
     ('home-environment
      ('packages
-      ('map ('compose 'list 'specification->package+output)
-            ('list)))
+      ('specifications->packages ('list)))
      ('services
       ('list ('service
               'home-bash-service-type