search-paths: Allow specs with #f as their separator.

This adds support for single-entry search paths.
Fixes <http://bugs.gnu.org/25422>.
Reported by Leo Famulari <leo@famulari.name>.

* guix/search-paths.scm (<search-path-specification>)[separator]:
Document as string or #f.
(evaluate-search-paths): Add case for SEPARATOR as #f.
(environment-variable-definition): Handle SEPARATOR being #f.
* guix/build/utils.scm (list->search-path-as-string): Add case for
SEPARATOR as #f.
(search-path-as-string->list): Likewise.
* guix/build/profiles.scm (abstract-profile): Likewise.
* tests/search-paths.scm: New file.
* Makefile.am (SCM_TESTS): Add it.
* tests/packages.scm ("--search-paths with single-item search path"):
New test.
* gnu/packages/version-control.scm (git)[native-search-paths](separator):
New field.

1 files changed, 14 insertions, 10 deletions

diff --git a/guix/build/profiles.scm b/guix/build/profiles.scm
index 6e316d5d2c..42eabfaf19 100644
--- a/guix/build/profiles.scm
+++ b/guix/build/profiles.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -39,17 +39,21 @@
 'GUIX_PROFILE' environment variable.  This allows users to specify what the
 user-friendly name of the profile is, for instance ~/.guix-profile rather than
 /gnu/store/...-profile."
-  (let ((replacement (string-append "${GUIX_PROFILE:-" profile "}")))
+  (let ((replacement (string-append "${GUIX_PROFILE:-" profile "}"))
+        (crop        (cute string-drop <> (string-length profile))))
     (match-lambda
       ((search-path . value)
-       (let* ((separator (search-path-specification-separator search-path))
-              (items     (string-tokenize* value separator))
-              (crop      (cute string-drop <> (string-length profile))))
-         (cons search-path
-               (string-join (map (lambda (str)
-                                   (string-append replacement (crop str)))
-                                 items)
-                            separator)))))))
+       (match (search-path-specification-separator search-path)
+         (#f
+          (cons search-path
+                (string-append replacement (crop value))))
+         ((? string? separator)
+          (let ((items (string-tokenize* value separator)))
+            (cons search-path
+                  (string-join (map (lambda (str)
+                                      (string-append replacement (crop str)))
+                                    items)
+                               separator)))))))))
 
 (define (write-environment-variable-definition port)
   "Write the given environment variable definition to PORT."