uuid: 'uuid' returns #f when 'string->uuid' returns #f.

* gnu/system/uuid.scm (uuid): When STR is not a literal, return #f when
'string->uuid' returns #f.
* tests/uuid.scm ("uuid, dynamic value"): New test.

1 files changed, 8 insertions, 1 deletions

diff --git a/tests/uuid.scm b/tests/uuid.scm
index 91a3482490..260614f079 100644
--- a/tests/uuid.scm
+++ b/tests/uuid.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -57,6 +57,13 @@
   "1234-ABCD"
   (uuid->string (uuid "1234-abcd" 'fat32)))
 
+(test-assert "uuid, dynamic value"
+  (let* ((good "4dab5feb-d176-45de-b287-9b0a6e4c01cb")
+         (bad  (string-drop good 3)))
+    (and (uuid? (uuid good))
+         (string=? good (uuid->string (uuid good)))
+         (not (uuid bad)))))
+
 (test-assert "uuid=?"
   (and (uuid=? (uuid-bytevector (uuid "1234-abcd" 'fat32))
                (uuid "1234-abcd" 'fat32))