01/10: services: pipefs: Correctly handle lack of extensions.

[guix-commits]

civodul pushed a commit to branch master
in repository guix.

commit 7855a9366b2f5248d8fffab93c108abef8146f40
Author: Ludovic Courtès <ludo@gnu.org>
AuthorDate: Mon May 2 23:24:46 2022 +0200

    services: pipefs: Correctly handle lack of extensions.
    
    Previously, in the absence of extensions of 'pipefs-service-type', we'd
    get a wrong-type-arg exception while folding services:
    
      In gnu/services/nfs.scm:
         134:37  1 (_ #<<pipefs-configuration> mount-point: "/var/lib/nfs…> …)
      In ice-9/boot-9.scm:
        1685:16  0 (raise-exception _ #:continuable? _)
      In procedure car: Wrong type argument in position 1 (expecting pair): ()
    
    * gnu/services/nfs.scm (pipefs-service-type)[extend]: Gracefully handle
    the case where VALUES is the empty list, as done in 'gss-service-type'.
---
 gnu/services/nfs.scm | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/gnu/services/nfs.scm b/gnu/services/nfs.scm
index 9b795c9e71..209cde24b3 100644
--- a/gnu/services/nfs.scm
+++ b/gnu/services/nfs.scm
@@ -131,7 +131,10 @@ use this facility."))))
      ;; configure and start this service.  Only one value can be provided.  We
      ;; override it with the value returned by the extending service.
      (compose identity)
-     (extend (lambda (config values) (first values)))
+     (extend (lambda (config values)
+               (match values
+                 ((first . rest) first)
+                 (_ config))))
      (default-value (pipefs-configuration))
      (description "Mount the pipefs file system, which is used to transfer
 NFS-related data between the kernel and user-space programs."))))