02/02: services: 'file-union' makes sure each source file exists.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix.

commit 37dd1e6a34698e5bccaf99b6681c503b1a4e5efc
Author: Ludovic Courtès <address@hidden>
Date:   Wed Feb 3 22:26:33 2016 +0100

    services: 'file-union' makes sure each source file exists.
    
    Before that, specifying an invalid timezone in 'operating-system' would
    lead to a dangling symlink in the 'etc' directory, which in turn would
    lead to a kernel panic at boot time.
    
    Reported by pizzaiolo on #guix.
    
    * gnu/services.scm (file-union): Add 'stat' call for SOURCE.
---
 gnu/services.scm |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/gnu/services.scm b/gnu/services.scm
index 056bb2a..1ad5737 100644
--- a/gnu/services.scm
+++ b/gnu/services.scm
@@ -291,7 +291,12 @@ file."
                      (chdir #$output)
                      #$@(map (match-lambda
                                ((target source)
-                                #~(symlink #$source #$target)))
+                                #~(begin
+                                    ;; Stat the source to abort early if it
+                                    ;; does not exist.
+                                    (stat #$source)
+
+                                    (symlink #$source #$target))))
                              files))))
 
 (define (directory-union name things)