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[bug#71928,v2] gnu: Throw error when extending services that do not use extensions.

Message ID 6afb44e7f09f2d8fdbbe4cd0bad92ca170aef1b0.1720045261.git.richard@freakingpenguin.com
State New
Headers show
Series [bug#71928,v2] gnu: Throw error when extending services that do not use extensions. | expand

Commit Message

Richard Sent July 3, 2024, 10:21 p.m. UTC 
* gnu/services.scm (fold-services): Add error handling when using service
extensions.

Fixes: https://issues.guix.gnu.org/71887
Change-Id: Ic8d631674bfddde495c93952d9e6cd5649bb287d
---
 gnu/services.scm | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)


base-commit: 85012e64819b39fd6112038134548b415fd5daff
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Patch

diff --git a/gnu/services.scm b/gnu/services.scm
index 88593e8091..f3a1041f14 100644
--- a/gnu/services.scm
+++ b/gnu/services.scm
@@ -53,6 +53,7 @@  (define-module (gnu services)
   #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-35)
   #:use-module (srfi srfi-71)
+  #:use-module (ice-9 format)
   #:use-module (ice-9 vlist)
   #:use-module (ice-9 match)
   #:autoload   (ice-9 pretty-print) (pretty-print)
@@ -1223,12 +1224,22 @@  (define* (fold-services services
                      (params     -> (service-value sink))
                      (service
                       ->
-                      ;; Distinguish COMPOSE and EXTEND because PARAMS typically
-                      ;; has a different type than the elements of EXTENSIONS.
-                      (if extend
-                          (service (service-kind sink)
-                                   (extend params (compose extensions)))
-                          sink)))
+                      (begin
+                        (unless (or (null? extensions)
+                                    ;; A value of #t is a convention for "make
+                                    ;; sure the service is present."
+                                    (every (cut eq? #t <>) extensions)
+                                    (and extend compose))
+                          (error (format #f "Extensions are not supported in \
+~a yet the following service types extend it:~{~%   ~a~}"
+                                         (service-kind sink)
+                                         (map service-kind dependents))))
+                        ;; Distinguish COMPOSE and EXTEND because PARAMS typically
+                        ;; has a different type than the elements of EXTENSIONS.
+                        (if extend
+                            (service (service-kind sink)
+                                     (extend params (compose extensions)))
+                            sink))))
                   (mbegin %state-monad
                     (set-current-state (vhash-consq sink service visited))
                     (return service))))