GNU bug report logs - #56799
(gnu services configuration) usage of *unspecified* is problematic

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From: Attila Lendvai <attila <at> lendvai.name>
To: 56799 <at> debbugs.gnu.org
Cc: Attila Lendvai <attila <at> lendvai.name>
Subject: bug#56799: [PATCH 5/5] services: configuration: Change the value of the unset marker.
Date: Wed, 24 Aug 2022 14:40:42 +0200

The new value of %unset-value sticks out more when something goes wrong, and
is also more unique; i.e. easier to search for.
---
 gnu/services/configuration.scm   | 5 +++--
 gnu/services/messaging.scm       | 2 +-
 tests/services/configuration.scm | 2 +-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/gnu/services/configuration.scm b/gnu/services/configuration.scm
index 60965486a7..83da63c1b3 100644
--- a/gnu/services/configuration.scm
+++ b/gnu/services/configuration.scm
@@ -305,12 +305,13 @@ (define serialize-package empty-serializer)
 
 ;; Ideally this should be an implementation detail, but we export it
 ;; to provide a simpler API that enables unsetting a configuration
-;; field that has a maybe type, but also a default value.
+;; field that has a maybe type, but also a default value.  We give it
+;; a value that sticks out to the reader when something goes wrong.
 ;;
 ;; An example use-case would be something like a network application
 ;; that uses a default port, but the field can explicitly be unset to
 ;; request a random port at startup.
-(define %unset-value 'unset)
+(define %unset-value '%unset-marker%)
 
 (define (maybe-value-set? value)
   "Predicate to check whether a 'maybe' value was explicitly provided."
diff --git a/gnu/services/messaging.scm b/gnu/services/messaging.scm
index 59cb486778..02712ede7c 100644
--- a/gnu/services/messaging.scm
+++ b/gnu/services/messaging.scm
@@ -95,7 +95,7 @@ (define (make-pred arg)
                                  ;; doesn't interfere with
                                  ;; define-configuration and define-maybe
                                  ;; internals.
-                                 #''unset def))
+                                 #''%unset-marker% def))
                            #'(def ...) #'(target ...)))
                      ((new-doc ...)
                       (map (lambda (doc target)
diff --git a/tests/services/configuration.scm b/tests/services/configuration.scm
index 8ed4ed4b66..4f8a74dc8a 100644
--- a/tests/services/configuration.scm
+++ b/tests/services/configuration.scm
@@ -150,7 +150,7 @@ (define-configuration config-with-maybe-symbol
   (protocol maybe-symbol ""))
 
 ;;; Maybe symbol values are currently seen as serializable, because the
-;;; unspecified value is 'unset, which is a symbol itself.
+;;; unspecified value is '%unset-marker%, which is a symbol itself.
 ;;; TODO: Remove expected fail marker after resolution.
 (test-expect-fail 1)
 (test-equal "symbol maybe value serialization, unspecified"
-- 
2.35.1

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