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bug#56799: [PATCH 1/5] services: configuration: Add a 'maybe-value-set?'
From: |
Attila Lendvai |
Subject: |
bug#56799: [PATCH 1/5] services: configuration: Add a 'maybe-value-set?' procedure. |
Date: |
Wed, 24 Aug 2022 14:40:38 +0200 |
From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
* gnu/services/configuration.scm (maybe-value-set?): New procedure.
* doc/guix.texi (Complex Configurations): Document it. Remove comment showing
usage of 'maybe-string' with a default value, which doesn't make sense.
Co-authored-by: Attila Lendvai <attila@lendvai.name>
---
doc/guix.texi | 7 ++++++-
gnu/services/configuration.scm | 15 ++++++++++-----
2 files changed, 16 insertions(+), 6 deletions(-)
diff --git a/doc/guix.texi b/doc/guix.texi
index 86cfe7d49c..039df29ebc 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -38999,7 +38999,7 @@ to be a string, or left unspecified.
(name
;; If set to a string, the `serialize-string' procedure will be used
;; to serialize the string. Otherwise this field is not serialized.
- maybe-string ; equivalent to (maybe-string *unspecified*)
+ maybe-string
"The name of this module."))
@end lisp
@@ -39030,6 +39030,11 @@ whether its value is set or not.
@end lisp
@end deffn
+@deffn (Scheme Procedure) maybe-value-set? @var{value}
+Predicate to check whether a user explicitly specified the value of a
+maybe field.
+@end deffn
+
@deffn {Scheme Procedure} serialize-configuration @var{configuration} @
@var{fields}
Return a G-expression that contains the values corresponding to the
diff --git a/gnu/services/configuration.scm b/gnu/services/configuration.scm
index 3007e8de35..e2c4fe9998 100644
--- a/gnu/services/configuration.scm
+++ b/gnu/services/configuration.scm
@@ -57,6 +57,7 @@ (define-module (gnu services configuration)
serialize-configuration
define-maybe
define-maybe/no-serialization
+ maybe-value-set?
generate-documentation
configuration->documentation
empty-serializer
@@ -142,7 +143,8 @@ (define (define-maybe-helper serialize? prefix syn)
(id #'stem #'serialize-maybe- #'stem))))
#`(begin
(define (maybe-stem? val)
- (or (eq? val 'unset) (stem? val)))
+ (or (not (maybe-value-set? val))
+ (stem? val)))
#,@(if serialize?
(list #'(define (serialize-maybe-stem field-name val)
(if (stem? val)
@@ -260,11 +262,10 @@ (define #,(id #'stem #'stem #'-fields)
(default-value-thunk
(lambda ()
(display '#,(id #'stem #'% #'stem))
- (if (eq? (syntax->datum field-default)
- 'unset)
+ (if (maybe-value-set? (syntax->datum field-default))
+ field-default
(configuration-missing-default-value
- '#,(id #'stem #'% #'stem) 'field)
- field-default)))
+ '#,(id #'stem #'% #'stem) 'field))))
(documentation doc))
...))))))))
@@ -300,6 +301,10 @@ (define-configuration stem (field field-type+def
(define (empty-serializer field-name val) "")
(define serialize-package empty-serializer)
+(define (maybe-value-set? value)
+ "Predicate to check whether a 'maybe' value was explicitly provided."
+ (not (eq? 'unset value)))
+
;; A little helper to make it easier to document all those fields.
(define (generate-documentation documentation documentation-name)
(define (str x) (object->string x))
--
2.35.1
- bug#56799: [PATCH 1/5] services: configuration: Add a 'maybe-value-set?' procedure.,
Attila Lendvai <=