[PATCH] gnu: services: Also accept 'undefined in maybe-foo? constructs.

DoneSubmitted by Attila Lendvai.
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2 participants
  • Attila Lendvai
  • Ludovic Courtès
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Attila Lendvai wrote on 31 Jan 16:27 +0100
(address . guix-patches@gnu.org)(name . Attila Lendvai)(address . attila@lendvai.name)
20220131152753.19880-1-attila@lendvai.name
This is a temporary bandaid until a more explicit handling of maybe types is
introduced for configurations (e.g. by using srfi-189). Until then, with this
change it becomes possible to have definitions like:

(define-maybe string (no-serialization))

(define-configuration my-configuration
(my-field (maybe-string))
(no-serialization))

i.e. without providing a default value for MY-FIELD.
---
gnu/services/configuration.scm | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

Toggle diff (17 lines)
diff --git a/gnu/services/configuration.scm b/gnu/services/configuration.scm
index 0de350a4df..c5f276eab5 100644
--- a/gnu/services/configuration.scm
+++ b/gnu/services/configuration.scm
@@ -141,7 +141,9 @@ (define (define-maybe-helper serialize? prefix syn)
                                     (id #'stem #'serialize-maybe- #'stem))))
        #`(begin
            (define (maybe-stem? val)
-             (or (eq? val 'disabled) (stem? val)))
+             (or (eq? val 'disabled)
+                 (eq? val 'undefined)
+                 (stem? val)))
            #,@(if serialize?
                   (list #'(define (serialize-maybe-stem field-name val)
                             (if (stem? val)
-- 
2.34.0
L
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Ludovic Courtès wrote on 1 Feb 10:53 +0100
(name . Attila Lendvai)(address . attila@lendvai.name)(address . 53663@debbugs.gnu.org)
87ilty6hgd.fsf@gnu.org
Hi!

Attila Lendvai <attila@lendvai.name> skribis:

Toggle quote (28 lines)
> This is a temporary bandaid until a more explicit handling of maybe types is
> introduced for configurations (e.g. by using srfi-189). Until then, with this
> change it becomes possible to have definitions like:
>
> (define-maybe string (no-serialization))
>
> (define-configuration my-configuration
> (my-field (maybe-string))
> (no-serialization))
>
> i.e. without providing a default value for MY-FIELD.
> ---
> gnu/services/configuration.scm | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/gnu/services/configuration.scm b/gnu/services/configuration.scm
> index 0de350a4df..c5f276eab5 100644
> --- a/gnu/services/configuration.scm
> +++ b/gnu/services/configuration.scm
> @@ -141,7 +141,9 @@ (define (define-maybe-helper serialize? prefix syn)
> (id #'stem #'serialize-maybe- #'stem))))
> #`(begin
> (define (maybe-stem? val)
> - (or (eq? val 'disabled) (stem? val)))
> + (or (eq? val 'disabled)
> + (eq? val 'undefined)
> + (stem? val)))

My understanding is that 'disabled is here precisely to allow users to
not provide a value, in which case the generated configuration file will
not contain anything for that field.

What would be different here?

Thanks,
Ludo’.
A
A
Attila Lendvai wrote on 2 Feb 12:47 +0100
(name . 53663-close@debbugs.gnu.org)(address . 53663-close@debbugs.gnu.org)
LZAnSJmgmdtLPRzpDhrfzSlilVJJq1MLXCWIIkE-yMLDeEXnFN5wPrWeMGAjZGo2vl1yUKPrilT3nCtusH9frolHVuqEM9boV1MLWgVr64U=@lendvai.name
Toggle quote (2 lines)
> What would be different here?

the possibility of writing:

(define-configuration my-cfg
(my-field (maybe-string)))

versus now having to write:

(define-configuration my-cfg
(my-field (maybe-string 'disabled)))

but now that i thought about it, i think everyone is better off if i
deal with this on my side, instead of having a discussion about the
exact shape of a bandaid.

closing this for now; more later in the form of a proper cleanup
proposal of the configuration code.

--
• attila lendvai
• PGP: 963F 5D5F 45C7 DFCD 0A39
--
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