GNU bug report logs - #53663
[PATCH] gnu: services: Also accept 'undefined in maybe-foo? constructs.

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 53663 in the body.
You can then email your comments to 53663 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Attila Lendvai <attila <at> lendvai.name>
To: guix-patches <at> gnu.org
Cc: Attila Lendvai <attila <at> lendvai.name>
Subject: [PATCH] gnu: services: Also accept 'undefined in maybe-foo?
 constructs.
Date: Mon, 31 Jan 2022 16:27:54 +0100

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)))
            #,@(if serialize?
                   (list #'(define (serialize-maybe-stem field-name val)
                             (if (stem? val)
-- 
2.34.0

Message #8 received at 53663 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: Attila Lendvai <attila <at> lendvai.name>
Cc: 53663 <at> debbugs.gnu.org
Subject: Re: bug#53663: [PATCH] gnu: services: Also accept 'undefined in
 maybe-foo? constructs.
Date: Tue, 01 Feb 2022 10:53:38 +0100

Hi!

Attila Lendvai <attila <at> lendvai.name> skribis:

> 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’.

Message #13 received at 53663-close <at> debbugs.gnu.org (full text, mbox):

From: Attila Lendvai <attila <at> lendvai.name>
To: "53663-close <at> debbugs.gnu.org" <53663-close <at> debbugs.gnu.org>
Subject: Fw: Re: bug#53663: [PATCH] gnu: services: Also accept 'undefined in
 maybe-foo? constructs.
Date: Wed, 02 Feb 2022 11:47:02 +0000

> 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
--
“There can be no greater stretch of arbitrary power than is required to seize children from their parents, teach them whatever the authorities decree they shall be taught, and expropriate from the parents the funds to pay for the procedure.”
	— Isabel Paterson (1886–1961), 'The God of the Machine' (1943)

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.