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Subject: |
(gnu services configuration) usage of *unspecified* is problematic |
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Date: |
Wed, 27 Jul 2022 12:23:58 -0400 |
Hello Guix,
Since commit 8cb1a49a3998c39f315a4199b7d4a121a6d66449, the
define-configuration machinery in (gnu services configuration) uses
*unspecified* instead of 'disabled for an unspecified field value.
While this is indeed an improvement in readability, it introduces an
extra complication: because this new value is not self-quoting, it
cannot be used as is in G-Exps, and values using it must be carefully
expanded outside the gexp context, which is error prone.
This broke the jami-service-type, when partially specifying a
jami-account like so:
--8<---------------cut here---------------start------------->8---
(service jami-service-type
(jami-configuration
(accounts
(list (jami-account
(archive "/etc/jami/some-jami-account.gz"))))))
--8<---------------cut here---------------end--------------->8---
When building the operating system containing the above fragment, the
following error is throw:
--8<---------------cut here---------------start------------->8---
guix system: error: #<unspecified>: invalid G-expression input
--8<---------------cut here---------------end--------------->8---
The following change to the jami-provisioning test can also reproduce
the problem:
--8<---------------cut here---------------start------------->8---
modified gnu/tests/telephony.scm
@@ -60,7 +60,7 @@ (define %moderators
'("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
(define %dummy-jami-account (jami-account
(archive %dummy-jami-account-archive)
(allowed-contacts %allowed-contacts)
- (moderators %moderators)
+; (moderators %moderators)
(rendezvous-point? #t)
(peer-discovery? #f)
(bootstrap-hostnames '("bootstrap.me"
--8<---------------cut here---------------end--------------->8---
--8<---------------cut here---------------start------------->8---
$ make check-system TESTS=jami-provisioning
Selected 1 system tests...
guix build: error: #<unspecified>: invalid G-expression input
make: *** [Makefile:6734: check-system] Error 1
--8<---------------cut here---------------end--------------->8---
I'd suggest we revisit 8cb1a49a3998c39f315a4199b7d4a121a6d66449 to use
'unspecified (the symbol) instead of *unspecified*, which *can* be
serialized without any fuss in gexps.
Thoughts?
Thanks,
Maxim
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--- Begin Message ---
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Subject: |
Re: bug#56799: (gnu services configuration) usage of *unspecified* is problematic |
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Date: |
Mon, 01 Aug 2022 12:55:19 -0400 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.1 (gnu/linux) |
Hi,
Tobias Geerinckx-Rice <me@tobias.gr> writes:
> Hi Maxim,
>
> Maxim Cournoyer 写道：
>> For some background reading, see [0].
>
> Thanks for the well-thought-out reply, and sharing this interesting
> link!
>
> Now, it's just the musings of one person, but now I think I do agree
> with (what I think is) the underlying vision: to hush up *unspecified*
> and sneakily replace it with true nothingness. OK, I can live with
> that. :-)
>
>> I think the semantic of the language is that it is to be used as the
>> lack of a return value from a procedure or syntax, e.g.:
>>
>> (unspecified? (if #f 'one-arm-if)) -> #t
>
> Well… in the above context I'd hesitate to even imply
> ‘semantics’. It's like undefined behaviour in C. Ascribe it meaning
> at your peril. Otherwise, point taken.
>
>> Having 'unspecified?' even defined in Guile seems to go against that
>> idea; perhaps because Wingo themselves seems to disagree in [0].
>
> Agreed. *This* was one of my reasons for supporting (field
> *unspecified*), so it's nice to have it validated, even if it is
> rejected.
>
>> I'm also thinking 'unspecified being too close to *unspecified* is
>> probably going to cause confusion down the line. Reverting to the
>> originally used 'disabled may be the lesser evil.
>
> Ah, here I can concentrate all my previous disagreement: hell no :-)
>
> It is the worstest evil; literally anything is better than
> (enable-foo? 'disabled) defaulting to #t.
>
> Bikeshed this all y'all want, but 'default or 'unset or 'whatever are
> miles better.
OK. The v2 and v3 idea ended up not working, among lesser issues :-).
So I went with v1, renaming the default value to 'unset; see commit
a2b89a3319dc1d621c546855f578acae5baaf6da. Thanks for the naming
suggestions.
I also added a 'jami-provisioning-partial' system test to ensure it
doesn't regress again if we decide to revisit this.
Thanks,
Closing.
Maxim
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