bug#56799: (gnu services configuration) usage of *unspecified* is problematic

[Maxim Cournoyer]

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