[bug#42146] [PATCH core-updates 1/?] build: substitute: Don't fail silently.

[Maxim Cournoyer]

Hi,

Simon Tournier <zimon.toutoune@gmail.com> writes:

> Hi Ludo,
>
> On Thu, 19 Oct 2023 at 22:40, Ludovic Courtès <ludo@gnu.org> wrote:
>
>>> +;;;
>>> +;;; Extend regexp objects with a pattern field.
>>> +;;;
>>> +(define-record-type <regexp*>
>>> +  (%make-regexp* pat flag rx)
>>> +  regexp*?
>>> +  (pat regexp*-pattern)                 ;the regexp pattern, a string
>>> +  (flag regexp*-flag)                   ;regexp flags
>>> +  (rx regexp*-rx))                      ;the compiled regexp object
>>> +
>>> +;;; Work around regexp implementation.
>>> +;;; This record allows to track the regexp pattern and then display it.
>>> +(define* (make-regexp* pat #:optional (flag regexp/extended))
>>
>> I’m skeptical about the concrete benefits.  I would not include it in
>> (guix build utils), or at least not in this patch series.
>>
>> (I tend to be super conservative about (guix build utils) because we
>> rarely get a chance to change it.)
>
> If I remember correctly, the record was introduced in #58660 [1].
> Basically, if you have,
>
>               (make-regexp "^gnu/packages/python(-.+|)\\.scm$")
>
> then you only have access to some #<regexp 7f6315fb3500>.  Other said,
> you lost the human-readable "^gnu/packages/python(-.+|)\\.scm$" regexp
> pattern.  The workaround just stores this human-readable regexp pattern.
> Later, it is thus possible to display it; for debugging or else.
>
> For the location of such feature, I do not have an opinion.  For the
> concrete benefits, I have one. :-)
>
> Well, maybe the feature – keep an access to the human-readable regexp
> pattern – could be implemented on Guile-side.

Agreed, for the long haul (as with many cool bits that are Guix specific
currently).

-- 
Thanks,
Maxim