bug#66326: 29.1.50; There should be a way to promote warnings to errors

[Eli Zaretskii <eliz@gnu.org>]

> From: sbaugh@catern.com
> Date: Sat, 14 Oct 2023 22:25:37 +0000 (UTC)
> Cc: Spencer Baugh <sbaugh@janestreet.com>, 66326@debbugs.gnu.org
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: Spencer Baugh <sbaugh@janestreet.com>
> >> Cc: sbaugh@catern.com,  66326@debbugs.gnu.org
> >> Date: Wed, 04 Oct 2023 08:20:49 -0400
> >> 
> >> Eli Zaretskii <eliz@gnu.org> writes:
> >> > And in this case, duplication is a lesser evil than reordering of
> >> > logic, since the chances of unintended consequences would be lower in
> >> > the former case.
> >> 
> >> OK, how about this version then?
> >
> > This is much better, thanks.  But it still fails to execute this part
> > right away:
> >
> >   (if (not (or after-init-time noninteractive (daemonp)))
> >       ;; Ensure warnings that happen early in the startup sequence
> >       ;; are visible when startup completes (bug#20792).
> >       (delay-warning type message level buffer-name)
> >
> > We must preserve this functionality, unaffected by these changes.  The
> > patch you propose doesn't seem to guarantee that, at least not
> > clearly enough for my palate.
> 
> Ah, actually that's deliberate.

If it's deliberate, it will have to come with an additional option to
enable it.  I don't want users to have their startup aborted just
because they want some warning later on converted to an error.
Startup is a delicate process where signaling errors is not always a
good idea, and we delay warnings there for a good reason.  Changing
this unconditionally is not acceptable.

> (And that's one of the motivations of this change: to make it easier to
> debug a warning that happens during startup, by turning it into an error
> that can be debug-init'd)

There's no difficulty in debugging a warning whatsoever, IME.  It is a
serious exaggeration to claim that there's a significant problem here
that needs a solution.  Nevertheless, I'm okay with people opting in
to shooting themselves in the foot, I just don't agree to doing that
without an explicit user's consent.