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

[Spencer Baugh <sbaugh@janestreet.com>]

sbaugh@catern.com writes:
> Stefan Kangas <stefankangas@gmail.com> writes:
>
>> Eli Zaretskii <eliz@gnu.org> writes:
>>
>>> More generally, I'm worried by the tendency of people to submit
>>> patches for Emacs as soon as they find something they think is missing
>>> in Emacs that they need for some one-time job.  Emacs is not supposed
>>> to be a huge heap of random features that someone at some time found
>>> useful for some random job.  Emacs is Free Software: you can easily
>>> implement this stuff in your local copy and use it as much as you
>>> want; no need to add that to the Emacs core, unless there's a real
>>> need for it expressed by enough people, and no better solutions in
>>> hand.  I do this for my local jobs all the time.
>>
>> FWIW, I'm generally always in favor of features that make the Emacs Lisp
>> developers' lives easier, and as much as I appreciate that some users
>> might want to debug warnings, I don't think I understand the use case(s).
>
> I see, let me try to explain further.  (BTW, before submitting I
> discussed the idea of this patch on #emacs on Libera IRC and people
> seemed interested and approving, which is why I assumed this would be
> uncontroversial.  If I had realized I would have sent it to
> emacs-devel.)
>
> I had some warnings and I went to debug them, and I assumed there would
> be some kind of debug-on-warning like how there is debug-on-error and
> debug-on-message and debug-on-quit.  But there is not.  So I figured it
> would be uncontroversial to add something which enables a
> debug-on-warning, since right now it is difficult to find out what code
> triggered some warning.
>
> The alternative which I've been using is
> (debug-on-entry 'display-warning)
> but this:
> 1. always debugs regardless of what kind of warning
> 2. isn't helpful for the "automated tests where warnings
>    should fail the test" use case

I just ran into a situation like this yet again.  Again, there was a
stray warning on startup (something about "Symbol’s value as variable is
void", definitely concerning), which the warning itself didn't provide
sufficient information to track down.  I did my usual (debug-on-entry
'display-warning)...

...but then I ran into the further issue that this Emacs had the
"editorconfig" package installed, which apparently calls display-warning
at :debug level on every buffer switch.  So I spent a while hitting c in
the debugger.

I would have like to be able to turn only :error level warnings
into... errors.  Which is what this feature would provide.