bug#65267: 30.0.50; modifying debug-ignored-errors during startup with --debug-init is broken, bug#65267: 30.0.50; modifying debug-ignored-errors during startup with --debug-init is broken

[Štěpán Němec]

On Thu, 17 Aug 2023 17:31:00 +0300
Eli Zaretskii wrote:

>> From: Štěpán Němec <stepnem@smrk.net>
>> Cc: 65267@debbugs.gnu.org, npostavs@users.sourceforge.net
>> Date: Thu, 17 Aug 2023 16:16:19 +0200
>> 
>> On Thu, 17 Aug 2023 16:28:31 +0300
>> Eli Zaretskii wrote:
>> 
>> Your patch preserves additions (although it moves them to the end of the
>> list, but that shouldn't matter for debug-ignored-errors), but doesn't
>> preserve removals
>
> If someone want to remove from the list, and use --debug-init on top
> of that, they will need to replace the value instead.  If that's the
> only downside of the patch I proposed, I think people will be able to
> live with it.

As you said, debug-ignored-errors is a user variable.  So some people
are likely to change it, and some (most?) of those people will do that
from their init file.  I don't see how adding vs removing is any
different in that respect.

As for --debug-init, why would anyone (who knows about that option and
cares about their setup) routinely start Emacs *without* it?

>> Have you considered my humble suggestion of reverting to pre-bug#64163
>> state and simply removing end-of-file from the default value of
>> debug-ignored-errors?
>
> Yes.  This cannot fly, since we had end-of-file there for a long time
> (I see it in Emacs 20).

I only wish someone would put forth an actual argument for having
end-of-file on debug-ignored-errors.

I agree backward compatibility/preserving behavior is important, but I
hope you'll agree that some behavior changes are more
serious/visible/disruptive/whatever than others, and I'd argue that in
that sense, messing with user option modification during startup is a
worse change than removing end-of-file from debug-ignored-errors.

So if we're again back to blessing the breakage, I suggest it at least
be documented.

On Thu, 17 Aug 2023 17:36:09 +0300
Eli Zaretskii wrote:

>> Cc: 65267@debbugs.gnu.org, monnier@iro.umontreal.ca,
>>  npostavs@users.sourceforge.net
>> Date: Thu, 17 Aug 2023 17:31:00 +0300
>> From: Eli Zaretskii <eliz@gnu.org>
>> 
>> > Have you considered my humble suggestion of reverting to pre-bug#64163
>> > state and simply removing end-of-file from the default value of
>> > debug-ignored-errors?
>> 
>> Yes.  This cannot fly, since we had end-of-file there for a long time
>> (I see it in Emacs 20).
>
> And, of course, end-of-file is just one of the errors in the list;
> bug#64163 could have been equally reported with any of those other
> ones, and the solution is the same.

"Equally" I don't think.  If it took many (tens of?) years for anybody
to be bothered by the end-of-file case (bug#64163), which IME indeed
occurs somewhat regularly during startup (missing closing paren), I find
the same happening with any of the other members of debug-ignored-errors
exceedingly unlikely.

I agree with Stefan that no good solution has so far emerged.  The
advantage of my suggestion would be that it only changes
debug-ignored-errors in a way that makes sense anyway (in absence of any
arguments to the contrary), preventing bug#64163 as a byproduct, rather
than adding to convoluted code nobody involved seems to really
understand in a way that nobody involved seems to really understand or
expect.

-- 
Štěpán