bug#71178: Batch ert wrongly aborts a test run, and wrongly fails to say why.

[J.P.]

Hi Alan,

Alan Mackenzie <acm@muc.de> writes:

>> It seems you have identified the underlying cause:
>
>>   https://lists.gnu.org/archive/html/emacs-devel/2024-05/msg01140.html
>
> I've been looking at lisp/emacs-lisp/ert.el, and I think that suppressing
> the debug output (or rather, not invoking a backtrace dump in batch mode)
> is where the problem lies.  However, when I enabled these in my own copy,
> they produced an erc.log of over 100 MB.  But that was in my customised
> Emacs where I've changed quite a few things always to get a complete
> backtrace.  So I'm not sure what is best, here.

I too have bumped into failures that don't produce a backtrace, at least
in recent versions. However, the ones I typically see look more like:

  Error in process sentinel
  Make[3] *** [Makefile:184 lisp/erc/erc-*.log] Error 255

  ...

  1 files did not finish:
    lisp/erc/erc-*.log

  Make *** [Makefile:266 check-lisp-erc] Error 2

With these, it seems debug output is being intentionally suppressed on
account of the error originating from some process sentinel or timer.
And when I enable `debug-on-error', a backtrace appears as expected.
This leads me to assume such occurrences are somewhat unrelated to what
you're experiencing. That said, I'm fairly convinced I've encountered
the odd mystery failure with no specified error. And the "aborted" line
in your excerpt does look familiar. Sadly, though, I cannot reliably
reproduce anything similar (yet).

>> The test itself is of minimal utility and is therefore rubbish (if not
>> outright vandalism), so I will remove it unless you'd rather it stick
>> around until the conversation on the list gets going.
>
> I think I'd rather the test should stay there a bit longer.  It
> highlights problems in pcase.el and ert.el which might get fixed sooner
> if the test is still there.  _MIGHT_ (here's hoping!).

Good point. I've added a FIXME to remind myself or some future person to
delete the test once things have settled.

Cheers,
J.P.