Subject: bug#32012: 27.0.50; jit-lock--run-functions broken

From: Andreas Röhler <[email-masked]>
Date: Sat, 30 Jun 2018 14:33:50 +0200

On 30.06.2018 13:42, Eli Zaretskii wrote:
>> Cc: [email-masked]
>> From: Andreas Röhler <[email-masked]>
>> Date: Sat, 30 Jun 2018 13:19:40 +0200
>>
>>>> Hmm, by looking at its signature
>>>>
>>>> (defun jit-lock-fontify-now (&optional start end)
>>>>
>>>> Why that shouldn't work?
>>>
>>> That's not what the backtrace suggests.  It suggests that you invoked
>>> jit-lock--run-functions via eval-last-sexp.
>>
>> Right. But the arguments are optional.
>> Wherefrom to expect it failing?
> 
> A function that has optional argument doesn't necessarily support
> invocation without arguments in any arbitrary context.  It could
> support that just in some specific cases.  You can clearly see in the
> function that when Start and END are nil, the function sets them to
> some values, but those values might not make sense in some arbitrary
> invocation context.
> 
> Anyway, this discussion would have been much less theoretical if you
> would to show what exactly did you do in ert tests that caused the
> problem.
> 
> 
> 

Okay. Will look to for a real-world example, not just some minimal one.
For the moment, maybe have a look at attachment how the function in 
question gets fontified from emacs -Q - obviously 
with-buffer-prepared-for-jit-lock as keyword missing.