On 30.06.2018 13:42, Eli Zaretskii wrote: >> Cc: 32012@debbugs.gnu.org >> From: Andreas Röhler >> 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.