bug#61356: 29.0.60; wrong-type-argument in treesit-indent-region when indenting a C buffer

[Yuan Fu]

> On Feb 24, 2023, at 6:24 PM, Daniel Martín <mardani29@yahoo.es> wrote:
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
>>> Date: Tue, 07 Feb 2023 23:20:09 +0100
>>> From:  Daniel Martín via "Bug reports for GNU Emacs,
>>> the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>>> 
>>> 
>>> Steps to reproduce the problem:
>>> 
>>> emacs -Q
>>> C-x C-f emacs/src/xdisp.c RET
>>> M-x c-ts-mode RET
>>> C-x h
>>> TAB
>>> 
>>> Expected result:
>>> 
>>> The buffer is reindented.
>>> 
>>> Actual results:
>>> 
>>> The operation fails with this error:
>>> 
>>> Debugger entered--Lisp error: (wrong-type-argument integer-or-marker-p nil)
>>>  treesit-indent-region(1 1214226)
>>>  indent-region(1 1214226)
>>>  indent-for-tab-command(nil)
>>>  funcall-interactively(indent-for-tab-command nil)
>>>  call-interactively(indent-for-tab-command nil nil)
>>>  command-execute(indent-for-tab-command)
>> 
>> Thank you for your report.
>> 
>> Yuan and Theo, could you please look into this?  I briefly stepped
>> through the code involved in the problem, and it sounds like it makes
>> some assumptions regarding the nodes which are not necessarily true in
>> Real Life.
> 
> c-ts-mode from the tip of the emacs-29 branch can indent xdisp.c without
> failures if I apply the patch from bug#61691 and the patch attached to
> this email message.
> 
> It is very slow, though, compared to c-mode.  I have a very fast machine
> and it took around 10 minutes to indent the whole file, while c-mode
> indented the file in 30-40 seconds.  I guess the algorithm in
> treesit-indent-region doesn't scale very well for very big files like
> xdisp.c.
> 

Thanks, I applied the patch. What you observed is certainly a regression due 
to, from what I can see from profiling, c-ts-common-statement-offset. It is 
added for more accurate indenting, by going up the parse tree and “count 
brackets”, more or less. This is probably a pretty inefficient when calculating 
indentation for every line. A change I just pushed helps a bit (in a block, 
make the first child calculate indentation as before, and children after than 
uses the previous sibling’s indentation), but still not enough.

I have some ideas to improve this, and get back once I have something.

Yuan