GNU bug report logs - #61617
M-x mark-defun doesn't work correctly in tree-sitter modes when comments exist between functions

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From: Yuan Fu <casouri <at> gmail.com>
To: Evgeni Kolev <evgenysw <at> gmail.com>
Cc: Theodor Thornhill <theo <at> thornhill.no>, 61617 <at> debbugs.gnu.org
Subject: bug#61617: M-x mark-defun doesn't work correctly in tree-sitter modes when comments exist between functions
Date: Sun, 26 Feb 2023 16:42:37 -0800

> On Feb 24, 2023, at 11:27 PM, Evgeni Kolev <evgenysw <at> gmail.com> wrote:
> 
> On Sat, Feb 25, 2023 at 7:08 AM Yuan Fu <casouri <at> gmail.com> wrote:
> 
>> Huh, with or without comments, mark-defun always includes the empty
>> lines before the defun for me. I get the same behavior in rust-ts-mode.
>> This seems intentional, because this is at the end of the definition of
>> mark-defun:
>> 
>> (skip-chars-backward "[:space:]\n")
>> (unless (bobp)
>>  (forward-line 1))
> 
> Did you check with my example or another example? With my example, the
> issue I get is that only the empty lines are marked, without the
> defun, without the comments. I'm attaching two screenshots - before
> and after mark-defun.
> 
> Note: I get the correct behaviour when there is just one defun in the
> file. But if there are more, or the defun at point is not at the top
> of the file - mark-defun does not work as expected.

Sorry, I used wrong go mode when testing your recipe. I used go-mode thinking it is go-ts-mode :-( Using go-ts-mode, I can reproduce what you see, yes.

The problem you discovered revealed some shortcoming in our tree-sitter navigation function, and requires quite a few non-trivial changes, I working on fixing it.

The direct cause is that (treesit-beginning-of-defun -1) is supposed to go to the beginning of next defun, but instead goes to the beginning of next next defun. That was a design decision I made but I can see it causing old functions to misbehave. 

Yuan

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