GNU bug report logs - #64321
29.0.92; Tree-Sitter/which-function Narrow/Widen causes modified buffer

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 64321 in the body.
You can then email your comments to 64321 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Troy Brown <brownts <at> troybrown.dev>
To: bug-gnu-emacs <at> gnu.org
Subject: 29.0.92;
 Tree-Sitter/which-function Narrow/Widen causes modified buffer
Date: Tue, 27 Jun 2023 22:23:52 -0400

This problem seems to manifest with multiple tree-sitter modes.  It
appears there is an interaction with which-function-mode and tree-sitter
which causes the buffer to be considered modified either after a narrow
or widen of the buffer.

To reproduce this, use a "hello_world.c" as follows:

--8<---------------cut here---------------start------------->8---
#include <stdio.h>

int main (void)
{
  printf("Hello, world!\n");
  return 0;
}
--8<---------------cut here---------------end--------------->8---

Running "emacs -Q" with the corresponding tree-sitter grammar library
installed.  Move into the main function and narrow-to-defun.  In some
modes, I've seen this cause the buffer to show as modified, however with
this example, it seems to occur after widening.

The following sequence of commands can be used to reproduce the issue:

C-x C-f ~/hello_world.c
M-x c-ts-mode
M-x which-function-mode
C-x n d
C-x n w

At this point, the modeline shows that the buffer is modified, and
running "M-: (buffer-modified-p)" indicates "t".  As previously
mentioned, this appears to only happen with tree-sitter modes when
which-function-mode is enabled in the buffer.

I then repeated the same but also triggered a backtrace on the first
change as follows:

M-: (add-to-list 'first-change-hook #'backtrace)

With that in place, the following is the generated traceback:

  backtrace()
  treesit--font-lock-notifier(((1 . 21)) #<treesit-parser for c>)
  treesit-buffer-root-node(c)
  treesit-node-at(68)
  treesit--things-around(68
"\\(?:class_specifier\\|enum_specifier\\|function_defi..."
c-ts-mode--defun-valid-p)
  treesit-thing-at-point(("\\(?:class_specifier\\|enum_specifier\\|function_defi..."
. c-ts-mode--defun-valid-p) top-level)
  treesit-defun-at-point()
  treesit-add-log-current-defun()
  c-ts-mode--emacs-current-defun-name()
  add-log-current-defun()
  which-function()
  which-func-update-1(#<window 3 on hello_world.c>)
  which-func-update()
  apply(which-func-update nil)
  timer-event-handler([t 0 0 500000 t which-func-update nil idle 0 nil])

Message #8 received at 64321 <at> debbugs.gnu.org (full text, mbox):

From: Yuan Fu <casouri <at> gmail.com>
To: Troy Brown <brownts <at> troybrown.dev>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 64321 <at> debbugs.gnu.org
Subject: Re: bug#64321: 29.0.92; Tree-Sitter/which-function Narrow/Widen
 causes modified buffer
Date: Tue, 27 Jun 2023 21:04:22 -0700

[Message part 1 (text/plain, inline)]

> On Jun 27, 2023, at 7:23 PM, Troy Brown <brownts <at> troybrown.dev> wrote:
> 
> This problem seems to manifest with multiple tree-sitter modes.  It
> appears there is an interaction with which-function-mode and tree-sitter
> which causes the buffer to be considered modified either after a narrow
> or widen of the buffer.
> 
> To reproduce this, use a "hello_world.c" as follows:
> 
> --8<---------------cut here---------------start------------->8---
> #include <stdio.h>
> 
> int main (void)
> {
>  printf("Hello, world!\n");
>  return 0;
> }
> --8<---------------cut here---------------end--------------->8---
> 
> Running "emacs -Q" with the corresponding tree-sitter grammar library
> installed.  Move into the main function and narrow-to-defun.  In some
> modes, I've seen this cause the buffer to show as modified, however with
> this example, it seems to occur after widening.
> 
> The following sequence of commands can be used to reproduce the issue:
> 
> C-x C-f ~/hello_world.c
> M-x c-ts-mode
> M-x which-function-mode
> C-x n d
> C-x n w
> 
> At this point, the modeline shows that the buffer is modified, and
> running "M-: (buffer-modified-p)" indicates "t".  As previously
> mentioned, this appears to only happen with tree-sitter modes when
> which-function-mode is enabled in the buffer.
> 
> I then repeated the same but also triggered a backtrace on the first
> change as follows:
> 
> M-: (add-to-list 'first-change-hook #'backtrace)
> 
> With that in place, the following is the generated traceback:
> 
>  backtrace()
>  treesit--font-lock-notifier(((1 . 21)) #<treesit-parser for c>)
>  treesit-buffer-root-node(c)
>  treesit-node-at(68)
>  treesit--things-around(68
> "\\(?:class_specifier\\|enum_specifier\\|function_defi..."
> c-ts-mode--defun-valid-p)
>  treesit-thing-at-point(("\\(?:class_specifier\\|enum_specifier\\|function_defi..."
> . c-ts-mode--defun-valid-p) top-level)
>  treesit-defun-at-point()
>  treesit-add-log-current-defun()
>  c-ts-mode--emacs-current-defun-name()
>  add-log-current-defun()
>  which-function()
>  which-func-update-1(#<window 3 on hello_world.c>)
>  which-func-update()
>  apply(which-func-update nil)
>  timer-event-handler([t 0 0 500000 t which-func-update nil idle 0 nil])

Thanks for the backtrace, it’s very helpful.

Narrowing and widening are transparent to tree-sitter, so when the buffer widens, from tree-sitter’s POV, text are added to the buffer. Which-func calling the tree-sitter current-defund function ultimately leads to tree-sitter calling treesit—font-lock-notifier which puts text properties on the “added” portion of the buffer, which changed the modified status.

treesit—font-lock-notifier should put text properties without changing modified status, like what jit-lock does. This patch should fix it.

Yuan

[silent.patch (application/octet-stream, attachment)]

[Message part 3 (text/plain, inline)]

Message #11 received at 64321 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Yuan Fu <casouri <at> gmail.com>
Cc: brownts <at> troybrown.dev, 64321 <at> debbugs.gnu.org
Subject: Re: bug#64321: 29.0.92; Tree-Sitter/which-function Narrow/Widen
 causes modified buffer
Date: Wed, 28 Jun 2023 15:01:07 +0300

> From: Yuan Fu <casouri <at> gmail.com>
> Date: Tue, 27 Jun 2023 21:04:22 -0700
> Cc: 64321 <at> debbugs.gnu.org,
>  Eli Zaretskii <eliz <at> gnu.org>
> 
> Thanks for the backtrace, it’s very helpful.
> 
> Narrowing and widening are transparent to tree-sitter, so when the buffer widens, from tree-sitter’s POV, text are added to the buffer. Which-func calling the tree-sitter current-defund function ultimately leads to tree-sitter calling treesit—font-lock-notifier which puts text properties on the “added” portion of the buffer, which changed the modified status.
> 
> treesit—font-lock-notifier should put text properties without changing modified status, like what jit-lock does. This patch should fix it.

Thanks.  If this solves the problem, please install in the emacs-29
release branch.

Message #14 received at 64321 <at> debbugs.gnu.org (full text, mbox):

From: Troy Brown <brownts <at> troybrown.dev>
To: Yuan Fu <casouri <at> gmail.com>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 64321 <at> debbugs.gnu.org
Subject: Re: bug#64321: 29.0.92; Tree-Sitter/which-function Narrow/Widen
 causes modified buffer
Date: Wed, 28 Jun 2023 12:25:02 -0400

On Wed, Jun 28, 2023 at 12:04 AM Yuan Fu <casouri <at> gmail.com> wrote:
>
> Narrowing and widening are transparent to tree-sitter, so when the buffer widens, from tree-sitter’s POV, text are added to the buffer. Which-func calling the tree-sitter current-defund function ultimately leads to tree-sitter calling treesit—font-lock-notifier which puts text properties on the “added” portion of the buffer, which changed the modified status.
>
> treesit—font-lock-notifier should put text properties without changing modified status, like what jit-lock does. This patch should fix it.
>

Thanks for the explanation and the supplied patch.  I can confirm that
this patch fixes the issue.

Message #19 received at 64321-done <at> debbugs.gnu.org (full text, mbox):

From: Yuan Fu <casouri <at> gmail.com>
To: Troy Brown <brownts <at> troybrown.dev>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 64321-done <at> debbugs.gnu.org
Subject: Re: bug#64321: 29.0.92; Tree-Sitter/which-function Narrow/Widen
 causes modified buffer
Date: Wed, 28 Jun 2023 13:09:41 -0700

> On Jun 28, 2023, at 9:25 AM, Troy Brown <brownts <at> troybrown.dev> wrote:
> 
> On Wed, Jun 28, 2023 at 12:04 AM Yuan Fu <casouri <at> gmail.com> wrote:
>> 
>> Narrowing and widening are transparent to tree-sitter, so when the buffer widens, from tree-sitter’s POV, text are added to the buffer. Which-func calling the tree-sitter current-defund function ultimately leads to tree-sitter calling treesit—font-lock-notifier which puts text properties on the “added” portion of the buffer, which changed the modified status.
>> 
>> treesit—font-lock-notifier should put text properties without changing modified status, like what jit-lock does. This patch should fix it.
>> 
> 
> Thanks for the explanation and the supplied patch.  I can confirm that
> this patch fixes the issue.

Cool, thanks, pushed.

Yuan

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.