bug#64283: 29.0.91; js-mode's mark-defun does not work correctly when functions have a comment on top

[Eli Zaretskii <eliz@gnu.org>]

> From: Yuan Fu <casouri@gmail.com>
> Date: Wed, 28 Jun 2023 13:11:43 -0700
> Cc: Daniel Martín <mardani29@yahoo.es>,
>  Dmitry Gutov <dmitry@gutov.dev>,
>  64283@debbugs.gnu.org
> 
> 
> 
> > On Jun 27, 2023, at 4:01 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> > 
> >> From: Yuan Fu <casouri@gmail.com>
> >> Date: Mon, 26 Jun 2023 18:42:41 -0700
> >> Cc: Eli Zaretskii <eliz@gnu.org>,
> >> Dmitry Gutov <dmitry@gutov.dev>,
> >> 64283@debbugs.gnu.org
> >> 
> >>> 
> >>> What I see is that, after 4489450f37deafb013b1f0fc00c89f0973fda14a,
> >>> defun movement may be subtly broken if beginning-of-defun-function does
> >>> not return non-nil when it found the beginning of a defun.  One of the
> >>> affected modes is js-mode, but who knows if there are more out there.
> >>> 
> >>> We could either revert 4489450f37deafb013b1f0fc00c89f0973fda14a, because
> >>> of the incompatibilities it may cause (Yuan, what is the bug it tries to
> >>> fix?), or maybe adjust js-mode so that it follows the documentation of
> >>> beginning-of-defun-function and returns non-nil when it found the
> >>> beginning of a defun.  I've attached a patch that follows this second
> >>> approach, with some unit tests.  It fixes the bug on my side.
> >>> 
> >>> <0001-Make-js-beginning-of-defun-return-non-nil-on-success.patch>
> >> 
> >> The original problem that I tried to solve is that sometimes end-of-defun-function was called when point isn’t at the beginning of a defun, contrary to what the documentation claims. 
> >> 
> >> I first find out about it when writing defun movement functions for tree-sitter, but if you revert the commit now tree-sitter defun functions wouldn’t break: they have change quite a bit since then and treesit-end-of-defun don’t need to be called at the beginning of the defun anymore.
> > 
> > Thanks.
> > 
> > Do you (or anyone else) see a problem with the alternative proposed by
> > Daniel?  If not, I'd prefer not to revert at this stage, but instead
> > to apply the simple fix Daniel suggested.
> 
> I don’t see any problem :-)

Thanks.  So I've now installed Daniel's patch on the released branch,
and I'm therefore closing this bug.