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

[Yuan Fu]

> 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 :-)

Yuan