bug#73900: 30.0.91; auto-fill adds extra space in js-ts-mode

[Yuan Fu <casouri@gmail.com>]

> On Oct 29, 2024, at 5:39 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Tue, 29 Oct 2024 00:33:05 -0700
>> Cc: Eli Zaretskii <eliz@gnu.org>,
>> Michael Kleehammer <michael@kleehammer.com>,
>> 73900@debbugs.gnu.org
>> 
>> 
>> 
>>> On Oct 27, 2024, at 8:10 PM, Dmitry Gutov <dmitry@gutov.dev> wrote:
>>> 
>>> On 27/10/2024 12:55, Eli Zaretskii wrote:
>>>>> From: Michael Kleehammer<michael@kleehammer.com>
>>>>> Date: Sat, 19 Oct 2024 22:46:55 -0500
>>>>> 
>>>>> In Emacs 30, js-ts-mode auto-fill chooses an incorrect prefix when
>>>>> wrapping comments.
>>>>> 
>>>>> 1) emacs -Q
>>>>> 
>>>>> 2) In the scratch buffer:
>>>>>   a) M-x js-ts-mode
>>>>>   b) M-x auto-fill-mode
>>>>>   c) M-x erase-buffer
>>>>>   3) Paste in a long JS comment:
>>>>> 
>>>>>   // This buffer is for text that is not saved, and for Lisp evaluation.  To create a file, visit it
>>>>> 
>>>>> 4) At end of line, press <Space>.
>>>>> 
>>>>> The text wraps like so:
>>>>> 
>>>>>   // This buffer is for text that is not saved, and for Lisp evaluation.
>>>>>   //   To create a file, visit it
>>>>> 
>>>>> In previous versions, it would wrap like so:
>>>>> 
>>>>>   // This buffer is for text that is not saved, and for Lisp evaluation.
>>>>>   // To create a file, visit it
>>>> Adding people who know about js-ts-mode, in the hope they will have
>>>> comments or suggestions.
>>> 
>>> I suppose the answer is somewhere around the fact that we have both normal-auto-fill-function and fill-paragraph-function, and that js-ts-mode (through c-ts-common-comment-setup) only configures the latter, while js-mode (in js--mode-setup) has settings for both.
>>> 
>>> Not sure why the default do-auto-fill doesn't skip over the space, though.
>> 
>> Ok, so the actually difference is in comment-line-break-function, which auto-fill-mode uses to insert line break. In js-mode, it’s set to c-indent-new-comment-line, which deletes the whitespace; in tree-sitter mode, it’s c-ts-common-comment-indent-new-line, which doesn’t. I fixed c-ts-common-comment-indent-new-line to do the same thing as c-indent-new-comment-line.
>> 
>> However, I did the foolish thing of pushing to master. Should I cherry pick the commit into emacs-30?
> 
> Yes, please.  Just first fix the problem I reported a few minutes ago.
> 
>> Would that create any merge conflict down the line?
> 
> No.

Ok, thanks. I fixed that problem and pushed both to emacs-30.

Yuan