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

[Dmitry Gutov <dmitry@gutov.dev>]

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.