bug#28003: 26.0.50; Auto fill broken in Message mode

[Stephen Berman]

On Wed, 09 Aug 2017 06:37:42 -0600 Tom Tromey <tom@tromey.com> wrote:

>>>>>> "Stephen" == Stephen Berman <stephen.berman@gmx.net> writes:
>
> Stephen> On Wed, 09 Aug 2017 12:33:01 +0900 Katsumi Yamaoka <yamaoka@jpl.org> 
> wrote:
>>> On Mon, 07 Aug 2017 21:56:42 +0200, Stephen Berman wrote:
>>>> This change:
>>> [...]
>>>> broke auto filling in Message mode; the breakage is due specifically to
>>>> this change in comment-indent-new-line:
>>> 
>>> This will probably be no more than a workaround, though.
>>> 
>>> --- message.el~     2017-08-08 22:08:28.694840400 +0000
>>> +++ message.el      2017-08-09 03:30:33.407170200 +0000
>>> @@ -3451,7 +3451,7 @@
>>> (defun message-do-auto-fill ()
>>> "Like `do-auto-fill', but don't fill in message header."
>>> (unless (message-point-in-header-p)
>>> -    (do-auto-fill)))
>>> +    (let ((comment-start nil)) (do-auto-fill))))
>>> 
>>> (defun message-insert-signature (&optional force)
>>> "Insert a signature.  See documentation for variable `message-signature'."
>
> Stephen> This change doesn't fix the problem.  I don't know what the 
> motivation
> Stephen> for the change that caused this problem was, so I don't know how to 
> fix
> Stephen> it; cc'ing Tom Tromey, who made the change.
>
> I've been discussing this off-list with another person who ran into this
> problem, but I haven't managed to reproduce it myself.

Strange; you did try the recipe of my OP?  That shows the problem for me
every time (with emacs -Q and well as with my initializations).  But see
below...

> I suspect the newcomment.el change is incorrect and should be reverted.
> Could you try that?  The other changes should, I think, remain in place 
> though.

Yes, restoring the variable comment-auto-fill-only-comments in
comment-indent-new-line restores auto-filling in Message mode.

> The basic idea of my patch is to make comment-auto-fill-only-comments
> work properly.  Without it, setting comment-auto-fill-only-comments and
> enabling auto-fill in js-mode will cause auto-filling even when typing a
> long line of code, which is clearly incorrect.

I haven't looked at js-mode, but it seems strange that setting
comment-auto-fill-only-comments to t there does auto-filling of
non-commented lines...

This prompted me to look closer at Katsumi Yamaoka's patch above, and it
turns out that message-do-auto-fill is not being called, although it is
the value of normal-auto-fill-function in the Message mode buffer I'm
typing in right now; instead, the default value do-auto-fill is called.
When you try my recipe is message-do-auto-fill being used?  That may
explain why you can't reproduce the problem.  I have no idea why
message-do-auto-fill isn't being called here...

Steve Berman