Re: Word completion in text modes

[Eli Zaretskii <eliz@gnu.org>]

> From: Eshel Yaron <me@eshelyaron.com>
> Cc: emacs-devel@gnu.org
> Date: Sat, 18 Nov 2023 16:53:28 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> It _is_ bound to `C-M-i` in `text-mode`, that's actually even mentioned
> >> in several places in the Emacs manual, e.g. in "(emacs) Text Mode":
> >>
> >>     Text mode binds ‘M-<TAB>’ to ‘ispell-complete-word’.
> >
> > I tried that in mail-mode and didn't see it bound.  But that's because
> > mail-mode binds C-M-i to another command.  Which IMO is a sign of a
> > problem we need to fix: it makes no sense to have a completion command
> > bound in Text mode but not in _all_ of its descendants.
> 
> Yes, `C-M-i` is bound to `completion-at-point` in `mail-mode-map`, which
> is exactly the binding I'm proposing for the parent, `text-mode`, no?

I was talking about ispell-complete-word, not about C-M-i.

And if you turn on Flyspell mode, as many users do in Mail buffers,
C-M-i gets rebound yet again.

> > In any case, back to the original issue: what you say about rebinding
> > ispell-complete-word can only be a problem if the new completion is
> > incompatible with ispell-complete-word.  So we should make sure it is
> > NOT incompatible.  Then the problem would not exist.
> 
> The way I see it `ispell-complete-word` predates `completion-at-point`,
> and in terms of functionality the latter subsumes the former.

Not according to your own description, below.

> `ispell-complete-word` reuses the spell correction UI of `ispell-word`
> for word completion.  That's something that I wouldn't necessarily try
> to port over to `completion-at-point` for compatibility sake, as we now
> have various proper completion (not spell correction) interfaces that
> were not available when `ispell-complete-word` came about.

If we don't preserve that UI, we will be making an incompatible
change, which from my POV is undesirable.  It doesn't matter whether
we like or dislike the ispell UI for this: compatibility means just
that.  We could make the old UI an opt-in behavior, but tossing it
altogether is not something I'd welcome.

> Either way it'd be compatible in the sense that you get the same
> completions, and `ispell-complete-word` wouldn't go anywhere so
> users could rebind it if they really want to.

That is not compatibility in my book, sorry.  We should actually offer
a very similar or identical UI.