Re: Add/remove an element into/from a cons.

[Hongyi Zhao <hongyi.zhao@gmail.com>]

On Thu, Oct 28, 2021 at 2:52 AM Tassilo Horn <tsdh@gnu.org> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> >> > However, I can imagine that you might not be able to use it in
> >> > major-mode hooks such as `emacs-lisp-mode' due to ordering issues,
> >> > i.e., I can easily imagine that `company-mode' (and this
> >> > company-tabnine thingy) is initialized *after* the major-mode hook
> >> > has run because usually, you activate minor-modes in major-mode
> >> > hooks.  In that case you would try to remove before the
> >> > company-tabnine entry has been added to company-backends.
> >> >
> >> > That's all just guesswork since I don't use company.
> >>
> >> [...]
> >
> > I also tried the following snippet, but still failed:
> >
> > (defun hz/company-tabnine-remove-company-ispell ()
> >     (make-local-variable 'company-backends)
> >     (cond
> >      (
> >       (derived-mode-p 'emacs-lisp-mode)
> >       (setf (alist-get 'company-tabnine company-backends)
> >             (remove 'company-ispell (alist-get 'company-tabnine
> > company-backends))))
> >      (
> >       t
> >       (setf (alist-get 'company-tabnine company-backends)
> >         (append (alist-get 'company-tabnine company-backends)
> >             '(company-ispell))))))
> >
> > (add-hook 'emacs-startup-hook #'hz/company-tabnine-remove-company-ispell)
>
> The first cond clause looks good but I don't see why you need the
> t-clause?  Isn't the thing that company-ispell is part of the default
> value of the company-tabnine entry of company-backends?  If that's the
> case, you want to make company-backends buffer-local and remove it in
> emacs-lisp-mode and derived modes but there is no need to add it again
> otherwise because the default value won't be altered.  So that'd be:
>
> --8<---------------cut here---------------start------------->8---
> (defun hz/company-tabnine-remove-company-ispell ()
>   (when (derived-mode-p 'emacs-lisp-mode)
>     (make-local-variable 'company-backends))
>     (setf (alist-get 'company-tabnine company-backends)
>             (remove 'company-ispell
>                     (alist-get 'company-tabnine company-backends))))
> --8<---------------cut here---------------end--------------->8---

A very strange result based on the above code is that it will remove
company-ispell in all modes, say, LaTeX mode. But the following code
works as expected:

(defun hz/company-tabnine-remove-company-ispell ()
    (when (derived-mode-p 'emacs-lisp-mode)
      (setq-local company-backends
          '((company-tabnine :separate company-capf company-dabbrev
company-keywords company-files))
          )))


> But most importantly, `emacs-startup-hook' is not the one you want.
> That runs once after emacs has loaded the init file.  I'm even not sure
> what buffer is current then.  I guess the most logical hook is
> `company-mode-hook'.
>
>   (add-hook 'company-mode-hook
>             #'hz/company-tabnine-remove-company-ispell)

This works. Thank you for pointing this out.

> Or maybe there is also some `company-tabnine-*-hook' that runs after
> that package has done its setup in a buffer?

Unfortunately, it doesn't supply these type hooks.

HZ