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

[Tassilo Horn <tsdh@gnu.org>]

Hongyi Zhao <hongyi.zhao@gmail.com> writes:

>> You mean, the above function changes the value not only in *scratch*
>> but all buffers?
>
> After using the above function, it disables me to check the value of
> `company-backends' when I switch from scratch to other buffers.

What?

> The following message will be triggered when I call `C-h v
> company-backends RET':
>
> Type "q" to restore previous buffer, SPC to scroll help.

Yes, but how does that message hinder you from checking the value of
`company-backends'?

> I'm using company-tabnine package and the following company-backends
> setting:
>
> (setq company-backends '((company-tabnine :separate company-dabbrev
> company-keywords company-files company-ispell company-capf)))
>
> I want to disable the company-ispell backend when I'm in
> emacs-lisp-mode. The following function will do the trick:
>
>   (defun hz/scratch-init ()
>     (with-current-buffer "*scratch*"
>        (setq-local company-backends
>                  '((company-tabnine :separate company-capf
> company-dabbrev company-keywords company-files)))
>   ))
>
> (add-hook 'emacs-lisp-mode-hook #'hz/scratch-init)

Well, your function will always run when `emacs-lisp-mode' or a mode
derived from it, like `lisp-interaction-mode', the major-mode of
*scratch*, is activated.  But it evaluates that code always in *scratch*
which defeats the purpose of disabling company-ispell in every buffer
having `emacs-lisp-mode' as major-mode.

> But as I've posted here, considering that I've also had a definite
> company-backends setting, so I want to remove the company-ispell from
> it programmatically.
>
> I hope this time I've clearly stated my intention.

I guess so.  In certain modes, you would like to have `company-ispell'
removed from the company-tabnine entry of company-backends.  Right?

In that respect, I think a function like

--8<---------------cut here---------------start------------->8---
(defun hz/company-tabnine-remove-company-ispell ()
  (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---

should do the trick.  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.

Bye,
Tassilo