Re: Seeking Advice about refactoring and advice snippet

[Narendra Joshi]

Filipe Silva <filipe.silva@gmail.com> writes:

> Dear good people of the emacs help list,
>
> I have a working snippet that advices both kill-buffer and kill-this-buffer
> to not kill the *scratch* buffer:
>
>       (defun ninrod/scratch-bodyguard (buffer-assassin &rest arguments)
>         (let ((buffer-to-kill (buffer-name (current-buffer))))
>           (if (equal buffer-to-kill "*scratch*")
>               (message "DENIED! don't kill my precious *scratch*!!")
>             (apply buffer-assassin arguments))))
>       (defun ninrod/scratch-protection (buffer-assassin &rest arguments)
>         (let ((buffer-to-kill (car arguments)))
>           (if (equal buffer-to-kill "*scratch*")
>               (message "DENIED! don't kill my precious *scratch*!!")
>             (apply buffer-assassin arguments))))
>       (advice-add #'kill-this-buffer :around #'ninrod/scratch-bodyguard)
>       (advice-add #'kill-buffer :around #'ninrod/scratch-protection)
>
> The problem is that these lines:
>
>       (message "DENIED! don't kill my precious *scratch*!!")
>      (apply buffer-assassin arguments))))
>
> Are repeated in both functions, so I thought that I could apply the DRY
> principle and refactor the snippet to this:
>
>     (defun ninrod--protection (buffer-assassin buffer-to-kill &rest
> arguments)
>       (if (equal buffer-to-kill "*scratch*")
>           (message "DENIED! don't kill my precious *scratch*!!")
>         (apply buffer-assassin arguments)))
>     (defun ninrod/scratch-bodyguard (buffer-assassin &rest arguments)
>       (let ((buffer-to-kill (buffer-name (current-buffer))))
>         (ninrod--protection 'buffer-assassin buffer-to-kill arguments)))
>     (defun ninrod/scratch-protection (buffer-assassin &rest arguments)
>       (let ((buffer-to-kill (car arguments)))
>         (ninrod--protection 'buffer-assassin buffer-to-kill arguments)))
>     (advice-add #'kill-this-buffer :around #'ninrod/scratch-bodyguard)
>     (advice-add #'kill-buffer :around #'ninrod/scratch-protection)
>
> This causes all hell to break loose. Now I can't even close emacs, because
> apparently emacs tries to kill all buffers
> and as I've just tampered with the kill buffer functions, well, it's bad.
> Very bad.

Why don't you call `called-interactively-p' to decide whether you would
want to kill *scratch* or not? No other function should kill *scratch*
anyways except `save-buffers-kill-terminal'. 

> I know I mean well, but I'm must be doing something very stupid. For
> starters, I don't know if I can really pass around
> functions as parameters? So it could be that?
>
> How would you refactor that snippet to apply the dry principle?
>
> thanks in advance,
>
> Filipe.

-- 
Narendra Joshi