Subject: bug#25187: Initialization of `shell-mode-map' is not safe

From: Lars Ingebrigtsen <[email-masked]>
Date: Wed, 09 Oct 2019 09:24:15 +0200

Alexander Shukaev <[email-masked]> writes:

> consider
>
> (defvar shell-mode-map
>   (let ((map (nconc (make-sparse-keymap) comint-mode-map)))

[...]

> from 'shell.el'.  When somebody decides to customize `comint-mode-map'
> by, for example, first wiping it out and then filling it again,
>
> (with-eval-after-load 'comint	
>   ;; Wipe `comint-mode-map':
>   (setcdr comint-mode-map nil)
>   ;; Fill `comint-mode-map':
>   ...)
>
> then when the `shell' feature is loaded, it will inevitably fail
> because `(lookup-key comint-mode-map [menu-bar completion])' may no
> longer return a keymap but rather nil or a number.

I've now fixed this in Emacs 27 by just removing the nconc from the
shell mode map -- shell-mode is derived from comint-mode, so it
automatically inherits its map.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no