bug#33808:

[Noam Postavsky]

On Wed, 19 Dec 2018 at 19:39, Spenser Truex <struex0@gmail.com> wrote:

> >It isn't possible to bind keys to eshell-mode-map using define-keys like 
> >this:
> >(define-key eshell-mode-map (kbd "<C-f12>") 'other-window)
> >instead a user must use an add-hook
> >(add-hook 'eshell-mode-hook (lambda () (define-key eshell-mode-map (kbd 
> >"<C-f12>") 'other-window)
> >The cause of this can be seen in the patch: eshell-mode-map is set to nil 
> >initially "for the byte compiler," then made buffer local (amusingly 
> >commented out with FIXME: What the hell?!). This patch resolves the issue 
> >and manages to byte compile.
> >
> >What is the benefit to setting it to nil initially with respect to the byte 
> >compiler? The comment above the defvar Also what is the benefit of setting 
> >it locally when it is already defined globally? The new version byte 
> >compiles okay, and the above test cases work.

It's not quite enough, because eshell-mode defines some more keys, so
settings like

(define-key eshell-command-map [(control ?a)] 'my-eshell-bol)

would still get overridden every time eshell starts. And there are
additional key definitions in other eshell files. The definitions set
up by eshell-command seem the most tricky to fix (probably requires
splitting out to a separate keymap):

    (defun eshell-return-exits-minibuffer ()
      (define-key eshell-mode-map [(control ?g)] 'abort-recursive-edit)
      (define-key eshell-mode-map [return] 'exit-minibuffer)
      ...)

    (defun eshell-command (&optional command arg)
       ...
        ;; Enable `eshell-mode' only in this minibuffer.
        (minibuffer-with-setup-hook #'(lambda ()
                                        (eshell-mode)
                                        (eshell-return-exits-minibuffer))


> And my recommended edit (to be put under the "5.4 Key rebinding" heading):
> Eshell currently suffers (version 27) from a bug concerning keybinding such 
> that
> >(define-key eshell-mode-map (kbd "key") 'command)
> cannot be used before the hooks are run.

We don't document bugs in the manual.