How to remap a function to another in Emacs? - emacs

Question

In coffee-mode RET is bound to coffee-newline-and-indent which works fine.
I also use evil-mode to have Vim emulation. evil-mode uses the standard newline-and-indent so the indentation is not correct for some vim commands such as o or O.
What would be the best way to rebind newline-and-indent to coffee-newline-and-indent ?
I'm still a newbie in ELisp and tried the line below but it doesn't work.
(add-hook 'coffee-mode-hook
(lambda ()
(setq newline-and-indent '(funcall coffee-newline-and-indent))))

Answer 1

Here's my attempt. It should work, but I don't really like it.
(add-hook
'coffee-mode-hook
(lambda ()
(defalias
'newline-and-indent
(lambda()
(interactive)
(if (eq major-mode 'coffee-mode)
(coffee-newline-and-indent)
(delete-horizontal-space t)
(newline)
(indent-according-to-mode))))))
I wish I could use something more elegant that just copying the source
of newline-and-indent, but make-variable-buffer-local doesn't work for this case,
and I couldn't get a deep copy for symbol-function either.
I'd be happy to see a better method.

Answer 2

The standard way to accomplish what you seem to be asking for is
(autoload 'coffee-newline-and-indent "coffee-mode") ; (or whatever)
(define-key evil-mode-map (kbd "RET") 'coffee-newline-and-indent)
EDIT: to enable coffee-newline-and-indent only in coffee-mode:
(define-key evil-mode-map (kbd "RET")
(lambda ()
(interactive)
(if (eq major-mode 'coffee-mode)
(coffee-newline-and-indent)
(newline-and-indent))))

Answer 3

Try the following:
(define-key evil-mode-map (kbd "RET") nil)
I know it looks overly simple, but if evil-mode works the way I think it does then it should work.
This will wipe the ret key from your evil-mode-map, which will let the binding of coffee-mode-map shine through.
In non-coffee buffers, the ret key will still work, because it's still bind in the global map.

Answer 4

I found the solution.
Evil-mode actually uses coffee-indent-line. The problem comes from coffee-indent-line which doesn't indent correctly. Evil-mode works correctly after patching it to behave like coffee-newline-and-indent:
(defadvice coffee-indent-line (after wants-indent activate)
(let ((tabs-needed (- (/ (coffee-previous-indent) coffee-tab-width) 1)))
(when (> tabs-needed 0)
(insert-tab tabs-needed)))
(when(coffee-line-wants-indent)
(insert-tab)))

Answer 5

if you want to remap a func, but only if some major mode is active
- create a func which defines an alias
and run the func (A)
- another func (B) calls (A)
- finally, a major mode can advice the func A to set the correct
func. It has to test major mode.
let's say A is define-my-indent-f
then it says (defalias my-indent 'newline-and-indent)
the func b runs A then run command my-indent.
finally coffe mode does defadice A to say
(if eq major mode coffee defalais my-indent 'coffe-newline-and-indent)
of course this is super heavy to define, but then
- each major mode can add its piece
- only loaded major mode will advice