How to turn off electric-indent-mode for specific Major mode?

Question

I have few Major modes (like: Yaml and NXML) that I don't want electric-indent-mode (I want it for C like languages) but I'm unable to turn if off. To enable I have:

(electric-indent-mode 1)

from documentation (for variable electric-indent-mode)

Non-nil if Electric-Indent mode is enabled. See the command electric-indent-mode' for a description of this minor mode. Setting this variable directly does not take effect; either customize it (see the info nodeEasy Customization') or call the function `electric-indent-mode'.

and for a function

Toggle on-the-fly reindentation (Electric Indent mode). With a prefix argument ARG, enable Electric Indent mode if ARG is positive, and disable it otherwise. If called from Lisp, enable the mode if ARG is omitted or nil.

so I try to turn it off in a hook:

(add-hook 'yaml-mode-hook (lambda ()                        
                             (electric-indent-mode -1)))

(Actualy I use after-change-major-mode-hook and check (memql major-mode '(yaml-mode python-mode nxml-mode)) where I can add more modes to the list).

But it don't work, I've also try:

(set (make-local-variable 'electric-indent-mode) nil)

No joy. But it work when I eval (electric-indent-mode -1) from .emacs files.

Answer 1

With a recent Emacs (probably Emacs snapshot only) you can use electric-indent-local-mode, e.g.:

(add-hook 'yaml-mode-hook (lambda () (electric-indent-local-mode -1)))

If your Emacs lacks this function, you can still sort of disable the mode via electric-indent-functions, e.g.

(add-hook 'yaml-mode-hook
          (lambda ()
             (add-hook 'electric-indent-functions
                            (lambda () 'no-indent) nil 'local)))

And in either case, you may probably want to restore C-j, via

(add-hook 'yaml-mode-hook 
          (lambda () (local-set-key (kbd "C-j") #'newline-and-indent)))

Answer 2

electric-indent-mode will be enabled by default in 24.4. To turn it off locally, you will be able to use electric-indent-local-mode as mentioned by lunaryorn. But to turn it off locally in 24.3, you can do:

(add-hook 'foo-mode-hook
          (lambda () (set (make-local-variable 'electric-indent-mode) nil)))

You mentioned that the first form didn't work for you, but it should (i.e. if it doesn't, it's because of the some other problem).

Answer 3

At least on emacs 24.3 you cannot disable electric indent mode locally, since it is a global-mode. Anyways the issue with yaml-mode is that the electric-indent functionality is built into it i.e. it will be enabled even without electric-indent-mode. The package does not provide a way to turn this behaviour off, maybe you should file an issue on its github repo.

Try this to disable the electric-indent functionality in yaml-mode

(define-key yaml-mode-map "|" nil)
(define-key yaml-mode-map ">" nil)
(define-key yaml-mode-map "-" nil)
(define-key yaml-mode-map "." nil)
(define-key yaml-mode-map [backspace] nil)

To restore the electric-indent behaviour afterwards, you can do

(define-key yaml-mode-map "|" 'yaml-electric-bar-and-angle)
(define-key yaml-mode-map ">" 'yaml-electric-bar-and-angle)
(define-key yaml-mode-map "-" 'yaml-electric-dash-and-dot)
(define-key yaml-mode-map "." 'yaml-electric-dash-and-dot)
(define-key yaml-mode-map [backspace] 'yaml-electric-backspace)