M-x haskell-mode-stylish-buffer to call stylish-haskell on the current buffer.
To use it on your Emacs before every save, you first need
haskell-mode-save-buffer. It is recommended to rebind
C-x C-s in haskell-mode to this. Add the following in your
(define-key haskell-mode-map (kbd "C-x C-s") 'haskell-mode-save-buffer)
To enable Stylish Haskell, pop the following somewhere in your Emacs configuration:
(setq haskell-stylish-on-save t)
Or in your custom set variables:
(custom-set-variables '(haskell-stylish-on-save t))
Or you can
M-x customize-group haskell and pretend none of this exists!