how to get correct indentation after pressing 'o' in haskell-mode using evil-mode in spacemacs

Question

When using haskell-mode (the Haskell layer) with evil-mode keybindings in spacemacs, the indentation created by pressing the o key is often incorrect.

For instance, imagine I want to write the following Haskell file:

module Foo where

foo :: Int
foo = 3

However, I've only written the following. I haven't yet created the function body for the foo function:

module Foo where

foo :: Int

If I am in insert mode and have my cursor after the "t" in Int and press Enter, the cursor goes to the next line in the first column, directly under the "f" in "foo". Using an underscore (_) for the cursor position, it looks like this:

module Foo where

foo :: Int
_

This is correct.

However, if I am in normal mode and have my cursor anywhere in the line with "foo" and press o, the cursor goes to then next line in the third column. It looks like this:

module Foo where

foo :: Int
  _

This is incorrect. I have to press Backspace twice to put the cursor in the first column before I can start writing the definition of foo.

It seems like indentation rules are getting messed up. Why is the indentation different depending on whether Enter is pressed in insert mode, or o is pressed in normal mode?

How can I get o to indent the same as Enter in insert mode?

---

Here is my current .spacemacs config file. To my knowledge, I don't have any settings set that effect indentation.

edit: Just so my intentions are clear, I do want indentation to be happening when I press either Enter or o. But I want it to be the appropriate indentation. Currently, pressing o results in incorrect indentation.

Answer 1

This appears to be a problem with the interaction between evil and haskell-mode.

Here are some relavent issues on the spacemacs and haskell-mode bug trackers:

• https://github.com/syl20bnr/spacemacs/issues/5010
• https://github.com/haskell/haskell-mode/issues/1265

Per a comment on the issue in the haskell-mode repository, here is a temporary fix for the "o" key. Put the following code into your ~/.spacemacs file:

(defun dotspacemacs/user-config ()
 (with-eval-after-load "haskell-mode"
    ;; This changes the evil "O" and "o" keys for haskell-mode to make sure that
    ;; indentation is done correctly. See
    ;; https://github.com/haskell/haskell-mode/issues/1265#issuecomment-252492026.
    (defun haskell-evil-open-above ()
      (interactive)
      (evil-digit-argument-or-evil-beginning-of-line)
      (haskell-indentation-newline-and-indent)
      (evil-previous-line)
      (haskell-indentation-indent-line)
      (evil-append-line nil))

    (defun haskell-evil-open-below ()
      (interactive)
      (evil-append-line nil)
      (haskell-indentation-newline-and-indent))

    (evil-define-key 'normal haskell-mode-map
      "o" 'haskell-evil-open-below
      "O" 'haskell-evil-open-above)
  )
)