Electric-pair-mode causes emacs to hang when writing comments in haskell-mode

Question

Electric-pair-mode causes emacs to hang when writing comments in haskell-mode

Closed this issue 5 years ago · 9 comments

Deleted user commented 7 years ago

Here's how to hang* emacs 10 out of 10 times in haskell mode:

Enter haskell-mode and electric-pair-mode
Enter a block comment

{--}

Try to insert hard brackets inside the comment, as such:

{-[]-}

This will hang* emacs but wont produce a error in ~/.xsession-errors

This previously said crash, but hang is more accurate (sorry :c)

Answer 1 · 2018-04-07T04:55:43.000Z

I can't reproduce this on a recent Emacs with the latest haskell-mode. Does it perhaps depend on the contents of the rest of the file?

Answer 2 · 2018-11-04T18:14:30.000Z

I get exactly the same results! Disabling electric-pair-mode will prevent the hanging.

Answer 3 · 2018-11-04T21:05:02.000Z

I get exactly the same results! Disabling electric-pair-mode will prevent the crash.

Could you provide reproduction instructions perhaps, including Emacs version?

Answer 4 · 2018-11-04T21:17:28.000Z

Sure! :)
Emacs ver: GNU Emacs 25.3.2 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
Haskell-mode ver: 20180917.923

the configs are pretty.. well nothing special really.
I do:

(use-package haskell-mode
  :ensure t)

electric-pair-mode is activated by default in general in my settings.

Answer 5 · 2018-11-04T22:29:05.000Z

Thanks. I can reproduce this in Emacs 25.1-25.3 inclusive, but not in 26.1 or later versions. So my feeling is that it's an Emacs bug. Unsure how much effort to put into working around this for that older version. There's a configurable inhibit function for electric pairing which could conceivably be used to short-cut this problem selectively in problematic Emacs versions.

Answer 6 · 2018-11-04T23:45:57.000Z

Yes, this might be exactly how it is. I currently have that version on my WSL and I'm not sure if I can upgrade my Emacs there. If anyone has info on if it is possible to run newer versions there I think I'd give it a go. Otherwise, I'm fine by just solving it by configuring electric-pairing differently when Haskell-mode is on for now :) Thanks for the sanity-check, though!

Answer 7 · 2018-11-05T01:35:55.000Z

A selective workaround is the following:

(when (eq 25 emacs-major-version)
  (defun sanityinc/inhibit-bracket-inside-comment-or-default (ch)
    (or (nth 4 (syntax-ppss))
        (funcall #'electric-pair-default-inhibit ch)))
  (add-hook 'haskell-mode-hook
            (lambda ()
              (setq-local electric-pair-inhibit-predicate 'sanityinc/inhibit-bracket-inside-comment-or-default))))

This disables pairing only inside comments, where the problems happen. Quotes don't cause this problem, btw: just (, [, {.

Answer 8 · 2018-11-07T06:26:03.000Z

Thanks for the good advice. :) Here's my variation on purcell's theme with use-package, for those who might be interested:

(use-package haskell-mode
  :ensure t
  :init (when (eq 25 emacs-major-version)
          (defun sanityinc/inhibit-brakcet-inside-comment-or-default (ch)
            (or (nth 4 (syntax-pss))
                (funcall #'electric-pair-default-inhibit ch))))
  :hook (haskell-mode . (lambda ()
                          (setq-local
                           electric-pair-inhibit-predicate
                           'sanityinc/inhibit-brakcet-inside-comment-or-default))))

Answer 9 · 2019-11-10T21:49:26.000Z

I've included this workaround in haskell-mode directly now.