haskell-mode and delete-trailing-whitespace delete content of buffer on save

[vlatkoB]

This is one very, very strange bug.
Happens on GNU Emacs 25.0.50.2 (x86_64-pc-linux-gnu, GTK+ Version 3.10.8), Mint,
but not on GNU Emacs 24.5.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.16.6), Arch

I tested to get most minimal example and here it is.

• Create empty .emacs.d/
• Put init.el:

(package-initialize)
(add-hook 'before-save-hook 'delete-trailing-whitespace)

• Create .emacs.d/elpa dir and copy just haskell-mode in
  (notice haskell-mode is not even required in init.el?)
• Create a .hs file with this content in external editor

....
....redirect 
....
..where
..

• Replace all dots with space in external editor
• Open file in emacs
• Make a change and save the file
• In buffer you see just

    redirect

where is gone.

This can happen in the middle of the file, at the end....
Not all content is deleted. Few lines here, few lines there.

Can anyone test and reproduce this?

[gracjan]

Related #395, #1137.

[vlatkoB]

Are you sure? I think this started to happen few months ago. But occasionally, so I didn't investigate.
I can't believe no one has noticed this before.

[fice-t]

Works as expected (only trailing whitespace deleted) in Emacs 25.0.92.1 -- you can try it here.

[geraldus]

Works as expected (only trailing whitespace deleted) in Emacs 25.0.92.1 -- you can try it here.

Also works for me in Emacs 25.0.91.1

[vlatkoB]

Thanks, I'll upgrade.

[vlatkoB]

Works fine on Emacs 25.1.50.2.

[gracjan]

Nice to hear!