Stepped indentation with haskell-indentation-mode and yasnippets

[eigengrau]

When haskell-indent-mode is active, using ghc-insert-template-or-signature to expand a class instance stub, or expanding from a yasnippet keyword, produces odd indentation. It looks as if the layout rule is applied after every line.

instance Num Token where
    x + y = _body
            x - y = _body
                    x * y = _body
                            …

[eigengrau]

I have noticed that when using haskell-indentation-mode instead, ghc-insert-template-or-signature yields the correct results, while yasnippet expansion (courtesy of haskell-snippets) still yields the stepping.

[gracjan]

Haskell-indent-mode is no longer supported I'm afraid.

[eigengrau]

Ah, okay, thanks. So this is for haskell-indentation-mode (no electric indent mode active). Yasnippets issue?

x = case var of
  cond -> value

          otherwise -> other

[gracjan]

yassnippets have their own github issues page, I guess it is better to report there.

[lukehoersten]

I'm seeing the same problem as you with haskell-indentation-mode and haskell-snippets.

Yasnippets really has no control over how the buffer treats indentation as the snippet goes in. All the haskell-snippets go in with spaces for indentation as well so I don't think tab characters are causing indentation to run or anything. You can see how straightforward the snippet is here:
https://github.com/haskell/haskell-snippets/blob/master/snippets/haskell-mode/case

My feeling at this point is that it's something to do with haskell-indentation-mode or yasnippet itself outside of the control of the snippet. In fact this used to work fine so my suspicion is that it's a regression.

[npostavs]

Hi, yasnippet dev here. It looks like there exists a case snippet in yasnippet-snippets which is where the snippet collection comes from in a typical install (MELPA). The yasnippet-snippets one lacks the # expand-env: ((yas-indent-line 'fixed)) which haskell-mode's has. Perhaps this is the reason for the problem?

Regardless, I suggest you ask @AndreaCrotti to update the haskell snippets in his repository, or else remove them entirely.

[AndreaCrotti]

Hi @npostavs yes well I can definitively update them, but just to be clear only the snippets in haskell mode that would have indentation need that right?
I think it's only class and case from what I can see so far, is that right?

[AndreaCrotti]

I tried and this works

AndreaCrotti/yasnippet-snippets#107

if that's all we need I'll merge that @npostavs @eigengrau
If anyone else could confirm that snippet works fine it would be great

[xuzhao9]

Still have this problem on haskell-mode-20160128.621 and yasnippet-20160122.1056.
My snippet that triggers this problem see here:
https://pastebin.com/DQLzy2rg

[gracjan]

@xuzhao9: Can you help us finding the root cause of this? Please do:

• restart Emacs
• try yassnippet with haskell-indent instead of haskell-indentation
• disable electric-indent-mode

Please report back what you found, thanks.

[xuzhao9]

Hello, I have restarted emacs.

1. The result of using haskell-indent instead of haskell-indentation is slightly different but still problematic.
   See: http://pastebin.com/pAZnPiw7.
2. Disabling electrc-indent-mode does not help either.

My emacs version is 24.5.1.

[jarmitage]

Hi,

I am also having this problem:

1. Type snippet shortcut
2. Use TAB or RET to expand
3. Haskell code indents

Any ideas of even a quick workaround?

Thanks

[npostavs]

Is this still with the case snippet or other snippets? Perhaps it's best to disable yasnippet auto indenting for haskell mode:

(defun set-yasnippet-fixed-indent ()
  (setq-local yas-indent-line 'fixed))
(add-hook 'haskell-mode-hook #'set-yasnippet-fixed-indent) ; EDIT: had the wrong hook name

[jarmitage]

This is with other snippets. That doesn't seem to work either I'm afraid. Currently I am just disabling haskell-indentation-mode (manually, see: #90)

[npostavs]

This is with other snippets.

Please show a concrete example so that others might have a chance of replicating your problem.

[jarmitage]

It's slightly complex, as I'm using Tidal which is built on Haskell and uses the same indentation mode.

An example snippet for Tidal would be:

# -*- mode: snippet -*-
# name: sustain 
# key: #s
# --
# sustain "$0"

And an example of using this in Tidal would be:

d1 $ sound "bd" # sustain "0.5"

or

d1 $ sound "bd"
    # sustain "0.5"

In either case, currently using the #s snippet causes indentation after triggering.

If you want I can try to see if the problem is exactly the same in plain haskell-mode, but you'll have to provide an example as I'm not a Haskell programmer.

[npostavs]

I'm neither a Haskell nor Tidal programmer :)

I had the wrong hook variable name in my suggestion above, edited now. After fixing that problem, it seems to work.

Started emacs with emacs -Q -L haskell-mode -L Tidal -L yasnippet -l haskell -l tidal.el -l yasnippet.el -f yas-global-mode

Evaluate

(progn (defun set-yasnippet-fixed-indent ()
         (setq-local yas-indent-line 'fixed))
       (add-hook 'haskell-mode-hook #'set-yasnippet-fixed-indent))

M-x tidal-mode
C-u M-x yas-new-snippet
Put

# -*- mode: snippet -*-
# name: sustain 
# key: #s
# --
# sustain "$0"

C-c C-l RET to load snippet
C-x b RET switch back to *scratch*
M-< C-w delete original text
Put

d1 $ sound "bd"
#s

Hit <tab>, now I have

d1 $ sound "bd"
# sustain ""

[jarmitage]

Wow amazing, can't wait to try this later! Thank you

[jarmitage]

That works for the case where the snippet is on a new line, but not when the snippet is in an existing line, which is much more common in Tidal. Any ideas for extending your function to include snippets in existing lines?

[npostavs]

I tried d1 $ sound "bd" #s and pressing <tab> gave me d1 $ sound "bd" # sustain "" with no change to indentation. Can you give an example where it doesn't work?

[jarmitage]

That's strange. Are you working with haskell-indentation-mode enabled too? I will have another go and check back here...

[npostavs]

Are you working with haskell-indentation-mode enabled too?

Yes, according to <f1> v haskell-indentation-mode RET (this is all using same emacs -Q -L haskell-mode -L Tidal ... setup detailed above).

[gracjan]

Looks to me that this issue is more about yasnippets than haskell-indentation. Therefore closing.

Thanks for participation!