WIP: Getting folding right in Elpy

[galaunay]

PR Summary

Follow (old) feature request #240.

This is an attempt to get nice folding functionalities in Elpy.
It is currently based on hs-minor-mode and heavily inspired from hideshowvis.

Any idea is welcome.

Todo list

Nice folding

• Add an overlay indicating the number of folded lines.
• Add a fringe indicator for folded code.
• Make fringe indicators clickable
• Make folding indicators clickable
• Add fringe indicators to mark the beginning of foldable regions.
• Add fringe indicator for dosctrings ?

Folding docstrings

• Add elpy-folding-toggle-docstrings to hide all the docstrings in the buffer.
• Add elpy-folding-hide-docstring-at-point functions to hide the docstring at point.
• Find a way to show the first docstring line when folding docstring.

Folding comments

• Add a function to hide all comments

DWIM

• Add a function to toggle folding dor the thing (block, docstring, region or comment) at point

Selective folding

• Add elpy-folding-hide-leafs to hide blocks not containing other blocks.

Keybindings

• Add elpy-folding-fold-at-point to fold the active region, the docstring, or the block at point.
• Bind elpy-folding-toggle-at-point (to C-c @ p).
• Bind elpy-folding-toggle-all-docstrings (to C-c @ b).
• Bind elpy-folding-hide-leafs (to C-c @ f).

Other modules incompatibilities

• Put flymake fringe indicators on the right fringe when folding module is activated to avoid fringe indicator overlap.

Others

• Clean and reorganize properly
• Write tests
• Update the documentation

[coveralls]

Coverage decreased (-0.01%) to 92.021% when pulling 08911cb on galaunay:Folding-module into d54e78e on jorgenschaefer:master.

[galaunay]

@jorgenschaefer, before I begin to add tests and documentation, do you have any feedback on this ?

Notably, I am not sure about the keybindings.

Also, It is inspired from here for the leafs hiding and hideshowvis (GPL v2) for the fringe and folding overlays. Not sure if we need to add that as source somewhere.

[jorgenschaefer]

This looks really nice. The only general feedback I have is "are you sure you want to maintain this in the future" – any such larger code base will need maintenance to keep up to date with dependent packages. But other than that, nice.

The key bindings are pretty standard for Emacs. I never liked C-c @, because @ is "right alt + q" on German keyboards, but that's a general problem. Being standard, I think this is fine.

Thank you again for all the great work you do!

[galaunay]

This is a good advice, I will try to keep it simple.
Notably, I am not sure that mouse integration is really necessary.

I'll stick to the standard key bindings then (not really convenient on the french keyboard as well, but I'll rebind that).

[peterewills]

Thanks for building this! 🙏 I've wanted code folding in elpy for a while, and now I'm running your branch and it works well. Would be nice to have this in master!

[galaunay]

Thanks for the feedback.
I kept this PR on the side because of lack of time for proper testing.
Apart of that, I think it is kind of ready to be merged.

So If you are saying it's working, I could give it a quick test and merge it.
Any additional features you would find useful ?

[peterewills]

I've actually been having some weird issues with hs-hide-level. These don't appear when I just use hs-minor-mode on top of the MELPA version of elpy.

Essentially, when I run hs-hide-level 2, it only hides every other block at level 2. This only appears on my (larger & more complicated) work files, which I can't share here, so I'll have to take some time to try and build a minimal example. I made a very simple .py file with a number of levels, and that seems to work fine, so it's something in the way that things get parsed on larger files with docstrings, comments, etc.

I'll pull down this branch at the latest commit and make sure I'm still seeing the bug, and then try to get a minimal example up here.

As for features: The only thing that I want is a function that does "hide all blocks that are either a leaf or at level n", which is like elpy-folding-hide-leafs but won't expand any blocks beyond level n. That's kind of idiosyncratic to my preferences, though. Do you think it's worth including here? I'm thinking I'll write up that functionality and then submit at PR to your branch.

UPDATE: When I run from 533eb6b, I'm not seeing these issues - might have been some weird fluke. However, I am having trouble with elpy-folding-hide-leafs; it throws Lisp nesting exceeds ‘max-lisp-eval-depth’.

[peterewills]

I think this needs to move the pointer back to the beginning of the block here.

Suggested change

	(setq end (1- (point))))
	(setq end (1- (point)))
	(goto-char beg))

[galaunay]

@peterewills I finally managed to finish and merge this PR.

The folding module is deactivated by default, you will have to activate it trough customize or by adding it to elpy-modules.
Hope you will find it useful.

[azzamsa]

instead of having independent module for folding, why don't we just tell user to use external package such us origami https://github.com/gregsexton/origami.el ?