Support for text folding via hs-minor-mode

[mplanchard]

It would be nice if eglot plugged into hs-minor-mode in order to provide code folding functionality, which I think would use the textDocument/foldingRange provider in language servers that support it.

[joaotavora]

That would be nice, I agree.

Unfortunately, last I look, hs-minor-mode didn't have a programmable API for Eglot to plug in the LSP information. This is not uncommon in Emacs land. Practically before starting Eglot, I redesigned Flymake to allow that. You need to bite the bullet and write a a hs2-minor-mode that copies that UI things of hs-minor-mode (which are reasonably good, like isearch integration, etc) but supports the LSP info (or other types of folding info).

Then do the same for all the other stuff: class diagrams, code lens, etc :-D

[mplanchard]

Well that's sad news. Thank you for the response though!

One thing is that treesit-fold works quite well for treesitter-enabled modes. Unfortunately for my main language (rust) treesitter mode currently breaks rustic's run-current-test functionality (brotzeit/rustic#571), so I have to hack it in with:

(use-package treesit-fold
  :ensure (:type git :host github :repo "emacs-tree-sitter/treesit-fold")
  :hook
  (rustic-mode . ((treesit-parser-create 'rust))
  :config
  (global-treesit-fold-mode))

It's a pretty nice package, but I like eglot's general philosophy of using emacs' builtin stuff wherever possible. It's possible that eventually treesitter will be widespread enough that LSP folding won't even be necessary I suppose

[joaotavora]

There's built in tree-sitter integration in core which is completely parallel to this one, including this util.

This is a completely different different situation, albeit analogously sad.

Eglot can have small amounts of integration code for some optional non Emacs-core things when it makes sense, is simple and provides value (examples: yasnippet, company, breadcrumb).

So if "they" write a hypothetical "foldyfoldy.el" mode that is robust and generic enough I could accept a PR for some kind of LSP integration.