Prior fix to outline-regexp prevents code folding

[jeffvalk]

outline-regexp was changed in b1ea6de to address #550. The updated regexp deleted one pattern too many.

tl;dr: In order to both fix the issue described in #550 and enable unified comment and code folding using bicycle (or a similar package), outline-regexp should be changed from ;;;;* to ;;;;* \\|(.

bicycle uses outline-regexp to identify code blocks as well as headings. It's just a light wrapper that unifies two built-in folding packages:outline-minor-mode (for comments) and hideshow (for code). Removing the alternate pattern \\|( in outline-regexp prevents bicycle from finding top-level code blocks to fold; it only permits comment folding. The alternate pattern to match top-level code blocks can be added back to outline-regexp without effecting the fix for outline-insert-heading:

;; Preserve the fix to issue #550, while enabling code + comment folding
(setq-local outline-regexp ";;;;* \\|(") 

Originally posted by @jeffvalk in #550 (comment)

[bbatsov]

@jeffvalk Long time, no see!

I'm fine your proposal - feel free to open a PR with the suggested change.

[jeffvalk]

Hey @bbatsov -- hope all is well!

PR coming up...

[jeffvalk]

It's worth mentioning that this change does alter the behavior of outline-promote and outline-demote...though not meaningfully. These functions didn't work correctly in clojure-mode before the change, and they don't after either. 😄 Of course, they also don't work correctly in emacs-lisp-mode, so presumably they're just not something anyone uses in a Lisp.

[bbatsov]

Thanks for all the details and the quick fix! 🙇