bug#75122: Treesit support for show-paren-mode

[Dmitry Gutov <dmitry@gutov.dev>]

Hi!

On 26/12/2024 20:31, Juri Linkov wrote:
> For example, ruby-mode used smie-setup that sets
> buffer-local show-paren-data-function.
> 
> This patch does the same for ts-modes: when point at the start/end
> of the sexp list, then both "def" and "end" are highlighted
> as opening and closing nodes:
> 
>    def method
>      puts "This is method definition"
>    end-!-

This is working great, thanks!

Some comments below.

> treesit-show-paren-data.patch
> 
> diff --git a/lisp/treesit.el b/lisp/treesit.el
> index 2616d16e800..a62f63d0d6c 100644
> --- a/lisp/treesit.el
> +++ b/lisp/treesit.el
> @@ -3331,6 +3333,34 @@ treesit-outline-level
>         (setq level (1+ level)))
>       (if (zerop level) 1 level)))
>   
> +;;; Show paren mode
> +
> +(defun treesit-show-paren-data ()
> +  "A function suitable for `show-paren-data-function' (which see)."
> +  (let* ((node (treesit-thing-at (point) 'sexp-list))
> +         (beg (when node (treesit-node-start node)))
> +         (end (when node (treesit-node-end node))))
> +    ;; When after the closing node, try the previous position inside the node

The comment doesn't seem to correspond to the code, or anyway to all the 
cases the code might be handling? I might misunderstand, though.

> +    (unless (or (eq (point) beg) (eq (point) end) (bobp))
> +      (setq node (treesit-thing-at (1- (point)) 'sexp-list)
> +            beg (when node (treesit-node-start node))
> +            end (when node (treesit-node-end node))))

Without getting into more details, it seems the user options 
show-paren-when-point-inside-paren and 
show-paren-when-point-in-periphery are not handled (don't have any effect).

Not sure what's needed for that, but FWIW SMIE's show-paren integration 
seems to react to the value of the first of these options (even though 
it's never referenced directly in smie.el), while the second one is not 
supported there either.