highlight-expression-with-click.el

(require 'tree-sitter)
(require 'seq)
(require 'cl-lib)

;;TODO: mapp grammar for other langauges and complete grammar for haskell
(setq modes-mapping '((haskell-mode . (exp_apply exp_infix exp_in exp_cond exp_literal))))

(defun expr-at-point ()
  "Highlight expression at point."
  (interactive)
  ;; remove all previous applied overlays
  (remove-overlays (point-min) (point-max) 'face 'tree-sitter-query-match)
  (when-let* ((node (get-text-node-at-point))
              (overlay (make-overlay (tsc-node-start-position node) (tsc-node-end-position node))))
    ;; Ensure the overlay is deleted when it becomes empty.
    (overlay-put overlay 'evaporate t)
    ;; defined in tsc package
    (overlay-put overlay 'face 'tree-sitter-query-match)))

(defun get-text-node-at-point ()
  "Get text node at point using predefined major mode options."
  (let ((types (alist-get major-mode modes-mapping)))
    (seq-some (lambda (x) (tree-sitter-node-at-pos x (point) t)) types)))

(defun mouse-click-handler (event)
  "Run `expr-at-point' using information of EVENT."
  (interactive "e")
  (save-excursion
    (goto-char (posn-point (event-start event)))
    (expr-at-point)))

(global-set-key [mouse-1] #'mouse-click-handler)