From 63f8a838eccf201d6290d0dc8f83881f41785afb Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Tue, 15 Nov 2022 02:30:50 -0800
Subject: [PATCH] Make tree-sitter fontification automatically update

Now nodes that are affected and changed during re-parse will be
correctly refontified.  Nodes can change even if it corresponding text
wasn't edited: additional text can complete the parse tree and resolve
error nodes, for example.

* lisp/progmodes/python.el (python-mode): Create Python parser before
calling treesit-major-mode-setup.
* lisp/treesit.el (treesit--font-lock-notifier): New function.
(treesit-major-mode-setup): Register fontifier with every existing
parser.
---
 lisp/progmodes/python.el |  1 +
 lisp/treesit.el          | 18 ++++++++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 7919484e096..ad4665eb19c 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -6548,6 +6548,7 @@ Add import for undefined name `%s' (empty to skip): "
   (cond
    ;; Tree-sitter.
    ((treesit-ready-p 'python-mode 'python)
+    (treesit-parser-create 'python)
     (setq-local treesit-font-lock-feature-list
                 '(( comment string function-name class-name)
                   ( keyword builtin constant type)
diff --git a/lisp/treesit.el b/lisp/treesit.el
index 31a31dda417..ef43391080c 100644
--- a/lisp/treesit.el
+++ b/lisp/treesit.el
@@ -838,6 +838,14 @@ If LOUDLY is non-nil, display some debugging information."
                              face (treesit-node-type node)))))))))))
   `(jit-lock-bounds ,start . ,end))
 
+(defun treesit--font-lock-notifier (ranges parser)
+  "Ensures updated parts of the parse-tree is refontified.
+RANGES is a list of (BEG . END) ranges, PARSER is the tree-sitter
+parser notifying of the change."
+  (with-current-buffer (treesit-parser-buffer parser)
+    (dolist (range ranges)
+      (put-text-property (car range) (cdr range) 'fontified nil))))
+
 ;;; Indent
 
 (define-error 'treesit-indent-error
@@ -1527,7 +1535,10 @@ enable `font-lock-mode'.
 If `treesit-simple-indent-rules' is non-nil, setup indentation.
 
 If `treesit-defun-type-regexp' is non-nil, setup
-`beginning/end-of-defun' functions."
+`beginning/end-of-defun' functions.
+
+Make sure necessary parsers are created for the current buffer
+before calling this function."
   ;; Font-lock.
   (when treesit-font-lock-settings
     ;; `font-lock-mode' wouldn't setup properly if
@@ -1537,7 +1548,10 @@ If `treesit-defun-type-regexp' is non-nil, setup
                    (font-lock-fontify-syntactically-function
                     . treesit-font-lock-fontify-region)))
     (font-lock-mode 1)
-    (treesit-font-lock-recompute-features))
+    (treesit-font-lock-recompute-features)
+    (dolist (parser (treesit-parser-list))
+      (treesit-parser-add-notifier
+       parser #'treesit--font-lock-notifier)))
   ;; Indent.
   (when treesit-simple-indent-rules
     (setq-local treesit-simple-indent-rules
-- 
2.39.2