From 3e99658ee9e1a2f38d7fe793f64671b027fb7200 Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Tue, 17 Sep 2024 21:17:13 -0700
Subject: [PATCH] Conservative heuristic for tree-sitter parser ranges
 (bug#73324)

* src/treesit.c (treesit_sync_visible_region): If the parser's original
ranges don't overlap with visible region, give it a zero range, rather
than don't set any range.
* test/src/treesit-tests.el (treesit-range-fixup-after-edit): Test new
behavior.

(cherry picked from commit f0daa2f2153a9d250d32ac1261a6fffb30860e31)
---
 src/treesit.c             | 41 +++++++++++++++++----------------------
 test/src/treesit-tests.el |  2 +-
 2 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/src/treesit.c b/src/treesit.c
index 3f5188a0b27..5deaa711aa8 100644
--- a/src/treesit.c
+++ b/src/treesit.c
@@ -1144,31 +1144,26 @@ treesit_sync_visible_region (Lisp_Object parser)
     prev_cons = lisp_ranges;
   }
 
+  /* We are in a weird situation here: none of the previous ranges
+     overlaps with the new visible region.  We don't have any good
+     options, so just throw the towel: just give the parser a zero
+     range.  (Perfect filling!!)   */
+  if (NILP (new_ranges_head))
+    new_ranges_head = Fcons (Fcons (make_fixnum (visible_beg),
+				    make_fixnum (visible_beg)),
+			     Qnil);
+
   XTS_PARSER (parser)->last_set_ranges = new_ranges_head;
 
-  if (NILP (new_ranges_head))
-    {
-      /* We are in a weird situation here: none of the previous ranges
-         overlaps with the new visible region.  We don't have any good
-         options, so just throw the towel: just remove ranges and hope
-         lisp world will soon update with reasonable ranges or just
-         delete this parser.   */
-      bool success;
-      success = ts_parser_set_included_ranges (XTS_PARSER (parser)->parser,
-					       NULL, 0);
-      eassert (success);
-    }
-  else
-    {
-      uint32_t len = 0;
-      TSRange *ts_ranges = treesit_make_ts_ranges (new_ranges_head, parser,
-						   &len);
-      bool success;
-      success = ts_parser_set_included_ranges (XTS_PARSER (parser)->parser,
-					       ts_ranges, len);
-      xfree (ts_ranges);
-      eassert (success);
-    }
+  uint32_t len = 0;
+  TSRange *ts_ranges = NULL;
+  ts_ranges = treesit_make_ts_ranges (new_ranges_head, parser,
+				      &len);
+  bool success;
+  success = ts_parser_set_included_ranges (XTS_PARSER (parser)->parser,
+					   ts_ranges, len);
+  xfree (ts_ranges);
+  eassert (success);
 }
 
 /* (ref:bytepos-range-pitfall) Suppose we have the following buffer
diff --git a/test/src/treesit-tests.el b/test/src/treesit-tests.el
index 4e55d97105e..7eecbdcfa94 100644
--- a/test/src/treesit-tests.el
+++ b/test/src/treesit-tests.el
@@ -743,7 +743,7 @@ visible_end.)"
       ;;              {     } narrow
       (narrow-to-region 1 10)
       (should (equal (treesit-parser-included-ranges parser)
-                     nil)))))
+                     '((1 . 1)))))))
 
 ;;; Multiple language
 
-- 
2.39.2