fix(treesitter): outdated highlight due to tree with outdated region

Problem:
A region managed by an injected parser may shrink after re-running the
injection query. If the updated region goes out of the range to be
parsed, then the corresponding tree will remain outdated, possibly
retaining the nodes that shouldn't exist anymore. This results in
outdated highlights.

Solution:
Re-parse an invalid tree if its region intersects the range to be
parsed.

2 files changed, 19 insertions, 1 deletions

diff --git a/runtime/lua/vim/treesitter/languagetree.lua b/runtime/lua/vim/treesitter/languagetree.lua
index 0171b416cd..a249a10f47 100644
--- a/runtime/lua/vim/treesitter/languagetree.lua
+++ b/runtime/lua/vim/treesitter/languagetree.lua
@@ -348,7 +348,13 @@ function LanguageTree:_parse_regions(range)
   -- If there are no ranges, set to an empty list
   -- so the included ranges in the parser are cleared.
   for i, ranges in pairs(self:included_regions()) do
-    if not self._valid[i] and intercepts_region(ranges, range) then
+    if
+      not self._valid[i]
+      and (
+        intercepts_region(ranges, range)
+        or (self._trees[i] and intercepts_region(self._trees[i]:included_ranges(false), range))
+      )
+    then
       self._parser:set_included_ranges(ranges)
       local parse_time, tree, tree_changes =
         tcall(self._parser.parse, self._parser, self._trees[i], self._source, true)
diff --git a/test/functional/treesitter/parser_spec.lua b/test/functional/treesitter/parser_spec.lua
index 6f386115ae..94642552d9 100644
--- a/test/functional/treesitter/parser_spec.lua
+++ b/test/functional/treesitter/parser_spec.lua
@@ -693,6 +693,18 @@ int x = INT_MAX;
           {2, 26, 3, 66}  -- READ_STRING(x, y) (char *)read_string((x), (size_t)(y))
                           -- READ_STRING_OK(x, y) (char *)read_string((x), (size_t)(y))
         }, get_ranges())
+
+        helpers.feed('7ggI//<esc>')
+        exec_lua([[parser:parse({6, 7})]])
+        eq("table", exec_lua("return type(parser:children().c)"))
+        eq(2, exec_lua("return #parser:children().c:trees()"))
+        eq({
+          {0, 0, 8, 0},   -- root tree
+          {4, 14, 5, 18}, -- VALUE 123
+                          -- VALUE1 123
+          {2, 26, 3, 66}  -- READ_STRING(x, y) (char *)read_string((x), (size_t)(y))
+                          -- READ_STRING_OK(x, y) (char *)read_string((x), (size_t)(y))
+        }, get_ranges())
       end)
     end)