From 63737e6e73d4a5c3fdd73b54e6e829c17a2c62b3 Mon Sep 17 00:00:00 2001
From: Jaehwang Jung <tomtomjhj@gmail.com>
Date: Mon, 15 Dec 2025 09:01:49 +0900
Subject: [PATCH] fix(treesitter): no injection highlighting on last line
 #36951

Problem:
If the last visible line in a window is not fully displayed, this line
may not get injection highlighting. This happens because line('w$')
actually means the last *completely displayed* line.

Solution:
Use line('w$') + 1 for the botline.

This reverts 4244a967746a1476831d990153d4de85450e54d4
"test: fix failing lsp/utils_spec #36609",
which changed the test based on the wrong behavior.
---
 runtime/lua/vim/treesitter/highlighter.lua | 5 ++++-
 test/functional/plugin/lsp/utils_spec.lua  | 4 ++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/runtime/lua/vim/treesitter/highlighter.lua b/runtime/lua/vim/treesitter/highlighter.lua
index 472b605e38..a5b60acc9b 100644
--- a/runtime/lua/vim/treesitter/highlighter.lua
+++ b/runtime/lua/vim/treesitter/highlighter.lua
@@ -561,7 +561,10 @@ function TSHighlighter._on_start()
       if not buf_ranges[buf] then
         buf_ranges[buf] = {}
       end
-      local topline, botline = vim.fn.line('w0', win) - 1, vim.fn.line('w$', win)
+      local topline = vim.fn.line('w0', win) - 1
+      -- +1 because w$ is the last completely displayed line (w_botline - 1), which may be -1 of the
+      -- last line that is at least partially visible.
+      local botline = vim.fn.line('w$', win) + 1
       table.insert(buf_ranges[buf], { topline, botline })
     end
   end
diff --git a/test/functional/plugin/lsp/utils_spec.lua b/test/functional/plugin/lsp/utils_spec.lua
index 0251fc7b2c..eb76470b6d 100644
--- a/test/functional/plugin/lsp/utils_spec.lua
+++ b/test/functional/plugin/lsp/utils_spec.lua
@@ -357,7 +357,7 @@ describe('vim.lsp.util', function()
     screen:expect([[
       ^                                                     |
       ┌─────────┐{1:                                          }|
-      │{101:local foo}│{1:                                          }|
+      │{100:local}{101: }{102:foo}│{1:                                          }|
       └─────────┘{1:                                          }|
       {1:~                                                    }|*9
                                                            |
@@ -384,7 +384,7 @@ describe('vim.lsp.util', function()
     screen:expect([[
       ^                                                     |
       ┌─────────┐{1:                                          }|
-      │{101:local foo}│{1:                                          }|
+      │{100:local}{101: }{102:foo}│{1:                                          }|
       └─────────┘{1:                                          }|
       {1:~                                                    }|*9
                                                            |