fix(treesitter): run FileType autocmds in the context of `<abuf>`

Problem: many FileType autocommands assume curbuf is the same as the target
buffer; this can cause &syntax to be restored for the wrong buffer in some cases
when TSHighlighter:destroy is called.

Solution: run nvim_exec_autocmds in the context of the target buffer via
nvim_buf_call.

(cherry picked from commit 3ec63cdab848f903d5e46245b7b2acbf7d5cc829)

1 files changed, 7 insertions, 4 deletions

diff --git a/runtime/lua/vim/treesitter/highlighter.lua b/runtime/lua/vim/treesitter/highlighter.lua
index 766f5f5416..11c9787669 100644
--- a/runtime/lua/vim/treesitter/highlighter.lua
+++ b/runtime/lua/vim/treesitter/highlighter.lua
@@ -182,10 +182,13 @@ function TSHighlighter:destroy()
     vim.b[self.bufnr].ts_highlight = nil
     api.nvim_buf_clear_namespace(self.bufnr, ns, 0, -1)
     if vim.g.syntax_on == 1 then
-      api.nvim_exec_autocmds(
-        'FileType',
-        { group = 'syntaxset', buffer = self.bufnr, modeline = false }
-      )
+      -- FileType autocmds commonly assume curbuf is the target buffer, so nvim_buf_call.
+      api.nvim_buf_call(self.bufnr, function()
+        api.nvim_exec_autocmds(
+          'FileType',
+          { group = 'syntaxset', buffer = self.bufnr, modeline = false }
+        )
+      end)
     end
   end
 end