feat: add `TSHighlightCapturesUnderCursor` to show hl matches under cursor

lua/nvim-treesitter-playground.lua

@@ -1,5 +1,9 @@
 local M = {}
 
+vim.cmd [[
+  command! TSHighlightCapturesUnderCursor :lua require'nvim-treesitter-playground.hl-info'.show_hl_captures()<cr>
+]]
+
 function M.init()
   require "nvim-treesitter".define_modules {
     playground = {

lua/nvim-treesitter-playground/hl-info.lua

@@ -0,0 +1,35 @@
+local parsers = require "nvim-treesitter.parsers"
+local queries = require'nvim-treesitter.query'
+local ts_utils = require'nvim-treesitter.ts_utils'
+local utils = require'nvim-treesitter.utils'
+
+local hlmap = vim.treesitter.highlighter.hl_map
+
+local M = {}
+
+function M.show_hl_captures()
+  local bufnr = vim.api.nvim_get_current_buf()
+  local lang = parsers.get_buf_lang(bufnr)
+  local hl_captures = vim.tbl_keys(hlmap)
+
+  if not lang then return end
+
+  local row, col = unpack(vim.api.nvim_win_get_cursor(0))
+  row = row - 1
+
+  local matches = {}
+  for m in queries.iter_group_results(bufnr, 'highlights') do
+    for _, c in pairs(hl_captures) do
+      local node = utils.get_at_path(m, c..'.node')
+      if node and ts_utils.is_in_node_range(node, row, col) then
+        table.insert(matches, '@'..c..' -> '..hlmap[c])
+      end
+    end
+  end
+  if #matches == 0 then
+    matches = {"No tree-sitter matches found!"}
+  end
+  vim.lsp.util.open_floating_preview(matches, "treesitter-hl-captures")
+end
+
+return M