Add highlight tests

tests/query/highlights/cpp/test.cpp

@@ -0,0 +1,17 @@
+#include <iostream>
+#include <cstdlib>
+//    ^ include
+//       ^ string
+
+auto main( int argc, char** argv ) -> int
+      //       ^ parameter
+      //    ^ type 
+      //    ^ TSType 
+      //                  ^ operator
+{
+    std::cout << "Hello world!" << std::endl;
+    
+    return EXIT_SUCCESS;
+    // ^ keyword.return
+    //      ^ constant
+}

tests/query/highlights_spec.lua

@@ -0,0 +1,90 @@
+require "nvim-treesitter.highlight" -- yes, this is necessary to set the hlmap
+local highlighter = require "vim.treesitter.highlighter"
+local utils = require "nvim-treesitter.utils"
+local ts_utils = require "nvim-treesitter.ts_utils"
+local parsers = require "nvim-treesitter.parsers"
+
+local function check_assertions(file)
+  local buf = vim.fn.bufadd(file)
+  vim.fn.bufload(file)
+  local lang = parsers.get_buf_lang(buf)
+  local assertions = vim.fn.json_decode(
+    vim.fn.system(
+      "highlight-assertions -p '" .. utils.get_parser_install_dir() .. "/" .. lang .. ".so'" .. " -s '" .. file .. "'"
+    )
+  )
+  local parser = parsers.get_parser(buf, lang)
+
+  local self = highlighter.new(parser, {})
+
+  for _, assertion in ipairs(assertions) do
+    local row = assertion.position.row
+    local col = assertion.position.column
+
+    local captures = {}
+    local highlights = {}
+    self.tree:for_each_tree(function(tstree, tree)
+      if not tstree then
+        return
+      end
+
+      local root = tstree:root()
+      local root_start_row, _, root_end_row, _ = root:range()
+
+      -- Only worry about trees within the line range
+      if root_start_row > row or root_end_row < row then
+        return
+      end
+
+      local query = self:get_query(tree:lang())
+
+      -- Some injected languages may not have highlight queries.
+      if not query:query() then
+        return
+      end
+
+      local iter = query:query():iter_captures(root, self.bufnr, row, row + 1)
+
+      for capture, node, _ in iter do
+        local hl = query.hl_cache[capture]
+        assert.is.truthy(hl)
+
+        assert.Truthy(node)
+        assert.is.number(row)
+        assert.is.number(col)
+        if hl and ts_utils.is_in_node_range(node, row, col) then
+          local c = query._query.captures[capture] -- name of the capture in the query
+          if c ~= nil then
+            captures[c] = true
+            local general_hl = query:_get_hl_from_capture(capture)
+            highlights[general_hl] = true
+          end
+        end
+      end
+    end, true)
+    assert.True(
+      captures[assertion.expected_capture_name] or highlights[assertion.expected_capture_name],
+      "Error in at "
+        .. file
+        .. ":"
+        .. (row + 1)
+        .. ":"
+        .. (col + 1)
+        .. ': expected "'
+        .. assertion.expected_capture_name
+        .. '", captures: '
+        .. vim.inspect(vim.tbl_keys(captures))
+        .. '", highlights: '
+        .. vim.inspect(vim.tbl_keys(highlights))
+    )
+  end
+end
+
+describe("highlight queries", function()
+  local files = vim.fn.split(vim.fn.glob "tests/query/highlights/**/*.*")
+  for _, file in ipairs(files) do
+    it(file, function()
+      check_assertions(file)
+    end)
+  end
+end)