content: # Copyright 2018 Google Inc. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  """Identify containers for lib2to3 trees.
  
  This module identifies containers and the elements in them. Each element points
  to the opening bracket and vice-versa.
  
    IdentifyContainers(): the main function exported by this module.
  """
  
  from yapf_third_party._ylib2to3.pgen2 import token as grammar_token
  
  from yapf.pytree import pytree_utils
  from yapf.pytree import pytree_visitor
  
  
  def IdentifyContainers(tree):
    """Run the identify containers visitor over the tree, modifying it in place.
  
    Arguments:
      tree: the top-level pytree node to annotate with subtypes.
    """
    identify_containers = _IdentifyContainers()
    identify_containers.Visit(tree)
  
  
  class _IdentifyContainers(pytree_visitor.PyTreeVisitor):
    """_IdentifyContainers - see file-level docstring for detailed description."""
  
    def Visit_trailer(self, node):  # pylint: disable=invalid-name
      for child in node.children:
        self.Visit(child)
  
      if len(node.children) != 3:
        return
      if node.children[0].type != grammar_token.LPAR:
        return
  
      if pytree_utils.NodeName(node.children[1]) == 'arglist':
        for child in node.children[1].children:
          pytree_utils.SetOpeningBracket(
              pytree_utils.FirstLeafNode(child), node.children[0])
      else:
        pytree_utils.SetOpeningBracket(
            pytree_utils.FirstLeafNode(node.children[1]), node.children[0])
  
    def Visit_atom(self, node):  # pylint: disable=invalid-name
      for child in node.children:
        self.Visit(child)
  
      if len(node.children) != 3:
        return
      if node.children[0].type != grammar_token.LPAR:
        return
  
      for child in node.children[1].children:
        pytree_utils.SetOpeningBracket(
            pytree_utils.FirstLeafNode(child), node.children[0])
  