Standard Visitor class for tree-sitter, support with `visit` and `leave` callbacks

visitor.py

# Very inspired by https://github.com/tree-sitter/py-tree-sitter/pull/90

class Visitor:
  def visit(self, _node):
    return True
  
  def leave(self, _node):
    pass
  
  def on_visit(self, node):
    visitor = getattr(self, f"visit_{node.type}", self.visit)
    return visitor(node)
  
  def on_leave(self, node):
    leaver = getattr(self, f"leave_{node.typ}", self.leave)
    leaver(node)
    
  def walk(self, tree):
    cursor = tree.walk()
    has_next = True
    postorder = []
    while has_next:
      node = cursor.node  # current node
      postorder.append(node)  # push to the stack for postorder leave
      
      # visit current node, and check subtree first
      has_next = cursor.goto_first_child() if self.on_visit(node) else False
      
      if not has_next:
        # check sibling, and call leave in postorder
        has_next = cursor.goto_next_sibling()
        self.on_leave(postorder.pop())
        
      while not has_next and cursor.goto_parent():
        # check parent's siblings, and call leave in postorder.
        has_next = cursor.goto_next_sibling()
        self.on_leave(postorder.pop())