Is there a way to find undecorated classes/functions in a Python module?

I'm trying to write a tool which will help me find implementation bugs in a large existing python code base that makes heavy use of decorators.

Lets say I have a file, rules.py:

manager = RuleManager()

@manager.register
class A:
    pass

class B:
    pass

Lets say I already know ahead of time what the Manager classes are that use the decorator.

How would I find that class B is undecorated?

Ideally the output would include something like /path/to/rules.py:`B` is undecorated by any manager

Use ast.parse to parse the syntax tree in each file, then fetch all ClassDef's with an empty decorator list and report their relative location:

from ast import parse, walk, ClassDef, Attribute

# define predicate to test decorator list for presence of @manager.register
def has_decorator(deco_list):
  for deco in deco_list:
    if isinstance(deco, Attribute) and d.value.id == 'manager' and d.attr == 'register':
      return True
  return False

# parse input text
with open("/path/to/file.py") as f:
  source_tree = parse(f.read())

# traverse the tree, inspect all class defs for the decorator
for node in walk(source_tree):
  if isinstance(node, ClassDef) and not has_decorator(node.decorator_list):
    print(f"Class '{node.name}' on line {node.lineno} has no expected decorators")