Here is a failing test.
code = '''
from dataclasses import dataclass
@dataclass
class Base:
pass
class Derived(Base):
pass
'''
with temporary_visited_module(code) as module:
obj = module["Derived"]
assert "dataclass" in obj.labels
For reference, the parallel test in core python is.
from dataclasses import dataclass, is_dataclass
@dataclass
class Base:
pass
class Derived(Base):
pass
assert is_dataclass(Derived)