diff options
Diffstat (limited to 'Lib')
| -rw-r--r-- | Lib/dataclasses.py | 5 | ||||
| -rwxr-xr-x | Lib/test/test_dataclasses.py | 26 |
2 files changed, 29 insertions, 2 deletions
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py index f778a27..9020c90 100644 --- a/Lib/dataclasses.py +++ b/Lib/dataclasses.py @@ -1015,13 +1015,14 @@ def fields(class_or_instance): def _is_dataclass_instance(obj): """Returns True if obj is an instance of a dataclass.""" - return not isinstance(obj, type) and hasattr(obj, _FIELDS) + return hasattr(type(obj), _FIELDS) def is_dataclass(obj): """Returns True if obj is a dataclass or an instance of a dataclass.""" - return hasattr(obj, _FIELDS) + cls = obj if isinstance(obj, type) else type(obj) + return hasattr(cls, _FIELDS) def asdict(obj, *, dict_factory=dict): diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py index ea42904..037bf4c 100755 --- a/Lib/test/test_dataclasses.py +++ b/Lib/test/test_dataclasses.py @@ -1300,6 +1300,32 @@ class TestCase(unittest.TestCase): self.assertTrue(is_dataclass(d.d)) self.assertFalse(is_dataclass(d.e)) + def test_is_dataclass_when_getattr_always_returns(self): + # See bpo-37868. + class A: + def __getattr__(self, key): + return 0 + self.assertFalse(is_dataclass(A)) + a = A() + + # Also test for an instance attribute. + class B: + pass + b = B() + b.__dataclass_fields__ = [] + + for obj in a, b: + with self.subTest(obj=obj): + self.assertFalse(is_dataclass(obj)) + + # Indirect tests for _is_dataclass_instance(). + with self.assertRaisesRegex(TypeError, 'should be called on dataclass instances'): + asdict(obj) + with self.assertRaisesRegex(TypeError, 'should be called on dataclass instances'): + astuple(obj) + with self.assertRaisesRegex(TypeError, 'should be called on dataclass instances'): + replace(obj, x=0) + def test_helper_fields_with_class_instance(self): # Check that we can call fields() on either a class or instance, # and get back the same thing. |