diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py index 0c4b47564b0605..97c961f1cf7915 100644 --- a/Lib/dataclasses.py +++ b/Lib/dataclasses.py @@ -851,7 +851,7 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen): # Only process classes that have been processed by our # decorator. That is, they have a _FIELDS attribute. base_fields = getattr(b, _FIELDS, None) - if base_fields: + if base_fields is not None: has_dataclass_bases = True for f in base_fields.values(): fields[f.name] = f diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py index 8887eb6461bc34..b2b0b82557d2b6 100644 --- a/Lib/test/test_dataclasses.py +++ b/Lib/test/test_dataclasses.py @@ -2594,6 +2594,30 @@ class D(C): self.assertEqual(d.i, 0) self.assertEqual(d.j, 10) + def test_inherit_nonfrozen_from_empty_frozen(self): + @dataclass(frozen=True) + class C: + pass + + with self.assertRaisesRegex(TypeError, + 'cannot inherit non-frozen dataclass from a frozen one'): + @dataclass + class D(C): + j: int + + def test_inherit_nonfrozen_from_empty(self): + @dataclass + class C: + pass + + @dataclass + class D(C): + j: int + + d = D(3) + self.assertEqual(d.j, 3) + self.assertIsInstance(d, C) + # Test both ways: with an intermediate normal (non-dataclass) # class and without an intermediate class. def test_inherit_nonfrozen_from_frozen(self): diff --git a/Misc/NEWS.d/next/Library/2021-02-09-07-24-29.bpo-43176.bocNQn.rst b/Misc/NEWS.d/next/Library/2021-02-09-07-24-29.bpo-43176.bocNQn.rst new file mode 100644 index 00000000000000..66a175d21255c2 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2021-02-09-07-24-29.bpo-43176.bocNQn.rst @@ -0,0 +1 @@ +Fixed processing of empty dataclasses. \ No newline at end of file