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bpo-32953: Dataclasses: frozen should not be inherited for non-dataclass derived classes (#6147)

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If a non-dataclass derives from a frozen dataclass, allow attributes to be set.
Require either all of the dataclasses in a class hierarchy to be frozen, or all non-frozen.
Store `@dataclass` parameters on the class object under `__dataclass_params__`. This is needed to detect frozen base classes.
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Eric V. Smith 2018-03-18 20:40:34 -04:00 • committed by GitHub
parent 3fe33043ee
commit f199bc655e
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3 changed files with 168 additions and 55 deletions
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99
Lib/test/test_dataclasses.py
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@ -2476,41 +2476,92 @@ class TestFrozen(unittest.TestCase):
d = D(0, 10)
with self.assertRaises(FrozenInstanceError):
d.i = 5
with self.assertRaises(FrozenInstanceError):
d.j = 6
self.assertEqual(d.i, 0)
self.assertEqual(d.j, 10)
def test_inherit_from_nonfrozen_from_frozen(self):
@dataclass(frozen=True)
class C:
i: int
# Test both ways: with an intermediate normal (non-dataclass)
# class and without an intermediate class.
def test_inherit_nonfrozen_from_frozen(self):
for intermediate_class in [True, False]:
with self.subTest(intermediate_class=intermediate_class):
@dataclass(frozen=True)
class C:
i: int
with self.assertRaisesRegex(TypeError,
'cannot inherit non-frozen dataclass from a frozen one'):
@dataclass
class D(C):
pass
if intermediate_class:
class I(C): pass
else:
I = C
def test_inherit_from_frozen_from_nonfrozen(self):
@dataclass
class C:
i: int
with self.assertRaisesRegex(TypeError,
'cannot inherit non-frozen dataclass from a frozen one'):
@dataclass
class D(I):
pass
with self.assertRaisesRegex(TypeError,
'cannot inherit frozen dataclass from a non-frozen one'):
@dataclass(frozen=True)
class D(C):
pass
def test_inherit_frozen_from_nonfrozen(self):
for intermediate_class in [True, False]:
with self.subTest(intermediate_class=intermediate_class):
@dataclass
class C:
i: int
if intermediate_class:
class I(C): pass
else:
I = C
with self.assertRaisesRegex(TypeError,
'cannot inherit frozen dataclass from a non-frozen one'):
@dataclass(frozen=True)
class D(I):
pass
def test_inherit_from_normal_class(self):
class C:
pass
for intermediate_class in [True, False]:
with self.subTest(intermediate_class=intermediate_class):
class C:
pass
if intermediate_class:
class I(C): pass
else:
I = C
@dataclass(frozen=True)
class D(I):
i: int
d = D(10)
with self.assertRaises(FrozenInstanceError):
d.i = 5
def test_non_frozen_normal_derived(self):
# See bpo-32953.
@dataclass(frozen=True)
class D(C):
i: int
class D:
x: int
y: int = 10
d = D(10)
class S(D):
pass
s = S(3)
self.assertEqual(s.x, 3)
self.assertEqual(s.y, 10)
s.cached = True
# But can't change the frozen attributes.
with self.assertRaises(FrozenInstanceError):
d.i = 5
s.x = 5
with self.assertRaises(FrozenInstanceError):
s.y = 5
self.assertEqual(s.x, 3)
self.assertEqual(s.y, 10)
self.assertEqual(s.cached, True)
if __name__ == '__main__':