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gh-150069: Test frozen dataclass and properties interaction #150070

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gh-150069: Test frozen dataclass and properties interaction #150070

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71 changes: 70 additions & 1 deletion Lib/test/test_dataclasses/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3328,35 +3328,104 @@ def test_non_frozen_normal_derived(self):
class D:
x: int
y: int = 10
z: int = 0

@property
def readonly(self) -> int:
return self.x

@property
def prop(self) -> int:
return self.z

@prop.setter
def prop(self, val: int) -> None:
object.__setattr__(self, 'z', val)

@prop.deleter
def prop(self) -> None:
object.__setattr__(self, 'z', 0)

d = D(5)
self.assertEqual(d.x, 5)
self.assertEqual(d.y, 10)
self.assertEqual(d.z, 0)
self.assertEqual(d.readonly, 5)
self.assertEqual(d.prop, 0)

with self.assertRaises(FrozenInstanceError):
d.x = 5
with self.assertRaises(FrozenInstanceError):
d.readonly = 5
with self.assertRaises(FrozenInstanceError):
d.z = 5
with self.assertRaises(FrozenInstanceError):
d.prop = 5
with self.assertRaises(FrozenInstanceError):
del d.prop

self.assertEqual(d.x, 5)
self.assertEqual(d.y, 10)
self.assertEqual(d.z, 0)
self.assertEqual(d.readonly, 5)
self.assertEqual(d.prop, 0)

class S(D):
pass

s = S(3)
self.assertEqual(s.x, 3)
self.assertEqual(s.y, 10)
self.assertEqual(s.z, 0)
self.assertEqual(s.readonly, 3)
self.assertEqual(s.prop, 0)
# Can set new attrs:
s.cached = True
# Can mutate them:
s.cached = False

# Can also change writable properties:
with self.assertRaises(AttributeError) as cm:
s.readonly = 5
self.assertNotIsInstance(cm.exception, FrozenInstanceError)
s.prop = 1
self.assertEqual(s.x, 3)
self.assertEqual(s.readonly, 3)
self.assertEqual(s.prop, 1)
self.assertEqual(s.z, 1)

# But can't change the frozen attributes.
with self.assertRaises(FrozenInstanceError):
s.x = 5
with self.assertRaises(FrozenInstanceError):
s.y = 5
with self.assertRaises(FrozenInstanceError):
s.z = 5
self.assertEqual(s.x, 3)
self.assertEqual(s.y, 10)
self.assertEqual(s.cached, True)
self.assertEqual(s.z, 1)
self.assertIs(s.cached, False)

with self.assertRaises(FrozenInstanceError):
del s.x
self.assertEqual(s.x, 3)
with self.assertRaises(FrozenInstanceError):
del s.y
self.assertEqual(s.y, 10)
with self.assertRaises(AttributeError) as cm:
del s.readonly
self.assertNotIsInstance(cm.exception, FrozenInstanceError)
self.assertEqual(s.x, 3)
self.assertEqual(s.readonly, 3)
del s.cached
self.assertNotHasAttr(s, 'cached')
with self.assertRaises(AttributeError) as cm:
del s.cached
self.assertNotIsInstance(cm.exception, FrozenInstanceError)
del s.prop
self.assertEqual(s.z, 0)
self.assertEqual(s.prop, 0)
del s.prop

def test_non_frozen_normal_derived_from_empty_frozen(self):
@dataclass(frozen=True)
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