bpo-42269: Add slots parameter to dataclass decorator (GH-24171)
Add slots parameter to dataclass decorator and make_dataclass function.
diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py
index 670648a..2fa0ae0 100644
--- a/Lib/test/test_dataclasses.py
+++ b/Lib/test/test_dataclasses.py
@@ -2781,6 +2781,59 @@ class Derived(Base):
# We can add a new field to the derived instance.
d.z = 10
+ def test_generated_slots(self):
+ @dataclass(slots=True)
+ class C:
+ x: int
+ y: int
+
+ c = C(1, 2)
+ self.assertEqual((c.x, c.y), (1, 2))
+
+ c.x = 3
+ c.y = 4
+ self.assertEqual((c.x, c.y), (3, 4))
+
+ with self.assertRaisesRegex(AttributeError, "'C' object has no attribute 'z'"):
+ c.z = 5
+
+ def test_add_slots_when_slots_exists(self):
+ with self.assertRaisesRegex(TypeError, '^C already specifies __slots__$'):
+ @dataclass(slots=True)
+ class C:
+ __slots__ = ('x',)
+ x: int
+
+ def test_generated_slots_value(self):
+ @dataclass(slots=True)
+ class Base:
+ x: int
+
+ self.assertEqual(Base.__slots__, ('x',))
+
+ @dataclass(slots=True)
+ class Delivered(Base):
+ y: int
+
+ self.assertEqual(Delivered.__slots__, ('x', 'y'))
+
+ @dataclass
+ class AnotherDelivered(Base):
+ z: int
+
+ self.assertTrue('__slots__' not in AnotherDelivered.__dict__)
+
+ def test_returns_new_class(self):
+ class A:
+ x: int
+
+ B = dataclass(A, slots=True)
+ self.assertIsNot(A, B)
+
+ self.assertFalse(hasattr(A, "__slots__"))
+ self.assertTrue(hasattr(B, "__slots__"))
+
+
class TestDescriptors(unittest.TestCase):
def test_set_name(self):
# See bpo-33141.