Issue #16453: Fix equality testing of dead weakref objects.
Also add tests for hashing.
diff --git a/Lib/test/test_weakref.py b/Lib/test/test_weakref.py
index f2e328b..b7c72bd 100644
--- a/Lib/test/test_weakref.py
+++ b/Lib/test/test_weakref.py
@@ -33,6 +33,27 @@
return C.method
+class Object:
+ def __init__(self, arg):
+ self.arg = arg
+ def __repr__(self):
+ return "<Object %r>" % self.arg
+ def __eq__(self, other):
+ if isinstance(other, Object):
+ return self.arg == other.arg
+ return NotImplemented
+ def __ne__(self, other):
+ if isinstance(other, Object):
+ return self.arg != other.arg
+ return NotImplemented
+ def __hash__(self):
+ return hash(self.arg)
+
+class RefCycle:
+ def __init__(self):
+ self.cycle = self
+
+
class TestBase(unittest.TestCase):
def setUp(self):
@@ -705,6 +726,54 @@
self.assertEqual(b(), None)
self.assertEqual(l, [a, b])
+ def test_equality(self):
+ # Alive weakrefs defer equality testing to their underlying object.
+ x = Object(1)
+ y = Object(1)
+ z = Object(2)
+ a = weakref.ref(x)
+ b = weakref.ref(y)
+ c = weakref.ref(z)
+ d = weakref.ref(x)
+ # Note how we directly test the operators here, to stress both
+ # __eq__ and __ne__.
+ self.assertTrue(a == b)
+ self.assertFalse(a != b)
+ self.assertFalse(a == c)
+ self.assertTrue(a != c)
+ self.assertTrue(a == d)
+ self.assertFalse(a != d)
+ del x, y, z
+ gc.collect()
+ for r in a, b, c:
+ # Sanity check
+ self.assertIs(r(), None)
+ # Dead weakrefs compare by identity: whether `a` and `d` are the
+ # same weakref object is an implementation detail, since they pointed
+ # to the same original object and didn't have a callback.
+ # (see issue #16453).
+ self.assertFalse(a == b)
+ self.assertTrue(a != b)
+ self.assertFalse(a == c)
+ self.assertTrue(a != c)
+ self.assertEqual(a == d, a is d)
+ self.assertEqual(a != d, a is not d)
+
+ def test_hashing(self):
+ # Alive weakrefs hash the same as the underlying object
+ x = Object(42)
+ y = Object(42)
+ a = weakref.ref(x)
+ b = weakref.ref(y)
+ self.assertEqual(hash(a), hash(42))
+ del x, y
+ gc.collect()
+ # Dead weakrefs:
+ # - retain their hash is they were hashed when alive;
+ # - otherwise, cannot be hashed.
+ self.assertEqual(hash(a), hash(42))
+ self.assertRaises(TypeError, hash, b)
+
class SubclassableWeakrefTestCase(TestBase):
@@ -809,17 +878,6 @@
self.assertEqual(self.cbcalled, 0)
-class Object:
- def __init__(self, arg):
- self.arg = arg
- def __repr__(self):
- return "<Object %r>" % self.arg
-
-class RefCycle:
- def __init__(self):
- self.cycle = self
-
-
class MappingTestCase(TestBase):
COUNT = 10