https://github.com/python/cpython/commit/565685f6e88fd333326baff6469f53cfff28e01e
commit: 565685f6e88fd333326baff6469f53cfff28e01e
branch: main
author: Serhiy Storchaka <[email protected]>
committer: serhiy-storchaka <[email protected]>
date: 2026-01-15T10:41:08+02:00
summary:
Add regression test for add() after remove() with hash collision in set
(GH-143781)
files:
M Lib/test/test_dict.py
M Lib/test/test_set.py
diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index 3b4e95015e5b4c..6583c0f2aefb2b 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -12,6 +12,15 @@
from test.support import import_helper
+class CustomHash:
+ def __init__(self, hash):
+ self.hash = hash
+ def __hash__(self):
+ return self.hash
+ def __repr__(self):
+ return f'<CustomHash {self.hash} at {id(self):#x}>'
+
+
class DictTest(unittest.TestCase):
def test_invalid_keyword_arguments(self):
@@ -1648,6 +1657,29 @@ class MyClass: pass
d[MyStr("attr1")] = 2
self.assertIsInstance(list(d)[0], MyStr)
+ def test_hash_collision_remove_add(self):
+ self.maxDiff = None
+ # There should be enough space, so all elements with unique hash
+ # will be placed in corresponding cells without collision.
+ n = 64
+ items = [(CustomHash(h), h) for h in range(n)]
+ # Keys with hash collision.
+ a = CustomHash(n)
+ b = CustomHash(n)
+ items += [(a, 'a'), (b, 'b')]
+ d = dict(items)
+ self.assertEqual(len(d), len(items), d)
+ del d[a]
+ # "a" has been replaced with a dummy.
+ del items[n]
+ self.assertEqual(len(d), len(items), d)
+ self.assertEqual(d, dict(items))
+ d[b] = 'c'
+ # "b" should not replace the dummy.
+ items[n] = (b, 'c')
+ self.assertEqual(len(d), len(items), d)
+ self.assertEqual(d, dict(items))
+
class CAPITest(unittest.TestCase):
diff --git a/Lib/test/test_set.py b/Lib/test/test_set.py
index 3539adc789c7e7..554716aed1e98b 100644
--- a/Lib/test/test_set.py
+++ b/Lib/test/test_set.py
@@ -20,6 +20,14 @@ def check_pass_thru():
raise PassThru
yield 1
+class CustomHash:
+ def __init__(self, hash):
+ self.hash = hash
+ def __hash__(self):
+ return self.hash
+ def __repr__(self):
+ return f'<CustomHash {self.hash} at {id(self):#x}>'
+
class BadCmp:
def __hash__(self):
return 1
@@ -675,6 +683,28 @@ def __hash__(self):
with self.assertRaises(KeyError):
myset.discard(elem2)
+ def test_hash_collision_remove_add(self):
+ self.maxDiff = None
+ # There should be enough space, so all elements with unique hash
+ # will be placed in corresponding cells without collision.
+ n = 64
+ elems = [CustomHash(h) for h in range(n)]
+ # Elements with hash collision.
+ a = CustomHash(n)
+ b = CustomHash(n)
+ elems += [a, b]
+ s = self.thetype(elems)
+ self.assertEqual(len(s), len(elems), s)
+ s.remove(a)
+ # "a" has been replaced with a dummy.
+ del elems[n]
+ self.assertEqual(len(s), len(elems), s)
+ self.assertEqual(s, set(elems))
+ s.add(b)
+ # "b" should not replace the dummy.
+ self.assertEqual(len(s), len(elems), s)
+ self.assertEqual(s, set(elems))
+
class SetSubclass(set):
pass
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