diff --git a/Lib/_py_abc.py b/Lib/_py_abc.py
index c870ae9048b4f1..291d4bfa756f8d 100644
--- a/Lib/_py_abc.py
+++ b/Lib/_py_abc.py
@@ -32,8 +32,7 @@ class ABCMeta(type):
# external code.
_abc_invalidation_counter = 0
- def __new__(mcls, name, bases, namespace, /, **kwargs):
- cls = super().__new__(mcls, name, bases, namespace, **kwargs)
+ def __init__(cls, name, bases, namespace, /, **kwargs):
# Compute set of abstract method names
abstracts = {name
for name, value in namespace.items()
@@ -49,7 +48,6 @@ def __new__(mcls, name, bases, namespace, /, **kwargs):
cls._abc_cache = WeakSet()
cls._abc_negative_cache = WeakSet()
cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
- return cls
def register(cls, subclass):
"""Register a virtual subclass of an ABC.
@@ -91,6 +89,8 @@ def _abc_caches_clear(cls):
def __instancecheck__(cls, instance):
"""Override for isinstance(instance, cls)."""
+ if '_abc_cache' not in cls.__dict__:
+ cls.__class__.__init__(cls, cls.__name__, cls.__bases__, cls.__dict__)
# Inline the cache checking
subclass = instance.__class__
if subclass in cls._abc_cache:
@@ -107,6 +107,8 @@ def __instancecheck__(cls, instance):
def __subclasscheck__(cls, subclass):
"""Override for issubclass(subclass, cls)."""
+ if '_abc_cache' not in cls.__dict__:
+ cls.__class__.__init__(cls, cls.__name__, cls.__bases__, cls.__dict__)
if not isinstance(subclass, type):
raise TypeError('issubclass() arg 1 must be a class')
# Check cache
diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py
index 5ce57cc209ea85..439cbb56339962 100644
--- a/Lib/test/test_abc.py
+++ b/Lib/test/test_abc.py
@@ -682,6 +682,62 @@ class B(A, metaclass=abc_ABCMeta, name="test"):
pass
self.assertEqual(saved_kwargs, dict(name="test"))
+
+ def test_subclasscheck_in_init_subclass1(self):
+ # test for gh-82266
+ class A(metaclass=abc_ABCMeta):
+ pass
+
+ class B(metaclass=abc_ABCMeta):
+ def __init_subclass__(cls):
+ assert not issubclass(cls, A)
+
+ class C(A):
+ pass
+
+ try:
+ class AB(A, B):
+ pass
+ except Exception:
+ pass
+
+ self.assertTrue(issubclass(C, A))
+ self.assertFalse(issubclass(C, B))
+
+ def test_subclasscheck_in_init_subclass2(self):
+ # test for gh-116093
+ class A(metaclass=abc_ABCMeta):
+ pass
+
+ class B(metaclass=abc_ABCMeta):
+ def __init_subclass__(cls, **kwargs):
+ super().__init_subclass__()
+ issubclass(A, A)
+ issubclass(A, B)
+
+ class AB(A, B):
+ pass
+
+ self.assertFalse(issubclass(A, B))
+
+ def test_subclasscheck_in_init_subclass3(self):
+ # test for gh-119699
+ class A(metaclass=abc_ABCMeta):
+ pass
+
+ class B(A):
+ def __init_subclass__(cls, **kwargs):
+ super().__init_subclass__()
+ issubclass(B, C)
+
+ class C(A):
+ pass
+
+ class BC(B, C):
+ pass
+
+ self.assertTrue(issubclass(B, B))
+
return TestLegacyAPI, TestABC, TestABCWithInitSubclass
TestLegacyAPI_Py, TestABC_Py, TestABCWithInitSubclass_Py = test_factory(abc.ABCMeta,
diff --git a/Misc/NEWS.d/next/Library/2024-05-29-10-32-59.gh-issue-116093.Gcb6Md.rst b/Misc/NEWS.d/next/Library/2024-05-29-10-32-59.gh-issue-116093.Gcb6Md.rst
new file mode 100644
index 00000000000000..73da45a5984b6a
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-05-29-10-32-59.gh-issue-116093.Gcb6Md.rst
@@ -0,0 +1,2 @@
+Fixed an issue with :meth:`~class.__subclasscheck__` where it can be called within :meth:`~object.__init_subclass__` before the subclass is initialized with the necessary ABC cache.
+Patch by Ben Hsing
diff --git a/Modules/_abc.c b/Modules/_abc.c
index 4f4b24b035db4a..fc00de68001d55 100644
--- a/Modules/_abc.c
+++ b/Modules/_abc.c
@@ -621,6 +621,11 @@ _abc__abc_instancecheck_impl(PyObject *module, PyObject *self,
if (impl == NULL) {
return NULL;
}
+ PyObject *dict = _PyType_GetDict((PyTypeObject *)self);
+ if (!PyDict_Contains(dict, &_Py_ID(_abc_impl))) {
+ _abc__abc_init(module, self);
+ impl = _get_impl(module, self);
+ }
subclass = PyObject_GetAttr(instance, &_Py_ID(__class__));
if (subclass == NULL) {
@@ -715,6 +720,11 @@ _abc__abc_subclasscheck_impl(PyObject *module, PyObject *self,
if (impl == NULL) {
return NULL;
}
+ PyObject *dict = _PyType_GetDict((PyTypeObject *)self);
+ if (!PyDict_Contains(dict, &_Py_ID(_abc_impl))) {
+ _abc__abc_init(module, self);
+ impl = _get_impl(module, self);
+ }
/* 1. Check cache. */
incache = _in_weak_set(impl, &impl->_abc_cache, subclass);
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