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bpo-44606: Fix __instancecheck__ and __subclasscheck__ for the union type. (GH-27120)

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* Fix issubclass() for None.
  E.g. issubclass(type(None), int | None) returns now True.
* Fix issubclass() for virtual subclasses.
  E.g. issubclass(dict, int | collections.abc.Mapping) returns now True.
* Fix crash in isinstance() if the check for one of items raises exception.
(cherry picked from commit 81989058de)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
This commit is contained in:
Miss Islington (bot) 2021-07-13 21:55:45 -07:00 • committed by GitHub
parent bb260c2a21
commit b42eee78e7
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 55 additions and 6 deletions
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37
Lib/test/test_types.py
View file

@ -661,6 +661,39 @@ class TypesTests(unittest.TestCase):
x.__args__ = [str, int]
(int | str ) == x
def test_instancecheck(self):
x = int | str
self.assertIsInstance(1, x)
self.assertIsInstance(True, x)
self.assertIsInstance('a', x)
self.assertNotIsInstance(None, x)
self.assertTrue(issubclass(int, x))
self.assertTrue(issubclass(bool, x))
self.assertTrue(issubclass(str, x))
self.assertFalse(issubclass(type(None), x))
x = int | None
self.assertIsInstance(None, x)
self.assertTrue(issubclass(type(None), x))
x = int | collections.abc.Mapping
self.assertIsInstance({}, x)
self.assertTrue(issubclass(dict, x))
def test_bad_instancecheck(self):
class BadMeta(type):
def __instancecheck__(cls, inst):
1/0
x = int | BadMeta('A', (), {})
self.assertTrue(isinstance(1, x))
self.assertRaises(ZeroDivisionError, isinstance, [], x)
def test_bad_subclasscheck(self):
class BadMeta(type):
def __subclasscheck__(cls, sub):
1/0
x = int | BadMeta('A', (), {})
self.assertTrue(issubclass(int, x))
self.assertRaises(ZeroDivisionError, issubclass, list, x)
def test_or_type_operator_with_TypeVar(self):
TV = typing.TypeVar('T')
assert TV | str == typing.Union[TV, str]
@ -744,9 +777,9 @@ class TypesTests(unittest.TestCase):
for type_ in union_ga:
with self.subTest(f"check isinstance/issubclass is invalid for {type_}"):
with self.assertRaises(TypeError):
isinstance(list, type_)
isinstance(1, type_)
with self.assertRaises(TypeError):
issubclass(list, type_)
issubclass(int, type_)
def test_or_type_operator_with_bad_module(self):
class TypeVar:

1
Misc/NEWS.d/next/Core and Builtins/2021-07-13-20-22-12.bpo-44606.S3Bv2w.rst Normal file
View file

@ -0,0 +1 @@
Fix ``__instancecheck__`` and ``__subclasscheck__`` for the union type.

23
Objects/unionobject.c
View file

@ -67,8 +67,14 @@ union_instancecheck(PyObject *self, PyObject *instance)
if (arg == Py_None) {
arg = (PyObject *)&_PyNone_Type;
}
if (PyType_Check(arg) && PyObject_IsInstance(instance, arg) != 0) {
Py_RETURN_TRUE;
if (PyType_Check(arg)) {
int res = PyObject_IsInstance(instance, arg);
if (res < 0) {
return NULL;
}
if (res) {
Py_RETURN_TRUE;
}
}
}
Py_RETURN_FALSE;
@ -90,8 +96,17 @@ union_subclasscheck(PyObject *self, PyObject *instance)
Py_ssize_t nargs = PyTuple_GET_SIZE(alias->args);
for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
PyObject *arg = PyTuple_GET_ITEM(alias->args, iarg);
if (PyType_Check(arg) && (PyType_IsSubtype((PyTypeObject *)instance, (PyTypeObject *)arg) != 0)) {
Py_RETURN_TRUE;
if (arg == Py_None) {
arg = (PyObject *)&_PyNone_Type;
}
if (PyType_Check(arg)) {
int res = PyObject_IsSubclass(instance, arg);
if (res < 0) {
return NULL;
}
if (res) {
Py_RETURN_TRUE;
}
}
}
Py_RETURN_FALSE;