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[3.7] bpo-35992: Use PySequence_GetItem only if sq_item is not NULL (GH-11857) #11910

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Merged
miss-islington merged 1 commit into from
Feb 17, 2019
Merged

[3.7] bpo-35992: Use PySequence_GetItem only if sq_item is not NULL (GH-11857) #11910

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9 changes: 8 additions & 1 deletion Lib/test/test_genericclass.py
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Original file line number Diff line number Diff line change
Expand Up @@ -248,7 +248,14 @@ def __class_getitem__(cls, item):
return f'{cls.__name__}[{item.__name__}]'
self.assertEqual(Meta[int], 'Meta[int]')

def test_class_getitem_metaclass_2(self):
def test_class_getitem_with_metaclass(self):
class Meta(type): pass
class C(metaclass=Meta):
def __class_getitem__(cls, item):
return f'{cls.__name__}[{item.__name__}]'
self.assertEqual(C[int], 'C[int]')

def test_class_getitem_metaclass_first(self):
class Meta(type):
def __getitem__(cls, item):
return 'from metaclass'
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2019-02-14-12-01-44.bpo-35992.nG9e2L.rst
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@@ -0,0 +1,2 @@
Fix ``__class_getitem__()`` not being called on a class with a custom
non-subscriptable metaclass.
7 changes: 5 additions & 2 deletions Objects/abstract.c
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Original file line number Diff line number Diff line change
Expand Up @@ -143,6 +143,7 @@ PyObject *
PyObject_GetItem(PyObject *o, PyObject *key)
{
PyMappingMethods *m;
PySequenceMethods *ms;

if (o == NULL || key == NULL) {
return null_error();
Expand All @@ -155,17 +156,19 @@ PyObject_GetItem(PyObject *o, PyObject *key)
return item;
}

if (o->ob_type->tp_as_sequence) {
ms = o->ob_type->tp_as_sequence;
if (ms && ms->sq_item) {
if (PyIndex_Check(key)) {
Py_ssize_t key_value;
key_value = PyNumber_AsSsize_t(key, PyExc_IndexError);
if (key_value == -1 && PyErr_Occurred())
return NULL;
return PySequence_GetItem(o, key_value);
}
else if (o->ob_type->tp_as_sequence->sq_item)
else {
return type_error("sequence index must "
"be integer, not '%.200s'", key);
}
}

if (PyType_Check(o)) {
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