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gh-141510: Fix frozendict.fromkeys() for subclasses#144947

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gh-141510: Fix frozendict.fromkeys() for subclasses #144947

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17 changes: 17 additions & 0 deletions Lib/test/test_dict.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -1787,6 +1787,23 @@ def test_hash(self):
with self.assertRaisesRegex(TypeError, "unhashable type: 'list'"):
hash(fd)

def test_fromkeys(self):
self.assertEqual(frozendict.fromkeys('abc'),
frozendict(a=None, b=None, c=None))

# frozendict.fromkeys() must not call subclass constructor
class FrozenDictSubclass(frozendict):
def __new__(self):
raise ValueError("must not be called")

fd = FrozenDictSubclass.fromkeys("abc")
self.assertEqual(fd, frozendict(a=None, b=None, c=None))
self.assertEqual(type(fd), FrozenDictSubclass)

fd = FrozenDictSubclass.fromkeys(frozendict(x=1))
self.assertEqual(fd, frozendict(x=None))
self.assertEqual(type(fd), FrozenDictSubclass)


if __name__ == "__main__":
unittest.main()
17 changes: 13 additions & 4 deletions Objects/dictobject.c
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Expand Up@@ -3285,10 +3285,17 @@ _PyDict_FromKeys(PyObject *cls, PyObject *iterable, PyObject *value)
PyObject *d;
int status;

d = _PyObject_CallNoArgs(cls);
if (d == NULL)
if (PyObject_IsSubclass(cls, (PyObject*)&PyFrozenDict_Type)) {
// Never call frozendict subclass constructor which would call
// arbitrary Python code.
d = frozendict_new(_PyType_CAST(cls), NULL, NULL);
}
else {
d = _PyObject_CallNoArgs(cls);
}
if (d == NULL) {
return NULL;

}

if (PyDict_CheckExact(d)) {
if (PyDict_CheckExact(iterable)) {
Expand DownExpand Up@@ -3359,7 +3366,7 @@ _PyDict_FromKeys(PyObject *cls, PyObject *iterable, PyObject *value)
dict_iter_exit:;
Py_END_CRITICAL_SECTION();
}
else if (PyFrozenDict_CheckExact(d)) {
else if (PyFrozenDict_Check(d)) {
while ((key = PyIter_Next(it)) != NULL) {
// anydict_setitem_take2 consumes a reference to key
status = anydict_setitem_take2((PyDictObject *)d,
Expand DownExpand Up@@ -7994,6 +8001,8 @@ frozendict_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
if (d == NULL) {
return NULL;
}
assert(Py_REFCNT(d) == 1);

PyFrozenDictObject *self = _PyFrozenDictObject_CAST(d);
self->ma_hash = -1;

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