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[3.10] bpo-44232: Fix type_new() error reporting (GH-26359) #26365

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Merged
vstinner merged 1 commit into from
May 26, 2021
Merged

[3.10] bpo-44232: Fix type_new() error reporting (GH-26359) #26365

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18 changes: 18 additions & 0 deletions Lib/test/test_types.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1334,6 +1334,24 @@ class N(type, metaclass=M):
N(5)
self.assertEqual(str(cm.exception), expected_message)

def test_metaclass_new_error(self):
# bpo-44232: The C function type_new() must properly report the
# exception when a metaclass constructor raises an exception and the
# winner class is not the metaclass.
class ModelBase(type):
def __new__(cls, name, bases, attrs):
super_new = super().__new__
new_class = super_new(cls, name, bases, {})
if name != "Model":
raise RuntimeWarning(f"{name=}")
return new_class

class Model(metaclass=ModelBase):
pass

with self.assertRaises(RuntimeWarning):
type("SouthPonies", (Model,), {})


class SimpleNamespaceTests(unittest.TestCase):

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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-05-25-18-20-10.bpo-44232.DMcCCf.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Fix a regression in :func:`type` when a metaclass raises an exception. The C
function :c:func:`type_new` must properly report the exception when a metaclass
constructor raises an exception and the winner class is not the metaclass.
Patch by Victor Stinner.
4 changes: 4 additions & 0 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3256,6 +3256,9 @@ type_new_get_bases(type_new_ctx *ctx, PyObject **type)
if (winner->tp_new != type_new) {
/* Pass it to the winner */
*type = winner->tp_new(winner, ctx->args, ctx->kwds);
if (*type == NULL) {
return -1;
}
return 1;
}

Expand Down Expand Up @@ -3307,6 +3310,7 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
PyObject *type = NULL;
int res = type_new_get_bases(&ctx, &type);
if (res < 0) {
assert(PyErr_Occurred());
return NULL;
}
if (res == 1) {
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