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[3.7] bpo-31506: Clarify error messages for object.__new__ and object.__init__ (GH-11641) #11939

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Merged
miss-islington merged 1 commit into from
Feb 19, 2019
Merged

[3.7] bpo-31506: Clarify error messages for object.__new__ and object.__init__ (GH-11641) #11939

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20 changes: 13 additions & 7 deletions Lib/test/test_class.py
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Original file line number Diff line number Diff line change
Expand Up @@ -602,19 +602,21 @@ def testConstructorErrorMessages(self):
class C:
pass

error_msg = r'C.__init__\(\) takes exactly one argument \(the instance to initialize\)'

with self.assertRaisesRegex(TypeError, r'C\(\) takes no arguments'):
C(42)

with self.assertRaisesRegex(TypeError, r'C\(\) takes no arguments'):
C.__new__(C, 42)

with self.assertRaisesRegex(TypeError, r'C\(\).__init__\(\) takes no arguments'):
with self.assertRaisesRegex(TypeError, error_msg):
C().__init__(42)

with self.assertRaisesRegex(TypeError, r'C\(\) takes no arguments'):
object.__new__(C, 42)

with self.assertRaisesRegex(TypeError, r'C\(\).__init__\(\) takes no arguments'):
with self.assertRaisesRegex(TypeError, error_msg):
object.__init__(C(), 42)

# Class with both `__init__` & `__new__` method overridden
Expand All @@ -624,24 +626,28 @@ def __new__(cls, *args, **kwargs):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)

with self.assertRaisesRegex(TypeError, r'object.__new__\(\) takes no argument'):
error_msg = r'object.__new__\(\) takes exactly one argument \(the type to instantiate\)'

with self.assertRaisesRegex(TypeError, error_msg):
D(42)

with self.assertRaisesRegex(TypeError, r'object.__new__\(\) takes no argument'):
with self.assertRaisesRegex(TypeError, error_msg):
D.__new__(D, 42)

with self.assertRaisesRegex(TypeError, r'object.__new__\(\) takes no argument'):
with self.assertRaisesRegex(TypeError, error_msg):
object.__new__(D, 42)

# Class that only overrides __init__
class E:
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)

with self.assertRaisesRegex(TypeError, r'object.__init__\(\) takes no argument'):
error_msg = r'object.__init__\(\) takes exactly one argument \(the instance to initialize\)'

with self.assertRaisesRegex(TypeError, error_msg):
E().__init__(42)

with self.assertRaisesRegex(TypeError, r'object.__init__\(\) takes no argument'):
with self.assertRaisesRegex(TypeError, error_msg):
object.__init__(E(), 42)

if __name__ == '__main__':
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2019-01-22-02-06-39.bpo-31506.eJ5FpV.rst
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@@ -0,0 +1,3 @@
Clarify the errors reported when ``object.__new__`` and ``object.__init__``
receive more than one argument.
Contributed by Sanyam Khurana.
9 changes: 6 additions & 3 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3654,11 +3654,13 @@ object_init(PyObject *self, PyObject *args, PyObject *kwds)
PyTypeObject *type = Py_TYPE(self);
if (excess_args(args, kwds)) {
if (type->tp_init != object_init) {
PyErr_SetString(PyExc_TypeError, "object.__init__() takes no arguments");
PyErr_SetString(PyExc_TypeError,
"object.__init__() takes exactly one argument (the instance to initialize)");
return -1;
}
if (type->tp_new == object_new) {
PyErr_Format(PyExc_TypeError, "%.200s().__init__() takes no arguments",
PyErr_Format(PyExc_TypeError,
"%.200s.__init__() takes exactly one argument (the instance to initialize)",
type->tp_name);
return -1;
}
Expand All @@ -3671,7 +3673,8 @@ object_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
if (excess_args(args, kwds)) {
if (type->tp_new != object_new) {
PyErr_SetString(PyExc_TypeError, "object.__new__() takes no arguments");
PyErr_SetString(PyExc_TypeError,
"object.__new__() takes exactly one argument (the type to instantiate)");
return NULL;
}
if (type->tp_init == object_init) {
Expand Down