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bpo-31506: Improve the error message logic for object_new & object_init #4740

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Merged
ncoghlan merged 3 commits into from
Dec 10, 2017
Merged

bpo-31506: Improve the error message logic for object_new & object_init #4740

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6bb1ce6
bpo-31506: Improve the error message logic for object_new & object_in…
CuriousLearner Dec 6, 2017
58c4926
bpo-31506: Fix error message for overriding __init__
CuriousLearner Dec 7, 2017
617e67a
bpo-31506: Adds test case for constructor error logic improvement
CuriousLearner Dec 9, 2017
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49 changes: 49 additions & 0 deletions Lib/test/test_class.py
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Original file line number Diff line number Diff line change
Expand Up @@ -595,5 +595,54 @@ class A:
with self.assertRaises(TypeError):
type.__setattr__(A, b'x', None)

def testConstructorErrorMessages(self):
# bpo-31506: Improves the error message logic for object_new & object_init

# Class without any method overrides
class C:
pass

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'):
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'):
object.__init__(C(), 42)

# Class with both `__init__` & `__new__` method overriden
class D:
def __new__(cls, *args, **kwargs):
super().__new__(cls, *args, **kwargs)
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)

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

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

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

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

if __name__ == '__main__':
unittest.main()
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2017-12-07-23-44-29.bpo-31506.j1U2fU.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improve the error message logic for object.__new__ and object.__init__.
Patch by Sanyam Khurana.
6 changes: 3 additions & 3 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3592,11 +3592,11 @@ 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() takes no arguments");
PyErr_SetString(PyExc_TypeError, "object.__init__() takes no arguments");
return -1;
}
if (type->tp_new == object_new) {
PyErr_Format(PyExc_TypeError, "%.200s() takes no arguments",
PyErr_Format(PyExc_TypeError, "%.200s().__init__() takes no arguments",
type->tp_name);
return -1;
}
Expand All @@ -3609,7 +3609,7 @@ object_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
if (excess_args(args, kwds)) {
if (type->tp_new != object_new) {
PyErr_SetString(PyExc_TypeError, "object() takes no arguments");
PyErr_SetString(PyExc_TypeError, "object.__new__() takes no arguments");
return NULL;
}
if (type->tp_init == object_init) {
Expand Down