gh-113212: Improve error message & document zero-arg super inside nested functions and generator expressions (GH-113307)

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Yan Yanchii 2023-12-22 16:12:08 +01:00 committed by GitHub
parent 237e2cff00
commit 4a3d2419bb
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4 changed files with 51 additions and 3 deletions

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@ -1800,6 +1800,13 @@ are always available. They are listed here in alphabetical order.
the second argument is a type, ``issubclass(type2, type)`` must be true (this the second argument is a type, ``issubclass(type2, type)`` must be true (this
is useful for classmethods). is useful for classmethods).
When called directly within an ordinary method of a class, both arguments may
be omitted ("zero-argument :func:`!super`"). In this case, *type* will be the
enclosing class, and *obj* will be the first argument of the immediately
enclosing function (typically ``self``). (This means that zero-argument
:func:`!super` will not work as expected within nested functions, including
generator expressions, which implicitly create nested functions.)
There are two typical use cases for *super*. In a class hierarchy with There are two typical use cases for *super*. In a class hierarchy with
single inheritance, *super* can be used to refer to parent classes without single inheritance, *super* can be used to refer to parent classes without
naming them explicitly, thus making the code more maintainable. This use naming them explicitly, thus making the code more maintainable. This use

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@ -396,6 +396,33 @@ class TestSuper(unittest.TestCase):
with self.assertRaisesRegex(TypeError, "argument 1 must be a type"): with self.assertRaisesRegex(TypeError, "argument 1 must be a type"):
C().method() C().method()
def test_supercheck_fail(self):
class C:
def method(self, type_, obj):
return super(type_, obj).method()
c = C()
err_msg = (
r"super\(type, obj\): obj \({} {}\) is not "
r"an instance or subtype of type \({}\)."
)
cases = (
(int, c, int.__name__, C.__name__, "instance of"),
# obj is instance of type
(C, list(), C.__name__, list.__name__, "instance of"),
# obj is type itself
(C, list, C.__name__, list.__name__, "type"),
)
for case in cases:
with self.subTest(case=case):
type_, obj, type_str, obj_str, instance_or_type = case
regex = err_msg.format(instance_or_type, obj_str, type_str)
with self.assertRaisesRegex(TypeError, regex):
c.method(type_, obj)
def test_super___class__(self): def test_super___class__(self):
class C: class C:
def method(self): def method(self):

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@ -0,0 +1 @@
Improve :py:class:`super` error messages.

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@ -10404,9 +10404,22 @@ supercheck(PyTypeObject *type, PyObject *obj)
Py_XDECREF(class_attr); Py_XDECREF(class_attr);
} }
PyErr_SetString(PyExc_TypeError, const char *type_or_instance, *obj_str;
"super(type, obj): "
"obj must be an instance or subtype of type"); if (PyType_Check(obj)) {
type_or_instance = "type";
obj_str = ((PyTypeObject*)obj)->tp_name;
}
else {
type_or_instance = "instance of";
obj_str = Py_TYPE(obj)->tp_name;
}
PyErr_Format(PyExc_TypeError,
"super(type, obj): obj (%s %.200s) is not "
"an instance or subtype of type (%.200s).",
type_or_instance, obj_str, type->tp_name);
return NULL; return NULL;
} }