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bpo-42073: allow classmethod to wrap other classmethod-like descriptors #27115

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Merged
merged 4 commits into from
Jul 15, 2021
Merged

bpo-42073: allow classmethod to wrap other classmethod-like descriptors #27115

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1ab4920
bpo-42073: allow classmethod to wrap other classmethod-like descriptors.
ambv Jul 13, 2021
b3dd8d3
Add blurb
ambv Jul 13, 2021
a3a65a0
Throw-away commit to check sanity of Azure Pipelines
ambv Jul 15, 2021
05e8247
Revert "Throw-away commit to check sanity of Azure Pipelines"
ambv Jul 15, 2021
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86 changes: 86 additions & 0 deletions Lib/test/test_decorators.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
from test import support
import unittest
from types import MethodType

def funcattrs(**kwds):
def decorate(func):
Expand Down Expand Up @@ -329,6 +330,91 @@ def outer(cls):
self.assertEqual(Class().inner(), 'spam')
self.assertEqual(Class().outer(), 'eggs')

def test_wrapped_classmethod_inside_classmethod(self):
class MyClassMethod1:
def __init__(self, func):
self.func = func

def __call__(self, cls):
if hasattr(self.func, '__get__'):
return self.func.__get__(cls, cls)()
return self.func(cls)

def __get__(self, instance, owner=None):
if owner is None:
owner = type(instance)
return MethodType(self, owner)

class MyClassMethod2:
def __init__(self, func):
if isinstance(func, classmethod):
func = func.__func__
self.func = func

def __call__(self, cls):
return self.func(cls)

def __get__(self, instance, owner=None):
if owner is None:
owner = type(instance)
return MethodType(self, owner)

for myclassmethod in [MyClassMethod1, MyClassMethod2]:
class A:
@myclassmethod
def f1(cls):
return cls

@classmethod
@myclassmethod
def f2(cls):
return cls

@myclassmethod
@classmethod
def f3(cls):
return cls

@classmethod
@classmethod
def f4(cls):
return cls

@myclassmethod
@MyClassMethod1
def f5(cls):
return cls

@myclassmethod
@MyClassMethod2
def f6(cls):
return cls

self.assertIs(A.f1(), A)
self.assertIs(A.f2(), A)
self.assertIs(A.f3(), A)
self.assertIs(A.f4(), A)
self.assertIs(A.f5(), A)
self.assertIs(A.f6(), A)
a = A()
self.assertIs(a.f1(), A)
self.assertIs(a.f2(), A)
self.assertIs(a.f3(), A)
self.assertIs(a.f4(), A)
self.assertIs(a.f5(), A)
self.assertIs(a.f6(), A)

def f(cls):
return cls

self.assertIs(myclassmethod(f).__get__(a)(), A)
self.assertIs(myclassmethod(f).__get__(a, A)(), A)
self.assertIs(myclassmethod(f).__get__(A, A)(), A)
self.assertIs(myclassmethod(f).__get__(A)(), type(A))
self.assertIs(classmethod(f).__get__(a)(), A)
self.assertIs(classmethod(f).__get__(a, A)(), A)
self.assertIs(classmethod(f).__get__(A, A)(), A)
self.assertIs(classmethod(f).__get__(A)(), type(A))

class TestClassDecorators(unittest.TestCase):

Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-07-13-17-47-32.bpo-42073.9wopiC.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
The ``@classmethod`` decorator can now wrap other classmethod-like
descriptors.
2 changes: 1 addition & 1 deletion Objects/funcobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -851,7 +851,7 @@ cm_descr_get(PyObject *self, PyObject *obj, PyObject *type)
type = (PyObject *)(Py_TYPE(obj));
if (Py_TYPE(cm->cm_callable)->tp_descr_get != NULL) {
return Py_TYPE(cm->cm_callable)->tp_descr_get(cm->cm_callable, type,
NULL);
type);
}
return PyMethod_New(cm->cm_callable, type);
}
Expand Down