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bpo-44904: Fix classmethod property bug in doctest module #28838

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Merged
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Oct 28, 2021
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bpo-44904: Fix classmethod property bug in doctest module #28838

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c534a63
bpo 44904: Fix classmethod property bug in doctest module
AlexWaygood Oct 9, 2021
7ffdd1d
Simplify
serhiy-storchaka Oct 10, 2021
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4 changes: 3 additions & 1 deletion Lib/doctest.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1037,7 +1037,9 @@ def _find(self, tests, obj, name, module, source_lines, globs, seen):
if isinstance(val, staticmethod):
val = getattr(obj, valname)
if isinstance(val, classmethod):
val = getattr(obj, valname).__func__
# Lookup via __dict__ instead of getattr
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This PR should not go forward until issue 45356 is resolved. Wrapping classmethod around property seems to have some intrinsic flaws that shouldn't be papered over.

Also, when replacing getattr with a dict lookup, we need to consider whether the entire __mro__ should be searched.

Lastly, any "solution" to this or the help() bug should probably share a standardized solution, perhaps some variant of hasattr() that doesn't have the __getattr__ hook and that doesn't trigger descriptor behavior.

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This all makes sense. Thanks for taking a look, anyhow!

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__mro__ is not related here. We iterate the class' __dict__ and look at methods defined in the class.

# in case it is a classmethod property.
val = obj.__dict__[valname].__func__

# Recurse to methods, properties, and nested classes.
if ((inspect.isroutine(val) or inspect.isclass(val) or
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15 changes: 15 additions & 0 deletions Lib/test/test_doctest.py
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Expand Up @@ -96,6 +96,17 @@ def a_classmethod(cls, v):
22
""")

a_class_attribute = 42

@classmethod
@property
def a_classmethod_property(cls):
"""
>>> print(SampleClass.a_classmethod_property)
42
"""
return cls.a_class_attribute

class NestedClass:
"""
>>> x = SampleClass.NestedClass(5)
Expand Down Expand Up @@ -501,6 +512,7 @@ def basics(): r"""
1 SampleClass.NestedClass.__init__
1 SampleClass.__init__
2 SampleClass.a_classmethod
1 SampleClass.a_classmethod_property
1 SampleClass.a_property
1 SampleClass.a_staticmethod
1 SampleClass.double
Expand Down Expand Up @@ -556,6 +568,7 @@ def basics(): r"""
1 some_module.SampleClass.NestedClass.__init__
1 some_module.SampleClass.__init__
2 some_module.SampleClass.a_classmethod
1 some_module.SampleClass.a_classmethod_property
1 some_module.SampleClass.a_property
1 some_module.SampleClass.a_staticmethod
1 some_module.SampleClass.double
Expand Down Expand Up @@ -597,6 +610,7 @@ def basics(): r"""
1 SampleClass.NestedClass.__init__
1 SampleClass.__init__
2 SampleClass.a_classmethod
1 SampleClass.a_classmethod_property
1 SampleClass.a_property
1 SampleClass.a_staticmethod
1 SampleClass.double
Expand All @@ -617,6 +631,7 @@ def basics(): r"""
0 SampleClass.NestedClass.square
1 SampleClass.__init__
2 SampleClass.a_classmethod
1 SampleClass.a_classmethod_property
1 SampleClass.a_property
1 SampleClass.a_staticmethod
1 SampleClass.double
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1 change: 1 addition & 0 deletions Misc/ACKS
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Expand Up @@ -1885,6 +1885,7 @@ Bob Watson
Colin Watson
David Watson
Aaron Watters
Alex Waygood
Henrik Weber
Leon Weber
Steve Weber
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2021-10-09-18-42-27.bpo-44904.RlW5h8.rst
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@@ -0,0 +1,3 @@
Fix bug in the :mod:`doctest` module that caused it to fail if a docstring
included an example with a ``classmethod`` ``property``. Patch by Alex
Waygood.