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Close #19030: inspect.getmembers and inspect.classify_class_attrs 

Order of search is now:
  1. Try getattr
  2. If that throws an exception, check __dict__ directly
  3. If still not found, walk the mro looking for the eldest class that has
     the attribute (e.g. things returned by __getattr__)
  4. If none of that works (e.g. due to a buggy __dir__, __getattr__, etc.
     method or missing __slot__ attribute), ignore the attribute entirely.
This commit is contained in:
Ethan Furman 2013-10-18 00:27:39 -07:00
parent 0e0cd46227
commit 63c141cacd
5 changed files with 131 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Doc/library/inspect.rst
View File

@ -173,9 +173,9 @@ attributes:
.. note::
:func:`getmembers` will only return metaclass attributes when the
argument is a class and those attributes have been listed in a custom
:meth:`__dir__`.
:func:`getmembers` will only return class attributes defined in the
metaclass when the argument is a class and those attributes have been
listed in the metaclass' custom :meth:`__dir__`.
.. function:: getmoduleinfo(path)

57
Lib/inspect.py
View File

@ -280,18 +280,22 @@ def getmembers(object, predicate=None):
except AttributeError:
pass
for key in names:
# First try to get the value via __dict__. Some descriptors don't
# like calling their __get__ (see bug #1785).
for base in mro:
if key in base.__dict__ and key not in processed:
# handle the normal case first; if duplicate entries exist
# they will be handled second
value = base.__dict__[key]
break
else:
try:
value = getattr(object, key)
except AttributeError:
# First try to get the value via getattr. Some descriptors don't
# like calling their __get__ (see bug #1785), so fall back to
# looking in the __dict__.
try:
value = getattr(object, key)
# handle the duplicate key
if key in processed:
raise AttributeError
except AttributeError:
for base in mro:
if key in base.__dict__:
value = base.__dict__[key]
break
else:
# could be a (currently) missing slot member, or a buggy
# __dir__; discard and move on
continue
if not predicate or predicate(value):
results.append((key, value))
@ -336,7 +340,7 @@ def classify_class_attrs(cls):
# add any virtual attributes to the list of names
# this may result in duplicate entries if, for example, a virtual
# attribute with the same name as a member property exists
for base in cls.__bases__:
for base in mro:
for k, v in base.__dict__.items():
if isinstance(v, types.DynamicClassAttribute):
names.append(k)
@ -356,36 +360,43 @@ def classify_class_attrs(cls):
homecls = None
get_obj = sentinel
dict_obj = sentinel
if name not in processed:
try:
get_obj = getattr(cls, name)
except Exception as exc:
pass
else:
homecls = getattr(get_obj, "__class__")
homecls = getattr(get_obj, "__objclass__", homecls)
if homecls not in possible_bases:
# if the resulting object does not live somewhere in the
# mro, drop it and go with the dict_obj version only
# mro, drop it and search the mro manually
homecls = None
get_obj = sentinel
last_cls = None
last_obj = None
for srch_cls in ((cls,) + mro):
srch_obj = getattr(srch_cls, name, None)
if srch_obj is get_obj:
last_cls = srch_cls
last_obj = srch_obj
if last_cls is not None:
homecls = last_cls
for base in possible_bases:
if name in base.__dict__:
dict_obj = base.__dict__[name]
homecls = homecls or base
break
if homecls is None:
# unable to locate the attribute anywhere, most likely due to
# buggy custom __dir__; discard and move on
continue
# Classify the object or its descriptor.
if get_obj is not sentinel:
obj = get_obj
else:
obj = dict_obj
if isinstance(obj, staticmethod):
if isinstance(dict_obj, staticmethod):
kind = "static method"
elif isinstance(obj, classmethod):
elif isinstance(dict_obj, classmethod):
kind = "class method"
elif isinstance(obj, property):
kind = "property"
@ -393,10 +404,8 @@ def classify_class_attrs(cls):
kind = "method"
else:
kind = "data"
result.append(Attribute(name, kind, homecls, obj))
processed.add(name)
return result
# ----------------------------------------------------------- class helpers

100
Lib/test/test_inspect.py
View File

@ -126,7 +126,6 @@ class TestPredicates(IsTestBase):
def test_get_slot_members(self):
class C(object):
__slots__ = ("a", "b")
x = C()
x.a = 42
members = dict(inspect.getmembers(x))
@ -469,13 +468,13 @@ class _BrokenDataDescriptor(object):
A broken data descriptor. See bug #1785.
"""
def __get__(*args):
raise AssertionError("should not __get__ data descriptors")
raise AttributeError("broken data descriptor")
def __set__(*args):
raise RuntimeError
def __getattr__(*args):
raise AssertionError("should not __getattr__ data descriptors")
raise AttributeError("broken data descriptor")
class _BrokenMethodDescriptor(object):
@ -483,10 +482,10 @@ class _BrokenMethodDescriptor(object):
A broken method descriptor. See bug #1785.
"""
def __get__(*args):
raise AssertionError("should not __get__ method descriptors")
raise AttributeError("broken method descriptor")
def __getattr__(*args):
raise AssertionError("should not __getattr__ method descriptors")
raise AttributeError("broken method descriptor")
# Helper for testing classify_class_attrs.
@ -656,13 +655,77 @@ class TestClassesAndFunctions(unittest.TestCase):
if isinstance(builtin, type):
inspect.classify_class_attrs(builtin)
def test_classify_VirtualAttribute(self):
class VA:
def test_classify_DynamicClassAttribute(self):
class Meta(type):
def __getattr__(self, name):
if name == 'ham':
return 'spam'
return super().__getattr__(name)
class VA(metaclass=Meta):
@types.DynamicClassAttribute
def ham(self):
return 'eggs'
should_find = inspect.Attribute('ham', 'data', VA, VA.__dict__['ham'])
self.assertIn(should_find, inspect.classify_class_attrs(VA))
should_find_dca = inspect.Attribute('ham', 'data', VA, VA.__dict__['ham'])
self.assertIn(should_find_dca, inspect.classify_class_attrs(VA))
should_find_ga = inspect.Attribute('ham', 'data', VA, 'spam')
self.assertIn(should_find_ga, inspect.classify_class_attrs(VA))
def test_classify_VirtualAttribute(self):
class Meta(type):
def __dir__(cls):
return ['__class__', '__module__', '__name__', 'BOOM']
def __getattr__(self, name):
if name =='BOOM':
return 42
return super().__getattr(name)
class Class(metaclass=Meta):
pass
should_find = inspect.Attribute('BOOM', 'data', Class, 42)
self.assertIn(should_find, inspect.classify_class_attrs(Class))
def test_classify_VirtualAttribute_multi_classes(self):
class Meta1(type):
def __dir__(cls):
return ['__class__', '__module__', '__name__', 'one']
def __getattr__(self, name):
if name =='one':
return 1
return super().__getattr__(name)
class Meta2(type):
def __dir__(cls):
return ['__class__', '__module__', '__name__', 'two']
def __getattr__(self, name):
if name =='two':
return 2
return super().__getattr__(name)
class Meta3(Meta1, Meta2):
def __dir__(cls):
return list(sorted(set(['__class__', '__module__', '__name__', 'three'] +
Meta1.__dir__(cls) + Meta2.__dir__(cls))))
def __getattr__(self, name):
if name =='three':
return 3
return super().__getattr__(name)
class Class1(metaclass=Meta1):
pass
class Class2(Class1, metaclass=Meta3):
pass
should_find1 = inspect.Attribute('one', 'data', Class1, 1)
should_find2 = inspect.Attribute('two', 'data', Class2, 2)
should_find3 = inspect.Attribute('three', 'data', Class2, 3)
cca = inspect.classify_class_attrs(Class2)
for sf in (should_find1, should_find2, should_find3):
self.assertIn(sf, cca)
def test_classify_class_attrs_with_buggy_dir(self):
class M(type):
def __dir__(cls):
return ['__class__', '__name__', 'missing']
class C(metaclass=M):
pass
attrs = [a[0] for a in inspect.classify_class_attrs(C)]
self.assertNotIn('missing', attrs)
def test_getmembers_descriptors(self):
class A(object):
@ -708,11 +771,26 @@ class TestClassesAndFunctions(unittest.TestCase):
self.assertIn(('f', b.f), inspect.getmembers(b, inspect.ismethod))
def test_getmembers_VirtualAttribute(self):
class A:
class M(type):
def __getattr__(cls, name):
if name == 'eggs':
return 'scrambled'
return super().__getattr__(name)
class A(metaclass=M):
@types.DynamicClassAttribute
def eggs(self):
return 'spam'
self.assertIn(('eggs', A.__dict__['eggs']), inspect.getmembers(A))
self.assertIn(('eggs', 'scrambled'), inspect.getmembers(A))
self.assertIn(('eggs', 'spam'), inspect.getmembers(A()))
def test_getmembers_with_buggy_dir(self):
class M(type):
def __dir__(cls):
return ['__class__', '__name__', 'missing']
class C(metaclass=M):
pass
attrs = [a[0] for a in inspect.getmembers(C)]
self.assertNotIn('missing', attrs)
_global_ref = object()

2
Lib/types.py
View File

@ -117,7 +117,7 @@ class DynamicClassAttribute:
self.fset = fset
self.fdel = fdel
# next two lines make DynamicClassAttribute act the same as property
self.__doc__ = doc or fget.__doc__ or self.__doc__
self.__doc__ = doc or fget.__doc__
self.overwrite_doc = doc is None
# support for abstract methods
self.__isabstractmethod__ = bool(getattr(fget, '__isabstractmethod__', False))

5
Misc/NEWS
View File

@ -135,6 +135,11 @@ Library
- Issue #4366: Fix building extensions on all platforms when --enable-shared
is used.
- Issue #19030: Fixed `inspect.getmembers` and `inspect.classify_class_attrs`
to attempt activating descriptors before falling back to a __dict__ search
for faulty descriptors. `inspect.classify_class_attrs` no longer returns
Attributes whose home class is None.
C API
-----