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import types
from pure_eval.utils import of_type, CannotEval
_sentinel = object()
def _static_getmro(klass):
return type.__dict__['__mro__'].__get__(klass)
def _check_instance(obj, attr):
instance_dict = {}
try:
instance_dict = object.__getattribute__(obj, "__dict__")
except AttributeError:
pass
return dict.get(instance_dict, attr, _sentinel)
def _check_class(klass, attr):
for entry in _static_getmro(klass):
if _shadowed_dict(type(entry)) is _sentinel:
try:
return entry.__dict__[attr]
except KeyError:
pass
else:
break
return _sentinel
def _is_type(obj):
try:
_static_getmro(obj)
except TypeError:
return False
return True
def _shadowed_dict(klass):
dict_attr = type.__dict__["__dict__"]
for entry in _static_getmro(klass):
try:
class_dict = dict_attr.__get__(entry)["__dict__"]
except KeyError:
pass
else:
if not (type(class_dict) is types.GetSetDescriptorType and
class_dict.__name__ == "__dict__" and
class_dict.__objclass__ is entry):
return class_dict
return _sentinel
def getattr_static(obj, attr):
"""Retrieve attributes without triggering dynamic lookup via the
descriptor protocol, __getattr__ or __getattribute__.
Note: this function may not be able to retrieve all attributes
that getattr can fetch (like dynamically created attributes)
and may find attributes that getattr can't (like descriptors
that raise AttributeError). It can also return descriptor objects
instead of instance members in some cases. See the
documentation for details.
"""
instance_result = _sentinel
if not _is_type(obj):
klass = type(obj)
dict_attr = _shadowed_dict(klass)
if (dict_attr is _sentinel or
type(dict_attr) is types.MemberDescriptorType):
instance_result = _check_instance(obj, attr)
else:
raise CannotEval
else:
klass = obj
klass_result = _check_class(klass, attr)
if instance_result is not _sentinel and klass_result is not _sentinel:
if (_check_class(type(klass_result), '__get__') is not _sentinel and
_check_class(type(klass_result), '__set__') is not _sentinel):
return _resolve_descriptor(klass_result, obj, klass)
if instance_result is not _sentinel:
return instance_result
if klass_result is not _sentinel:
get = _check_class(type(klass_result), '__get__')
if get is _sentinel:
return klass_result
else:
if obj is klass:
instance = None
else:
instance = obj
return _resolve_descriptor(klass_result, instance, klass)
if obj is klass:
# for types we check the metaclass too
for entry in _static_getmro(type(klass)):
if _shadowed_dict(type(entry)) is _sentinel:
try:
result = entry.__dict__[attr]
get = _check_class(type(result), '__get__')
if get is not _sentinel:
raise CannotEval
return result
except KeyError:
pass
raise CannotEval
class _foo:
__slots__ = ['foo']
method = lambda: 0
slot_descriptor = _foo.foo
wrapper_descriptor = str.__dict__['__add__']
method_descriptor = str.__dict__['startswith']
user_method_descriptor = _foo.__dict__['method']
safe_descriptors_raw = [
slot_descriptor,
wrapper_descriptor,
method_descriptor,
user_method_descriptor,
]
safe_descriptor_types = list(map(type, safe_descriptors_raw))
def _resolve_descriptor(d, instance, owner):
try:
return type(of_type(d, *safe_descriptor_types)).__get__(d, instance, owner)
except AttributeError as e:
raise CannotEval from e
|
