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import os
import sys
import functools
import operator
import weakref
import inspect
PY2 = sys.version_info[0] == 2
if PY2:
string_types = basestring,
else:
string_types = str,
def with_metaclass(meta, *bases):
"""Create a base class with a metaclass."""
return meta("NewBase", bases, {})
class _ObjectProxyMethods(object):
# We use properties to override the values of __module__ and
# __doc__. If we add these in ObjectProxy, the derived class
# __dict__ will still be setup to have string variants of these
# attributes and the rules of descriptors means that they appear to
# take precedence over the properties in the base class. To avoid
# that, we copy the properties into the derived class type itself
# via a meta class. In that way the properties will always take
# precedence.
@property
def __module__(self):
return self.__wrapped__.__module__
@__module__.setter
def __module__(self, value):
self.__wrapped__.__module__ = value
@property
def __doc__(self):
return self.__wrapped__.__doc__
@__doc__.setter
def __doc__(self, value):
self.__wrapped__.__doc__ = value
# We similar use a property for __dict__. We need __dict__ to be
# explicit to ensure that vars() works as expected.
@property
def __dict__(self):
return self.__wrapped__.__dict__
# Need to also propagate the special __weakref__ attribute for case
# where decorating classes which will define this. If do not define
# it and use a function like inspect.getmembers() on a decorator
# class it will fail. This can't be in the derived classes.
@property
def __weakref__(self):
return self.__wrapped__.__weakref__
class _ObjectProxyMetaType(type):
def __new__(cls, name, bases, dictionary):
# Copy our special properties into the class so that they
# always take precedence over attributes of the same name added
# during construction of a derived class. This is to save
# duplicating the implementation for them in all derived classes.
dictionary.update(vars(_ObjectProxyMethods))
return type.__new__(cls, name, bases, dictionary)
class ObjectProxy(with_metaclass(_ObjectProxyMetaType)):
__slots__ = '__wrapped__'
def __init__(self, wrapped):
object.__setattr__(self, '__wrapped__', wrapped)
# Python 3.2+ has the __qualname__ attribute, but it does not
# allow it to be overridden using a property and it must instead
# be an actual string object instead.
try:
object.__setattr__(self, '__qualname__', wrapped.__qualname__)
except AttributeError:
pass
# Python 3.10 onwards also does not allow itself to be overridden
# using a property and it must instead be set explicitly.
try:
object.__setattr__(self, '__annotations__', wrapped.__annotations__)
except AttributeError:
pass
@property
def __name__(self):
return self.__wrapped__.__name__
@__name__.setter
def __name__(self, value):
self.__wrapped__.__name__ = value
@property
def __class__(self):
return self.__wrapped__.__class__
@__class__.setter
def __class__(self, value):
self.__wrapped__.__class__ = value
def __dir__(self):
return dir(self.__wrapped__)
def __str__(self):
return str(self.__wrapped__)
if not PY2:
def __bytes__(self):
return bytes(self.__wrapped__)
def __repr__(self):
return '<{} at 0x{:x} for {} at 0x{:x}>'.format(
type(self).__name__, id(self),
type(self.__wrapped__).__name__,
id(self.__wrapped__))
def __reversed__(self):
return reversed(self.__wrapped__)
if not PY2:
def __round__(self):
return round(self.__wrapped__)
if sys.hexversion >= 0x03070000:
def __mro_entries__(self, bases):
return (self.__wrapped__,)
def __lt__(self, other):
return self.__wrapped__ < other
def __le__(self, other):
return self.__wrapped__ <= other
def __eq__(self, other):
return self.__wrapped__ == other
def __ne__(self, other):
return self.__wrapped__ != other
def __gt__(self, other):
return self.__wrapped__ > other
def __ge__(self, other):
return self.__wrapped__ >= other
def __hash__(self):
return hash(self.__wrapped__)
def __nonzero__(self):
return bool(self.__wrapped__)
def __bool__(self):
return bool(self.__wrapped__)
def __setattr__(self, name, value):
if name.startswith('_self_'):
object.__setattr__(self, name, value)
elif name == '__wrapped__':
object.__setattr__(self, name, value)
try:
object.__delattr__(self, '__qualname__')
except AttributeError:
pass
try:
object.__setattr__(self, '__qualname__', value.__qualname__)
except AttributeError:
pass
try:
object.__delattr__(self, '__annotations__')
except AttributeError:
pass
try:
object.__setattr__(self, '__annotations__', value.__annotations__)
except AttributeError:
pass
elif name == '__qualname__':
setattr(self.__wrapped__, name, value)
object.__setattr__(self, name, value)
elif name == '__annotations__':
setattr(self.__wrapped__, name, value)
object.__setattr__(self, name, value)
elif hasattr(type(self), name):
object.__setattr__(self, name, value)
else:
setattr(self.__wrapped__, name, value)
def __getattr__(self, name):
# If we are being to lookup '__wrapped__' then the
# '__init__()' method cannot have been called.
if name == '__wrapped__':
raise ValueError('wrapper has not been initialised')
return getattr(self.__wrapped__, name)
def __delattr__(self, name):
if name.startswith('_self_'):
object.__delattr__(self, name)
elif name == '__wrapped__':
raise TypeError('__wrapped__ must be an object')
elif name == '__qualname__':
object.__delattr__(self, name)
delattr(self.__wrapped__, name)
elif hasattr(type(self), name):
object.__delattr__(self, name)
else:
delattr(self.__wrapped__, name)
def __add__(self, other):
return self.__wrapped__ + other
def __sub__(self, other):
return self.__wrapped__ - other
def __mul__(self, other):
return self.__wrapped__ * other
def __div__(self, other):
return operator.div(self.__wrapped__, other)
def __truediv__(self, other):
return operator.truediv(self.__wrapped__, other)
def __floordiv__(self, other):
return self.__wrapped__ // other
def __mod__(self, other):
return self.__wrapped__ % other
def __divmod__(self, other):
return divmod(self.__wrapped__, other)
def __pow__(self, other, *args):
return pow(self.__wrapped__, other, *args)
def __lshift__(self, other):
return self.__wrapped__ << other
def __rshift__(self, other):
return self.__wrapped__ >> other
def __and__(self, other):
return self.__wrapped__ & other
def __xor__(self, other):
return self.__wrapped__ ^ other
def __or__(self, other):
return self.__wrapped__ | other
def __radd__(self, other):
return other + self.__wrapped__
def __rsub__(self, other):
return other - self.__wrapped__
def __rmul__(self, other):
return other * self.__wrapped__
def __rdiv__(self, other):
return operator.div(other, self.__wrapped__)
def __rtruediv__(self, other):
return operator.truediv(other, self.__wrapped__)
def __rfloordiv__(self, other):
return other // self.__wrapped__
def __rmod__(self, other):
return other % self.__wrapped__
def __rdivmod__(self, other):
return divmod(other, self.__wrapped__)
def __rpow__(self, other, *args):
return pow(other, self.__wrapped__, *args)
def __rlshift__(self, other):
return other << self.__wrapped__
def __rrshift__(self, other):
return other >> self.__wrapped__
def __rand__(self, other):
return other & self.__wrapped__
def __rxor__(self, other):
return other ^ self.__wrapped__
def __ror__(self, other):
return other | self.__wrapped__
def __iadd__(self, other):
self.__wrapped__ += other
return self
def __isub__(self, other):
self.__wrapped__ -= other
return self
def __imul__(self, other):
self.__wrapped__ *= other
return self
def __idiv__(self, other):
self.__wrapped__ = operator.idiv(self.__wrapped__, other)
return self
def __itruediv__(self, other):
self.__wrapped__ = operator.itruediv(self.__wrapped__, other)
return self
def __ifloordiv__(self, other):
self.__wrapped__ //= other
return self
def __imod__(self, other):
self.__wrapped__ %= other
return self
def __ipow__(self, other):
self.__wrapped__ **= other
return self
def __ilshift__(self, other):
self.__wrapped__ <<= other
return self
def __irshift__(self, other):
self.__wrapped__ >>= other
return self
def __iand__(self, other):
self.__wrapped__ &= other
return self
def __ixor__(self, other):
self.__wrapped__ ^= other
return self
def __ior__(self, other):
self.__wrapped__ |= other
return self
def __neg__(self):
return -self.__wrapped__
def __pos__(self):
return +self.__wrapped__
def __abs__(self):
return abs(self.__wrapped__)
def __invert__(self):
return ~self.__wrapped__
def __int__(self):
return int(self.__wrapped__)
def __long__(self):
return long(self.__wrapped__)
def __float__(self):
return float(self.__wrapped__)
def __complex__(self):
return complex(self.__wrapped__)
def __oct__(self):
return oct(self.__wrapped__)
def __hex__(self):
return hex(self.__wrapped__)
def __index__(self):
return operator.index(self.__wrapped__)
def __len__(self):
return len(self.__wrapped__)
def __contains__(self, value):
return value in self.__wrapped__
def __getitem__(self, key):
return self.__wrapped__[key]
def __setitem__(self, key, value):
self.__wrapped__[key] = value
def __delitem__(self, key):
del self.__wrapped__[key]
def __getslice__(self, i, j):
return self.__wrapped__[i:j]
def __setslice__(self, i, j, value):
self.__wrapped__[i:j] = value
def __delslice__(self, i, j):
del self.__wrapped__[i:j]
def __enter__(self):
return self.__wrapped__.__enter__()
def __exit__(self, *args, **kwargs):
return self.__wrapped__.__exit__(*args, **kwargs)
def __iter__(self):
return iter(self.__wrapped__)
def __copy__(self):
raise NotImplementedError('object proxy must define __copy__()')
def __deepcopy__(self, memo):
raise NotImplementedError('object proxy must define __deepcopy__()')
def __reduce__(self):
raise NotImplementedError(
'object proxy must define __reduce_ex__()')
def __reduce_ex__(self, protocol):
raise NotImplementedError(
'object proxy must define __reduce_ex__()')
class CallableObjectProxy(ObjectProxy):
def __call__(*args, **kwargs):
def _unpack_self(self, *args):
return self, args
self, args = _unpack_self(*args)
return self.__wrapped__(*args, **kwargs)
class PartialCallableObjectProxy(ObjectProxy):
def __init__(*args, **kwargs):
def _unpack_self(self, *args):
return self, args
self, args = _unpack_self(*args)
if len(args) < 1:
raise TypeError('partial type takes at least one argument')
wrapped, args = args[0], args[1:]
if not callable(wrapped):
raise TypeError('the first argument must be callable')
super(PartialCallableObjectProxy, self).__init__(wrapped)
self._self_args = args
self._self_kwargs = kwargs
def __call__(*args, **kwargs):
def _unpack_self(self, *args):
return self, args
self, args = _unpack_self(*args)
_args = self._self_args + args
_kwargs = dict(self._self_kwargs)
_kwargs.update(kwargs)
return self.__wrapped__(*_args, **_kwargs)
class _FunctionWrapperBase(ObjectProxy):
__slots__ = ('_self_instance', '_self_wrapper', '_self_enabled',
'_self_binding', '_self_parent')
def __init__(self, wrapped, instance, wrapper, enabled=None,
binding='function', parent=None):
super(_FunctionWrapperBase, self).__init__(wrapped)
object.__setattr__(self, '_self_instance', instance)
object.__setattr__(self, '_self_wrapper', wrapper)
object.__setattr__(self, '_self_enabled', enabled)
object.__setattr__(self, '_self_binding', binding)
object.__setattr__(self, '_self_parent', parent)
def __get__(self, instance, owner):
# This method is actually doing double duty for both unbound and
# bound derived wrapper classes. It should possibly be broken up
# and the distinct functionality moved into the derived classes.
# Can't do that straight away due to some legacy code which is
# relying on it being here in this base class.
#
# The distinguishing attribute which determines whether we are
# being called in an unbound or bound wrapper is the parent
# attribute. If binding has never occurred, then the parent will
# be None.
#
# First therefore, is if we are called in an unbound wrapper. In
# this case we perform the binding.
#
# We have one special case to worry about here. This is where we
# are decorating a nested class. In this case the wrapped class
# would not have a __get__() method to call. In that case we
# simply return self.
#
# Note that we otherwise still do binding even if instance is
# None and accessing an unbound instance method from a class.
# This is because we need to be able to later detect that
# specific case as we will need to extract the instance from the
# first argument of those passed in.
if self._self_parent is None:
if not inspect.isclass(self.__wrapped__):
descriptor = self.__wrapped__.__get__(instance, owner)
return self.__bound_function_wrapper__(descriptor, instance,
self._self_wrapper, self._self_enabled,
self._self_binding, self)
return self
# Now we have the case of binding occurring a second time on what
# was already a bound function. In this case we would usually
# return ourselves again. This mirrors what Python does.
#
# The special case this time is where we were originally bound
# with an instance of None and we were likely an instance
# method. In that case we rebind against the original wrapped
# function from the parent again.
if self._self_instance is None and self._self_binding == 'function':
descriptor = self._self_parent.__wrapped__.__get__(
instance, owner)
return self._self_parent.__bound_function_wrapper__(
descriptor, instance, self._self_wrapper,
self._self_enabled, self._self_binding,
self._self_parent)
return self
def __call__(*args, **kwargs):
def _unpack_self(self, *args):
return self, args
self, args = _unpack_self(*args)
# If enabled has been specified, then evaluate it at this point
# and if the wrapper is not to be executed, then simply return
# the bound function rather than a bound wrapper for the bound
# function. When evaluating enabled, if it is callable we call
# it, otherwise we evaluate it as a boolean.
if self._self_enabled is not None:
if callable(self._self_enabled):
if not self._self_enabled():
return self.__wrapped__(*args, **kwargs)
elif not self._self_enabled:
return self.__wrapped__(*args, **kwargs)
# This can occur where initial function wrapper was applied to
# a function that was already bound to an instance. In that case
# we want to extract the instance from the function and use it.
if self._self_binding in ('function', 'classmethod'):
if self._self_instance is None:
instance = getattr(self.__wrapped__, '__self__', None)
if instance is not None:
return self._self_wrapper(self.__wrapped__, instance,
args, kwargs)
# This is generally invoked when the wrapped function is being
# called as a normal function and is not bound to a class as an
# instance method. This is also invoked in the case where the
# wrapped function was a method, but this wrapper was in turn
# wrapped using the staticmethod decorator.
return self._self_wrapper(self.__wrapped__, self._self_instance,
args, kwargs)
def __set_name__(self, owner, name):
# This is a special method use to supply information to
# descriptors about what the name of variable in a class
# definition is. Not wanting to add this to ObjectProxy as not
# sure of broader implications of doing that. Thus restrict to
# FunctionWrapper used by decorators.
if hasattr(self.__wrapped__, "__set_name__"):
self.__wrapped__.__set_name__(owner, name)
def __instancecheck__(self, instance):
# This is a special method used by isinstance() to make checks
# instance of the `__wrapped__`.
return isinstance(instance, self.__wrapped__)
def __subclasscheck__(self, subclass):
# This is a special method used by issubclass() to make checks
# about inheritance of classes. We need to upwrap any object
# proxy. Not wanting to add this to ObjectProxy as not sure of
# broader implications of doing that. Thus restrict to
# FunctionWrapper used by decorators.
if hasattr(subclass, "__wrapped__"):
return issubclass(subclass.__wrapped__, self.__wrapped__)
else:
return issubclass(subclass, self.__wrapped__)
class BoundFunctionWrapper(_FunctionWrapperBase):
def __call__(*args, **kwargs):
def _unpack_self(self, *args):
return self, args
self, args = _unpack_self(*args)
# If enabled has been specified, then evaluate it at this point
# and if the wrapper is not to be executed, then simply return
# the bound function rather than a bound wrapper for the bound
# function. When evaluating enabled, if it is callable we call
# it, otherwise we evaluate it as a boolean.
if self._self_enabled is not None:
if callable(self._self_enabled):
if not self._self_enabled():
return self.__wrapped__(*args, **kwargs)
elif not self._self_enabled:
return self.__wrapped__(*args, **kwargs)
# We need to do things different depending on whether we are
# likely wrapping an instance method vs a static method or class
# method.
if self._self_binding == 'function':
if self._self_instance is None:
# This situation can occur where someone is calling the
# instancemethod via the class type and passing the instance
# as the first argument. We need to shift the args before
# making the call to the wrapper and effectively bind the
# instance to the wrapped function using a partial so the
# wrapper doesn't see anything as being different.
if not args:
raise TypeError('missing 1 required positional argument')
instance, args = args[0], args[1:]
wrapped = PartialCallableObjectProxy(self.__wrapped__, instance)
return self._self_wrapper(wrapped, instance, args, kwargs)
return self._self_wrapper(self.__wrapped__, self._self_instance,
args, kwargs)
else:
# As in this case we would be dealing with a classmethod or
# staticmethod, then _self_instance will only tell us whether
# when calling the classmethod or staticmethod they did it via an
# instance of the class it is bound to and not the case where
# done by the class type itself. We thus ignore _self_instance
# and use the __self__ attribute of the bound function instead.
# For a classmethod, this means instance will be the class type
# and for a staticmethod it will be None. This is probably the
# more useful thing we can pass through even though we loose
# knowledge of whether they were called on the instance vs the
# class type, as it reflects what they have available in the
# decoratored function.
instance = getattr(self.__wrapped__, '__self__', None)
return self._self_wrapper(self.__wrapped__, instance, args,
kwargs)
class FunctionWrapper(_FunctionWrapperBase):
__bound_function_wrapper__ = BoundFunctionWrapper
def __init__(self, wrapped, wrapper, enabled=None):
# What it is we are wrapping here could be anything. We need to
# try and detect specific cases though. In particular, we need
# to detect when we are given something that is a method of a
# class. Further, we need to know when it is likely an instance
# method, as opposed to a class or static method. This can
# become problematic though as there isn't strictly a fool proof
# method of knowing.
#
# The situations we could encounter when wrapping a method are:
#
# 1. The wrapper is being applied as part of a decorator which
# is a part of the class definition. In this case what we are
# given is the raw unbound function, classmethod or staticmethod
# wrapper objects.
#
# The problem here is that we will not know we are being applied
# in the context of the class being set up. This becomes
# important later for the case of an instance method, because in
# that case we just see it as a raw function and can't
# distinguish it from wrapping a normal function outside of
# a class context.
#
# 2. The wrapper is being applied when performing monkey
# patching of the class type afterwards and the method to be
# wrapped was retrieved direct from the __dict__ of the class
# type. This is effectively the same as (1) above.
#
# 3. The wrapper is being applied when performing monkey
# patching of the class type afterwards and the method to be
# wrapped was retrieved from the class type. In this case
# binding will have been performed where the instance against
# which the method is bound will be None at that point.
#
# This case is a problem because we can no longer tell if the
# method was a static method, plus if using Python3, we cannot
# tell if it was an instance method as the concept of an
# unnbound method no longer exists.
#
# 4. The wrapper is being applied when performing monkey
# patching of an instance of a class. In this case binding will
# have been perfomed where the instance was not None.
#
# This case is a problem because we can no longer tell if the
# method was a static method.
#
# Overall, the best we can do is look at the original type of the
# object which was wrapped prior to any binding being done and
# see if it is an instance of classmethod or staticmethod. In
# the case where other decorators are between us and them, if
# they do not propagate the __class__ attribute so that the
# isinstance() checks works, then likely this will do the wrong
# thing where classmethod and staticmethod are used.
#
# Since it is likely to be very rare that anyone even puts
# decorators around classmethod and staticmethod, likelihood of
# that being an issue is very small, so we accept it and suggest
# that those other decorators be fixed. It is also only an issue
# if a decorator wants to actually do things with the arguments.
#
# As to not being able to identify static methods properly, we
# just hope that that isn't something people are going to want
# to wrap, or if they do suggest they do it the correct way by
# ensuring that it is decorated in the class definition itself,
# or patch it in the __dict__ of the class type.
#
# So to get the best outcome we can, whenever we aren't sure what
# it is, we label it as a 'function'. If it was already bound and
# that is rebound later, we assume that it will be an instance
# method and try an cope with the possibility that the 'self'
# argument it being passed as an explicit argument and shuffle
# the arguments around to extract 'self' for use as the instance.
if isinstance(wrapped, classmethod):
binding = 'classmethod'
elif isinstance(wrapped, staticmethod):
binding = 'staticmethod'
elif hasattr(wrapped, '__self__'):
if inspect.isclass(wrapped.__self__):
binding = 'classmethod'
else:
binding = 'function'
else:
binding = 'function'
super(FunctionWrapper, self).__init__(wrapped, None, wrapper,
enabled, binding)
try:
if not os.environ.get('WRAPT_DISABLE_EXTENSIONS'):
from ._wrappers import (ObjectProxy, CallableObjectProxy,
PartialCallableObjectProxy, FunctionWrapper,
BoundFunctionWrapper, _FunctionWrapperBase)
except ImportError:
pass
# Helper functions for applying wrappers to existing functions.
def resolve_path(module, name):
if isinstance(module, string_types):
__import__(module)
module = sys.modules[module]
parent = module
path = name.split('.')
attribute = path[0]
# We can't just always use getattr() because in doing
# that on a class it will cause binding to occur which
# will complicate things later and cause some things not
# to work. For the case of a class we therefore access
# the __dict__ directly. To cope though with the wrong
# class being given to us, or a method being moved into
# a base class, we need to walk the class hierarchy to
# work out exactly which __dict__ the method was defined
# in, as accessing it from __dict__ will fail if it was
# not actually on the class given. Fallback to using
# getattr() if we can't find it. If it truly doesn't
# exist, then that will fail.
def lookup_attribute(parent, attribute):
if inspect.isclass(parent):
for cls in inspect.getmro(parent):
if attribute in vars(cls):
return vars(cls)[attribute]
else:
return getattr(parent, attribute)
else:
return getattr(parent, attribute)
original = lookup_attribute(parent, attribute)
for attribute in path[1:]:
parent = original
original = lookup_attribute(parent, attribute)
return (parent, attribute, original)
def apply_patch(parent, attribute, replacement):
setattr(parent, attribute, replacement)
def wrap_object(module, name, factory, args=(), kwargs={}):
(parent, attribute, original) = resolve_path(module, name)
wrapper = factory(original, *args, **kwargs)
apply_patch(parent, attribute, wrapper)
return wrapper
# Function for applying a proxy object to an attribute of a class
# instance. The wrapper works by defining an attribute of the same name
# on the class which is a descriptor and which intercepts access to the
# instance attribute. Note that this cannot be used on attributes which
# are themselves defined by a property object.
class AttributeWrapper(object):
def __init__(self, attribute, factory, args, kwargs):
self.attribute = attribute
self.factory = factory
self.args = args
self.kwargs = kwargs
def __get__(self, instance, owner):
value = instance.__dict__[self.attribute]
return self.factory(value, *self.args, **self.kwargs)
def __set__(self, instance, value):
instance.__dict__[self.attribute] = value
def __delete__(self, instance):
del instance.__dict__[self.attribute]
def wrap_object_attribute(module, name, factory, args=(), kwargs={}):
path, attribute = name.rsplit('.', 1)
parent = resolve_path(module, path)[2]
wrapper = AttributeWrapper(attribute, factory, args, kwargs)
apply_patch(parent, attribute, wrapper)
return wrapper
# Functions for creating a simple decorator using a FunctionWrapper,
# plus short cut functions for applying wrappers to functions. These are
# for use when doing monkey patching. For a more featured way of
# creating decorators see the decorator decorator instead.
def function_wrapper(wrapper):
def _wrapper(wrapped, instance, args, kwargs):
target_wrapped = args[0]
if instance is None:
target_wrapper = wrapper
elif inspect.isclass(instance):
target_wrapper = wrapper.__get__(None, instance)
else:
target_wrapper = wrapper.__get__(instance, type(instance))
return FunctionWrapper(target_wrapped, target_wrapper)
return FunctionWrapper(wrapper, _wrapper)
def wrap_function_wrapper(module, name, wrapper):
return wrap_object(module, name, FunctionWrapper, (wrapper,))
def patch_function_wrapper(module, name):
def _wrapper(wrapper):
return wrap_object(module, name, FunctionWrapper, (wrapper,))
return _wrapper
def transient_function_wrapper(module, name):
def _decorator(wrapper):
def _wrapper(wrapped, instance, args, kwargs):
target_wrapped = args[0]
if instance is None:
target_wrapper = wrapper
elif inspect.isclass(instance):
target_wrapper = wrapper.__get__(None, instance)
else:
target_wrapper = wrapper.__get__(instance, type(instance))
def _execute(wrapped, instance, args, kwargs):
(parent, attribute, original) = resolve_path(module, name)
replacement = FunctionWrapper(original, target_wrapper)
setattr(parent, attribute, replacement)
try:
return wrapped(*args, **kwargs)
finally:
setattr(parent, attribute, original)
return FunctionWrapper(target_wrapped, _execute)
return FunctionWrapper(wrapper, _wrapper)
return _decorator
# A weak function proxy. This will work on instance methods, class
# methods, static methods and regular functions. Special treatment is
# needed for the method types because the bound method is effectively a
# transient object and applying a weak reference to one will immediately
# result in it being destroyed and the weakref callback called. The weak
# reference is therefore applied to the instance the method is bound to
# and the original function. The function is then rebound at the point
# of a call via the weak function proxy.
def _weak_function_proxy_callback(ref, proxy, callback):
if proxy._self_expired:
return
proxy._self_expired = True
# This could raise an exception. We let it propagate back and let
# the weakref.proxy() deal with it, at which point it generally
# prints out a short error message direct to stderr and keeps going.
if callback is not None:
callback(proxy)
class WeakFunctionProxy(ObjectProxy):
__slots__ = ('_self_expired', '_self_instance')
def __init__(self, wrapped, callback=None):
# We need to determine if the wrapped function is actually a
# bound method. In the case of a bound method, we need to keep a
# reference to the original unbound function and the instance.
# This is necessary because if we hold a reference to the bound
# function, it will be the only reference and given it is a
# temporary object, it will almost immediately expire and
# the weakref callback triggered. So what is done is that we
# hold a reference to the instance and unbound function and
# when called bind the function to the instance once again and
# then call it. Note that we avoid using a nested function for
# the callback here so as not to cause any odd reference cycles.
_callback = callback and functools.partial(
_weak_function_proxy_callback, proxy=self,
callback=callback)
self._self_expired = False
if isinstance(wrapped, _FunctionWrapperBase):
self._self_instance = weakref.ref(wrapped._self_instance,
_callback)
if wrapped._self_parent is not None:
super(WeakFunctionProxy, self).__init__(
weakref.proxy(wrapped._self_parent, _callback))
else:
super(WeakFunctionProxy, self).__init__(
weakref.proxy(wrapped, _callback))
return
try:
self._self_instance = weakref.ref(wrapped.__self__, _callback)
super(WeakFunctionProxy, self).__init__(
weakref.proxy(wrapped.__func__, _callback))
except AttributeError:
self._self_instance = None
super(WeakFunctionProxy, self).__init__(
weakref.proxy(wrapped, _callback))
def __call__(*args, **kwargs):
def _unpack_self(self, *args):
return self, args
self, args = _unpack_self(*args)
# We perform a boolean check here on the instance and wrapped
# function as that will trigger the reference error prior to
# calling if the reference had expired.
instance = self._self_instance and self._self_instance()
function = self.__wrapped__ and self.__wrapped__
# If the wrapped function was originally a bound function, for
# which we retained a reference to the instance and the unbound
# function we need to rebind the function and then call it. If
# not just called the wrapped function.
if instance is None:
return self.__wrapped__(*args, **kwargs)
return function.__get__(instance, type(instance))(*args, **kwargs)
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