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author | brenda-br | 2023-03-04 11:32:15 +0530 |
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committer | brenda-br | 2023-03-04 11:32:15 +0530 |
commit | 3cbdd4238867bc860282f7cf702d73b5be6e3f86 (patch) | |
tree | 7a9323daf6923801a61bb10b5aa35ad4795c52b1 /src/main/python/venv/Lib/site-packages/wrapt/wrappers.py | |
parent | 7cf8eca28f9ca77e6195aa43e3bd9ae319518b66 (diff) | |
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Revert "Restructuring Finalized for App Bundling"
This reverts commit 7af3526e105cc330422f8742ec5edec1c4a0a98f.
Diffstat (limited to 'src/main/python/venv/Lib/site-packages/wrapt/wrappers.py')
-rw-r--r-- | src/main/python/venv/Lib/site-packages/wrapt/wrappers.py | 943 |
1 files changed, 943 insertions, 0 deletions
diff --git a/src/main/python/venv/Lib/site-packages/wrapt/wrappers.py b/src/main/python/venv/Lib/site-packages/wrapt/wrappers.py new file mode 100644 index 0000000..1d6131d --- /dev/null +++ b/src/main/python/venv/Lib/site-packages/wrapt/wrappers.py @@ -0,0 +1,943 @@ +import os +import sys +import functools +import operator +import weakref +import inspect + +PY2 = sys.version_info[0] == 2 +PY3 = sys.version_info[0] == 3 + +if PY3: + string_types = str, +else: + string_types = basestring, + +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 + + @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 + + @property + def __annotations__(self): + return self.__wrapped__.__annotations__ + + @__annotations__.setter + def __annotations__(self, value): + self.__wrapped__.__annotations__ = value + + def __dir__(self): + return dir(self.__wrapped__) + + def __str__(self): + return str(self.__wrapped__) + + if PY3: + 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 PY3: + def __round__(self): + return round(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 + + elif name == '__qualname__': + 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__(self, *args, **kwargs): + return self.__wrapped__(*args, **kwargs) + +class PartialCallableObjectProxy(ObjectProxy): + + def __init__(self, *args, **kwargs): + 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__(self, *args, **kwargs): + _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__(self, *args, **kwargs): + # 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 == 'function': + 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) + +class BoundFunctionWrapper(_FunctionWrapperBase): + + def __call__(self, *args, **kwargs): + # 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] + + original = getattr(parent, attribute) + for attribute in path[1:]: + parent = original + + # 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. + + if inspect.isclass(original): + for cls in inspect.getmro(original): + if attribute in vars(cls): + original = vars(cls)[attribute] + break + else: + original = getattr(original, attribute) + + else: + original = getattr(original, 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__(self, *args, **kwargs): + # 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) |