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import inspect
import sys
PY2 = sys.version_info[0] == 2
if PY2:
string_types = basestring,
else:
string_types = str,
from .__wrapt__ import FunctionWrapper
# 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, enabled=None):
def _wrapper(wrapper):
return wrap_object(module, name, FunctionWrapper, (wrapper, enabled))
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
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