Release Notes¶

Version 2.1.2¶

Bugs Fixed

Building of Python wheels for riscv64 Linux platform had been accidentally removed from the build configuration. This has now been added back in.
When a weak function proxy was created for a bound method and the instance it was bound to was garbage collected, calling the proxy would silently call the function as unbound instead of raising a ReferenceError.
When deleting an attribute named __annotations__ on an object proxy, the attribute was only being deleted from the proxy and not also from the wrapped object.

Version 2.1.1¶

Bugs Fixed

Search field for documentation hosted on Read the Docs wasn’t working correctly due to JavaScript error.
Missing tox.ini from source distribution package has been added.

Version 2.1.0¶

Features Changed

Drop support for Python 3.8. Python version 3.9 or later is now required.

Bugs Fixed

Improved type hints so that mypy and ty work better for methods of classes when using wrapt.decorator and wrapt.function_wrapper. Note that applying these to static methods still does not work correctly due to possibly limitations in those type checkers. The pyrefly tool still does not work correctly with wrapt.decorator and wrapt.function_wrapper applied to any methods of classes. Overall pyright provides the best experience when using wrapt with type checking.

Version 2.0.1¶

Bugs Fixed

The wrapt.lazy_import() function wasn’t included in the __all__ attribute of the wrapt module, meaning that it wasn’t accessible when using from wrapt import * and type checkers such as mypy or pylance may not see it as part of the public API.
When using wrapt.lazy_import() to lazily import a function of a module, the resulting proxy object wasn’t marked as callable until something triggered the import of the module via the proxy. This meant a callable() check on the proxy would return False until the module was actually imported. Further, calling the proxy before the module was imported would raise TypeError: 'LazyObjectProxy' object is not callable rather than importing the module and calling the function as expected. In order to address this issue, an additional keyword argument interface has been added to wrapt.lazy_import() which can be used to specify the expected interface type of the wrapped object. This will default to Callable when an attribute name is supplied, and to ModuleType when no attribute name is supplied. If using wrapt.lazy_import() and supplying an attribute argument, and you expect the wrapped object to be something other than a callable, you should now also supply interface=... with the appropriate type from collections.abc to ensure the proxy behaves correctly prior to the module being imported. This should only be necessary where the wrapped object has special dunder methods on its type which need to exist on the proxy prior to the module being imported.

Version 2.0.0¶

There have been subtle changes in various corner cases of the behaviour of the ObjectProxy class, which although not expected to cause problems, still has the potential for causing issues if code was for some reason dependent on prior behaviour. All existing code related to Python 2.X has also been removed. Finally it has also been a while since the last significant release. For all these reasons a major version bump is being made.

New Features

Added __all__ attribute to wrapt module to expose the public API.
The wrapt.PartialCallableObjectProxy class can now be accessed via the alias wrapt.partial, which is a convenience for users who are used to using functools.partial and want to use the wrapt version of it.
Type hints have been added to the wrapt module. The type hints are available when using Python 3.10 or later, and can be used with static type checkers such as pylance or mypy. Note that due to limitations in Python’s type hinting system, type checking is not always able to be applied or details such as default values may not be available. See the documentation for more details on limitations and workarounds.
Added wrapt.BaseObjectProxy class which is the base class for all object proxy classes. This class is either the pure Python or C extension variant of the object proxy depending on whether the C extension is available. This used to be the ObjectProxy class, but has been renamed to BaseObjectProxy to better reflect its role as the foundational class for all object proxies. This variant does though no longer provide a proxy implementation for the __iter__() special method as it was originally a mistake to include it in the ObjectProxy class as its presence could cause issues when the wrapped object is not iterable. A wrapt.ObjectProxy class is still provided but this is now a pure Python subclass of BaseObjectProxy which adds a proxy implementation for the __iter__() special method. This is done for backwards compatibility reasons as ObjectProxy with the __iter__() special method has been part of the public API for a long time.
Added wrapt.AutoObjectProxy class which is a pure Python subclass of BaseObjectProxy which overrides the __new__() method to dynamically generate a custom subclass which includes methods for callable, descriptor and iterator protocols, as well as other select special methods. This is done using a dynamically generated subclass as the special methods for these protocols must be defined on the class itself and not on the instance. Because AutoObjectProxy dynamically generates a custom subclass for each instance, it has a notable memory overhead for every instance created, and thus should only be used where you know you will not be needing many instances of it. If you know what additional special methods you need, it is preferable to use BaseObjectProxy directly and add them to a subclass as needed. If you only need __iter__() support for backwards compatibility then use ObjectProxy instead.
Added wrapt.LazyObjectProxy class which is a variant of AutoObjectProxy which takes a callable which returns the object to be wrapped. The callable is only invoked the first time an attribute of the wrapped object is accessed. This can be useful for deferring creation of expensive objects until they are actually needed. Note that the callable is only invoked once and protection is in place to ensure that if multiple threads try to access the wrapped object at the same time, only one thread will invoke the callable and the other threads will wait for the result. Because LazyObjectProxy is a subclass of AutoObjectProxy, it has the same memory overhead considerations as AutoObjectProxy and should only be used where you know you will not be needing many instances of it.
Added wrapt.lazy_import() function which takes a module name and returns a LazyObjectProxy which will import the module when it is first needed. This can be useful for deferring import of modules until they are actually needed. If the module name is a dotted name, then the full dotted name is imported and the last component returned. An optional attribute argument can be supplied which is the name of an attribute of the module to return instead of the module itself.

Features Changed

Code related to Python 2.X and workarounds for older Python 3.X versions has been removed.
Dependency at runtime on setuptools for calculating package entry points has been removed. Instead the importlib.metadata module is now used for this purpose. The wrapt package no longer requires setuptools to be installed at runtime. It is still required for building and installing the package from source, but not for installation using Python wheels, and not for using it.
For reasons to do with backward/forward compatibility the wrapt module included references to getcallargs() and formatargspec() functions which were part of the inspect module at one time or another. These were provided as convenience for users of the wrapt module, but were not actually part of the public API. They have now been removed from the wrapt module and are no longer available. If you need these functions, you should use the inspect module directly.
The enabled, adapter and proxy arguments to the @decorator decorator had to be keyword parameters, and the initial wrapped argument had to be positional only. Because though Python 2.X was still being supported it was not possible to use appropriate syntax to mark them as such. These arguments are now marked as positional and keyword only parameters in the function signature as appropriate.
The object proxy classes now raise a WrapperNotInitializedError exception rather than Python builtin ValueError exception when an attempt is made to access an attribute of the wrapped object before the wrapper has been initialized. The WrapperNotInitializedError exception inherits from both ValueError and AttributeError so that it can be caught by code which wants to handle both cases. This is being done to allow IDEs such as PyCharm to give a live view of Python objects and their attributes. Previously a ValueError exception was being raised, which was problematic because PyCharm would see it as an actual error and fail. By using a custom exception that also inherits from AttributeError it is hoped the IDE will see it as a normal attribute access error rather than an actual error and so just not attempt to show the attribute within the IDE.

Bugs Fixed

Reference count was not being incremented on type object for C implementation of the partial callable object proxy when module was initialized. If wrapt was being used in Python sub interpreters which were deleted it could lead to the process crashing. Note that this change was also back ported and included in version 1.17.3 and 1.14.2 releases.
Wasn’t chaining __mro_entries__() calls when the wrapped object was not a type (class) and itself had a __mro_entries__() method. This meant that if using the object proxy as a base class for a generic class, the generic parameters were being ignored.
When an object proxy wrapped an immutable type, such as an integer, and the object proxy had been assigned to a second variable, the result of an in-place operation on the second variable was also affecting the first variable, when instead the lifetime of the two variables should have been independent to reflect what occurs for normal immutable types.

Version 1.17.3¶

Bugs Fixed

Reference count was not being incremented on type object for C implementation of the partial callable object proxy when module was initialized. If wrapt was being used in Python sub interpreters which were deleted it could lead to the process crashing.

Version 1.17.2¶

New Features

Added universal binary wheels for macOS. That is, contains both x86_64 and arm64 architectures in the same wheel.

Version 1.17.1¶

Bugs Fixed

Due to GitHub actions changes, binary wheels were missing for macOS Intel.
Not implemented error for __reduce__() on ObjectProxy was incorrectly displaying the error as being on __reduce_ex__().

Version 1.17.0¶

Note that version 1.17.0 drops support for Python 3.6 and 3.7. Python version 3.8 or later is required.

New Features

Add __format__() method to ObjectProxy class to allow formatting of wrapped object.
Added C extension internal flag to indicate that wrapt should be safe for Python 3.13 free threading mode. Releases will include free threading variants of Python wheels. Note that as free threading is new, one should be cautious about using it in production until it has been more widely tested.

Bugs Fixed

When a normal function or builtin function which had wrapt.decorator or a function wrapper applied, was assigned as a class attribute, and the function attribute called via the class or an instance of the class, an additional argument was being passed, inserted as the first argument, which was the class or instance. This was not the correct behaviour and the class or instance should not have been passed as the first argument.
When an instance of a callable class object was wrapped which didn’t not have a __get__() method for binding, and it was called in context where binding would be attempted, it would fail with error that __get__() did not exist when instead it should have been called directly, ignoring that binding was not possible.
The __round__ hook for the object proxy didn’t accept ndigits argument.

Version 1.16.0¶

Note that version 1.16.0 drops support for Python 2.7 and 3.5. Python version 3.6 or later is required.

New Features

The patch_function_wrapper() decorator now accepts an enabled argument, which can be a literal boolean value, object that evaluates as boolean, or a callable object which returns a boolean. In the case of a callable, determination of whether the wrapper is invoked will be left until the point of the call. In the other cases, the wrapper will not be applied if the value evaluates false at the point of applying the wrapper.

Features Changed

The import hook loader and finder objects are now implemented as transparent object proxies so they properly proxy pass access to attributes/functions of the wrapped loader or finder.
Code files in the implementation have been reorganized such that the pure Python version of the ObjectProxy class is directly available even if the C extension variant is being used. This is to allow the pure Python variant to be used in exceptional cases where the C extension variant is not fully compatible with the pure Python implementation and the behaviour of the pure Python variant is what is required. This should only be relied upon if have absolutely no choice. The pure Python variant is not as performant as the C extension.

To access the pure Python variant use from wrapt.wrappers import ObjectProxy instead of just from wrapt import ObjectProxy. Note that prior to this version if you had used from wrapt.wrappers import ObjectProxy you would have got the C extension variant of the class rather than the pure Python version if the C extension variant was available.

Bugs Fixed

It was not possible to update the __class__ attribute through the transparent object proxy when relying on the C implementation.

Version 1.15.0¶

Bugs Fixed

When the C extension for wrapt was being used, and a property was used on an object proxy wrapping another object to intercept access to an attribute of the same name on the wrapped object, if the function implementing the property raised an exception, then the exception was ignored and not propagated back to the caller. What happened instead was that the original value of the attribute from the wrapped object was returned, thus silently suppressing that an exception had occurred in the wrapper. This behaviour was not happening when the pure Python version of wrapt was being used, with it raising the exception. The pure Python and C extension implementations thus did not behave the same.

Note that in the specific case that the exception raised is AttributeError it still wouldn’t be raised. This is the case for both Python and C extension implementations. If a wrapper for an attribute internally raises an AttributeError for some reason, the wrapper should if necessary catch the exception and deal with it, or propagate it as a different exception type if it is important that an exception still be passed back.
Address issue where the post import hook mechanism of wrapt wasn’t transparent and left the __loader__ and __spec__.loader attributes of a module as the wrapt import hook loader and not the original loader. That the original loader wasn’t preserved could interfere with code which needed access to the original loader.
Address issues where a thread deadlock could occur within the wrapt module import handler, when code executed from a post import hook created a new thread and code executed in the context of the new thread itself tried to register a post import hook, or imported a new module.
When using CallableObjectProxy as a wrapper for a type or function and calling the wrapped object, it was not possible to pass a keyword argument named self. This only occurred when using the pure Python version of wrapt and did not occur when using the C extension based implementation.
When using PartialCallableObjectProxy as a wrapper for a type or function, when constructing the partial object and when calling the partial object, it was not possible to pass a keyword argument named self. This only occurred when using the pure Python version of wrapt and did not occur when using the C extension based implementation.
When using FunctionWrapper as a wrapper for a type or function and calling the wrapped object, it was not possible to pass a keyword argument named self. Because FunctionWrapper is also used by decorators, this also affected decorators on functions and class types. A similar issue also arose when these were applied to class and instance methods where binding occurred when the method was accessed. In that case it was in BoundFunctionWrapper that the problem could arise. These all only occurred when using the pure Python version of wrapt and did not occur when using the C extension based implementation.
When using WeakFunctionProxy as a wrapper for a function, when calling the function via the proxy object, it was not possible to pass a keyword argument named self.

Version 1.14.2¶

Bugs Fixed

Reference count was not being incremented on type object for C implementation of the partial callable object proxy when module was initialized. If wrapt was being used in Python sub interpreters which were deleted it could lead to the process crashing.

Version 1.14.1¶

Bugs Fixed

When the post import hooks mechanism was being used, and a Python package with its own custom module importer was used, importing modules could fail if the custom module importer didn’t use the latest Python import hook finder/loader APIs and instead used the deprecated API. This was actually occurring with the zipimporter in Python itself, which was not updated to use the newer Python APIs until Python 3.10.

Version 1.14.0¶

Bugs Fixed

Python 3.11 dropped inspect.formatargspec() which was used in creating signature changing decorators. Now bundling a version of this function which uses Parameter and Signature from inspect module when available. The replacement function is exposed as wrapt.formatargspec() if need it for your own code.
When using a decorator on a class, isinstance() checks wouldn’t previously work as expected and you had to manually use Type.__wrapped__ to access the real type when doing instance checks. The __instancecheck__ hook is now implemented such that you don’t have to use Type.__wrapped__ instead of Type as last argument to isinstance().
Eliminated deprecation warnings related to Python module import system, which would have turned into broken code in Python 3.12. This was used by the post import hook mechanism.

New Features

Binary wheels provided on PyPi for aarch64 Linux systems and macOS native silicon where supported by Python when using pypa/cibuildwheel.

Version 1.13.3¶

New Features

Adds wheels for Python 3.10 on PyPi and where possible also now generating binary wheels for musllinux.

Version 1.13.2¶

Features Changed

On the Windows platform when using Python 2.7, by default the C extension will not be installed and the pure Python implementation will be used. This is because too often on Windows when using Python 2.7, there is no working compiler available. Prior to version 1.13.0, when installing the package it would fallback to using the pure Python implementation automatically but that relied on a workaround to do it when there was no working compiler. With the changes in 1.13.0 to use the builtin mechanism of Python to not fail when a C extension cannot be compiled, this fallback doesn’t work when the compiler doesn’t exist, as the builtin mechanism in Python regards lack of a compiler as fatal and not a condition for which it is okay to ignore the fact that the extension could not be compiled.

If you are using Python 2.7 on Windows, have a working compiler, and still want to attempt to install the C extension, you can do so by setting the WRAPT_INSTALL_EXTENSIONS environment variable to true when installing the wrapt package.

Note that the next significant release of wrapt will drop support for Python 2.7 and Python 3.5. The change described here is to ensure that wrapt can be used with Python 2.7 on Windows for just a little bit longer. If using Python 2.7 on non Windows platforms, it will still attempt to install the C extension.

Version 1.13.1¶

Bugs Fixed

Fix Python version constraint so PyPi classifier for pip requires Python 2.7 or Python 3.5+.

Version 1.13.0¶

Bugs Fixed

When a reference to a class method was taken out of a class, and then wrapped in a function wrapper, and called, the class type was not being passed as the instance argument, but as the first argument in args, with the instance being None. The class type should have been passed as the instance argument.
If supplying an adapter function for a signature changing decorator using input in the form of a function argument specification, name lookup exceptions would occur where the adaptor function had annotations which referenced non builtin Python types. Although the issues have been addressed where using input data in the format usually returned by inspect.getfullargspec() to pass the function argument specification, you can still have problems when supplying a function signature as string. In the latter case only Python builtin types can be referenced in annotations.
When a decorator was applied on top of a data/non-data descriptor in a class definition, the call to the special method __set_name__() to notify the descriptor of the variable name was not being propagated. Note that this issue has been addressed in the FunctionWrapper used by @wrapt.decorator but has not been applied to the generic ObjectProxy class. If using ObjectProxy directly to construct a custom wrapper which is applied to a descriptor, you will need to propagate the __set_name__() call yourself if required.
The issubclass() builtin method would give incorrect results when used with a class which had a decorator applied to it. Note that this has only been able to be fixed for Python 3.7+. Also, due to what is arguably a bug (https://bugs.python.org/issue44847) in the Python standard library, you will still have problems when the class hierarchy uses a base class which has the abc.ABCMeta metaclass. In this later case an exception will be raised of TypeError: issubclass() arg 1 must be a class.

Version 1.12.1¶

Bugs Fixed

Applying a function wrapper to a static method of a class using the wrap_function_wrapper() function, or wrapper for the same, wasn’t being done correctly when the static method was the immediate child of the target object. It was working when the name path had multiple name components. A failure would subsequently occur when the static method was called via an instance of the class, rather than the class.

Version 1.12.0¶

Features Changed

Provided that you only want to support Python 3.7, when deriving from a base class which has a decorator applied to it, you no longer need to access the true type of the base class using __wrapped__ in the inherited class list of the derived class.

Bugs Fixed

When using the synchronized decorator on instance methods of a class, if the class declared special methods to override the result for when the class instance was tested as a boolean so that it returned False all the time, the synchronized method would fail when called.
When using an adapter function to change the signature of the decorated function, inspect.signature() was returning the wrong signature when an instance method was inspected by accessing the method via the class type.

Version 1.11.2¶

Bugs Fixed

Fix possible crash when garbage collection kicks in when invoking a destructor of wrapped object.

Version 1.11.1¶

Bugs Fixed

Fixed memory leak in C extension variant of PartialCallableObjectProxy class introduced in 1.11.0, when it was being used to perform binding, when a call of an instance method was made through the class type, and the self object passed explicitly as first argument.
The C extension variant of the PartialCallableObjectProxy class introduced in 1.11.0, which is a version of functools.partial which correctly handles binding when applied to methods of classes, couldn’t be used when no positional arguments were supplied.
When the C extension variant of PartialCallableObjectProxy was used and multiple positional arguments were supplied, the first argument would be replicated and used to all arguments, instead of correct values, when the partial was called.
When the C extension variant of PartialCallableObjectProxy was used and keyword arguments were supplied, it would fail as was incorrectly using the positional arguments where the keyword arguments should have been used.

Version 1.11.0¶

Bugs Fixed

When using arithmetic operations through a proxy object, checks about the types of arguments were not being performed correctly, which could result in an exception being raised to indicate that a proxy object had not been initialised when in fact the argument wasn’t even an instance of a proxy object.

Because an incorrect cast in C level code was being performed and an attribute in memory checked on the basis of it being a type different to what it actually was, technically it may have resulted in a process crash if the size of the object was smaller than the type being casted to.
The __complex__() special method wasn’t implemented and using complex() on a proxy object would give wrong results or fail.
When using the C extension, if an exception was raised when using inplace or, ie., |=, the error condition wasn’t being correctly propagated back which would result in an exception showing up as wrong location in subsequent code.
Type of long was used instead of Py_hash_t for Python 3.3+. This caused compiler warnings on Windows, which depending on what locale was set to, would cause pip to fail when installing the package.
If calling Class.instancemethod and passing self explicitly, the ability to access __name__ and __module__ on the final bound method were not preserved. This was due to a partial being used for this special case, and it doesn’t preserve introspection.
Fixed typo in the getter property of ObjectProxy for accessing __annotations__. Appeared that it was still working as would fall back to using generic __getattr__() to access attribute on wrapped object.

Features Changed

Dropped support for Python 2.6 and 3.3.
If copy.copy() or copy.deepcopy() is used on an instance of the ObjectProxy class, a NotImplementedError exception is raised, with a message indicating that the object proxy must implement the __copy__() or __deepcopy__() method. This is in place of the default TypeError exception with message indicating a pickle error.
If pickle.dump() or pickle.dumps() is used on an instance of the ObjectProxy class, a NotImplementedError exception is raised, with a message indicating that the object proxy must implement the __reduce_ex__() method. This is in place of the default TypeError exception with message indicating a pickle error.

Version 1.10.11¶

Bugs Fixed

When wrapping a @classmethod in a class used as a base class, when the method was called via the derived class type, the base class type was being passed for the cls argument instead of the derived class type through which the call was made.

New Features

The C extension can be disabled at runtime by setting the environment variable WRAPT_DISABLE_EXTENSIONS. This may be necessary where there is currently a difference in behaviour between pure Python implementation and C extension and the C extension isn’t having the desired result.

Version 1.10.10¶

Features Changed

Added back missing description and categorisations when releasing to PyPi.

Version 1.10.9¶

Bugs Fixed

Code for inspect.getargspec() when using Python 2.6 was missing import of sys module.

Version 1.10.8¶

Bugs Fixed

Ensure that inspect.getargspec() is only used with Python 2.6 where required, as function has been removed in Python 3.6.

Version 1.10.7¶

Bugs Fixed

The mod operator ‘%’ was being incorrectly proxied in Python variant of object proxy to the xor operator ‘^’.

Version 1.10.6¶

Bugs Fixed

Registration of post import hook would fail with an exception if registered after another import hook for the same target module had been registered and the target module also imported.

New Features

Support for testing with Travis CI added to repository.

Version 1.10.5¶

Bugs Fixed

Post import hook discovery was not working correctly where multiple target modules were registered in the same entry point list. Only the callback for the last would be called regardless of the target module.
If a WeakFunctionProxy wrapper was used around a method of a class which was decorated using a wrapt decorator, the decorator wasn’t being invoked when the method was called via the weakref proxy.

Features Changed

The register_post_import_hook() function, modelled after the function of the same name in PEP-369 has been extended to allow a string name to be supplied for the import hook. This needs to be of the form module::function and will result in an import hook proxy being used which will only load and call the function of the specified module when the import hook is required. This avoids needing to load the code needed to operate on the target module unless required.

Version 1.10.4¶

Bugs Fixed

Fixup botched package version number from 1.10.3 release.

Version 1.10.3¶

Bugs Fixed

Post import hook discovery from third party modules declared via setuptools entry points was failing due to typo in temporary variable name. Also added the discover_post_import_hooks() to the public API as was missing.

Features Changed

To ensure parity between pure Python and C extension variants of the ObjectProxy class, allow the __wrapped__ attribute to be set in a derived class when the ObjectProxy.__init__() method hasn’t been called.

Version 1.10.2¶

Bugs Fixed

When creating a derived ObjectProxy, if the base class __init__() method wasn’t called and the __wrapped__ attribute was accessed, in the pure Python implementation a recursive call of __getattr__() would occur and the maximum stack depth would be reached and an exception raised.
When creating a derived ObjectProxy, if the base class __init__() method wasn’t called, in the C extension implementation, if that instance was then used in a binary arithmetic operation the process would crash.

Version 1.10.1¶

Bugs Fixed

When using FunctionWrapper around a method of an existing instance of a class, rather than on the type, then a memory leak could occur in two different scenarios.

The first issue was that wrapping a method on an instance of a class was causing an unwanted reference to the class meaning that if the class type was transient, such as it is being created inside of a function call, the type object would leak.

The second issue was that wrapping a method on an instance of a class and then calling the method was causing an unwanted reference to the instance meaning that if the instance was transient, it would leak.

This was only occurring when the C extension component for the wrapt module was being used.

Version 1.10.0¶

New Features

When specifying an adapter for a decorator, it is now possible to pass in, in addition to passing in a callable, a tuple of the form which is returned by inspect.getargspec(), or a string of the form which is returned by inspect.formatargspec(). In these two cases the decorator will automatically compile a stub function to use as the adapter. This eliminates the need for a caller to generate the stub function if generating the signature on the fly.
```
def argspec_factory(wrapped):
    argspec = inspect.getargspec(wrapped)

    args = argspec.args[1:]
    defaults = argspec.defaults and argspec.defaults[-len(argspec.args):]

    return inspect.ArgSpec(args, argspec.varargs,
            argspec.keywords, defaults)

def session(wrapped):
    @wrapt.decorator(adapter=argspec_factory(wrapped))
    def _session(wrapped, instance, args, kwargs):
        with transaction() as session:
            return wrapped(session, *args, **kwargs)

    return _session(wrapped)
```
This mechanism and the original mechanism to pass a function, meant that the adapter function had to be created in advance. If the adapter needed to be generated on demand for the specific function to be wrapped, then it would have been necessary to use a closure around the definition of the decorator as above, such that the generator could be passed in.

As a convenience, instead of using such a closure, it is also now possible to write:
```
def argspec_factory(wrapped):
    argspec = inspect.getargspec(wrapped)

    args = argspec.args[1:]
    defaults = argspec.defaults and argspec.defaults[-len(argspec.args):]

    return inspect.ArgSpec(args, argspec.varargs,
            argspec.keywords, defaults)

@wrapt.decorator(adapter=wrapt.adapter_factory(argspec_factory))
def _session(wrapped, instance, args, kwargs):
    with transaction() as session:
        return wrapped(session, *args, **kwargs)
```
The result of wrapt.adapter_factory() will be recognised as indicating that the creation of the adapter is to be deferred until the decorator is being applied to a function. The factory function for generating the adapter function or specification on demand will be passed the function being wrapped by the decorator.

If wishing to create a library of routines for generating adapter functions or specifications dynamically, then you can do so by creating classes which derive from wrapt.AdapterFactory as that is the type which is recognised as indicating lazy evaluation of the adapter function. For example, wrapt.adapter_factory() is itself implemented as:
```
class DelegatedAdapterFactory(wrapt.AdapterFactory):
    def __init__(self, factory):
        super(DelegatedAdapterFactory, self).__init__()
        self.factory = factory
    def __call__(self, wrapped):
        return self.factory(wrapped)

adapter_factory = DelegatedAdapterFactory
```

Bugs Fixed

The inspect.signature() function was only added in Python 3.3. Use fallback when doesn’t exist and on Python 3.2 or earlier Python 3 versions.

Note that testing is only performed for Python 3.3+, so it isn’t actually known if the wrapt package works on Python 3.2.

Version 1.9.0¶

Features Changed

When using wrapt.wrap_object(), it is now possible to pass an arbitrary object in addition to a module object, or a string name identifying a module. Similar for underlying wrapt.resolve_path() function.

Bugs Fixed

It is necessary to proxy the special __weakref__ attribute in the pure Python object proxy else using inspect.getmembers() on a decorator class will fail.
The FunctionWrapper class was not passing through the instance correctly to the wrapper function when it was applied to a method of an existing instance of a class.
The FunctionWrapper was not always working when applied around a method of a class type by accessing the method to be wrapped using getattr(). Instead it is necessary to access the original unbound method from the class __dict__. Updated the FunctionWrapper to work better in such situations, but also modify resolve_path() to always grab the class method from the class __dict__ when wrapping methods using wrapt.wrap_object() so wrapping is more predictable. When doing monkey patching wrapt.wrap_object() should always be used to ensure correct operation.
The AttributeWrapper class used internally to the function wrap_object_attribute() had wrongly named the __delete__ method for the descriptor as __del__.

Version 1.8.0¶

Features Changed

Previously using @wrapt.decorator on a class type didn’t really yield anything which was practically useful. This is now changed and when applied to a class an instance of the class will be automatically created to be used as the decorator wrapper function. The requirement for this is that the __call__() method be specified in the style as would be done for the decorator wrapper function.
```
@wrapt.decorator
class mydecoratorclass:
    def __init__(self, arg=None):
        self.arg = arg
    def __call__(self, wrapped, instance, args, kwargs):
        return wrapped(*args, **kwargs)

@mydecoratorclass
def function():
    pass
```
If the resulting decorator class is to be used with no arguments, the __init__() method of the class must have all default arguments. These arguments can be optionally supplied though, by using keyword arguments to the resulting decorator when applied to the function to be decorated.
```
@mydecoratorclass(arg=1)
def function():
    pass
```

Version 1.7.0¶

New Features

Provide wrapt.getcallargs() for determining how arguments mapped to a wrapped function. For Python 2.7 this is actually inspect.getcallargs() with a local copy being used in the case of Python 2.6.
Added wrapt.wrap_object_attribute() as a way of wrapping or otherwise modifying the result of trying to access the attribute of an object instance. It works by adding a data descriptor with the same name as the attribute, to the class type, allowing reading of the attribute to be intercepted. It does not affect updates to or deletion of the attribute.

Bugs Fixed

Need to explicitly proxy special methods __bytes__(), __reversed__() and __round__() as they are only looked up on the class type and not the instance, so can’t rely on __getattr__() fallback.
Raise more appropriate TypeError, with corresponding message, rather than IndexError, when a decorated instance or class method is called via the class but the required 1st argument of the instance or class is not supplied.

Version 1.6.0¶

Bugs Fixed

The ObjectProxy class would return that the __call__() method existed even though the wrapped object didn’t have one. Similarly, callable() would always return True even if the wrapped object was not callable.

This resulted due to the existence of the __call__() method on the wrapper, required to support the possibility that the wrapped object may be called via the proxy object even if it may not turn out that the wrapped object was callable.

Because checking for the existence of a __call__() method or using callable() can sometimes be used to indirectly infer the type of an object, this could cause issues. To ensure that this now doesn’t occur, the ability to call a wrapped object via the proxy object has been removed from ObjectProxy. Instead, a new class CallableObjectProxy is now provided, with it being necessary to make a conscious choice as to which should be used based on whether the object to be wrapped is in fact callable.

Note that neither before this change, or with the introduction of the class CallableObjectProxy, does the object proxy perform binding. If binding behaviour is required it still needs to be implemented explicitly to match the specific requirements of the use case. Alternatively, the FunctionWrapper class should be used which does implement binding, but also enforces a wrapper mechanism for manipulating what happens at the time of the call.

Version 1.5.1¶

Bugs Fixed

Instance method locking for the synchronized decorator was not correctly locking on the instance but the class, if a synchronized class method had been called prior to the synchronized instance method.

Version 1.5.0¶

New Features

Enhanced @wrapt.transient_function_wrapper so it can be applied to instance methods and class methods with the self/cls argument being supplied correctly. This allows instance and class methods to be used for this type of decorator, with the instance or class type being able to be used to hold any state required for the decorator.

Bugs Fixed

If the wrong details for a function to be patched was given to the decorator @wrapt.transient_function_wrapper, the exception indicating this was being incorrectly swallowed up and mutating to a different more obscure error about local variable being access before being set.

Version 1.4.2¶

Bugs Fixed

A process could crash if the C extension module was used and when using the ObjectProxy class a reference count cycle was created that required the Python garbage collector to kick in to break the cycle. This was occurring as the C extension had not implemented GC support in the ObjectProxy class correctly.

Version 1.4.1¶

Bugs Fixed

Overriding __wrapped__ attribute directly on any wrapper more than once could cause corruption of memory due to incorrect reference count decrement.

Version 1.4.0¶

New Features

Enhanced @wrapt.decorator and @wrapt.function_wrapper so they can be applied to instance methods and class methods with the self/cls argument being supplied correctly. This allows instance and class methods to be used as decorators, with the instance or class type being able to be used to hold any state required for the decorator.

Bugs Fixed

Fixed process crash in extension when the wrapped object passed as first argument to FunctionWrapper did not have a tp_descr_get callback for the type at C code level. Now raised an AttributeError exception in line with what Python implementation does.

Version 1.3.1¶

Bugs Fixed

The discover_post_import_hooks() function had not been added to the top level wrapt module.

Version 1.3.0¶

New Features

Added a @transient_function_wrapper decorator for applying a wrapper function around a target function only for the life of a single function call. The decorator is useful for performing mocking or pass through data validation/modification when doing unit testing of packages.

Version 1.2.1¶

Bugs Fixed

In C implementation, not dealing with unbound method type creation properly which would cause later problems when calling instance method via the class type in certain circumstances. Introduced problem in 1.2.0.
Eliminated compiler warnings due to missing casts in C implementation.

Version 1.2.0¶

New Features

Added an enabled option to @decorator and FunctionWrapper which can be provided a boolean, or a function returning a boolean to allow the work of the decorator to be disabled dynamically. When a boolean, is used for @decorator, the wrapper will not even be applied if enabled is False. If a function, then will be called prior to wrapper being called and if returns False, then original wrapped function called directly rather than the wrapper being called.
Added in an implementation of a post import hook mechanism in line with that described in PEP 369.
Added in helper functions specifically designed to assist in performing monkey patching of existing code.

Features Changed

Collapsed functionality of _BoundMethodWrapper into _BoundFunctionWrapper and renamed the latter to BoundFunctionWrapper. If deriving from the FunctionWrapper class and needing to override the type of the bound wrapper, the class attribute __bound_function_wrapper__ should be set in the derived FunctionWrapper class to the replacement type.

Bugs Fixed

When creating a custom proxy by deriving from ObjectProxy and the custom proxy needed to override __getattr__(), it was not possible to called the base class ObjectProxy.__getattr__() when the C implementation of ObjectProxy was being used. The derived class __getattr__() could also get ignored.
Using inspect.getargspec() now works correctly on bound methods when an adapter function can be provided to @decorator.

Version 1.1.3¶

New Features

Added a _self_parent attribute to FunctionWrapper and bound variants. For the FunctionWrapper the value will always be None. In the case of the bound variants of the function wrapper, the attribute will refer back to the unbound FunctionWrapper instance. This can be used to get a back reference to the parent to access or cache data against the persistent function wrapper, the bound wrappers often being transient and only existing for the single call.

Improvements

Use interned strings to optimise name comparisons in the setattro() method of the C implementation of the object proxy.

Bugs Fixed

The pypy interpreter is missing operator.__index__() so proxying of that method in the object proxy would fail. This is a bug in pypy which is being addressed. Use operator.index() instead which pypy does provide and which also exists for CPython.
The pure Python implementation allowed the __wrapped__ attribute to be deleted which could cause problems. Now raise a TypeError exception.
The C implementation of the object proxy would crash if an attempt was made to delete the __wrapped__ attribute from the object proxy. Now raise a TypeError exception.

Version 1.1.2¶

Improvements

Reduced performance overhead from previous versions. Most notable in the C implementation. Benchmark figures have been updated in documentation.

Version 1.1.1¶

Bugs Fixed

Python object memory leak was occurring due to incorrect increment of object reference count in C implementation of object proxy when an instance method was called via the class and the instance passed in explicitly.
In place operators in pure Python object proxy for __idiv__ and __itruediv__ were not replacing the wrapped object with the result of the operation on the wrapped object.
In place operators in C implementation of Python object proxy were not replacing the wrapped object with the result of the operation on the wrapped object.

Version 1.1.0¶

New Features

Added a synchronized decorator for performing thread mutex locking on functions, object instances or classes. This is the same decorator as covered as an example in the wrapt documentation.
Added a WeakFunctionProxy class which can wrap references to instance methods as well as normal functions.
Exposed from the C extension the classes _FunctionWrapperBase, _BoundFunctionWrapper and _BoundMethodWrapper so that it is possible to create new variants of FunctionWrapper in pure Python code.

Bugs Fixed

When deriving from ObjectProxy, and the C extension variant was being used, if a derived class overrode __new__() and tried to access attributes of the ObjectProxy created using the base class __new__() before __init__() was called, then an exception would be raised indicating that the ‘wrapper has not been initialised’.
When deriving from ObjectProxy, and the C extension variant was being used, if a derived class __init__() attempted to update attributes, even the special _self_ attributed before calling the base class __init__() method, then an exception would be raised indicating that the ‘wrapper has not been initialised’.

Version 1.0.0¶

Initial release.