deb-python-wrapt/docs/changes.rst

Release Notes

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 moduled 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(object):
      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.