Refactor code so pure Python version usable even when extension compiled.

GrahamDumpleton · GrahamDumpleton · commit f7a28f43b3dc · 2023-11-05T11:40:56.000+11:00
diff --git a/src/wrapt/__init__.py b/src/wrapt/__init__.py
@@ -1,12 +1,15 @@
 __version_info__ = ('1', '16', '0rc2')
 __version__ = '.'.join(__version_info__)
 
-from .wrappers import (ObjectProxy, CallableObjectProxy, FunctionWrapper,
-        BoundFunctionWrapper, WeakFunctionProxy, PartialCallableObjectProxy,
-        resolve_path, apply_patch, wrap_object, wrap_object_attribute,
+from .variants import (ObjectProxy, CallableObjectProxy, FunctionWrapper,
+        BoundFunctionWrapper, PartialCallableObjectProxy)
+
+from .patches import (resolve_path, apply_patch, wrap_object, wrap_object_attribute,
         function_wrapper, wrap_function_wrapper, patch_function_wrapper,
         transient_function_wrapper)
 
+from .weakrefs import WeakFunctionProxy
+
 from .decorators import (adapter_factory, AdapterFactory, decorator,
         synchronized)
 
diff --git a/src/wrapt/__wrapt__.py b/src/wrapt/__wrapt__.py
@@ -0,0 +1,14 @@
+import os
+
+from .wrappers import (ObjectProxy, CallableObjectProxy,
+        PartialCallableObjectProxy, FunctionWrapper,
+        BoundFunctionWrapper, _FunctionWrapperBase)
+
+try:
+    if not os.environ.get('WRAPT_DISABLE_EXTENSIONS'):
+        from ._wrappers import (ObjectProxy, CallableObjectProxy,
+            PartialCallableObjectProxy, FunctionWrapper,
+            BoundFunctionWrapper, _FunctionWrapperBase)
+
+except ImportError:
+    pass
diff --git a/src/wrapt/decorators.py b/src/wrapt/decorators.py
@@ -41,7 +41,7 @@ def exec_(_code_, _globs_=None, _locs_=None):
 except ImportError:
     pass
 
-from .wrappers import (FunctionWrapper, BoundFunctionWrapper, ObjectProxy,
+from .variants import (FunctionWrapper, BoundFunctionWrapper, ObjectProxy,
     CallableObjectProxy)
 
 # Adapter wrapper for the wrapped function which will overlay certain
diff --git a/src/wrapt/importer.py b/src/wrapt/importer.py
@@ -15,7 +15,7 @@
     string_types = str,
     from importlib.util import find_spec
 
-from .wrappers import ObjectProxy
+from .variants import ObjectProxy
 
 # The dictionary registering any post import hooks to be triggered once
 # the target module has been imported. Once a module has been imported
diff --git a/src/wrapt/patches.py b/src/wrapt/patches.py
@@ -0,0 +1,141 @@
+import inspect
+import sys
+
+PY2 = sys.version_info[0] == 2
+
+if PY2:
+    string_types = basestring,
+else:
+    string_types = str,
+
+from .variants 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
diff --git a/src/wrapt/weakrefs.py b/src/wrapt/weakrefs.py
@@ -0,0 +1,98 @@
+import functools
+import weakref
+
+from .variants import ObjectProxy, _FunctionWrapperBase
+
+# A weak function proxy. This will work on instance methods, class
+# methods, static methods and regular functions. Special treatment is
+# needed for the method types because the bound method is effectively a
+# transient object and applying a weak reference to one will immediately
+# result in it being destroyed and the weakref callback called. The weak
+# reference is therefore applied to the instance the method is bound to
+# and the original function. The function is then rebound at the point
+# of a call via the weak function proxy.
+
+def _weak_function_proxy_callback(ref, proxy, callback):
+    if proxy._self_expired:
+        return
+
+    proxy._self_expired = True
+
+    # This could raise an exception. We let it propagate back and let
+    # the weakref.proxy() deal with it, at which point it generally
+    # prints out a short error message direct to stderr and keeps going.
+
+    if callback is not None:
+        callback(proxy)
+
+class WeakFunctionProxy(ObjectProxy):
+
+    __slots__ = ('_self_expired', '_self_instance')
+
+    def __init__(self, wrapped, callback=None):
+        # We need to determine if the wrapped function is actually a
+        # bound method. In the case of a bound method, we need to keep a
+        # reference to the original unbound function and the instance.
+        # This is necessary because if we hold a reference to the bound
+        # function, it will be the only reference and given it is a
+        # temporary object, it will almost immediately expire and
+        # the weakref callback triggered. So what is done is that we
+        # hold a reference to the instance and unbound function and
+        # when called bind the function to the instance once again and
+        # then call it. Note that we avoid using a nested function for
+        # the callback here so as not to cause any odd reference cycles.
+
+        _callback = callback and functools.partial(
+                _weak_function_proxy_callback, proxy=self,
+                callback=callback)
+
+        self._self_expired = False
+
+        if isinstance(wrapped, _FunctionWrapperBase):
+            self._self_instance = weakref.ref(wrapped._self_instance,
+                    _callback)
+
+            if wrapped._self_parent is not None:
+                super(WeakFunctionProxy, self).__init__(
+                        weakref.proxy(wrapped._self_parent, _callback))
+
+            else:
+                super(WeakFunctionProxy, self).__init__(
+                        weakref.proxy(wrapped, _callback))
+
+            return
+
+        try:
+            self._self_instance = weakref.ref(wrapped.__self__, _callback)
+
+            super(WeakFunctionProxy, self).__init__(
+                    weakref.proxy(wrapped.__func__, _callback))
+
+        except AttributeError:
+            self._self_instance = None
+
+            super(WeakFunctionProxy, self).__init__(
+                    weakref.proxy(wrapped, _callback))
+
+    def __call__(*args, **kwargs):
+        def _unpack_self(self, *args):
+            return self, args
+
+        self, args = _unpack_self(*args)
+
+        # We perform a boolean check here on the instance and wrapped
+        # function as that will trigger the reference error prior to
+        # calling if the reference had expired.
+
+        instance = self._self_instance and self._self_instance()
+        function = self.__wrapped__ and self.__wrapped__
+
+        # If the wrapped function was originally a bound function, for
+        # which we retained a reference to the instance and the unbound
+        # function we need to rebind the function and then call it. If
+        # not just called the wrapped function.
+
+        if instance is None:
+            return self.__wrapped__(*args, **kwargs)
+
+        return function.__get__(instance, type(instance))(*args, **kwargs)
diff --git a/src/wrapt/wrappers.py b/src/wrapt/wrappers.py
