Fix looking up interfaces implemented/providedBy proxies around builtin types (in pure-Python.).

3 files changed, 85 insertions, 3 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 86bede0..53c6fad 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -5,7 +5,11 @@ Changes
 ------------------
 
 - Made subclasses of ProxyBase properly delegate ``__module__`` to the
-  wrapped object.
+  wrapped object. This fixes some ``zope.interface`` lookups under
+  PyPy.
+- Made the pure-Python implementation of ProxyBase properly report the
+  ``zope.interface`` interfaces implemented by builtin types like
+  ``list``. This fixes some ``zope.interface`` lookups under PyPy.
 
 4.1.5 (2015-05-19)
 ------------------
diff --git a/src/zope/proxy/__init__.py b/src/zope/proxy/__init__.py
index 4a38e59..fd3e531 100644
--- a/src/zope/proxy/__init__.py
+++ b/src/zope/proxy/__init__.py
@@ -21,7 +21,6 @@ import sys
 from zope.interface import moduleProvides
 from zope.proxy.interfaces import IProxyIntrospection
 
-
 moduleProvides(IProxyIntrospection)
 __all__ = tuple(IProxyIntrospection)
 
@@ -56,6 +55,35 @@ def _get_wrapped(self):
     """
     return super(AbstractPyProxyBase, self).__getattribute__('_wrapped')
 
+class _EmptyInterfaceDescriptor(object):
+    """A descriptor for the attributes used on the class by the
+    Python implementation of `zope.interface`.
+
+    When wrapping builtin types, these descriptors prevent the objects
+    we find in the AbstractPyProxyBase from being used.
+    """
+
+    def __get__(self, inst, klass):
+        raise AttributeError()
+
+    def __set__(self, inst, value):
+        raise TypeError()
+
+    def __delete__(self, inst):
+        pass
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        raise StopIteration()
+    next = __next__
+
+class _ProxyMetaclass(type):
+    # The metaclass is applied after the class definition
+    # for Py2/Py3 compatibility.
+    __implemented__ = _EmptyInterfaceDescriptor()
+
 class AbstractPyProxyBase(object):
     """
     A reference implementation that cannot be instantiated. Most users
@@ -424,6 +452,9 @@ class AbstractPyProxyBase(object):
             self._wrapped = pow(self._wrapped, other, modulus)
         return self
 
+AbstractPyProxyBase = _ProxyMetaclass(str('AbstractPyProxyBase'), (),
+                                      dict(AbstractPyProxyBase.__dict__))
+
 class PyProxyBase(AbstractPyProxyBase):
     """Reference implementation.
     """
diff --git a/src/zope/proxy/tests/test_proxy.py b/src/zope/proxy/tests/test_proxy.py
index 59b0a04..dd11b54 100644
--- a/src/zope/proxy/tests/test_proxy.py
+++ b/src/zope/proxy/tests/test_proxy.py
@@ -706,6 +706,53 @@ class PyProxyBaseTestCase(unittest.TestCase):
         self.assertRaises(AttributeError, setattr, proxy, 'attr', 42)
         self.assertEqual(proxy.attr, "constant value")
 
+    def _check_wrapping_builtin_returns_correct_provided_by(self, proxy_class, builtin_type):
+        # We get the __implemented__ (fallback) of the type, not our own
+        from zope.interface import Interface
+        from zope.interface import classImplements
+        from zope.interface import classImplementsOnly
+        from zope.interface import implementedBy
+        from zope.interface import providedBy
+        from zope.interface import implementedBy
+
+        # Set up the builtin interface
+        class IFoo(Interface):
+            pass
+        impl_before = list(implementedBy(builtin_type))
+        classImplements(builtin_type, IFoo)
+
+        builtin = builtin_type()
+        self.assertTrue(IFoo in list(providedBy(builtin)))
+
+        try:
+            proxy_instance = proxy_class(builtin)
+            provided_instance = providedBy(proxy_instance)
+            proxy_type = proxy_class(builtin_type)
+            provided_type = implementedBy(proxy_type)
+            # The asserts must be before we remove the interface
+            # because there's a single object that gets mutated
+            self.assertTrue(IFoo in list(provided_instance))
+            self.assertTrue(IFoo in list(provided_type))
+        finally:
+            classImplementsOnly(builtin_type, *impl_before)
+
+    def test_wrapping_builtin_type_returns_correct_provided_by(self):
+        self._check_wrapping_builtin_returns_correct_provided_by(self._getTargetClass(), list)
+
+    def _check_wrapping_builtin_with_subclass_returns_correct_provided_by(self, builtin_type):
+        class Proxy(self._getTargetClass()):
+            pass
+
+        self._check_wrapping_builtin_returns_correct_provided_by(Proxy, builtin_type)
+        # Our new class did not gain an __implemented__ attribute, unless we're
+        # the pure-python version
+        if hasattr(Proxy, '__implemented__'):
+            from zope.proxy import PyProxyBase
+            self.assertTrue(self._getTargetClass() is PyProxyBase)
+
+    def test_wrapping_builtin_with_subclass_returns_correct_provided_by(self):
+        self._check_wrapping_builtin_with_subclass_returns_correct_provided_by(list)
+
     def test_method_in_proxy_subclass(self):
         class Proxy(self._getTargetClass()):
             def __getitem__(self, k):
@@ -727,7 +774,7 @@ class PyProxyBaseTestCase(unittest.TestCase):
             self.assertEqual(14, int(proxy))
         except TypeError:
             from zope.proxy import PyProxyBase
-            self.assertNotEqual(self._getTargetClass, PyProxyBase)
+            self.assertNotEqual(self._getTargetClass(), PyProxyBase)
 
 class ProxyBaseTestCase(PyProxyBaseTestCase):