Fix #7. Make the Python Acquirer cooperatively call super, and test this. Also...

Fix #7. Make the Python Acquirer cooperatively call super, and test this. Also provides a more informative traceback if lookup failed in that case which assists debugging if the inheritance hierarchy is complex.

CHANGES.rst

@@ -4,7 +4,9 @@ Changelog
 4.2.2 (unreleased)
 ------------------
 
-- TBD
+- Make the pure-Python Acquirer objects cooperatively use the
+  superclass ``__getattribute__`` method, like the C implementation.
+  See https://github.com/zopefoundation/Acquisition/issues/7.
 
 4.2.1 (2015-04-23)
 ------------------

src/Acquisition/__init__.py

@@ -44,12 +44,21 @@ if sys.version_info < (3,):
         if isinstance(method, types.MethodType):
             method = types.MethodType(method.im_func, wrapper, method.im_class)
         return method
+    exec("""def _reraise(tp, value, tb=None):
+    raise tp, value, tb
+""")
 else: # pragma: no cover (python 2 is currently our reference)
     def _rebound_method(method, wrapper):
         """Returns a version of the method with self bound to `wrapper`"""
         if isinstance(method, types.MethodType):
             method = types.MethodType(method.__func__, wrapper)
         return method
+    def _reraise(tp, value, tb=None):
+        if value is None:
+            value = tp()
+        if value.__traceback__ is not tb:
+            raise value.with_traceback(tb)
+        raise value
 
 ###
 # Wrapper object protocol, mostly ported from C directly
@@ -684,11 +693,12 @@ class _Acquirer(ExtensionClass.Base):
 
     def __getattribute__(self, name):
         try:
-            return ExtensionClass.Base.__getattribute__(self, name)
+            return super(_Acquirer,self).__getattribute__(name)
         except AttributeError:
             # the doctests have very specific error message
-            # requirements
-            raise AttributeError(name)
+            # requirements (but at least we can preserve the traceback)
+            t, v, tb = sys.exc_info()
+            _reraise(AttributeError, AttributeError(name), tb)
 
     def __of__(self, context):
         return type(self)._Wrapper(self, context)

src/Acquisition/tests.py

@@ -3124,6 +3124,30 @@ class TestAcquire(unittest.TestCase):
         found = self.acquire(self.a.b.c, AQ_PARENT)
         self.assertTrue(found.aq_self is self.a.b.aq_self)
 
+class TestCooperativeBase(unittest.TestCase):
+
+    def _make_acquirer(self, kind):
+        from ExtensionClass import Base
+
+        class ExtendsBase(Base):
+            def __getattribute__(self, name):
+                if name == 'magic':
+                    return 42
+                return super(ExtendsBase,self).__getattribute__(name)
+
+        class Acquirer(kind, ExtendsBase):
+            pass
+
+        return Acquirer()
+
+    def _check___getattribute___is_cooperative(self, acquirer):
+        self.assertEqual(getattr(acquirer, 'magic'), 42)
+
+    def test_implicit___getattribute__is_cooperative(self):
+        self._check___getattribute___is_cooperative(self._make_acquirer(Acquisition.Implicit))
+
+    def test_explicit___getattribute__is_cooperative(self):
+        self._check___getattribute___is_cooperative(self._make_acquirer(Acquisition.Explicit))
 
 class TestUnicode(unittest.TestCase):
 
@@ -3537,6 +3561,7 @@ def test_suite():
         unittest.makeSuite(TestAcquire),
         unittest.makeSuite(TestUnicode),
         unittest.makeSuite(TestProxying),
+        unittest.makeSuite(TestCooperativeBase),
     ]
 
     # This file is only available in a source checkout, skip it