Fix implementerOnly when duplicating something inherited from the parent.issue199

Seen in plone.app.testing as a problem in Products.GenericSetup.

Added tests for that.

2 files changed, 89 insertions, 79 deletions

diff --git a/src/zope/interface/declarations.py b/src/zope/interface/declarations.py
index 1c343a2..b8af418 100644
--- a/src/zope/interface/declarations.py
+++ b/src/zope/interface/declarations.py
@@ -431,8 +431,13 @@ def classImplementsOnly(cls, *interfaces):
     in *interfaces*. This can be used to alter the interface resolution order.
     """
     spec = implementedBy(cls)
+    # Clear out everything inherited. It's important to
+    # also clear the bases right now so that we don't improperly discard
+    # interfaces that are already implemented by *old* bases that we're
+    # about to get rid of.
     spec.declared = ()
     spec.inherit = None
+    spec.__bases__ = ()
     _classImplements_ordered(spec, interfaces, ())
 
 
diff --git a/src/zope/interface/tests/test_declarations.py b/src/zope/interface/tests/test_declarations.py
index c69b645..a730fdd 100644
--- a/src/zope/interface/tests/test_declarations.py
+++ b/src/zope/interface/tests/test_declarations.py
@@ -784,27 +784,58 @@ class Test_implementedBy(Test_implementedByFallback,
         return implementedBy
 
 
-class Test_classImplementsOnly(unittest.TestCase):
+class _ImplementsTestMixin(object):
+    FUT_SETS_PROVIDED_BY = True
 
-    def _callFUT(self, *args, **kw):
-        from zope.interface.declarations import classImplementsOnly
-        return classImplementsOnly(*args, **kw)
+    def _callFUT(self, cls, iface):
+        # Declare that *cls* implements *iface*; return *cls*
+        raise NotImplementedError
 
-    def test_no_existing(self):
+    def _check_implementer(self, Foo,
+                           orig_spec=None,
+                           spec_name=__name__ + '.Foo',
+                           inherit="not given"):
         from zope.interface.declarations import ClassProvides
         from zope.interface.interface import InterfaceClass
+        IFoo = InterfaceClass('IFoo')
+
+        returned = self._callFUT(Foo, IFoo)
+
+        self.assertIs(returned, Foo)
+        spec = Foo.__implemented__
+        if orig_spec is not None:
+            self.assertIs(spec, orig_spec)
+
+        self.assertEqual(spec.__name__,
+                         spec_name)
+        inherit = Foo if inherit == "not given" else inherit
+        self.assertIs(spec.inherit, inherit)
+        self.assertIs(Foo.__implemented__, spec)
+        if self.FUT_SETS_PROVIDED_BY:
+            self.assertIsInstance(Foo.__providedBy__, ClassProvides)
+            self.assertIsInstance(Foo.__provides__, ClassProvides)
+            self.assertEqual(Foo.__provides__, Foo.__providedBy__)
+
+        return Foo, IFoo
+
+    def test_oldstyle_class(self):
+        # This only matters on Python 2
+        class Foo:
+            pass
+        self._check_implementer(Foo)
+
+    def test_newstyle_class(self):
         class Foo(object):
             pass
-        ifoo = InterfaceClass('IFoo')
-        self._callFUT(Foo, ifoo)
-        spec = Foo.__implemented__ # pylint:disable=no-member
-        self.assertEqual(spec.__name__,
-                         'zope.interface.tests.test_declarations.Foo')
-        self.assertIsNone(spec.inherit)
-        self.assertIs(Foo.__implemented__, spec) # pylint:disable=no-member
-        self.assertIsInstance(Foo.__providedBy__, ClassProvides) # pylint:disable=no-member
-        self.assertIsInstance(Foo.__provides__, ClassProvides) # pylint:disable=no-member
-        self.assertEqual(Foo.__provides__, Foo.__providedBy__) # pylint:disable=no-member
+        self._check_implementer(Foo)
+
+class Test_classImplementsOnly(_ImplementsTestMixin, unittest.TestCase):
+    FUT_SETS_PROVIDED_BY = False
+
+    def _callFUT(self, cls, iface):
+        from zope.interface.declarations import classImplementsOnly
+        classImplementsOnly(cls, iface)
+        return cls
 
     def test_w_existing_Implements(self):
         from zope.interface.declarations import Implements
@@ -822,50 +853,52 @@ class Test_classImplementsOnly(unittest.TestCase):
         self.assertEqual(impl.inherit, None)
         self.assertEqual(impl.declared, (IBar,))
 
+    def test_oldstyle_class(self):
+        from zope.interface.declarations import Implements
+        from zope.interface.interface import InterfaceClass
+        IBar = InterfaceClass('IBar')
+        old_spec = Implements(IBar)
 
-class Test_classImplements(unittest.TestCase):
-
-    def _callFUT(self, cls, iface):
-        from zope.interface.declarations import classImplements
-        result = classImplements(cls, iface) # pylint:disable=assignment-from-no-return
-        self.assertIsNone(result)
-        return cls
+        class Foo:
+            __implemented__ = old_spec
+        self._check_implementer(Foo, old_spec, '?', inherit=None)
 
-    def __check_implementer(self, Foo):
-        from zope.interface.declarations import ClassProvides
+    def test_newstyle_class(self):
+        from zope.interface.declarations import Implements
         from zope.interface.interface import InterfaceClass
-        IFoo = InterfaceClass('IFoo')
-
-        returned = self._callFUT(Foo, IFoo)
+        IBar = InterfaceClass('IBar')
+        old_spec = Implements(IBar)
 
-        self.assertIs(returned, Foo)
-        spec = Foo.__implemented__
+        class Foo(object):
+            __implemented__ = old_spec
+        self._check_implementer(Foo, old_spec, '?', inherit=None)
 
-        self.assertEqual(spec.__name__,
-                         'zope.interface.tests.test_declarations.Foo')
-        self.assertIs(spec.inherit, Foo)
-        self.assertIs(Foo.__implemented__, spec)
-        self.assertIsInstance(Foo.__providedBy__, ClassProvides)
-        self.assertIsInstance(Foo.__provides__, ClassProvides)
-        self.assertEqual(Foo.__provides__, Foo.__providedBy__)
 
-        return Foo, IFoo
+    def test_redundant_with_super_still_implements(self):
+        Base, IBase = self._check_implementer(
+            type('Foo', (object,), {}),
+            inherit=None,
+        )
 
-    def test_oldstyle_class(self):
-        # This only matters on Python 2
-        class Foo:
+        class Child(Base):
             pass
-        self.__check_implementer(Foo)
 
-    def test_newstyle_class(self):
-        class Foo(object):
-            pass
-        self.__check_implementer(Foo)
+        self._callFUT(Child, IBase)
+        self.assertTrue(IBase.implementedBy(Child))
+
+
+class Test_classImplements(_ImplementsTestMixin, unittest.TestCase):
+
+    def _callFUT(self, cls, iface):
+        from zope.interface.declarations import classImplements
+        result = classImplements(cls, iface) # pylint:disable=assignment-from-no-return
+        self.assertIsNone(result)
+        return cls
 
     def __check_implementer_redundant(self, Base):
         # If we @implementer exactly what was already present, we write
         # no declared attributes on the parent (we still set everything, though)
-        Base, IBase = self.__check_implementer(Base)
+        Base, IBase = self._check_implementer(Base)
 
         class Child(Base):
             pass
@@ -1026,7 +1059,7 @@ class Test_implementer(Test_classImplements):
 
 
 
-class Test_implementer_only(unittest.TestCase):
+class Test_implementer_only(Test_classImplementsOnly):
 
     def _getTargetClass(self):
         from zope.interface.declarations import implementer_only
@@ -1035,6 +1068,10 @@ class Test_implementer_only(unittest.TestCase):
     def _makeOne(self, *args, **kw):
         return self._getTargetClass()(*args, **kw)
 
+    def _callFUT(self, cls, iface):
+        decorator = self._makeOne(iface)
+        return decorator(cls)
+
     def test_function(self):
         from zope.interface.interface import InterfaceClass
         IFoo = InterfaceClass('IFoo')
@@ -1052,38 +1089,6 @@ class Test_implementer_only(unittest.TestCase):
                 raise NotImplementedError()
         self.assertRaises(ValueError, decorator, Bar._method)
 
-    def test_oldstyle_class(self):
-        # TODO Py3 story
-        from zope.interface.declarations import Implements
-        from zope.interface.interface import InterfaceClass
-        IFoo = InterfaceClass('IFoo')
-        IBar = InterfaceClass('IBar')
-        old_spec = Implements(IBar)
-        class Foo:
-            __implemented__ = old_spec
-        decorator = self._makeOne(IFoo)
-        returned = decorator(Foo)
-        self.assertTrue(returned is Foo)
-        spec = Foo.__implemented__
-        self.assertEqual(spec.__name__, '?')
-        self.assertTrue(spec.inherit is None)
-        self.assertTrue(Foo.__implemented__ is spec)
-
-    def test_newstyle_class(self):
-        from zope.interface.declarations import Implements
-        from zope.interface.interface import InterfaceClass
-        IFoo = InterfaceClass('IFoo')
-        IBar = InterfaceClass('IBar')
-        old_spec = Implements(IBar)
-        class Foo(object):
-            __implemented__ = old_spec
-        decorator = self._makeOne(IFoo)
-        returned = decorator(Foo)
-        self.assertTrue(returned is Foo)
-        spec = Foo.__implemented__
-        self.assertEqual(spec.__name__, '?')
-        self.assertTrue(spec.inherit is None)
-        self.assertTrue(Foo.__implemented__ is spec)
 
 
 # Test '_implements' by way of 'implements{,Only}', its only callers.