#83: Add special handling for __call__ to interface_only().

pure_interface.py

@@ -629,6 +629,8 @@ def interface_only(cls, implementation):
         if cls._pi.impl_wrapper_type is None:
             type_name = '_{}Only'.format(cls.__name__)
             attributes = {'__module__': cls.__module__}
+            if '__call__' in cls._pi.interface_names:
+                attributes['__call__'] = getattr(implementation, '__call__')
             cls._pi.impl_wrapper_type = type(type_name, (_ImplementationWrapper,), attributes)
             abc.ABCMeta.register(cls, cls._pi.impl_wrapper_type)
         return cls._pi.impl_wrapper_type(implementation, cls)

tests/test_adaption.py

@@ -114,6 +114,23 @@ def speak(self, volume):
         super(SleepTalker, self).speak(volume)
 
 
+class DunderInterface(pure_interface.Interface):
+    def __call__(self, a):
+        pass
+
+    def __len__(self):
+        pass
+
+
+class DunderClass(DunderInterface, object):
+
+    def __call__(self, a):
+        super().__call__(a)
+
+    def __len__(self):
+        return 5
+
+
 class TestAdaption(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
@@ -350,3 +367,16 @@ def test_adapt_interface_only(self):
             ISpeaker.adapt(talker_only)
         except:
             self.fail('adaption of interface only failed.')
+
+    def test_adapt_callable_is_callable(self):
+        dunder = DunderClass()
+        dunder_only = DunderInterface.adapt(dunder)
+        try:
+            dunder_only(1)
+        except TypeError:
+            self.fail('calling interface only failed')
+
+        try:
+            len(dunder)
+        except:
+            self.fail('len() interface only failed')