Add properties for accessing the object implementing an interface

Author: danabr

src/runtime/converter.cs

@@ -176,7 +176,7 @@ internal static IntPtr ToPython(object value, Type type)
             if (type.IsInterface)
             {
                 var ifaceObj = (InterfaceObject)ClassManager.GetClass(type);
-                return CLRObject.GetInstHandle(value, ifaceObj.pyHandle);
+                return ifaceObj.WrapObject(value);
             }
 
             // We need to special case interface array handling to ensure we

src/runtime/interfaceobject.cs

@@ -71,7 +71,43 @@ public static IntPtr tp_new(IntPtr tp, IntPtr args, IntPtr kw)
                 return IntPtr.Zero;
             }
 
-            return CLRObject.GetInstHandle(obj, self.pyHandle);
+            return self.WrapObject(obj);
+        }
+
+        /// <summary>
+        /// Wrap the given object in an interface object, so that only methods
+        /// of the interface are available.
+        /// </summary>
+        public IntPtr WrapObject(object impl)
+        {
+            var objPtr = CLRObject.GetInstHandle(impl, pyHandle);
+            return objPtr;
+        }
+
+        /// <summary>
+        /// Expose the wrapped implementation through attributes in both
+        /// converted/encoded (__implementation__) and raw (__raw_implementation__) form.
+        /// </summary>
+        public static IntPtr tp_getattro(IntPtr ob, IntPtr key)
+        {
+            var clrObj = (CLRObject)GetManagedObject(ob);
+
+            if (!Runtime.PyString_Check(key))
+            {
+                return Exceptions.RaiseTypeError("string expected");
+            }
+
+            string name = Runtime.GetManagedString(key);
+            if (name == "__implementation__")
+            {
+                return Converter.ToPython(clrObj.inst);
+            }
+            else if (name == "__raw_implementation__")
+            {
+                return CLRObject.GetInstHandle(clrObj.inst);
+            }
+
+            return Runtime.PyObject_GenericGetAttr(ob, key);
         }
     }
 }

src/tests/test_interface.py

@@ -61,6 +61,8 @@ def test_explicit_cast_to_interface():
     assert hasattr(i1, 'SayHello')
     assert i1.SayHello() == 'hello 1'
     assert not hasattr(i1, 'HelloProperty')
+    assert i1.__implementation__ == ob
+    assert i1.__raw_implementation__ == ob
 
     i2 = Test.ISayHello2(ob)
     assert type(i2).__name__ == 'ISayHello2'
@@ -76,6 +78,7 @@ def test_interface_object_returned_through_method():
     ob = InterfaceTest()
     hello1 = ob.GetISayHello1()
     assert type(hello1).__name__ == 'ISayHello1'
+    assert hello1.__implementation__.__class__.__name__ == "InterfaceTest"
 
     assert hello1.SayHello() == 'hello 1'
 
@@ -107,3 +110,13 @@ def test_interface_array_returned():
     ob = InterfaceTest()
     hellos = ob.GetISayHello1Array()
     assert type(hellos[0]).__name__ == 'ISayHello1'
+    assert hellos[0].__implementation__.__class__.__name__ == "InterfaceTest"
+
+def test_implementation_access():
+    """Test the __implementation__ and __raw_implementation__ properties"""
+    import System
+    clrVal =  System.Int32(100)
+    i = System.IComparable(clrVal)
+    assert 100 == i.__implementation__
+    assert clrVal == i.__raw_implementation__
+    assert i.__implementation__ != i.__raw_implementation__