It was not possible to update __class__ attribute via the ObjectProxy…

… when using C implementation.

src/wrapt/_wrappers.c

@@ -1464,6 +1464,19 @@ static PyObject *WraptObjectProxy_get_class(
 
 /* ------------------------------------------------------------------------- */
 
+static int WraptObjectProxy_set_class(WraptObjectProxyObject *self,
+        PyObject *value)
+{
+    if (!self->wrapped) {
+      PyErr_SetString(PyExc_ValueError, "wrapper has not been initialized");
+      return -1;
+    }
+
+    return PyObject_SetAttrString(self->wrapped, "__class__", value);
+}
+
+/* ------------------------------------------------------------------------- */
+
 static PyObject *WraptObjectProxy_get_annotations(
         WraptObjectProxyObject *self)
 {
@@ -1779,7 +1792,7 @@ static PyGetSetDef WraptObjectProxy_getset[] = {
     { "__doc__",            (getter)WraptObjectProxy_get_doc,
                             (setter)WraptObjectProxy_set_doc, 0 },
     { "__class__",          (getter)WraptObjectProxy_get_class,
-                            NULL, 0 },
+                            (setter)WraptObjectProxy_set_class, 0 },
     { "__annotations__",    (getter)WraptObjectProxy_get_annotations,
                             (setter)WraptObjectProxy_set_annotations, 0 },
     { "__wrapped__",        (getter)WraptObjectProxy_get_wrapped,

tests/test_object_proxy.py

@@ -2417,5 +2417,23 @@ def function(_self, self, *args, **kwargs):
 
         self.assertEqual(result, ('self', (), dict(arg1='arg1')))
 
+class TestOverridingSpecialAttributes(unittest.TestCase):
+
+    def test_overriding_class_attribute(self):
+        class Object1: pass
+        class Object2(Object1): pass
+
+        o1 = Object1()
+
+        self.assertEqual(o1.__class__, type(o1))
+
+        o2 = Object2()
+
+        self.assertEqual(o2.__class__, type(o2))
+
+        o2.__class__ = type(o1)
+
+        self.assertEqual(o2.__class__, type(o1))
+
 if __name__ == '__main__':
     unittest.main()