Check for property deletion (#67)

traits/ctraits.c

@@ -2594,8 +2594,12 @@ setattr_validate_property ( trait_object      * traito,
                             PyObject          * value ) {
 
     int result;
+    PyObject * validated;
+
+    if ( value == NULL )
+        return set_delete_property_error( obj, name );
 
-    PyObject * validated = traitd->validate( traitd, obj, name, value );
+    validated = traitd->validate( traitd, obj, name, value );
     if ( validated == NULL )
         return -1;
     result = ((trait_setattr) traitd->post_setattr)( traito, traitd, obj, name,

traits/tests/test_property_delete.py

@@ -0,0 +1,31 @@
+"""
+Unit tests to ensure that we can call reset_traits/delete on a
+property trait (regression tests for Github issue #67).
+
+"""
+
+from traits import _py2to3
+from traits.api import Any, HasTraits, Int, Property, TraitError
+from traits.testing.unittest_tools import unittest
+
+
+class E(HasTraits):
+
+    a = Property(Any)
+
+    b = Property(Int)
+
+
+class TestPropertyDelete(unittest.TestCase):
+
+    def test_property_delete(self):
+        e = E()
+        with self.assertRaises(TraitError):
+            del e.a
+        with self.assertRaises(TraitError):
+            del e.b
+
+    def test_property_reset_traits(self):
+        e = E()
+        unresetable = e.reset_traits()
+        _py2to3.assertCountEqual(self, unresetable, ['a', 'b'])