fixes accessing the affected_root_keys property on the diff object re…

…turned by DeepDiff fails when one of the dicts is empty #508

deepdiff/diff.py

@@ -1846,9 +1846,13 @@ def affected_root_keys(self):
             value = self.tree.get(key)
             if value:
                 if isinstance(value, SetOrdered):
-                    result |= SetOrdered([i.get_root_key() for i in value])
+                    values_list = value
                 else:
-                    result |= SetOrdered([i.get_root_key() for i in value.keys()])
+                    values_list = value.keys()
+                for item in values_list:
+                    root_key = item.get_root_key()
+                    if root_key is not notpresent:
+                        result.add(root_key)
         return result
 
 

deepdiff/model.py

@@ -665,7 +665,9 @@ def get_root_key(self, use_t2=False):
         else:
             next_rel = root_level.t1_child_rel or root_level.t2_child_rel  # next relationship object to get a formatted param from
 
-        return next_rel.param
+        if next_rel:
+            return next_rel.param
+        return notpresent
 
     def path(self, root="root", force=None, get_parent_too=False, use_t2=False, output_format='str'):
         """

tests/test_diff_text.py

@@ -807,6 +807,24 @@ class ClassB:
         result = {'attribute_removed': ['root.y']}
         assert result == ddiff
 
+    def test_custom_objects_slot_in_group_change(self):
+        class ClassA:
+            __slots__ = ('x', 'y')
+
+            def __init__(self, x, y):
+                self.x = x
+                self.y = y
+
+        class ClassB(ClassA):
+            pass
+
+        t1 = ClassA(1, 1)
+        t2 = ClassB(1, 1)
+        ddiff = DeepDiff(t1, t2, ignore_type_in_groups=[(ClassA, ClassB)])
+        result = {}
+        assert result == ddiff
+
+
     def test_custom_class_changes_none_when_ignore_type(self):
         ddiff1 = DeepDiff({'a': None}, {'a': 1}, ignore_type_subclasses=True, ignore_type_in_groups=[(int, float)])
         result = {
@@ -2226,3 +2244,10 @@ def test_group_by_with_none_key_and_ignore_case(self):
                                         }
                     }
         assert expected == diff
+
+    def test_affected_root_keys_when_dict_empty(self):
+        diff = DeepDiff({}, {1:1, 2:2}, threshold_to_diff_deeper=0)
+        assert [1, 2] == diff.affected_root_keys
+
+        diff2 = DeepDiff({}, {1:1, 2:2})
+        assert [] == diff2.affected_root_keys