Add specific error for duplicate additional/copy_variables in normali…

…ze_entity

featuretools/entityset/entityset.py

@@ -753,10 +753,16 @@ def normalize_entity(self, base_entity_id, new_entity_id, index,
             raise TypeError("'additional_variables' must be a list, but received type {}"
                             .format(type(additional_variables)))
 
+        if len(additional_variables) != len(set(additional_variables)):
+            raise ValueError("'additional_variables' contains duplicate variables. All variables must be unique.")
+
         if not isinstance(copy_variables, list):
             raise TypeError("'copy_variables' must be a list, but received type {}"
                             .format(type(copy_variables)))
 
+        if len(copy_variables) != len(set(copy_variables)):
+            raise ValueError("'copy_variables' contains duplicate variables. All variables must be unique.")
+
         for v in additional_variables + copy_variables:
             if v == index:
                 raise ValueError("Not copying {} as both index and variable".format(v))

featuretools/tests/entityset_tests/test_es.py

@@ -843,6 +843,20 @@ def test_normalize_time_index_from_none(entityset):
     assert entityset['birthdays'].time_index == 'date_of_birth'
 
 
+def test_raise_error_if_dupicate_additional_variables_passed(entityset):
+    error_text = "'additional_variables' contains duplicate variables. All variables must be unique."
+    with pytest.raises(ValueError, match=error_text):
+        entityset.normalize_entity('sessions', 'device_types', 'device_type',
+                                   additional_variables=['device_name', 'device_name'])
+
+
+def test_raise_error_if_dupicate_copy_variables_passed(entityset):
+    error_text = "'copy_variables' contains duplicate variables. All variables must be unique."
+    with pytest.raises(ValueError, match=error_text):
+        entityset.normalize_entity('sessions', 'device_types', 'device_type',
+                                   copy_variables=['device_name', 'device_name'])
+
+
 def test_normalize_entity_copies_variable_types(entityset):
     entityset['log'].convert_variable_type(
         'value', variable_types.Ordinal, convert_data=False)