Merge pull request #2014 from garyd203/dynamodb-set-comparison

Make EQ conditions on sets work reliably in DynamoDB

tests/test_dynamodb2/test_dynamodb_table_without_range_key.py

@@ -750,6 +750,47 @@ def test_boto3_update_item_conditions_pass_because_expect_exists_by_compare_to_n
     returned_item = table.get_item(Key={'username': 'johndoe'})
     assert dict(returned_item)['Item']['foo'].should.equal("baz")
 
+
+@mock_dynamodb2
+def test_boto3_update_settype_item_with_conditions():
+    class OrderedSet(set):
+        """A set with predictable iteration order"""
+        def __init__(self, values):
+            super(OrderedSet, self).__init__(values)
+            self.__ordered_values = values
+
+        def __iter__(self):
+            return iter(self.__ordered_values)
+
+    table = _create_user_table()
+    table.put_item(Item={'username': 'johndoe'})
+    table.update_item(
+        Key={'username': 'johndoe'},
+        UpdateExpression='SET foo=:new_value',
+        ExpressionAttributeValues={
+            ':new_value': OrderedSet(['hello', 'world']),
+        },
+    )
+
+    table.update_item(
+        Key={'username': 'johndoe'},
+        UpdateExpression='SET foo=:new_value',
+        ExpressionAttributeValues={
+            ':new_value': set(['baz']),
+        },
+        Expected={
+            'foo': {
+                'ComparisonOperator': 'EQ',
+                'AttributeValueList': [
+                    OrderedSet(['world', 'hello']),  # Opposite order to original
+                ],
+            }
+        },
+    )
+    returned_item = table.get_item(Key={'username': 'johndoe'})
+    assert dict(returned_item)['Item']['foo'].should.equal(set(['baz']))
+
+
 @mock_dynamodb2
 def test_boto3_put_item_conditions_pass():
     table = _create_user_table()