ReceiveMessage does not filter out MessageAttribute

[zsiddique]

http://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_ReceiveMessage.html
So the AWS API is a little vague on this but testing shows that when ReceiveMessage is called with no MessageAttributeName defined ReceiveMessage returns messages with no MessageAttribute. But elaticmq will return MessageAttribute regardless what is asked in MessageAttributeName.
This caused a problem for us as we are using elasticmq to test our usage of SQS and we had a bug in which we neglected to request an MessageAttribute but would work in testing but failed once we got to integration testing with real SQS.
Example using boto. First with Elasticmq

In [6]: c.send_message(MessageBody="ABody", MessageAttributes={'version': {  'StringValue': '1', 'DataType': 'String'}})
Out[6]:
{u'MD5OfMessageAttributes': '75cba0c5eb8ce78d6a41a35f99bfd7a8',
 u'MD5OfMessageBody': '3aff89437ced3559d5e62a20eeb3ea52',
 u'MessageId': '18791ce9-b66e-4ed5-ad31-e93064fcd673',
 'ResponseMetadata': {'HTTPHeaders': {'content-length': '579',
   'content-type': 'text/plain; charset=UTF-8',
   'date': 'Tue, 07 Mar 2017 00:30:02 GMT',
   'server': 'akka-http/2.3.15'},
  'HTTPStatusCode': 200,
  'RequestId': '00000000-0000-0000-0000-000000000000',
  'RetryAttempts': 0}}

In [7]: m = c.receive_messages()

In [8]: m[0].message_attributes
Out[8]: {'version': {u'DataType': 'String', u'StringValue': '1'}}

With AWS SQS:

In [5]: c.send_message(MessageBody="ABody", MessageAttributes={'version': {  'StringValue': '1', 'DataType': 'String'}})
Out[5]:
{u'MD5OfMessageAttributes': '75cba0c5eb8ce78d6a41a3xxxxx',
 u'MD5OfMessageBody': '3aff89437ced3559d5e62a20xxxxxx',
 u'MessageId': '283c0711-6abd-42a5-b4d4-6b95c8cef099',
 'ResponseMetadata': {'HTTPHeaders': {'connection': 'keep-alive',
   'content-length': '459',
   'content-type': 'text/xml',
   'date': 'Tue, 07 Mar 2017 01:27:43 GMT',
   'server': 'Server',
   'x-amzn-requestid': 'bface69a-2ca7-5b7f-bb32-xxxxxxx'},
  'HTTPStatusCode': 200,
  'RequestId': 'bface69a-2ca7-5b7f-bb32-xxxxxxxx',
  'RetryAttempts': 0}}

In [6]: m = c.receive_messages()
In [7]: m[0].message_attributes

In [8]:

[DeepSpawn]

Yea we noticed the same difference between real SQS and Elasticmq tests. I have raised a PR which changes the Elasticmq behaviour to be in line with SQS so hopefully nobody runs into this in the future :)

[adamw]

Should be fixed in 0.13.4