2380 - Validate parameter-list for duplicates in dynamodb.batch_get_item

moto/dynamodb2/responses.py

@@ -318,6 +318,9 @@ class DynamoHandler(BaseResponse):
 
         for table_name, table_request in table_batches.items():
             keys = table_request['Keys']
+            if self._contains_duplicates(keys):
+                er = 'com.amazon.coral.validate#ValidationException'
+                return self.error(er, 'Provided list of item keys contains duplicates')
             attributes_to_get = table_request.get('AttributesToGet')
             results["Responses"][table_name] = []
             for key in keys:
@@ -333,6 +336,15 @@ class DynamoHandler(BaseResponse):
             })
         return dynamo_json_dump(results)
 
+    def _contains_duplicates(self, keys):
+        unique_keys = []
+        for k in keys:
+            if k in unique_keys:
+                return True
+            else:
+                unique_keys.append(k)
+        return False
+
     def query(self):
         name = self.body['TableName']
         # {u'KeyConditionExpression': u'#n0 = :v0', u'ExpressionAttributeValues': {u':v0': {u'S': u'johndoe'}}, u'ExpressionAttributeNames': {u'#n0': u'username'}}