return validation error for empty attribute

moto/dynamodb2/responses.py

@@ -144,6 +144,16 @@ class DynamoHandler(BaseResponse):
     def put_item(self):
         name = self.body['TableName']
         item = self.body['Item']
+
+        res = re.search('\"\"', json.dumps(item))
+        if res:
+            er = 'com.amazonaws.dynamodb.v20111205#ValidationException'
+            return 400, {'server': 'amazon.com'}, dynamo_json_dump(
+                {'__type': er,
+                'message': ('One or more parameter values were invalid: '
+                'An AttributeValue may not contain an empty string')
+                })
+
         overwrite = 'Expected' not in self.body
         if not overwrite:
             expected = self.body['Expected']

tests/test_dynamodb2/test_dynamodb.py

@@ -149,3 +149,33 @@ def test_list_not_found_table_tags():
         conn.list_tags_of_resource(ResourceArn=arn)
     except ClientError as exception:
         assert exception.response['Error']['Code'] == "ResourceNotFoundException"
+
+
+@requires_boto_gte("2.9")
+@mock_dynamodb2
+def test_item_add_empty_string_exception():
+    name = 'TestTable'
+    conn = boto3.client('dynamodb',
+                        region_name='us-west-2',
+                        aws_access_key_id="ak",
+                        aws_secret_access_key="sk")
+    conn.create_table(TableName=name,
+                      KeySchema=[{'AttributeName':'forum_name','KeyType':'HASH'}],
+                      AttributeDefinitions=[{'AttributeName':'forum_name','AttributeType':'S'}],
+                      ProvisionedThroughput={'ReadCapacityUnits':5,'WriteCapacityUnits':5})
+    session = boto3.Session()
+    dynamodb = session.resource('dynamodb',
+                                region_name='us-west-2',
+                                aws_access_key_id="ak",
+                                aws_secret_access_key="sk")
+    table = dynamodb.Table('TestTable')
+    try:
+        response = table.put_item(Item={
+            'forum_name': 'LOLCat Forum',
+            'subject': 'Check this out!',
+            'Body': 'http://url_to_lolcat.gif',
+            'SentBy': "",
+            'ReceivedTime': '12/9/2011 11:36:03 PM',
+        })
+    except ClientError as exception:
+        assert exception.response['Error']['Code'] == "ValidationException"