Implement vpc-id Instance filter

moto/ec2/models.py

@@ -286,6 +286,7 @@ class Instance(BotoInstance, TaggedEC2Resource):
         self.user_data = user_data
         self.security_groups = security_groups
         self.instance_type = kwargs.get("instance_type", "m1.small")
+        self.vpc_id = None
         self.subnet_id = kwargs.get("subnet_id")
         self.key_name = kwargs.get("key_name")
         self.source_dest_check = "true"
@@ -309,6 +310,10 @@ class Instance(BotoInstance, TaggedEC2Resource):
                 # string will have a "u" prefix -- need to get rid of it
                 self.user_data[0] = self.user_data[0].encode('utf-8')
 
+        if self.subnet_id:
+            subnet = ec2_backend.get_subnet(self.subnet_id)
+            self.vpc_id = subnet.vpc_id
+
         self.prep_nics(kwargs.get("nics", {}),
                        subnet_id=kwargs.get("subnet_id",None),
                        private_ip=kwargs.get("private_ip",None),

moto/ec2/utils.py

@@ -274,6 +274,7 @@ filter_dict_attribute_mapping = {
     'instance-id': 'id',
     'state-reason-code': '_state_reason.code',
     'source-dest-check': 'source_dest_check',
+    'vpc-id': 'vpc_id',
 }
 
 def get_instance_value(instance, instance_attr):