person.proto

message Person {
  required int32 id = 1;
  required string name = 2;
  optional string email = 3;
  repeated Address addresses = 4;

  extensions 10 to max;
}

message Address {
  required string street = 1;
}

message Phone {
    extend Person { repeated Phone phones = 10;}
    enum PHONE_TYPE{
        MOBILE = 1;
        HOME = 2;
    }
    optional string num = 1;
    optional PHONE_TYPE type = 2;
}

test.lua

package.path = package.path .. ';../protobuf/?.lua'
package.cpath = package.cpath .. ';../protobuf/?.so'

require 'person_pb'

local person= person_pb.Person()
person.id = 1000
person.name = "Alice"
person.email = "Alice@example.com"

local home = person.Extensions[person_pb.Phone.phones]:add()
home.num = "2147483647"
home.type = person_pb.Phone.HOME

local addr = person.addresses:add()
addr.street = "Gade1"
local addr = person.addresses:add()
addr.street = "Gade2"

-- person.addresses = { addr1, addr2 }

local data = person:SerializeToString()

local msg = person_pb.Person()

msg:ParseFromString(data)

print(msg.addresses[1])

print(msg)