Support tarantool serializable about msgpack-crystal

[kostya]

ArraySerializable module in shard since v0.15

[kostya]

I also think about doing compact mapping with arrays (sounds like protobuf format actually jeromegn/protobuf.cr#26), because packed data should be much smaller. Btw, it should be new Serializable module like SerializableCompact.

Until this not supported, you can do it like this (And also write macro that generate such code):

require "msgpack"

class MessagePackPersonArray
  def initialize(pull : MessagePack::Unpacker)
    token = pull.prefetch_token
    raise "expected array" unless token.type == :ARRAY

    size = token.size
    raise "expected array with size > 2" if size < 2
    token.used = true

    @name = String.new(pull)
    @age = Int32.new(pull)
    (size - 2).times { pull.skip_value }
  end
end

person = MessagePackPersonArray.from_msgpack(["John", 30, "1", 2, [1, 2, 3]].to_msgpack)
p person # => #<MessagePackPersonArray:0x102ef0e80 @name="John", @age=30>

[kostya]

i add this in compact_serializable branch, you can read specs, about how it works https://github.com/crystal-community/msgpack-crystal/blob/compact_serializable/spec/compact_serializable_spec.cr

require "./src/msgpack"

class MessagePackPersonArray
  include MessagePack::CompactSerializable
  include MessagePack::CompactSerializable::Unmapped

  property name : String
  property age : Int32?
end

person = MessagePackPersonArray.from_msgpack(["John", 30, "1", 2, [1, 2, 3]].to_msgpack)
p person 
#=> #<MessagePackPersonArray:0x100aadea0 @msgpack_unmapped={2 => "1", 3 => 2_u8, 4 => [1_u8, 2_u8, 3_u8]}, @name="John", @age=30>

0, 1 it indexed by default, you can change it.