Re: [Caml-list] [ANN] ppx_protobuf

[Peter Zotov <whitequark@whitequark.org>]

On 2014-05-03 20:08, Malcolm Matalka wrote:
> Nice, great work!
> 
> I'm not actually a huge fan of mixing type definitions and the 
> protocols
> they can be encoded/decoded from.  How hard would it be to take a 
> module
> definition accessors on a type and produce a new module with
> encode/decode functions?  That way I could create JSON, XML, Protobufs,
> etc modules from one module.

Do you suggest generating the following signature instead of the current
one?

type t = ... [@@protobuf]
module Protobuf_t : sig
   val decode : Protobuf.Decoder.t -> t
   val encode : Protobuf.Encoder.t -> t -> unit
end

This would be similar to what deriving currently does.

In principle, this is not a complex change. It would add just a few 
lines
to ppx_protobuf.

However, I don't like it conceptually. I think the flat signature is
more natural, it mimics what one would usually write by hand without
introducing too much deep nesting of modules. You may notice how
ppx_protobuf doesn't generate the signature items for you; this is
because ppx_protobuf is a mere implementation detail, a convenient
way to generate the serializer/deserializer.

I'm not going to oppose addition of such a mode for two reasons:
   * I don't like fighting over minute details.
   * More importantly, deriving, when rewritten with ppx in mind,
     will surely contain this mode for compatibility. ppx_protobuf
     will be (ideally) rewritten over deriving some day.

I will happily merge a PR adding such a mode to ppx_protobuf.

> 
> Just an idea!
> 
> Peter Zotov <whitequark@whitequark.org> writes:
> 
>> Greetings.
>> 
>> I have just released the first version of ppx_protobuf, a complete
>> Protocol Buffers implementation. Unlike Google's implementation,
>> ppx_protobuf derives the message structure directly from OCaml type
>> definitions, which allows a much more seamless integration with
>> OCaml's types. In particular, ppx_protobuf natively supports
>> sum types, while maintaining full backwards compatibility with
>> protoc.
>> 
>> ppx_protobuf uses the extension points API, and thus requires
>> a recent (>= 2014-04-29) 4.02 (trunk) compiler. It also requires
>> an unreleased version of ppx_tools. It is probably easiest
>> to install both from the source repositories[1][2].
>> 
>> The API is extensively documented at [3].
>> 
>> [1]: https://github.com/whitequark/ocaml-ppx_protobuf.git
>> [2]: https://github.com/alainfrisch/ppx_tools.git
>> [3]: 
>> https://github.com/whitequark/ocaml-ppx_protobuf/blob/master/README.md
>> 
>> --
>>   WBR, Peter Zotov.

-- 
Peter Zotov
sip:whitequark@sipnet.ru