package ppx_protocol_conv_json

Ppx Protocol Conv

Ppx protocol conv (de)serialisers using deriving, which allows for plugable (de)serialisers.

Example Usage

open Protocol_conv
open Protocol_conv_json
type a = {
  x: int;
  y: string [@key "Y"]
} [@@deriving protocol ~driver:(module Json) ~flags:(`Mangle Json.mangle)]

type b = A of int
       | B of int [@key "b"]
       | C
[@@deriving protocol ~driver:(module Json)]

will generate the functions:

val a_to_json: a -> Json.t
val a_of_json: Json.t -> a

val b_to_json: a -> Json.t
val b_of_json: Json.t -> a

a_to_json { x=42; y:"really" }

Evaluates to

[ "x", `Int 42; "Y", `String "really"] (* Yojson.Safe.json *)

to_protocol deriver will generate serilization of the type. of_protocol deriver generates de-serilization of the type, while protocol deriver will generate both serilizarion and de-serilization functions.

Flags can be specified using the driver argument ~flags. For the json module, the mangle function transforms record label names to be lower camelcase: a_bc_de -> aBcDe and a_bc_de_ -> aBcDe. Beware that this may cause name collisions, which can only be determined at compile time.

Attributes

Record label names can be changed using [@key <string>]

Variant constructors names can also be changed using the [@key <string>] attribute.

Signatures

The ppx also handles signature, but disallows [@key ...] and ~flags:... as these does not impact signatures.

Drivers

The protocol deriver implements:

• Json which serializes to Yojson.Safe.t

• Xml_light which serializes to Xml.xml list

• Msgpack which serializes to Msgpck.t

Custom drivers

It should be easy to provide custom drivers by implementing the signature:

include Lib.Driver with type t = ... and type flags = ...

See the drivers directory for examples on how to implemented new drivers. Submissions of useful drivers are welcome

Limitations

The json driver will currently serialize type t option option as t option. This means that Some None and None is both mapped to Null.