Decco

Project Status

Decco is not being actively maintained, but PRs will be accepted and appreciated.

What is it?

A Bucklescript PPX which generates JSON serializers and deserializers for user-defined types.

Example:

``reason
/ Define types /
[@decco] type variant('a) = A | B(int) | C(int, 'a);
type dict = Js.Dict.t(string);
[@decco] type mytype = {
s: string,
i: int,
o: option(int),
complex: array(option(list(variant(string)))),
[@decco.default 1.0] f: float,
[@decco.key "other_key"] otherKey: string,
magic: [@decco.codec Decco.Codecs.magic] dict,
};

/ Use _encode to encode /
let encoded = mytype_encode({
s: "hello",
i: 12,
o: None,
complex: [| Some([ C(25, "bullseye") ]) |],
f: 13.,
otherKey: "other",
magic: Js.Dict.fromArray([|("key","value")|]),
});

Js.log(Js.Json.stringifyWithSpace(encoded, 2));
/* {
"s": "hello",
"i": 12,
"o": null,
"complex": [ [ ["C", 25, "bullseye"] ] ],
"f": 13,
"other_key": "other",
"magic": { "key": "value" }
} */

/ Use _decode to decode /
let { s, i, o, complex, f, otherKey, magic } =
mytype_decode(encoded)
|> Belt.Result.getExn;
`

How do I install it?


1. Install package
`
npm i decco
`

2. Update your bsconfig.json
`json
{
...,
"bs-dependencies": [ "decco" ],
"ppx-flags": [ "decco/ppx" ],
...
}
`

Adding decco/ppx to ppx-flags will enable the PPX. Adding decco to bs-dependencies is required because the code generated by the PPX references the Decco module.

Note: If you need to use decco with BuckleScript 5, install @ryb73/decco version ^0.1.0 by following the old ReadMe here.

How do I use it?

See test.re for some examples.

Reference

$3

#### [@decco]
Applies to: type declarations, type signatures

Indicates that an encoder and decoder should be generated for the given type.

#### [@decco.encode]
Applies to: type declarations, type signatures

Indicates than an encoder (but no decoder) should be generated for the given type.

#### [@decco.decode]
Applies to: type declarations, type signatures

Indicates than an decoder (but no encoder) should be generated for the given type.

#### [@decco.codec]
Applies to: type expressions

Specifies custom encoders and decoders for the type. Note that both an encoder and decoder must be specified, even if the type expression is within a type for which [@decco.encode] or [@decco.decode] was specified.

`reason
[@decco] type t = [@decco.codec (fancyEncoder, fancyDecoder)] fancyType;
`

#### [@decco.key]
Applies to: record fields

By default, Reason record fields map to JS object fields of the same name. Use [@decco.key] to specify a custom JS field name. Useful if the JS field name is invalid as a Reason record field name.

`reason
[@decco]
type record = {
[@decco.key "other_key"] otherKey: string,
};
`

#### [@decco.default]
Applies to: record fields
Default: Js.Json.null

When decoding a record, the default value will be used for keys that are missing from the JSON object being decoded.

`reason
[@decco] type record = {
[@decco.default "def"] s: string,
};

let {s} = Js.Json.parseExn("{}") |> record_decode |> Belt.Result.getExn;
Js.log(s); / def /
``

Contributing

Please read the CONTRIBUTING.md