Decco

Project Status

I'm no longer using Reason, and thus am not actively making updates to Decco. PRs will still be accepted and are appreciated. Thanks!

What is it?

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

Example:

/* Define types */
[@decco] typevariant('a) =A | B(int) | C(int, 'a);typedict=Js.Dict.t(string);
[@decco] typemytype= {
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.codecDecco.Codecs.magic] dict,
};/* Use <typename>_encode to encode */letencoded= 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 <typename>_decode to decode */let { s, i, o, complex, f, otherKey, magic } =
mytype_decode(encoded)
|>Belt.Result.getExn;

What state is it in?

Working fine in active production code.

How do I install it?

1. Install package

npm i decco

2. Update your bsconfig.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

Attributes

[@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.

[@decco] typet= [@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.

[@decco]
typerecord= {
[@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.

[@decco] typerecord= {
[@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