Require all keys of an object decoder to be specified

[tobiwild]

This change requires all keys of an object decoder to be specified, even if they are optional. At the moment this would compile without an error:

    type User = {
      firstname: string;
      lastname: string;
      email?: string;
    };

    const userDecoder = JsonDecoder.object<User>(
      {
        firstname: JsonDecoder.string,
        lastname: JsonDecoder.string
      },
      'User'
    );

I like the idea of adding a new optional property and being forced to be specific about the way it's being decoded. Most of the time I probably want

    email: JsonDecoder.optional(JsonDecoder.string)

If I want it to be ignored, I could use

    email: JsonDecoder.constant<undefined>(undefined),

Does this make sense?

[jorroll]

This functionality already exists in the JsonDecoder.objectStrict decoder. See the docs.

[tobiwild]

I think JsonDecoder.objectStrict is about the JSON data passed in on runtime having only the keys specified by the decoder. But I think my change is not the best idea anyway, because with it you are not able to leave the optional keys out anymore, Object.keys(obj) would always include all the keys.

I think I'm fine with specifying the decoder from the outside like this:

type DecoderObjectAllRequired<a> = { [p in keyof Required<a>]: JsonDecoder.Decoder<a[p]> };
function objectAllRequired<a>(
    decoders: DecoderObjectAllRequired<a>,
    decoderName: string,
    keyMap?: JsonDecoder.DecoderObjectKeyMap<a>
  ): JsonDecoder.Decoder<a> {
    return JsonDecoder.object(decoders, decoderName, keyMap);
  }
const userDecoder = objectAllRequired<User>(

[joanllenas]

@tobiwild Thanks for your contribution! I get your point and it totally makes sense, will merge this, probably write some docs about it, and release a major version (this is a breaking change) during the weekend.

[jorroll]

I think JsonDecoder.objectStrict is about the JSON data passed in on runtime having only the keys specified by the decoder

Ahhh. I misunderstood your goal.

And somewhat tangentially related, I made a custom object decoder for myself which accepts a "removeUndefinedProperties" option. When specified, after an input is successfully decoded any properties which are undefined are deleted from the result. Something similar might provide you with the flexibility you're looking for.

[joanllenas]

Hey @tobiwild , your changes are included in the latest release (v1.0.0).

Thanks!

[tobiwild]

NIce, I'll upgrade my app then, thanks!