Plans for optional records support

[youngkidwarrior]

Rescript v10 has implemented support for optional record fields
rescript-lang/rescript#5654

Any plans on implementing this instead of using Option?

Is it even feasible with the API. I might take a look at it myself if you think it is possible

[glennsl]

Hi. I'm not aware of any syntax for conditionally setting an @optional field individually (the issue you reference seems to just be about a printing bug), but if there is I don't see why it wouldn't work with the existing API. Whether it uses options directly, or branching on an option. I don't know how else it would work.

[glennsl]

I'm assuming this has been answered adequately. But feel free to re-open if necessary.

[hellos3b]

I'm facing this as well, when using the optional ? syntax, the field.optional doesn't resolve right

type foo = {
  a: string,
  b?: string,
}

let decoder = {
  open Json.Decode
  object(field => {
    a: field.required(. "a", string),
    b: field.optional(. "b", string),
  })
}

I think it would make more sense if field.optional<'a> returns 'a instead of option<'a>, and then use the Decode.option(string) for the explicit option type

let decoder = object(field => {
  a: field.required(. "a", option(string)),
  b: field.optional(. "b", string)
}

[glennsl]

I'm facing this as well, when using the optional ? syntax, the field.optional doesn't resolve right

According to the documentation, if you want to assign an option to an optional field, you need to prefix it with ?:

type foo = {
  a: string,
  b?: string,
}

let decoder = {
  open Json.Decode
  object(field => {
    a: field.required(. "a", string),
    b: ?field.optional(. "b", string),
  })
}

I think it would make more sense if field.optional<'a> returns 'a instead of option<'a>, and then use the Decode.option(string) for the explicit option type

Then it wouldn't be optional... You can get this behavior by using field.required instead, but the implication of using ´option´ is that you're not able to distinguish between the field not being present and the the type being wrong. Edit: Strike that, this is how it used to work with bs-json, which was closer to Elm's decoders. option now only returns None if it's null, not if the inner decoder fails, and not if it's undefined either, since undefined is not a JSON value

[hellos3b]

b: ?field.optional(. "b", string),

Ah man thanks, this is the syntax I didn't know existed! My suggestion was based off trying to get the types to agree on my own fork, you can disregard it :)