Parse variant or polymorphic variant

[mununki]

I realized that parsing the variant or polymorphic variant doesn't work with just a string that is the same as the variant or polymorphic variant. I found that the JSON value should be an array type. For example,

// Not working
let responseJson1 = `{
  "status": "SUCCESS"
}`

// Working
let responseJson2 = `{
  "status": [ "SUCCESS" ]
}`

@decco
type staus = SUCCESS | FAIL

@decco
type response = {
  status,
  ...
}

I think it is reasonable in a way. But, parsing "SUCCESS" into variant or polymorphic variant would be also reasonable. Is there any workaround to parse it in this way or any plan?

[ryb73]

Hi @mattdamon108 – please see #36

As for a workaround, you can use [@decco.codec] or manually override the *type*_encode and *type*_decode functions.

[mununki]

Working lovely! Thanks!

@decco
type orderStatus = PROCESSING | SUCCESS | FAIL

@decco
type order = {
  @decco.key("order-status") orderStatus: @decco.codec(Decco.Codecs.magic) orderStatus,
}

[mununki]

I found that the above my workaround is parsing it to a string, not a variant. Therefore, I had to make a custom encoder and decoder to parse as a result.

type orderStatus = PROCESSING | SUCCESS | FAIL

let encoderOrderStatus = v =>
  switch v {
  | PROCESSING => "CREATE"
  | SUCCESS => "STANDBY"
  | FAIL => "DELIVERING"
  }->Js.Json.string

let decoderOrderStatus = json => {
  switch json |> Js.Json.classify {
  | Js.Json.JSONString(str) =>
    switch str {
    | "PROCESSING" => PROCESSING->Ok
    | "SUCCESS" => SUCCESS->Ok
    | "FAIL" => FAIL->Ok
    | _ => Error({Decco.path: "", message: "Expected JSONString", value: json})
    }
  | _ => Error({Decco.path: "", message: "Expected JSONString", value: json})
  }
}

let codecOrderStatus: Decco.codec<orderStatus> = (encoderOrderStatus, decoderOrderStatus)

@decco
type order = {
  @decco.key("order-status") orderStatus: @decco.codec(codecOrderStatus) orderStatus,,
}