Inconsistency between Js output for the optional field record

[mununki]

@spice
type tOp = {
  label: option<string>,
  value?: int,
}

let sample2 = Js.Dict.empty()
sample2->Js.Dict.set("label", Js.Json.string("sample"))
let sampleJson2 = sample2->Js.Json.object_

let sampleRecord2: Records.tOp = {
  label: Some("sample"),
}

let encoded = sampleRecord2->Records.tOp_encode
t->testEqual(`encode omit optional field`, encoded, sampleJson2) // ok

let decoded = sampleJson2->Records.tOp_decode
t->testEqual(`decode omit optional field`, decoded, Ok(sampleRecord2))
// { TAG: 'Ok', _0: { label: 'sample', value: undefined } } { TAG: 'Ok', _0: { label: 'sample' } }

[mununki]

rescript-lang/rescript#6485