Either<A,B> translate to A | B

[abersnaze]

I was wondering if there is support scala.util.Either type? Is there some way to plug in support for it?

[vojtechhabarta]

scala.util.Either is not currently supported.

What exactly is your use case?

I tried to serialize Either values using Jackson with DefaultScalaModule. Following Java code:

List<Either<String, Number>> list = Arrays.asList(
        new Left<>("test"),
        new Right<>(42)
);
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new DefaultScalaModule());
System.out.println(objectMapper.writeValueAsString(list));

produces this output:

[
    {
        "l": "test"
    },
    {
        "r": 42
    }
]

So instead of translating Either<A, B>> to just A | B we would need to translate it to something like this:

type Either<L, R> = {
    "l": L;
    "r"?: undefined;
} | {
    "l"?: undefined;
    "r": R;
}

BTW are you aware of Tagged unions - another form of disjoint unions - which uses some discriminant property and is well supported in Jackson, typescript-generator and TypeScript itself?

[abersnaze]

The tagged unions look like a better options because of the discriminant.