Can EitherAsync.chain support both Either and EitherAsync?

[lightDer]

Hi! It's really a neat and lightweight libs.
I wonder if EitherAsync.chain can support both Either and EitherAsync?

For example, if I want to chain getTitle, I need add async in the chain method.
Or any recommendations for handling this? Thanks.

async function getPost (postId: number): Promise<Either<Error, Post>> {
  const response = await fetch(`/posts/${postId}`);
  return response
    ? Right((response.json() as unknown) as Post)
    : Left(new Error(`Problem fetching post with id: ${postId}`));
}

function getTitle (post: Post): Either<Error, string> {
  return post.title
    ? Right(post.title)
    : Left(new Error("This post should have a title"));
}

function getPostTitle (req: Request): EitherAsync<Error, string> {
  return EitherAsync.liftEither(validateRequest(req))
    .chain((request) => getPost(request.postId))
    .chain(async (post) => getTitle(post));
}

[leepowelldev]

I too would like to see this - the EitherAsync api is great - but I end up littering the code with lots of EitherAsync.liftEither - if there's a nicer way to handle I'd also like to know.

[probablykabari]

Your getPostTitle function can be written as:

function getPostTitle (req: Request): EitherAsync<Error, string> {
  return EitherAsync(async ({ fromPromise, liftEither }) => {
     const request = await liftEither(validateRequest(req))
     const post = await fromPromise(getPost(request.postId))
     return await liftEither(getTitle(post))
  })
}

I often find this to be cleaner for composing functions than the chained interface.