How to unwrap an async

I just upgraded from Cvdm.ErrorHandling to this. In Cvdm.ErrorHandling, I could unwrap an Async<Result<User, string>> by using let! operator without piping into any of the AsyncResult or Result module conversion functions.

// tryGetUser = int -> Async<Result<User, string>>
let! myResult = tryGetUser(1) // returns a Result<User, string>

Now this fails because it’s trying to look at the result type. But in this case, I don’t want to fully unwrap it to be just a User – I actually want it to be a Result<User, string> so that I can do some custom logic for the error case.

Is there a way to do this? I’m looking through the AsyncResult module, but I don’t see anything relevant.

[JordanMarr]

Would you consider adding this helper function to the AsyncResult module?

module AsyncResult =
    /// Awaits a result type without resolving it.
    let awaitResult (f: Async<Result<_, _>>) =
        f |> Async.map Ok

// Usage
// tryGetUser = int -> Async<Result<User, string>>
let! myResult = tryGetUser(1) |> AsyncResult.awaitResult // returns a Result<User, string>
match myResult with
| Ok user -> printfn "User: %A" user
| Error err -> printfn "Error: %s" err

[TheAngryByrd]

For a more concrete example, you can an async CE inline and do something like this:

let doTheThing () = asyncResult {
    let! user = async {
        let! myResult = tryGetUser(1)
        match myResult with
        | Ok user -> user
        | Error msg -> //custom errorHandling
    }
}