Convenience function to move AsyncResult from "railway world" back to "exception world"

[njlr]

Is your feature request related to a problem? Please describe.

Exceptions are an important part of the F# ecosystem.

Sometimes error-handling is best done "railway style" and sometimes it's better to use exceptions. And sometimes we want different styles in different areas of a program.

We already have a way to go from "exception world" to "railway world", using AsyncResult.catch.

This feature request is to include a small helper function for going the other way: Async<Result<'ok, exn>> -> Async<'ok>.

Describe the solution you'd like

Add a helper function for this.

For example:

module AsyncResult =

  open System.Runtime.ExceptionServices

  let orReraise (workflow : Async<Result<'a, exn>>) : Async<'a> =
    async {
      match! workflow with
      | Ok a ->
        return a
      | Error exn ->
        ExceptionDispatchInfo.Capture(exn).Throw()
        return Unchecked.defaultof<_>
    }

Describe alternatives you've considered

Everyone writes their own!

Additional context

None

[TheAngryByrd]

Yeah I think this makes sense. Slight modification is to make it inline so it doesn't polute the stacktrace. I would also call it getOrReraise.

Testing this might prove tricky since you'd need to look at the stacktrace but ignore line numbers since that can be brittle.