Async.CancelAfter

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// inspired by http://stackoverflow.com/a/11191070

open System

type private Completed<'T>(value : 'T) =
    inherit Exception()
    member __.Value = value

exception private Timeout

type Async with
    static member CancelAfter timeout (f : Async<'T>) =
        let econt e = Async.FromContinuations(fun (_,econt,_) -> econt e)
        let worker = async {
            let! r = f
            return! econt <| Completed(r)
        }
        let timer = async {
            do! Async.Sleep timeout
            return! econt Timeout
        }

        async {
            try 
                let! _ = Async.Parallel [worker ; timer]
                return failwith "unreachable exception reached."
            with 
            | :? Completed<'T> as t -> return Some t.Value
            | Timeout -> return None
        }

// example
Async.Sleep 400 |> Async.CancelAfter 500 |> Async.RunSynchronously
Async.Sleep 400 |> Async.CancelAfter 300 |> Async.RunSynchronously

namespace System

Multiple items
type private Completed<'T> =
  inherit Exception
  new : value:'T -> Completed<'T>
  member Value : 'T

Full name: Script.Completed<_>

--------------------
private new : value:'T -> Completed<'T>

val value : 'T

Multiple items
type Exception =
  new : unit -> Exception + 2 overloads
  member Data : IDictionary
  member GetBaseException : unit -> Exception
  member GetObjectData : info:SerializationInfo * context:StreamingContext -> unit
  member GetType : unit -> Type
  member HelpLink : string with get, set
  member InnerException : Exception
  member Message : string
  member Source : string with get, set
  member StackTrace : string
  ...

Full name: System.Exception

--------------------
Exception() : unit
Exception(message: string) : unit
Exception(message: string, innerException: exn) : unit
Exception(info: Runtime.Serialization.SerializationInfo, context: Runtime.Serialization.StreamingContext) : unit

member private Completed.Value : 'T

Full name: Script.Completed`1.Value

exception private Timeout

Full name: Script.Timeout

Multiple items
type Async
static member AsBeginEnd : computation:('Arg -> Async<'T>) -> ('Arg * AsyncCallback * obj -> IAsyncResult) * (IAsyncResult -> 'T) * (IAsyncResult -> unit)
static member AwaitEvent : event:IEvent<'Del,'T> * ?cancelAction:(unit -> unit) -> Async<'T> (requires delegate and 'Del :> Delegate)
static member AwaitIAsyncResult : iar:IAsyncResult * ?millisecondsTimeout:int -> Async<bool>
static member AwaitTask : task:Task<'T> -> Async<'T>
static member AwaitWaitHandle : waitHandle:WaitHandle * ?millisecondsTimeout:int -> Async<bool>
static member CancelDefaultToken : unit -> unit
static member Catch : computation:Async<'T> -> Async<Choice<'T,exn>>
static member FromBeginEnd : beginAction:(AsyncCallback * obj -> IAsyncResult) * endAction:(IAsyncResult -> 'T) * ?cancelAction:(unit -> unit) -> Async<'T>
static member FromBeginEnd : arg:'Arg1 * beginAction:('Arg1 * AsyncCallback * obj -> IAsyncResult) * endAction:(IAsyncResult -> 'T) * ?cancelAction:(unit -> unit) -> Async<'T>
static member FromBeginEnd : arg1:'Arg1 * arg2:'Arg2 * beginAction:('Arg1 * 'Arg2 * AsyncCallback * obj -> IAsyncResult) * endAction:(IAsyncResult -> 'T) * ?cancelAction:(unit -> unit) -> Async<'T>
static member FromBeginEnd : arg1:'Arg1 * arg2:'Arg2 * arg3:'Arg3 * beginAction:('Arg1 * 'Arg2 * 'Arg3 * AsyncCallback * obj -> IAsyncResult) * endAction:(IAsyncResult -> 'T) * ?cancelAction:(unit -> unit) -> Async<'T>
static member FromContinuations : callback:(('T -> unit) * (exn -> unit) * (OperationCanceledException -> unit) -> unit) -> Async<'T>
static member Ignore : computation:Async<'T> -> Async<unit>
static member OnCancel : interruption:(unit -> unit) -> Async<IDisposable>
static member Parallel : computations:seq<Async<'T>> -> Async<'T []>
static member RunSynchronously : computation:Async<'T> * ?timeout:int * ?cancellationToken:CancellationToken -> 'T
static member Sleep : millisecondsDueTime:int -> Async<unit>
static member Start : computation:Async<unit> * ?cancellationToken:CancellationToken -> unit
static member StartAsTask : computation:Async<'T> * ?taskCreationOptions:TaskCreationOptions * ?cancellationToken:CancellationToken -> Task<'T>
static member StartChild : computation:Async<'T> * ?millisecondsTimeout:int -> Async<Async<'T>>
static member StartChildAsTask : computation:Async<'T> * ?taskCreationOptions:TaskCreationOptions -> Async<Task<'T>>
static member StartImmediate : computation:Async<unit> * ?cancellationToken:CancellationToken -> unit
static member StartWithContinuations : computation:Async<'T> * continuation:('T -> unit) * exceptionContinuation:(exn -> unit) * cancellationContinuation:(OperationCanceledException -> unit) * ?cancellationToken:CancellationToken -> unit
static member SwitchToContext : syncContext:SynchronizationContext -> Async<unit>
static member SwitchToNewThread : unit -> Async<unit>
static member SwitchToThreadPool : unit -> Async<unit>
static member TryCancelled : computation:Async<'T> * compensation:(OperationCanceledException -> unit) -> Async<'T>
static member CancellationToken : Async<CancellationToken>
static member DefaultCancellationToken : CancellationToken

Full name: Microsoft.FSharp.Control.Async

--------------------
type Async<'T>

Full name: Microsoft.FSharp.Control.Async<_>

static member Async.CancelAfter : timeout:int -> f:Async<'T> -> Async<'T option>

Full name: Script.CancelAfter

val timeout : int

val f : Async<'T>

val econt : (exn -> Async<'a>)

val e : exn

static member Async.FromContinuations : callback:(('T -> unit) * (exn -> unit) * (OperationCanceledException -> unit) -> unit) -> Async<'T>

val econt : (exn -> unit)

val worker : Async<obj>

val async : AsyncBuilder

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.async

val r : 'T

val timer : Async<obj>

static member Async.Sleep : millisecondsDueTime:int -> Async<unit>

static member Async.Parallel : computations:seq<Async<'T>> -> Async<'T []>

val failwith : message:string -> 'T

Full name: Microsoft.FSharp.Core.Operators.failwith

val t : Completed<'T>

union case Option.Some: Value: 'T -> Option<'T>

property Completed.Value: 'T

union case Option.None: Option<'T>

static member Async.CancelAfter : timeout:int -> f:Async<'T> -> Async<'T option>

static member Async.RunSynchronously : computation:Async<'T> * ?timeout:int * ?cancellationToken:Threading.CancellationToken -> 'T