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Wrapping Tasks.Task to async

This code wraps System.Threading.Tasks.Task (that has no return value), properly, so that cancellations and exceptions are preserved, and exceptions keep their stack-traces. It is to be used when the Task only denotes a single computation or value, as it only picks the first exception from the list of exceptions.

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open System
open System.Threading.Tasks

type Microsoft.FSharp.Control.Async with
  static member Raise (e : #exn) = 
    Async.FromContinuations(fun (_,econt,_) -> econt e)

let awaitTask (t : System.Threading.Tasks.Task) =
  let flattenExns (e : AggregateException) = e.Flatten().InnerExceptions |> Seq.nth 1
  let rewrapAsyncExn (it : Async<unit>) =
    async { try do! it with :? AggregateException as ae -> return! flattenExns ae |> Async.Raise }
  let tcs = new TaskCompletionSource<unit>()
  t.ContinueWith((fun t' ->
    if t.IsFaulted then tcs.SetException(t.Exception |> flattenExns)
    elif t.IsCanceled then tcs.SetCanceled ()
    else tcs.SetResult(())), TaskContinuationOptions.ExecuteSynchronously)
  |> ignore
  tcs.Task |> Async.AwaitTask
namespace System
namespace System.Threading
namespace System.Threading.Tasks
namespace Microsoft
namespace Microsoft.FSharp
namespace Microsoft.FSharp.Control
Multiple items
type Async<'T>

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

--------------------
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
static member Async.Raise : e:#exn -> Async<'b>

Full name: Script.Raise
val e : #exn
type exn = Exception

Full name: Microsoft.FSharp.Core.exn
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.FromContinuations : callback:(('T -> unit) * (exn -> unit) * (OperationCanceledException -> unit) -> unit) -> Async<'T>
val econt : (exn -> unit)
val awaitTask : t:Task -> Async<unit>

Full name: Script.awaitTask
val t : Task
Multiple items
type Task<'TResult> =
  inherit Task
  new : function:Func<'TResult> -> Task<'TResult> + 7 overloads
  member ContinueWith : continuationAction:Action<Task<'TResult>> -> Task + 9 overloads
  member Result : 'TResult with get, set
  static member Factory : TaskFactory<'TResult>

Full name: System.Threading.Tasks.Task<_>

--------------------
type Task =
  new : action:Action -> Task + 7 overloads
  member AsyncState : obj
  member ContinueWith : continuationAction:Action<Task> -> Task + 9 overloads
  member CreationOptions : TaskCreationOptions
  member Dispose : unit -> unit
  member Exception : AggregateException
  member Id : int
  member IsCanceled : bool
  member IsCompleted : bool
  member IsFaulted : bool
  ...

Full name: System.Threading.Tasks.Task

--------------------
Task(function: Func<'TResult>) : unit
Task(function: Func<'TResult>, cancellationToken: Threading.CancellationToken) : unit
Task(function: Func<'TResult>, creationOptions: TaskCreationOptions) : unit
Task(function: Func<obj,'TResult>, state: obj) : unit
Task(function: Func<'TResult>, cancellationToken: Threading.CancellationToken, creationOptions: TaskCreationOptions) : unit
Task(function: Func<obj,'TResult>, state: obj, cancellationToken: Threading.CancellationToken) : unit
Task(function: Func<obj,'TResult>, state: obj, creationOptions: TaskCreationOptions) : unit
Task(function: Func<obj,'TResult>, state: obj, cancellationToken: Threading.CancellationToken, creationOptions: TaskCreationOptions) : unit

--------------------
Task(action: Action) : unit
Task(action: Action, cancellationToken: Threading.CancellationToken) : unit
Task(action: Action, creationOptions: TaskCreationOptions) : unit
Task(action: Action<obj>, state: obj) : unit
Task(action: Action, cancellationToken: Threading.CancellationToken, creationOptions: TaskCreationOptions) : unit
Task(action: Action<obj>, state: obj, cancellationToken: Threading.CancellationToken) : unit
Task(action: Action<obj>, state: obj, creationOptions: TaskCreationOptions) : unit
Task(action: Action<obj>, state: obj, cancellationToken: Threading.CancellationToken, creationOptions: TaskCreationOptions) : unit
val flattenExns : (AggregateException -> exn)
val e : AggregateException
Multiple items
type AggregateException =
  inherit Exception
  new : unit -> AggregateException + 6 overloads
  member Flatten : unit -> AggregateException
  member GetBaseException : unit -> Exception
  member GetObjectData : info:SerializationInfo * context:StreamingContext -> unit
  member Handle : predicate:Func<Exception, bool> -> unit
  member InnerExceptions : ReadOnlyCollection<Exception>
  member ToString : unit -> string

Full name: System.AggregateException

--------------------
AggregateException() : unit
AggregateException(message: string) : unit
AggregateException(innerExceptions: Collections.Generic.IEnumerable<exn>) : unit
AggregateException([<ParamArray>] innerExceptions: exn []) : unit
AggregateException(message: string, innerException: exn) : unit
AggregateException(message: string, innerExceptions: Collections.Generic.IEnumerable<exn>) : unit
AggregateException(message: string, [<ParamArray>] innerExceptions: exn []) : unit
AggregateException.Flatten() : AggregateException
module Seq

from Microsoft.FSharp.Collections
val nth : index:int -> source:seq<'T> -> 'T

Full name: Microsoft.FSharp.Collections.Seq.nth
val rewrapAsyncExn : (Async<unit> -> Async<unit>)
val it : Async<unit>
type unit = Unit

Full name: Microsoft.FSharp.Core.unit
val async : AsyncBuilder

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.async
val ae : AggregateException
static member Async.Raise : e:#exn -> Async<'b>
val tcs : TaskCompletionSource<unit>
Multiple items
type TaskCompletionSource<'TResult> =
  new : unit -> TaskCompletionSource<'TResult> + 3 overloads
  member SetCanceled : unit -> unit
  member SetException : exception:Exception -> unit + 1 overload
  member SetResult : result:'TResult -> unit
  member Task : Task<'TResult>
  member TrySetCanceled : unit -> bool
  member TrySetException : exception:Exception -> bool + 1 overload
  member TrySetResult : result:'TResult -> bool

Full name: System.Threading.Tasks.TaskCompletionSource<_>

--------------------
TaskCompletionSource() : unit
TaskCompletionSource(creationOptions: TaskCreationOptions) : unit
TaskCompletionSource(state: obj) : unit
TaskCompletionSource(state: obj, creationOptions: TaskCreationOptions) : unit
Task.ContinueWith<'TResult>(continuationFunction: Func<Task,'TResult>) : Task<'TResult>
Task.ContinueWith(continuationAction: Action<Task>) : Task
Task.ContinueWith<'TResult>(continuationFunction: Func<Task,'TResult>, continuationOptions: TaskContinuationOptions) : Task<'TResult>
Task.ContinueWith<'TResult>(continuationFunction: Func<Task,'TResult>, scheduler: TaskScheduler) : Task<'TResult>
Task.ContinueWith<'TResult>(continuationFunction: Func<Task,'TResult>, cancellationToken: Threading.CancellationToken) : Task<'TResult>
Task.ContinueWith(continuationAction: Action<Task>, continuationOptions: TaskContinuationOptions) : Task
Task.ContinueWith(continuationAction: Action<Task>, scheduler: TaskScheduler) : Task
Task.ContinueWith(continuationAction: Action<Task>, cancellationToken: Threading.CancellationToken) : Task
Task.ContinueWith<'TResult>(continuationFunction: Func<Task,'TResult>, cancellationToken: Threading.CancellationToken, continuationOptions: TaskContinuationOptions, scheduler: TaskScheduler) : Task<'TResult>
Task.ContinueWith(continuationAction: Action<Task>, cancellationToken: Threading.CancellationToken, continuationOptions: TaskContinuationOptions, scheduler: TaskScheduler) : Task
val t' : Task
property Task.IsFaulted: bool
TaskCompletionSource.SetException(exceptions: Collections.Generic.IEnumerable<exn>) : unit
TaskCompletionSource.SetException(exception: exn) : unit
property Task.Exception: AggregateException
property Task.IsCanceled: bool
TaskCompletionSource.SetCanceled() : unit
TaskCompletionSource.SetResult(result: unit) : unit
type TaskContinuationOptions =
  | None = 0
  | PreferFairness = 1
  | LongRunning = 2
  | AttachedToParent = 4
  | NotOnRanToCompletion = 65536
  | NotOnFaulted = 131072
  | NotOnCanceled = 262144
  | OnlyOnRanToCompletion = 393216
  | OnlyOnFaulted = 327680
  | OnlyOnCanceled = 196608
  ...

Full name: System.Threading.Tasks.TaskContinuationOptions
field TaskContinuationOptions.ExecuteSynchronously = 524288
val ignore : value:'T -> unit

Full name: Microsoft.FSharp.Core.Operators.ignore
property TaskCompletionSource.Task: Task<unit>
static member Async.AwaitTask : task:Task<'T> -> Async<'T>
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More information

Link:http://fssnip.net/in
Posted:11 years ago
Author:haf
Tags: async task tpl

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The first version of fssnip.net has been created by @tomaspetricek back in 2010. This web site is a new, open-source and contribution-friendly version.