Documentation says there's a TaskSeq.toAsyncSeq function, but it does not exist #214

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1. abelbraaksma

   added

   topic: surface areaAdds functions to the public surface areaAdds functions to the public surface area

   feature requestNew feature or enhancement requestNew feature or enhancement request

   compatibilityRelated to backward or forwards, or F# Core or .NET version compatibilityRelated to backward or forwards, or F# Core or .NET version compatibility

   on Dec 19, 2023
2. abelbraaksma

   added this to the vNext milestone on Mar 18, 2024
3. njlr commented on Oct 24, 2025

   

   njlr

   on Oct 24, 2025

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   I needed this internally and came up with this implementation:

   #r "nuget: FSharp.Control.TaskSeq, 0.4.0"
   #r "nuget: FSharp.Control.AsyncSeq, 3.2.1"
   
   open FSharp.Control
   
   [<RequireQualifiedAccess>]
   module TaskSeq =
   
     let toAsyncSeq (xs : TaskSeq<'a>) : AsyncSeq<'a> =
       asyncSeq {
         let! ct = Async.CancellationToken
   
         let en = xs.GetAsyncEnumerator(ct)
   
         try
           while! en.MoveNextAsync().AsTask() |> Async.AwaitTask do
             yield en.Current
         finally
           en.DisposeAsync().AsTask()
           |> Async.AwaitTask
           |> Async.RunSynchronously
       }
   
   let main () =
     let input =
       taskSeq {
         yield "h"
         yield "e"
         yield "l"
         yield "l"
         yield "o"
         yield " "
         yield "w"
         yield "o"
         yield "r"
         yield "l"
         yield "d"
       }
   
     let output =
       input
       |> TaskSeq.toAsyncSeq
   
     async {
       for x in output do
         printfn $"%s{x}"
     }
     |> Async.RunSynchronously
   
   main ()

   Any gotchas I have missed?

   The dispose logic feels nasty.

   Happy to send a PR.
4. abelbraaksma commented on Nov 14, 2025

   

   abelbraaksma

   on Nov 14, 2025

   Last edited by abelbraaksma

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   @njlr thanks, as a quick look, this looks like a fine approach. However, we wouldn't want to have a dependency on AsyncSeq, that would be bad practice. Currently, this lib has zero dependencies and I like it that way.

   The inverse is, as you've mentioned, easier, because the IAsyncEnumerable<'T> type is part of the .NET standard library. But the AsyncSeq library does not use a common interface that I could use.

   I haven't looked at this for a while, I should probably get back into it.
5. njlr commented on Nov 14, 2025

   

   njlr

   on Nov 14, 2025

   Last edited by njlr

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   Happy to make a PR to https://github.com/fsprojects/FSharp.Control.AsyncSeq for this

   Perhaps names reversed? AsyncSeq.ofTaskSeq

   👍React with 👍1Reacted by Ruben Bartelink
6. dsyme commented on Mar 7, 2026

   

   dsyme

   on Mar 7, 2026

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   Latest versions of FSharp.Control.AsyncSeq use

   type AsyncSeq<'T> = System.Collections.Generic.IAsyncEnumerable<'T>
   

   So we have the somewhat strange but highly interoperable situation of

   TaskSeq<'T> = AsyncSeq<'T> = IAsyncEnumerable<'T>
   
7. dsyme commented on Mar 7, 2026

   

   dsyme

   on Mar 7, 2026

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   In short, no need to convert anything :)
8. dsyme

   closed this as completedon Mar 7, 2026