resolves #96 adding .NET IAsyncEnumerable conversion functions (ofAsyncEnum and toAsyncEnum)

Author: mvkra

.travis.yml

@@ -6,10 +6,10 @@ matrix:
       dist: trusty
       sudo: false
       mono: latest
-      dotnet: 2.1.300
+      dotnet: 3.0.100
     - os: osx # OSX 10.12
       osx_image: xcode9.1
-      dotnet: 2.1.300
+      dotnet: 3.0.100
       mono: latest
       sudo: false
 

appveyor.yml

@@ -1,6 +1,6 @@
 environment:
-  CLI_VERSION: 2.0.0
-image: Visual Studio 2017
+  CLI_VERSION: 3.0.100
+image: Visual Studio 2019
 init:
   - git config --global core.autocrlf input
 build_script:

global.json

@@ -1,5 +1,5 @@
 {
   "sdk": {
-    "version": "2.1.300"
+    "version": "3.0.100"
   }
 }

src/FSharp.Control.AsyncSeq/AsyncSeq.fs

@@ -1654,6 +1654,48 @@ module AsyncSeq =
          return Choice1Of2 (asyncSeq { for v in res do yield v })
        }
 
+  #if (NETSTANDARD2_1 || NETCOREAPP3_0)
+
+  let ofAsyncEnum (source: Collections.Generic.IAsyncEnumerable<_>) = asyncSeq {
+      let! ct = Async.CancellationToken
+      let e = source.GetAsyncEnumerator(ct)
+      use _ = 
+          { new IDisposable with 
+              member __.Dispose() = 
+                  e.DisposeAsync().AsTask() |> Async.AwaitTask |> Async.RunSynchronously }
+
+      let mutable currentResult = true
+      while currentResult do
+          let! r = e.MoveNextAsync().AsTask() |> Async.AwaitTask
+          currentResult <- r
+          if r then yield e.Current
+  }
+
+  let toAsyncEnum (source: AsyncSeq<'a>) = {
+    new Collections.Generic.IAsyncEnumerable<'a> with
+      member __.GetAsyncEnumerator(cancellationToken: CancellationToken) = 
+          let mutable current = Unchecked.defaultof<_>
+          let enumerator = source.GetEnumerator()
+          { new Collections.Generic.IAsyncEnumerator<'a> with
+              member __.Current = current
+              member __.MoveNextAsync() = 
+                  let moveNextAsync = async {
+                      let! enumerationResult = enumerator.MoveNext()
+                      match enumerationResult with
+                      | Some(v) -> 
+                          current <- v
+                          return true
+                      | _ -> return false
+                  }
+
+                  Async.StartAsTask(moveNextAsync, cancellationToken = cancellationToken) |> ValueTask<bool>
+              member __.DisposeAsync() =
+                enumerator.Dispose()
+                ValueTask()
+          }
+  }
+  #endif
+
   module AsyncSeqSrcImpl =
 
     let private createNode () =

src/FSharp.Control.AsyncSeq/AsyncSeq.fsi

@@ -494,6 +494,16 @@ module AsyncSeq =
     /// completion of sub-sequences depends on completion of other sub-sequences.
     val groupBy<'T, 'Key when 'Key : equality> : projection:('T -> 'Key) -> source:AsyncSeq<'T> -> AsyncSeq<'Key * AsyncSeq<'T>>
 
+    #if (NETSTANDARD2_1 || NETCOREAPP3_0)
+
+    /// Creates an asynchronous computation that asynchronously yields results from the provided .NET IAsyncEnumerable.
+    val ofAsyncEnum<'T> : source: Collections.Generic.IAsyncEnumerable<'T> -> AsyncSeq<'T>
+
+    /// Creates an .NET IAsyncEnumerable from the provided AsyncSeq computation.
+    val toAsyncEnum<'T> : source: AsyncSeq<'T> -> Collections.Generic.IAsyncEnumerable<'T>
+    
+    #endif
+
 /// An automatically-opened module that contains the `asyncSeq` builder and an extension method 
 [<AutoOpen>]
 module AsyncSeqExtensions = 

src/FSharp.Control.AsyncSeq/FSharp.Control.AsyncSeq.fsproj

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net45</TargetFrameworks>
+    <TargetFrameworks>netstandard2.1;netstandard2.0;net45</TargetFrameworks>
     <Authors>Tomas Petricek;Don Syme;Lev Gorodinski</Authors>
     <Summary>Asynchronous sequences for F#</Summary>
     <Description>Asynchronous sequences for F#</Description>

tests/FSharp.Control.AsyncSeq.Tests/AsyncSeqTests.fs

@@ -1696,4 +1696,12 @@ let ``Async.concat should work``() =
         |> AsyncSeq.ofSeq
         |> AsyncSeq.concatSeq
 
-      Assert.True(EQ expected actual)
+      Assert.True(EQ expected actual)
+
+#if (NETSTANDARD2_1 || NETCOREAPP3_0)
+[<Test>]
+let ``AsyncSeq.ofAsyncEnum should roundtrip successfully``() = 
+  let data = [ 1 .. 10 ] |> AsyncSeq.ofSeq
+  let actual = data |> AsyncSeq.toAsyncEnum |> AsyncSeq.ofAsyncEnum
+  Assert.True(EQ data actual)
+#endif

tests/FSharp.Control.AsyncSeq.Tests/FSharp.Control.AsyncSeq.Tests.fsproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net462</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.0;net462</TargetFrameworks>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
   <ItemGroup>