Add support for IAsyncEnumerable #175 (#176)

* add iasyncenumerable support for netstandard2.1

* add missing withoutresult implementation

* remove compile condition

* add tests and sample endpoint

sample/Sample.FunctionalTests/AuthorEndpoints/StreamEndpoint.cs

@@ -0,0 +1,40 @@
+using Ardalis.HttpClientTestExtensions;
+using Sample.FunctionalTests.Models;
+using SampleEndpointApp;
+using SampleEndpointApp.DataAccess;
+using SampleEndpointApp.DomainModel;
+using Xunit;
+
+namespace Sample.FunctionalTests.AuthorEndpoints;
+
+public class StreamEndpoint : IClassFixture<CustomWebApplicationFactory<Startup>>
+{
+  private readonly HttpClient _client;
+
+  public StreamEndpoint(CustomWebApplicationFactory<Startup> factory)
+  {
+    _client = factory.CreateClient();
+  }
+
+  [Fact]
+  public async Task ReturnsTwoGivenTwoAuthors()
+  {
+    var result = await _client.GetAndDeserialize<IEnumerable<Author>>(Routes.Authors.Stream());
+
+    Assert.NotNull(result);
+    Assert.Equal(SeedData.Authors().Count, result.Count());
+  }
+
+  [Fact]
+  public async Task GivenLongRunningListRequest_WhenTokenSourceCallsForCancellation_RequestIsTerminated()
+  {
+    // Arrange, generate a token source that times out instantly
+    var tokenSource = new CancellationTokenSource(TimeSpan.Zero);
+
+    // Act
+    var request = _client.GetAsync(Routes.Authors.Stream(), tokenSource.Token);
+
+    // Assert
+    var response = await Assert.ThrowsAsync<OperationCanceledException>(async () => await request);
+  }
+}

sample/Sample.FunctionalTests/Models/Routes.cs

@@ -16,6 +16,8 @@ public static class Authors
 
     public static string List(int perPage, int page) => $"{BaseRoute}?perPage={perPage}&page={page}";
 
+    public static string Stream() => $"{BaseRoute}/stream";
+
     public static string Get(int id) => $"{BaseRoute}/{id}";
 
     public static string Delete(int id) => $"{BaseRoute}/{id}";

sample/Sample.FunctionalTests/Sample.FunctionalTests.csproj

@@ -19,7 +19,8 @@
   </ItemGroup>
 
   <ItemGroup>
-    <ProjectReference Include="..\SampleEndpointApp\SampleEndpointApp.csproj" />
+      <ProjectReference Include="..\..\src\Ardalis.ApiEndpoints\Ardalis.ApiEndpoints.csproj"></ProjectReference>
+      <ProjectReference Include="..\SampleEndpointApp\SampleEndpointApp.csproj" />
   </ItemGroup>
 
 </Project>

sample/SampleEndpointApp/Endpoints/Authors/Stream.cs

@@ -0,0 +1,37 @@
+using System.Runtime.CompilerServices;
+using Ardalis.ApiEndpoints;
+using AutoMapper;
+using Microsoft.AspNetCore.Mvc;
+using SampleEndpointApp.DomainModel;
+
+namespace SampleEndpointApp.Endpoints.Authors;
+
+public class Stream : EndpointBaseAsync
+    .WithoutRequest
+    .WithAsyncEnumerableResult<AuthorListResult>
+{
+  private readonly IAsyncRepository<Author> repository;
+  private readonly IMapper mapper;
+
+  public Stream(
+      IAsyncRepository<Author> repository,
+      IMapper mapper)
+  {
+    this.repository = repository;
+    this.mapper = mapper;
+  }
+
+  /// <summary>
+  /// Stream all authors with a one second delay between entries
+  /// </summary>
+  [HttpGet("api/[namespace]/stream")]
+  public override async IAsyncEnumerable<AuthorListResult> HandleAsync([EnumeratorCancellation] CancellationToken cancellationToken)
+  {
+    var result = await repository.ListAllAsync(cancellationToken);
+    foreach (var author in result)
+    {
+      yield return mapper.Map<AuthorListResult>(author);
+      await Task.Delay(1000, cancellationToken);
+    }
+  }
+}

sample/SampleEndpointApp/SampleEndpointApp.csproj

@@ -25,7 +25,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\src\Ardalis.ApiEndpoints.CodeAnalyzers\Ardalis.ApiEndpoints.CodeAnalyzers.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
     <ProjectReference Include="..\..\src\Ardalis.ApiEndpoints.Swashbuckle\Ardalis.ApiEndpoints.Swashbuckle.csproj" />
-    <ProjectReference Include="..\..\src\Ardalis.ApiEndpoints\Ardalis.ApiEndpoints.csproj" />
+      <ProjectReference Include="..\..\src\Ardalis.ApiEndpoints\Ardalis.ApiEndpoints.csproj"></ProjectReference>
   </ItemGroup>
 
 

src/Ardalis.ApiEndpoints/FluentGenerics/EndpointBaseAsync.cs

@@ -40,6 +40,13 @@ public abstract Task<ActionResult> HandleAsync(
           CancellationToken cancellationToken = default
       );
     }
+    public abstract class WithAsyncEnumerableResult<T> : EndpointBase
+    {
+      public abstract IAsyncEnumerable<T> HandleAsync(
+        TRequest request,
+        CancellationToken cancellationToken = default
+      );
+    }
   }
 
   public static class WithoutRequest
@@ -71,5 +78,12 @@ public abstract Task<ActionResult> HandleAsync(
           CancellationToken cancellationToken = default
       );
     }
+
+    public abstract class WithAsyncEnumerableResult<T> : EndpointBase
+    {
+      public abstract IAsyncEnumerable<T> HandleAsync(
+        CancellationToken cancellationToken = default
+      );
+    }
   }
 }