Add UniTask.WhenEach

README.md

@@ -160,7 +160,7 @@ UniTask provides three pattern of extension methods.
 
 > Note: AssetBundleRequest has `asset` and `allAssets`, default await returns `asset`. If you want to get `allAssets`, you can use `AwaitForAllAssets()` method.
 
-The type of `UniTask` can use utilities like `UniTask.WhenAll`, `UniTask.WhenAny`. They are like `Task.WhenAll`/`Task.WhenAny` but the return type is more useful. They return value tuples so you can deconstruct each result and pass multiple types.
+The type of `UniTask` can use utilities like `UniTask.WhenAll`, `UniTask.WhenAny`, `UniTask.WhenEach`. They are like `Task.WhenAll`/`Task.WhenAny` but the return type is more useful. They return value tuples so you can deconstruct each result and pass multiple types.
 
 ```csharp
 public async UniTaskVoid LoadManyAsync()
@@ -716,6 +716,19 @@ await UniTaskAsyncEnumerable.EveryUpdate().ForEachAsync(_ =>
 }, token);
 ```
 
+`UniTask.WhenEach` that is similar to .NET 9's `Task.WhenEach` can consume new way for await multiple tasks.
+
+```csharp
+await foreach (var result in UniTask.WhenEach(task1, task2, task3))
+{
+    // The result is of type WhenEachResult<T>.
+    // It contains either `T Result` or `Exception Exception`.
+    // You can check `IsCompletedSuccessfully` or `IsFaulted` to determine whether to access `.Result` or `.Exception`.
+    // If you want to throw an exception when `IsFaulted` and retrieve the result when successful, use `GetResult()`.
+    Debug.Log(result.GetResult());
+}
+```
+
 UniTaskAsyncEnumerable implements asynchronous LINQ, similar to LINQ in `IEnumerable<T>` or Rx in `IObservable<T>`. All standard LINQ query operators can be applied to asynchronous streams. For example, the following code shows how to apply a Where filter to a button-click asynchronous stream that runs once every two clicks.
 
 ```csharp
@@ -1026,6 +1039,7 @@ Use UniTask type.
 | `Task.Run` | `UniTask.RunOnThreadPool` |
 | `Task.WhenAll` | `UniTask.WhenAll` |
 | `Task.WhenAny` | `UniTask.WhenAny` |
+| `Task.WhenEach` | `UniTask.WhenEach` |
 | `Task.CompletedTask` | `UniTask.CompletedTask` |
 | `Task.FromException` | `UniTask.FromException` |
 | `Task.FromResult` | `UniTask.FromResult` |

src/UniTask.NetCoreTests/WhenEachTest.cs

@@ -0,0 +1,69 @@
+using Cysharp.Threading.Tasks;
+using FluentAssertions;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace NetCoreTests
+{
+    public class WhenEachTest
+    {
+        [Fact]
+        public async Task Each()
+        {
+            var a = Delay(1, 3000);
+            var b = Delay(2, 1000);
+            var c = Delay(3, 2000);
+
+            var l = new List<int>();
+            await foreach (var item in UniTask.WhenEach(a, b, c))
+            {
+                l.Add(item.Result);
+            }
+
+            l.Should().Equal(2, 3, 1);
+        }
+
+        [Fact]
+        public async Task Error()
+        {
+            var a = Delay2(1, 3000);
+            var b = Delay2(2, 1000);
+            var c = Delay2(3, 2000);
+
+            var l = new List<WhenEachResult<int>>();
+            await foreach (var item in UniTask.WhenEach(a, b, c))
+            {
+                l.Add(item);
+            }
+
+            l[0].IsCompletedSuccessfully.Should().BeTrue();
+            l[0].IsFaulted.Should().BeFalse();
+            l[0].Result.Should().Be(2);
+
+            l[1].IsCompletedSuccessfully.Should().BeFalse();
+            l[1].IsFaulted.Should().BeTrue();
+            l[1].Exception.Message.Should().Be("ERROR");
+
+            l[2].IsCompletedSuccessfully.Should().BeTrue();
+            l[2].IsFaulted.Should().BeFalse();
+            l[2].Result.Should().Be(1);
+        }
+
+        async UniTask<int> Delay(int id, int sleep)
+        {
+            await Task.Delay(sleep);
+            return id;
+        }
+
+        async UniTask<int> Delay2(int id, int sleep)
+        {
+            await Task.Delay(sleep);
+            if (id == 3) throw new Exception("ERROR");
+            return id;
+        }
+    }
+}

src/UniTask/Assets/Plugins/UniTask/Runtime/UniTask.WhenEach.cs

@@ -0,0 +1,183 @@
+using Cysharp.Threading.Tasks.Internal;
+using System;
+using System.Collections.Generic;
+using System.Runtime.ExceptionServices;
+using System.Threading;
+
+namespace Cysharp.Threading.Tasks
+{
+    public partial struct UniTask
+    {
+        public static IUniTaskAsyncEnumerable<WhenEachResult<T>> WhenEach<T>(IEnumerable<UniTask<T>> tasks)
+        {
+            return new WhenEachEnumerable<T>(tasks);
+        }
+
+        public static IUniTaskAsyncEnumerable<WhenEachResult<T>> WhenEach<T>(params UniTask<T>[] tasks)
+        {
+            return new WhenEachEnumerable<T>(tasks);
+        }
+    }
+
+    public readonly struct WhenEachResult<T>
+    {
+        public T Result { get; }
+        public Exception Exception { get; }
+
+        //[MemberNotNullWhen(false, nameof(Exception))]
+        public bool IsCompletedSuccessfully => Exception == null;
+
+        //[MemberNotNullWhen(true, nameof(Exception))]
+        public bool IsFaulted => Exception != null;
+
+        public WhenEachResult(T result)
+        {
+            this.Result = result;
+            this.Exception = null;
+        }
+
+        public WhenEachResult(Exception exception)
+        {
+            if (exception == null) throw new ArgumentNullException(nameof(exception));
+            this.Result = default!;
+            this.Exception = exception;
+        }
+
+        public void TryThrow()
+        {
+            if (IsFaulted)
+            {
+                ExceptionDispatchInfo.Capture(Exception).Throw();
+            }
+        }
+
+        public T GetResult()
+        {
+            if (IsFaulted)
+            {
+                ExceptionDispatchInfo.Capture(Exception).Throw();
+            }
+            return Result;
+        }
+
+        public override string ToString()
+        {
+            if (IsCompletedSuccessfully)
+            {
+                return Result?.ToString() ?? "";
+            }
+            else
+            {
+                return $"Exception{{{Exception.Message}}}";
+            }
+        }
+    }
+
+    internal enum WhenEachState : byte
+    {
+        NotRunning,
+        Running,
+        Completed
+    }
+
+    internal sealed class WhenEachEnumerable<T> : IUniTaskAsyncEnumerable<WhenEachResult<T>>
+    {
+        IEnumerable<UniTask<T>> source;
+
+        public WhenEachEnumerable(IEnumerable<UniTask<T>> source)
+        {
+            this.source = source;
+        }
+
+        public IUniTaskAsyncEnumerator<WhenEachResult<T>> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            return new Enumerator(source, cancellationToken);
+        }
+
+        sealed class Enumerator : IUniTaskAsyncEnumerator<WhenEachResult<T>>
+        {
+            readonly IEnumerable<UniTask<T>> source;
+            CancellationToken cancellationToken;
+
+            Channel<WhenEachResult<T>> channel;
+            IUniTaskAsyncEnumerator<WhenEachResult<T>> channelEnumerator;
+            int completeCount;
+            WhenEachState state;
+
+            public Enumerator(IEnumerable<UniTask<T>> source, CancellationToken cancellationToken)
+            {
+                this.source = source;
+                this.cancellationToken = cancellationToken;
+            }
+
+            public WhenEachResult<T> Current => channelEnumerator.Current;
+
+            public UniTask<bool> MoveNextAsync()
+            {
+                cancellationToken.ThrowIfCancellationRequested();
+
+                if (state == WhenEachState.NotRunning)
+                {
+                    state = WhenEachState.Running;
+                    channel = Channel.CreateSingleConsumerUnbounded<WhenEachResult<T>>();
+                    channelEnumerator = channel.Reader.ReadAllAsync().GetAsyncEnumerator(cancellationToken);
+
+                    if (source is UniTask<T>[] array)
+                    {
+                        ConsumeAll(this, array, array.Length);
+                    }
+                    else
+                    {
+                        using (var rentArray = ArrayPoolUtil.Materialize(source))
+                        {
+                            ConsumeAll(this, rentArray.Array, rentArray.Length);
+                        }
+                    }
+                }
+
+                return channelEnumerator.MoveNextAsync();
+            }
+
+            static void ConsumeAll(Enumerator self, UniTask<T>[] array, int length)
+            {
+                for (int i = 0; i < length; i++)
+                {
+                    RunWhenEachTask(self, array[i], length).Forget();
+                }
+
+                static async UniTaskVoid RunWhenEachTask(Enumerator self, UniTask<T> task, int length)
+                {
+                    try
+                    {
+                        var result = await task;
+                        self.channel.Writer.TryWrite(new WhenEachResult<T>(result));
+                    }
+                    catch (Exception ex)
+                    {
+                        self.channel.Writer.TryWrite(new WhenEachResult<T>(ex));
+                    }
+
+                    if (Interlocked.Increment(ref self.completeCount) == length)
+                    {
+                        self.state = WhenEachState.Completed;
+                        self.channel.Writer.TryComplete();
+                    }
+                }
+            }
+
+            public async UniTask DisposeAsync()
+            {
+                if (channelEnumerator != null)
+                {
+                    await channelEnumerator.DisposeAsync();
+                }
+
+                if (state != WhenEachState.Completed)
+                {
+                    state = WhenEachState.Completed;
+                    channel.Writer.TryComplete(new OperationCanceledException());
+                }
+            }
+        }
+    }
+}

src/UniTask/Assets/Scenes/SandboxMain.cs

@@ -119,7 +119,28 @@ public void Dispose()
         connection.Dispose();
     }
 }
+public class WhenEachTest
+{
+    public async UniTask Each()
+    {
+        var a = Delay(1, 3000);
+        var b = Delay(2, 1000);
+        var c = Delay(3, 2000);
+
+        var l = new List<int>();
+        await foreach (var item in UniTask.WhenEach(a, b, c))
+        {
+            Debug.Log(item.Result);
+        }
+    }
 
+    async UniTask<int> Delay(int id, int sleep)
+    {
+        await UniTask.Delay(sleep);
+        return id;
+    }
+
+}
 
 public class SandboxMain : MonoBehaviour
 {
@@ -147,6 +168,18 @@ async UniTask<int> FooAsync()
 
         Debug.Log("Again");
 
+
+        // var foo = InstantiateAsync<SandboxMain>(this).ToUniTask();
+
+
+
+
+
+        // var tako = await foo;
+
+
+
+
         return 10;
     }
 
@@ -557,6 +590,7 @@ private static async UniTask TestAsync(CancellationToken ct)
 
     async UniTaskVoid Start()
     {
+        await new WhenEachTest().Each();
 
 
         // UniTask.Delay(TimeSpan.FromSeconds(1)).TimeoutWithoutException