Implement the Mvc PushFileStreamResult API

src/Mvc/Mvc.Core/src/ControllerBase.cs

@@ -1705,6 +1705,65 @@ public virtual PhysicalFileResult PhysicalFile(string physicalPath, string conte
             EnableRangeProcessing = enableRangeProcessing,
         };
     }
+
+    /// <summary>
+    /// Writes the file directly to the response body with the specified <paramref name="streamWriterCallback" /> (<see cref="StatusCodes.Status200OK"/>), and the
+    /// specified <paramref name="contentType" /> as the Content-Type.
+    /// </summary>
+    /// <param name="streamWriterCallback">The callback that allows users to write directly to the response body.</param>
+    /// <param name="contentType">The Content-Type of the file.</param>
+    /// <returns>The created <see cref="PushFileStreamResult"/> for the response.</returns>
+    [NonAction]
+    public virtual PushFileStreamResult File(Func<Stream, Task> streamWriterCallback, string contentType)
+        => File(streamWriterCallback, contentType, fileDownloadName: null);
+
+    /// <summary>
+    /// Writes the file directly to the response body with the specified <paramref name="streamWriterCallback" /> (<see cref="StatusCodes.Status200OK"/>), the
+    /// specified <paramref name="contentType" /> as the Content-Type, and the specified <paramref name="fileDownloadName" /> as the suggested file name.
+    /// </summary>
+    /// <param name="streamWriterCallback">The callback that allows users to write directly to the response body.</param>
+    /// <param name="contentType">The Content-Type of the file.</param>
+    /// <param name="fileDownloadName">The suggested file name.</param>
+    /// <returns>The created <see cref="PushFileStreamResult"/> for the response.</returns>
+    [NonAction]
+    public virtual PushFileStreamResult File(Func<Stream, Task> streamWriterCallback, string contentType, string? fileDownloadName)
+        => new PushFileStreamResult(streamWriterCallback, contentType) { FileDownloadName = fileDownloadName };
+
+    /// <summary>
+    /// Writes the file directly to the response body with the specified <paramref name="streamWriterCallback" /> (<see cref="StatusCodes.Status200OK"/>), and the
+    /// specified <paramref name="contentType" /> as the Content-Type.
+    /// </summary>
+    /// <param name="streamWriterCallback">The callback that allows users to write directly to the response body.</param>
+    /// <param name="contentType">The Content-Type of the file.</param>
+    /// <param name="lastModified">The <see cref="DateTimeOffset"/> of when the file was last modified.</param>
+    /// <param name="entityTag">The <see cref="EntityTagHeaderValue"/> associated with the file.</param>
+    /// <returns>The created <see cref="PushFileStreamResult"/> for the response.</returns>
+    [NonAction]
+    public virtual PushFileStreamResult File(Func<Stream, Task> streamWriterCallback, string contentType, DateTimeOffset? lastModified, EntityTagHeaderValue entityTag)
+        => new PushFileStreamResult(streamWriterCallback, contentType)
+        {
+            LastModified = lastModified,
+            EntityTag = entityTag,
+        };
+
+    /// <summary>
+    /// Writes the file directly to the response body with the specified <paramref name="streamWriterCallback" /> (<see cref="StatusCodes.Status200OK"/>), the
+    /// specified <paramref name="contentType" /> as the Content-Type, and the specified <paramref name="fileDownloadName" /> as the suggested file name.
+    /// </summary>
+    /// <param name="streamWriterCallback">The callback that allows users to write directly to the response body.</param>
+    /// <param name="contentType">The Content-Type of the file.</param>
+    /// <param name="fileDownloadName">The suggested file name.</param>
+    /// <param name="lastModified">The <see cref="DateTimeOffset"/> of when the file was last modified.</param>
+    /// <param name="entityTag">The <see cref="EntityTagHeaderValue"/> associated with the file.</param>
+    /// <returns>The created <see cref="PushFileStreamResult"/> for the response.</returns>
+    [NonAction]
+    public virtual PushFileStreamResult File(Func<Stream, Task> streamWriterCallback, string contentType, string? fileDownloadName, DateTimeOffset? lastModified, EntityTagHeaderValue entityTag)
+        => new PushFileStreamResult(streamWriterCallback, contentType)
+        {
+            LastModified = lastModified,
+            EntityTag = entityTag,
+            FileDownloadName = fileDownloadName,
+        };
     #endregion
 
     /// <summary>

src/Mvc/Mvc.Core/src/DependencyInjection/MvcCoreServiceCollectionExtensions.cs

@@ -236,6 +236,7 @@ internal static void AddMvcCoreServices(IServiceCollection services)
         services.TryAddSingleton<IActionResultExecutor<PhysicalFileResult>, PhysicalFileResultExecutor>();
         services.TryAddSingleton<IActionResultExecutor<VirtualFileResult>, VirtualFileResultExecutor>();
         services.TryAddSingleton<IActionResultExecutor<FileStreamResult>, FileStreamResultExecutor>();
+        services.TryAddSingleton<IActionResultExecutor<PushFileStreamResult>, PushFileStreamResultExecutor>();
         services.TryAddSingleton<IActionResultExecutor<FileContentResult>, FileContentResultExecutor>();
         services.TryAddSingleton<IActionResultExecutor<RedirectResult>, RedirectResultExecutor>();
         services.TryAddSingleton<IActionResultExecutor<LocalRedirectResult>, LocalRedirectResultExecutor>();

src/Mvc/Mvc.Core/src/Infrastructure/PushFileStreamResultExecutor.cs

@@ -0,0 +1,84 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics;
+using Microsoft.Extensions.Logging;
+using Microsoft.Net.Http.Headers;
+
+namespace Microsoft.AspNetCore.Mvc.Infrastructure;
+
+/// <summary>
+/// A <see cref="IActionResultExecutor{PushFileStreamResult}"/> for <see cref="PushFileStreamResult"/>.
+/// </summary>
+public partial class PushFileStreamResultExecutor : FileResultExecutorBase, IActionResultExecutor<PushFileStreamResult>
+{
+    /// <summary>
+    /// Initializes a new <see cref="PushFileStreamResultExecutor"/>.
+    /// </summary>
+    /// <param name="loggerFactory">The factory used to create loggers.</param>
+    public PushFileStreamResultExecutor(ILoggerFactory loggerFactory)
+        : base(CreateLogger<PushFileStreamResultExecutor>(loggerFactory))
+    {
+    }
+
+    /// <inheritdoc />
+    public virtual async Task ExecuteAsync(ActionContext context, PushFileStreamResult result)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        ArgumentNullException.ThrowIfNull(result);
+
+        Log.ExecutingFileResult(Logger, result);
+
+        var (range, rangeLength, serveBody) = SetHeadersAndLog(
+            context,
+            result,
+            fileLength: null,
+            result.EnableRangeProcessing,
+            result.LastModified,
+            result.EntityTag);
+
+        if (!serveBody)
+        {
+            return;
+        }
+
+        await WriteFileAsync(context, result, range, rangeLength);
+    }
+
+    /// <summary>
+    /// Write the contents of the PushFileStreamResult to the response body.
+    /// </summary>
+    /// <param name="context">The <see cref="ActionContext"/>.</param>
+    /// <param name="result">The PushFileStreamResult to write.</param>
+    /// <param name="range">The <see cref="RangeItemHeaderValue"/>.</param>
+    /// <param name="rangeLength">The range length.</param>
+    protected virtual async Task WriteFileAsync(
+        ActionContext context,
+        PushFileStreamResult result,
+        RangeItemHeaderValue? range,
+        long rangeLength)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        ArgumentNullException.ThrowIfNull(result);
+
+        Debug.Assert(range == null);
+        Debug.Assert(rangeLength == 0);
+
+        await result.StreamWriterCallback(context.HttpContext.Response.Body);
+    }
+
+    private static partial class Log
+    {
+        public static void ExecutingFileResult(ILogger logger, FileResult fileResult)
+        {
+            if (logger.IsEnabled(LogLevel.Information))
+            {
+                var fileResultType = fileResult.GetType().Name;
+                ExecutingFileResultWithNoFileName(logger, fileResultType, fileResult.FileDownloadName);
+            }
+        }
+
+        [LoggerMessage(1, LogLevel.Information, "Executing {FileResultType}, sending file with download name '{FileDownloadName}' ...", EventName = "ExecutingFileResultWithNoFileName", SkipEnabledCheck = true)]
+        private static partial void ExecutingFileResultWithNoFileName(ILogger logger, string fileResultType, string fileDownloadName);
+    }
+}

src/Mvc/Mvc.Core/src/PublicAPI.Unshipped.txt

@@ -1,6 +1,17 @@
 #nullable enable
 *REMOVED*virtual Microsoft.AspNetCore.Mvc.ControllerBase.Problem(string? detail = null, string? instance = null, int? statusCode = null, string? title = null, string? type = null) -> Microsoft.AspNetCore.Mvc.ObjectResult!
 *REMOVED*virtual Microsoft.AspNetCore.Mvc.ControllerBase.ValidationProblem(string? detail = null, string? instance = null, int? statusCode = null, string? title = null, string? type = null, Microsoft.AspNetCore.Mvc.ModelBinding.ModelStateDictionary? modelStateDictionary = null) -> Microsoft.AspNetCore.Mvc.ActionResult!
+Microsoft.AspNetCore.Mvc.Infrastructure.PushFileStreamResultExecutor
+Microsoft.AspNetCore.Mvc.Infrastructure.PushFileStreamResultExecutor.PushFileStreamResultExecutor(Microsoft.Extensions.Logging.ILoggerFactory! loggerFactory) -> void
+Microsoft.AspNetCore.Mvc.PushFileStreamResult
+Microsoft.AspNetCore.Mvc.PushFileStreamResult.PushFileStreamResult(System.Func<System.IO.Stream!, System.Threading.Tasks.Task!>! streamWriterCallback, string! contentType) -> void
+Microsoft.AspNetCore.Mvc.PushFileStreamResult.StreamWriterCallback.get -> System.Func<System.IO.Stream!, System.Threading.Tasks.Task!>!
+Microsoft.AspNetCore.Mvc.PushFileStreamResult.StreamWriterCallback.set -> void
+override Microsoft.AspNetCore.Mvc.PushFileStreamResult.ExecuteResultAsync(Microsoft.AspNetCore.Mvc.ActionContext! context) -> System.Threading.Tasks.Task!
+virtual Microsoft.AspNetCore.Mvc.ControllerBase.File(System.Func<System.IO.Stream!, System.Threading.Tasks.Task!>! streamWriterCallback, string! contentType) -> Microsoft.AspNetCore.Mvc.PushFileStreamResult!
+virtual Microsoft.AspNetCore.Mvc.ControllerBase.File(System.Func<System.IO.Stream!, System.Threading.Tasks.Task!>! streamWriterCallback, string! contentType, string? fileDownloadName) -> Microsoft.AspNetCore.Mvc.PushFileStreamResult!
+virtual Microsoft.AspNetCore.Mvc.ControllerBase.File(System.Func<System.IO.Stream!, System.Threading.Tasks.Task!>! streamWriterCallback, string! contentType, string? fileDownloadName, System.DateTimeOffset? lastModified, Microsoft.Net.Http.Headers.EntityTagHeaderValue! entityTag) -> Microsoft.AspNetCore.Mvc.PushFileStreamResult!
+virtual Microsoft.AspNetCore.Mvc.ControllerBase.File(System.Func<System.IO.Stream!, System.Threading.Tasks.Task!>! streamWriterCallback, string! contentType, System.DateTimeOffset? lastModified, Microsoft.Net.Http.Headers.EntityTagHeaderValue! entityTag) -> Microsoft.AspNetCore.Mvc.PushFileStreamResult!
 virtual Microsoft.AspNetCore.Mvc.ControllerBase.Problem(string? detail, string? instance, int? statusCode, string? title, string? type) -> Microsoft.AspNetCore.Mvc.ObjectResult!
 virtual Microsoft.AspNetCore.Mvc.ControllerBase.Problem(string? detail = null, string? instance = null, int? statusCode = null, string? title = null, string? type = null, System.Collections.Generic.IDictionary<string!, object?>? extensions = null) -> Microsoft.AspNetCore.Mvc.ObjectResult!
 virtual Microsoft.AspNetCore.Mvc.ControllerBase.ValidationProblem(string? detail, string? instance, int? statusCode, string? title, string? type, Microsoft.AspNetCore.Mvc.ModelBinding.ModelStateDictionary? modelStateDictionary) -> Microsoft.AspNetCore.Mvc.ActionResult!
@@ -9,3 +20,5 @@ Microsoft.AspNetCore.Mvc.Infrastructure.DefaultProblemDetailsFactory
 Microsoft.AspNetCore.Mvc.Infrastructure.DefaultProblemDetailsFactory.DefaultProblemDetailsFactory(Microsoft.Extensions.Options.IOptions<Microsoft.AspNetCore.Mvc.ApiBehaviorOptions!>! options, Microsoft.Extensions.Options.IOptions<Microsoft.AspNetCore.Http.ProblemDetailsOptions!>? problemDetailsOptions = null) -> void
 override Microsoft.AspNetCore.Mvc.Infrastructure.DefaultProblemDetailsFactory.CreateProblemDetails(Microsoft.AspNetCore.Http.HttpContext! httpContext, int? statusCode = null, string? title = null, string? type = null, string? detail = null, string? instance = null) -> Microsoft.AspNetCore.Mvc.ProblemDetails!
 override Microsoft.AspNetCore.Mvc.Infrastructure.DefaultProblemDetailsFactory.CreateValidationProblemDetails(Microsoft.AspNetCore.Http.HttpContext! httpContext, Microsoft.AspNetCore.Mvc.ModelBinding.ModelStateDictionary! modelStateDictionary, int? statusCode = null, string? title = null, string? type = null, string? detail = null, string? instance = null) -> Microsoft.AspNetCore.Mvc.ValidationProblemDetails!
+virtual Microsoft.AspNetCore.Mvc.Infrastructure.PushFileStreamResultExecutor.ExecuteAsync(Microsoft.AspNetCore.Mvc.ActionContext! context, Microsoft.AspNetCore.Mvc.PushFileStreamResult! result) -> System.Threading.Tasks.Task!
+virtual Microsoft.AspNetCore.Mvc.Infrastructure.PushFileStreamResultExecutor.WriteFileAsync(Microsoft.AspNetCore.Mvc.ActionContext! context, Microsoft.AspNetCore.Mvc.PushFileStreamResult! result, Microsoft.Net.Http.Headers.RangeItemHeaderValue? range, long rangeLength) -> System.Threading.Tasks.Task!

src/Mvc/Mvc.Core/src/PushFileStreamResult.cs

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.AspNetCore.Mvc.Infrastructure;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Microsoft.AspNetCore.Mvc;
+
+/// <summary>
+/// A <see cref="FileResult" /> that on execution writes the file using the specified stream writer callback.
+/// </summary>
+public class PushFileStreamResult : FileResult
+{
+    /// <summary>
+    /// The callback that writes the file to the provided stream.
+    /// </summary>
+    public Func<Stream, Task> StreamWriterCallback { get; set; }
+
+    /// <summary>
+    /// Creates a new <see cref="PushFileStreamResult"/> instance with
+    /// the provided <paramref name="streamWriterCallback"/> and the provided <paramref name="contentType"/>.
+    /// </summary>
+    /// <param name="streamWriterCallback">The callback that writes the file to the provided stream.</param>
+    /// <param name="contentType">The Content-Type header of the response.</param>
+    public PushFileStreamResult(Func<Stream, Task> streamWriterCallback, string contentType) : base(contentType)
+    {
+        ArgumentNullException.ThrowIfNull(streamWriterCallback);
+
+        StreamWriterCallback = streamWriterCallback;
+    }
+
+    /// <inheritdoc />
+    public override Task ExecuteResultAsync(ActionContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+
+        var executor = context.HttpContext.RequestServices.GetRequiredService<IActionResultExecutor<PushFileStreamResult>>();
+        return executor.ExecuteAsync(context, this);
+    }
+}

src/Mvc/Mvc.Core/test/PushFileStreamResultTest.cs

@@ -0,0 +1,75 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Internal;
+using Microsoft.AspNetCore.Mvc.Infrastructure;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Net.Http.Headers;
+
+namespace Microsoft.AspNetCore.Mvc;
+
+public class PushFileStreamResultTest : PushFileStreamResultTestBase
+{
+    protected override Task ExecuteAsync(
+        HttpContext httpContext,
+        Func<Stream, Task> streamWriterCallback,
+        string contentType,
+        DateTimeOffset? lastModified = null,
+        EntityTagHeaderValue entityTag = null)
+    {
+        httpContext.RequestServices = new ServiceCollection()
+            .AddSingleton<ILoggerFactory, NullLoggerFactory>()
+            .AddSingleton<IActionResultExecutor<PushFileStreamResult>, PushFileStreamResultExecutor>()
+            .BuildServiceProvider();
+
+        var actionContext = new ActionContext(httpContext, new(), new());
+        var fileStreamResult = new PushFileStreamResult(streamWriterCallback, contentType)
+        {
+            LastModified = lastModified,
+            EntityTag = entityTag,
+        };
+
+        return fileStreamResult.ExecuteResultAsync(actionContext);
+    }
+
+    [Fact]
+    public void Constructor_SetsContentType()
+    {
+        // Arrange
+        var streamWriterCallback = (Stream _) => Task.CompletedTask;
+        var contentType = "text/plain; charset=us-ascii; p1=p1-value";
+        var expectedMediaType = contentType;
+
+        // Act
+        var result = new PushFileStreamResult(streamWriterCallback, contentType);
+
+        // Assert
+        Assert.Equal(expectedMediaType, result.ContentType);
+    }
+
+    [Fact]
+    public void Constructor_SetsLastModifiedAndEtag()
+    {
+        // Arrange
+        var streamWriterCallback = (Stream _) => Task.CompletedTask;
+        var contentType = "text/plain";
+        var expectedMediaType = contentType;
+        var lastModified = new DateTimeOffset();
+        var entityTag = new EntityTagHeaderValue("\"Etag\"");
+
+        // Act
+        var result = new PushFileStreamResult(streamWriterCallback, contentType)
+        {
+            LastModified = lastModified,
+            EntityTag = entityTag,
+        };
+
+        // Assert
+        Assert.Equal(lastModified, result.LastModified);
+        Assert.Equal(entityTag, result.EntityTag);
+        Assert.Equal(expectedMediaType, result.ContentType);
+    }
+}