Use FileBufferingWriteStream in ViewComponentResultExecutor (#9523)

Fixes https://github.com/aspnet/AspNetCore/issues/9443

src/Mvc/Mvc.ViewFeatures/src/ViewComponentResultExecutor.cs

@@ -12,6 +12,7 @@ using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.AspNetCore.Mvc.Rendering;
 using Microsoft.AspNetCore.Mvc.ViewFeatures.Buffers;
 using Microsoft.AspNetCore.Mvc.ViewFeatures.Filters;
+using Microsoft.AspNetCore.WebUtilities;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
@@ -148,14 +149,13 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
                 }
                 else
                 {
-                    using var memoryStream = new MemoryStream();
+                    using var bufferingStream = new FileBufferingWriteStream();
-                    using (var intermediateWriter = _writerFactory.CreateWriter(response.Body, resolvedContentTypeEncoding))
+                    using (var intermediateWriter = _writerFactory.CreateWriter(bufferingStream, resolvedContentTypeEncoding))
                     {
                         viewComponentResult.WriteTo(intermediateWriter, _htmlEncoder);
                     }
 
-                    memoryStream.Position = 0;
+                    await bufferingStream.DrainBufferAsync(response.Body);
-                    await memoryStream.CopyToAsync(response.Body);
                 }
             }
         }

src/Mvc/Mvc.ViewFeatures/test/ViewComponentResultTest.cs

@@ -439,6 +439,48 @@ namespace Microsoft.AspNetCore.Mvc
             Assert.Equal(expected, body);
         }
 
+        [Fact]
+        public async Task ExecuteResultAsync_WithCustomViewComponentHelper_ForLargeText()
+        {
+            // Arrange
+            var expected = new string('a', 64 * 1024 * 1024);
+            var methodInfo = typeof(TextViewComponent).GetMethod(nameof(TextViewComponent.Invoke));
+            var descriptor = new ViewComponentDescriptor()
+            {
+                FullName = "Full.Name.Text",
+                ShortName = "Text",
+                TypeInfo = typeof(TextViewComponent).GetTypeInfo(),
+                MethodInfo = methodInfo,
+                Parameters = methodInfo.GetParameters(),
+            };
+            var result = Task.FromResult<IHtmlContent>(new HtmlContentBuilder().AppendHtml(expected));
+
+            var helper = Mock.Of<IViewComponentHelper>(h => h.InvokeAsync(It.IsAny<Type>(), It.IsAny<object>()) == result);
+
+            var httpContext = new DefaultHttpContext();
+            var services = CreateServices(diagnosticListener: null, httpContext, new[] { descriptor });
+            services.AddSingleton<IViewComponentHelper>(helper);
+
+            httpContext.RequestServices = services.BuildServiceProvider();
+            httpContext.Response.Body = new MemoryStream();
+
+            var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
+
+            var viewComponentResult = new ViewComponentResult()
+            {
+                Arguments = new { name = "World!" },
+                ViewComponentType = typeof(TextViewComponent),
+                TempData = _tempDataDictionary,
+            };
+
+            // Act
+            await viewComponentResult.ExecuteResultAsync(actionContext);
+
+            // Assert
+            var body = ReadBody(actionContext.HttpContext.Response);
+            Assert.Equal(expected, body);
+        }
+
         [Fact]
         public async Task ExecuteResultAsync_SetsStatusCode()
         {