Use view buffers during pre-rendering (dotnet#39465)

* Use view buffers during rendering

This change removes about 8kb of string[] allocations per request during pre-rendering and replaces them with a ViewBuffer that uses array pooling. The allocations come from list resizing as part of HtmlRenderer operations (such as https://github.com/dotnet/aspnetcore/blob/main/src/Mvc/Mvc.ViewFeatures/src/RazorComponents/HtmlRenderer.cs#L133-L134). Also includes a couple of other clean up items:

* Uses ValueTask instead of `Task<T>`
* Moves top-level types to a separate file.
* Some formatting cleanup

src/Components/Server/test/Microsoft.AspNetCore.Components.Server.Tests.csproj

@@ -1,11 +1,12 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>$(DefaultNetCoreTargetFramework)</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
     <Reference Include="Microsoft.AspNetCore.Components.Server" />
+    <Reference Include="Microsoft.AspNetCore.Html.Abstractions" />
   </ItemGroup>
 
   <PropertyGroup>

src/Mvc/Mvc.TagHelpers/test/ComponentTagHelperTest.cs

@@ -75,7 +75,7 @@ private ViewContext GetViewContext()
     {
         var htmlContent = new HtmlContentBuilder().AppendHtml("Hello world");
         var renderer = Mock.Of<IComponentRenderer>(c =>
-            c.RenderComponentAsync(It.IsAny<ViewContext>(), It.IsAny<Type>(), It.IsAny<RenderMode>(), It.IsAny<object>()) == Task.FromResult<IHtmlContent>(htmlContent));
+            c.RenderComponentAsync(It.IsAny<ViewContext>(), It.IsAny<Type>(), It.IsAny<RenderMode>(), It.IsAny<object>()) == new ValueTask<IHtmlContent>(htmlContent));
 
         var httpContext = new DefaultHttpContext
         {

src/Mvc/Mvc.TagHelpers/test/PersistComponentStateTagHelperTest.cs

@@ -9,6 +9,7 @@
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc.Rendering;
 using Microsoft.AspNetCore.Mvc.ViewFeatures;
+using Microsoft.AspNetCore.Mvc.ViewFeatures.Buffers;
 using Microsoft.AspNetCore.Razor.TagHelpers;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
@@ -180,7 +181,7 @@ private ViewContext GetViewContext()
     {
         var htmlContent = new HtmlContentBuilder().AppendHtml("Hello world");
         var renderer = Mock.Of<IComponentRenderer>(c =>
-            c.RenderComponentAsync(It.IsAny<ViewContext>(), It.IsAny<Type>(), It.IsAny<RenderMode>(), It.IsAny<object>()) == Task.FromResult<IHtmlContent>(htmlContent));
+            c.RenderComponentAsync(It.IsAny<ViewContext>(), It.IsAny<Type>(), It.IsAny<RenderMode>(), It.IsAny<object>()) == new ValueTask<IHtmlContent>(htmlContent));
 
         var httpContext = new DefaultHttpContext
         {
@@ -191,6 +192,7 @@ private ViewContext GetViewContext()
                 .AddSingleton(_ephemeralProvider)
                 .AddSingleton<ILoggerFactory>(NullLoggerFactory.Instance)
                 .AddSingleton(HtmlEncoder.Default)
+                .AddScoped<IViewBufferScope, TestViewBufferScope>()
                 .BuildServiceProvider(),
         };
 

src/Mvc/Mvc.ViewFeatures/src/RazorComponents/ComponentRenderedText.cs

@@ -1,17 +1,19 @@
 // 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.Html;
+
 namespace Microsoft.AspNetCore.Components.Rendering;
 
 internal readonly struct ComponentRenderedText
 {
-    public ComponentRenderedText(int componentId, IEnumerable<string> tokens)
+    public ComponentRenderedText(int componentId, IHtmlContent htmlContent)
     {
         ComponentId = componentId;
-        Tokens = tokens;
+        HtmlContent = htmlContent;
     }
 
     public int ComponentId { get; }
 
-    public IEnumerable<string> Tokens { get; }
+    public IHtmlContent HtmlContent { get; }
 }

src/Mvc/Mvc.ViewFeatures/src/RazorComponents/ComponentRenderer.cs

@@ -5,29 +5,30 @@
 using Microsoft.AspNetCore.Html;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc.Rendering;
+using Microsoft.AspNetCore.Mvc.ViewFeatures.Buffers;
 
 namespace Microsoft.AspNetCore.Mvc.ViewFeatures;
 
-internal class ComponentRenderer : IComponentRenderer
+internal sealed class ComponentRenderer : IComponentRenderer
 {
     private static readonly object ComponentSequenceKey = new object();
     private static readonly object InvokedRenderModesKey = new object();
 
     private readonly StaticComponentRenderer _staticComponentRenderer;
     private readonly ServerComponentSerializer _serverComponentSerializer;
-    private readonly WebAssemblyComponentSerializer _WebAssemblyComponentSerializer;
+    private readonly IViewBufferScope _viewBufferScope;
 
     public ComponentRenderer(
         StaticComponentRenderer staticComponentRenderer,
         ServerComponentSerializer serverComponentSerializer,
-        WebAssemblyComponentSerializer WebAssemblyComponentSerializer)
+        IViewBufferScope viewBufferScope)
     {
         _staticComponentRenderer = staticComponentRenderer;
         _serverComponentSerializer = serverComponentSerializer;
-        _WebAssemblyComponentSerializer = WebAssemblyComponentSerializer;
+        _viewBufferScope = viewBufferScope;
     }
 
-    public async Task<IHtmlContent> RenderComponentAsync(
+    public async ValueTask<IHtmlContent> RenderComponentAsync(
         ViewContext viewContext,
         Type componentType,
         RenderMode renderMode,
@@ -117,14 +118,12 @@ internal static InvokedRenderModes.Mode GetPersistStateRenderMode(ViewContext vi
         }
     }
 
-    private async Task<IHtmlContent> StaticComponentAsync(HttpContext context, Type type, ParameterView parametersCollection)
+    private ValueTask<IHtmlContent> StaticComponentAsync(HttpContext context, Type type, ParameterView parametersCollection)
     {
-        var result = await _staticComponentRenderer.PrerenderComponentAsync(
+        return _staticComponentRenderer.PrerenderComponentAsync(
             parametersCollection,
             context,
             type);
-
-        return new ComponentHtmlContent(result);
     }
 
     private async Task<IHtmlContent> PrerenderedServerComponentAsync(HttpContext context, ServerComponentInvocationSequence invocationId, Type type, ParameterView parametersCollection)
@@ -145,13 +144,15 @@ private async Task<IHtmlContent> PrerenderedServerComponentAsync(HttpContext con
             context,
             type);
 
-        return new ComponentHtmlContent(
-            ServerComponentSerializer.GetPreamble(currentInvocation),
-            result,
-            ServerComponentSerializer.GetEpilogue(currentInvocation));
+        var viewBuffer = new ViewBuffer(_viewBufferScope, nameof(ComponentRenderer), ViewBuffer.ViewPageSize);
+        ServerComponentSerializer.AppendPreamble(viewBuffer, currentInvocation);
+        viewBuffer.AppendHtml(result);
+        ServerComponentSerializer.AppendEpilogue(viewBuffer, currentInvocation);
+
+        return viewBuffer;
     }
 
-    private async Task<IHtmlContent> PrerenderedWebAssemblyComponentAsync(HttpContext context, Type type, ParameterView parametersCollection)
+    private async ValueTask<IHtmlContent> PrerenderedWebAssemblyComponentAsync(HttpContext context, Type type, ParameterView parametersCollection)
     {
         var currentInvocation = WebAssemblyComponentSerializer.SerializeInvocation(
             type,
@@ -163,10 +164,12 @@ private async Task<IHtmlContent> PrerenderedWebAssemblyComponentAsync(HttpContex
             context,
             type);
 
-        return new ComponentHtmlContent(
-            WebAssemblyComponentSerializer.GetPreamble(currentInvocation),
-            result,
-            WebAssemblyComponentSerializer.GetEpilogue(currentInvocation));
+        var viewBuffer = new ViewBuffer(_viewBufferScope, nameof(ComponentRenderer), ViewBuffer.ViewPageSize);
+        WebAssemblyComponentSerializer.AppendPreamble(viewBuffer, currentInvocation);
+        viewBuffer.AppendHtml(result);
+        WebAssemblyComponentSerializer.AppendEpilogue(viewBuffer, currentInvocation);
+
+        return viewBuffer;
     }
 
     private IHtmlContent NonPrerenderedServerComponent(HttpContext context, ServerComponentInvocationSequence invocationId, Type type, ParameterView parametersCollection)
@@ -178,31 +181,16 @@ private IHtmlContent NonPrerenderedServerComponent(HttpContext context, ServerCo
 
         var currentInvocation = _serverComponentSerializer.SerializeInvocation(invocationId, type, parametersCollection, prerendered: false);
 
-        return new ComponentHtmlContent(ServerComponentSerializer.GetPreamble(currentInvocation));
+        var viewBuffer = new ViewBuffer(_viewBufferScope, nameof(ComponentRenderer), ServerComponentSerializer.PreambleBufferSize);
+        ServerComponentSerializer.AppendPreamble(viewBuffer, currentInvocation);
+        return viewBuffer;
     }
 
-    private static IHtmlContent NonPrerenderedWebAssemblyComponent(HttpContext context, Type type, ParameterView parametersCollection)
+    private IHtmlContent NonPrerenderedWebAssemblyComponent(HttpContext context, Type type, ParameterView parametersCollection)
     {
         var currentInvocation = WebAssemblyComponentSerializer.SerializeInvocation(type, parametersCollection, prerendered: false);
-
-        return new ComponentHtmlContent(WebAssemblyComponentSerializer.GetPreamble(currentInvocation));
-    }
-}
-
-internal class InvokedRenderModes
-{
-    public InvokedRenderModes(Mode mode)
-    {
-        Value = mode;
-    }
-
-    public Mode Value { get; set; }
-
-    internal enum Mode
-    {
-        None,
-        Server,
-        WebAssembly,
-        ServerAndWebAssembly
+        var viewBuffer = new ViewBuffer(_viewBufferScope, nameof(ComponentRenderer), ServerComponentSerializer.PreambleBufferSize);
+        WebAssemblyComponentSerializer.AppendPreamble(viewBuffer, currentInvocation);
+        return viewBuffer;
     }
 }