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Implement optional server-side prerendering support
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,215 @@ | ||
| using System.IO; | ||
| using System.Reflection; | ||
| using System.Text; | ||
| using System.Threading.Tasks; | ||
| using Blazor.Components; | ||
| using Blazor.Routing; | ||
| using Blazor.VirtualDom; | ||
| using MiniJSON; | ||
| using System.Collections.Generic; | ||
| using System; | ||
| using System.Runtime.Loader; | ||
| using System.Linq; | ||
| using Blazor.Sdk.Host; | ||
| using Blazor.Runtime.Components; | ||
| using Microsoft.AspNetCore.Http; | ||
| using System.Diagnostics; | ||
|
|
||
| namespace Blazor.Host | ||
| { | ||
| // The code here is incomplete and uses (uncached) reflection to access internals on Blazor.Runtime | ||
| // just as a shortcut to avoid refactoring properly. To clean this up, consider exposing | ||
| // the relevant APIs from Blazor.Runtime properly or even using InternalsVisibleTo. | ||
|
|
||
| internal static class Prerendering | ||
| { | ||
| private static string[] viewReferenceAssemblies; | ||
|
|
||
| internal static void EnablePrerendering(string clientBinDir, string assemblyName) | ||
| { | ||
| var clientAppAssemblyPath = Path.Combine(clientBinDir, assemblyName); | ||
| var entrypointAssembly = AssemblyLoadContext.Default.LoadFromAssemblyPath(clientAppAssemblyPath); | ||
| var entrypoint = entrypointAssembly.EntryPoint; | ||
| entrypoint.Invoke(null, new[] { new string[0] }); | ||
| var envField = typeof(Blazor.Runtime.Env) | ||
| .GetField("_isServer", BindingFlags.Static | BindingFlags.NonPublic); | ||
| envField.SetValue(null, true); | ||
| viewReferenceAssemblies = Directory.EnumerateFiles(clientBinDir, "*.dll") | ||
| .Where(binDirEntry => !string.Equals(binDirEntry, assemblyName, StringComparison.OrdinalIgnoreCase)) | ||
| .ToArray(); | ||
| } | ||
|
|
||
| private static async Task<string> PrerenderUrl(string rootDir, HttpContext httpContext, IEnumerable<Assembly> viewAssemblies) | ||
| { | ||
| var mountPageFromUrlMethod = typeof(Router).GetMethod("MountPageFromUrl", BindingFlags.Static | BindingFlags.NonPublic); | ||
|
|
||
| Router.ViewAssemblies = viewAssemblies; | ||
| var component = (Component)mountPageFromUrlMethod.Invoke(null, new object[] { | ||
| httpContext.Request.Path.Value, | ||
| new BlazorContext(GetAbsoluteUrl(httpContext.Request)) | ||
| }); | ||
| return await RenderComponentHtml(component); | ||
| } | ||
|
|
||
| private static string GetAbsoluteUrl(HttpRequest request) | ||
| { | ||
| return string.Concat( | ||
| request.Scheme, | ||
| "://", | ||
| request.Host.ToUriComponent(), | ||
| request.PathBase.ToUriComponent(), | ||
| request.Path.ToUriComponent(), | ||
| request.QueryString.ToUriComponent()); | ||
| } | ||
|
|
||
| private static async Task<string> RenderComponentHtml(Component component) | ||
| { | ||
| var sb = new StringBuilder(); | ||
| await AppendComponentHtml(sb, component); | ||
| return sb.ToString(); | ||
| } | ||
|
|
||
| private static async Task AppendComponentHtml(StringBuilder sb, Component component) | ||
| { | ||
| var builder = (VDomBuilder)typeof(Component).GetField("builder", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(component); | ||
| if (builder == null) | ||
| { | ||
| throw new NullReferenceException("BAD2"); | ||
| } | ||
| var vdomItems = (VDomItem[])typeof(VDomBuilder).GetProperty("Items", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(builder); | ||
| await AppendVDom(sb, component, vdomItems, 0); | ||
| } | ||
|
|
||
| private static async Task AppendVDom(StringBuilder sb, Component ownerComponent, VDomItem[] vdom, int rootIndex) | ||
| { | ||
| var rootItem = vdom[rootIndex]; | ||
| switch (rootItem.ItemType) | ||
| { | ||
| case VDomItemType.Element: | ||
| sb.AppendFormat("<{0}", rootItem.ElementTagName); | ||
| var hasClosedTag = false; | ||
| for (var childIndex = rootIndex + 1; childIndex <= rootItem.DescendantsEndIndex; childIndex++) | ||
| { | ||
| // Need to close the tag when we see the first non-attribute child | ||
| var childItem = vdom[childIndex]; | ||
| if (!hasClosedTag) | ||
| { | ||
|
|
||
| if (childItem.ItemType != VDomItemType.Attribute) | ||
| { | ||
| sb.Append(">"); | ||
| hasClosedTag = true; | ||
| } | ||
| } | ||
|
|
||
| await AppendVDom(sb, ownerComponent, vdom, childIndex); | ||
|
|
||
| // Skip descendants of children | ||
| if (childItem.ItemType == VDomItemType.Element) | ||
| { | ||
| childIndex = childItem.DescendantsEndIndex; | ||
| } | ||
| } | ||
| if (!hasClosedTag) | ||
| { | ||
| sb.Append(">"); | ||
| } | ||
| sb.AppendFormat("</{0}>", rootItem.ElementTagName); | ||
| break; | ||
| case VDomItemType.Attribute: | ||
| var attributeValue = GetAttributeStringValue(rootItem); | ||
| if (rootItem.AttributeName.Equals("href", StringComparison.OrdinalIgnoreCase) && attributeValue.StartsWith("~/")) | ||
| { | ||
| // When rendering on server, convert virtual paths to regular URLs | ||
| attributeValue = attributeValue.Substring(1); | ||
| } | ||
| sb.AppendFormat(" {0}=\"{1}\"", | ||
| rootItem.AttributeName, | ||
| HtmlAttributeEncode(attributeValue)); | ||
| break; | ||
| case VDomItemType.TextNode: | ||
| sb.Append(HtmlTextEncode(rootItem.TextNodeContents)); | ||
| break; | ||
| case VDomItemType.Component: | ||
| var componentInstance = rootItem.ComponentInstance; | ||
| if (componentInstance == null) | ||
| { | ||
| var childComponent = Interop.Components.InstantiateAndMountComponent( | ||
| "ignored", // elementRef | ||
| ownerComponent, | ||
| rootIndex); | ||
| if (childComponent == null) | ||
| { | ||
| throw new InvalidOperationException("Could not find child component immediately after instantiation."); | ||
| } | ||
| await AppendComponentHtml(sb, childComponent); | ||
| } | ||
| else | ||
| { | ||
| componentInstance.MountAsComponent("ignoredElemRef"); | ||
| var firstRenderCompletedTask = (Task)typeof(Component).GetProperty("FirstRenderCompletedTask", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(componentInstance); | ||
| if (firstRenderCompletedTask != null) | ||
| { | ||
| await firstRenderCompletedTask; | ||
| } | ||
| await AppendComponentHtml(sb, componentInstance); | ||
| } | ||
| break; | ||
| } | ||
| } | ||
|
|
||
| internal static async Task<string> PrerenderPage(string clientRootDir, string clientAppAssemblyName, HttpContext httpContext) | ||
| { | ||
| // TODO: Obviously there's no need to be reading this on every request | ||
| var pageTemplate = File.ReadAllText(Path.Combine(clientRootDir, "wwwroot", "index.html")); | ||
|
|
||
| // TODO: Don't reload view assembly on every request. Only do so when changed. | ||
| // It's crazily inefficient to keep loading new copies of the same assembly like this. | ||
| var viewsAssembly = GetCompiledViewsAssembly(clientRootDir, clientAppAssemblyName, viewReferenceAssemblies); | ||
|
|
||
| return pageTemplate.Replace( | ||
| "<div id=\"app\">Loading...</div>", | ||
| "<div id=\"app\">" + await PrerenderUrl(clientRootDir, httpContext, new[] { viewsAssembly })) + "</div>"; | ||
| } | ||
|
|
||
| private static string GetAttributeStringValue(VDomItem attributeItem) | ||
| { | ||
| return attributeItem.AttributeStringValue | ||
| ?? attributeItem.AttributeObjectValue?.ToString() | ||
| ?? string.Empty; // No need to serialise references to delegates, etc, since we can't call them in prerendering anyway | ||
| } | ||
|
|
||
| private static string HtmlTextEncode(string textNodeContents) | ||
| { | ||
| // TODO: Actually encode | ||
| return textNodeContents; | ||
| } | ||
|
|
||
| private static string HtmlAttributeEncode(string attributeValue) | ||
| { | ||
| // TODO: Actually encode | ||
| return attributeValue; | ||
| } | ||
|
|
||
| private static Component FindComponentById(int id) | ||
| { | ||
| return (Component)typeof(Component) | ||
| .GetMethod("FindById", BindingFlags.Static | BindingFlags.NonPublic) | ||
| .Invoke(null, new object[] { id }); | ||
| } | ||
|
|
||
| private static int viewAssemblyCount = 0; | ||
| private static Assembly GetCompiledViewsAssembly(string rootPath, string appAssemblyName, string[] referenceAssemblies) | ||
| { | ||
| var viewsAssemblyName = appAssemblyName.Replace(".dll", $".{ ++viewAssemblyCount }.Views.dll"); | ||
| var viewAssemblyBytes = RazorCompilation.GetCompiledViewsAssembly( | ||
| rootPath, | ||
| viewsAssemblyName, | ||
| referenceAssemblies); | ||
| using (var ms = new MemoryStream(viewAssemblyBytes)) | ||
| { | ||
| return AssemblyLoadContext.Default.LoadFromStream(ms); | ||
| } | ||
| } | ||
| } | ||
| } |
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