Support loading embedded resources for server-side execution too

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Boot.Server.ts

@@ -6,10 +6,16 @@ import { MessagePackHubProtocol } from '@aspnet/signalr-protocol-msgpack';
 import { OutOfProcessRenderBatch } from './Rendering/RenderBatch/OutOfProcessRenderBatch';
 import { internalFunctions as uriHelperFunctions } from './Services/UriHelper';
 import { renderBatch } from './Rendering/Renderer';
+import { fetchBootConfigAsync, loadEmbeddedResourcesAsync } from './BootCommon';
 
 let connection : signalR.HubConnection;
 
 function boot() {
+  // In the background, start loading the boot config and any embedded resources
+  const embeddedResourcesPromise = fetchBootConfigAsync().then(bootConfig => {
+    return loadEmbeddedResourcesAsync(bootConfig);
+  });
+
   connection = new signalR.HubConnectionBuilder()
     .withUrl('/_blazor')
     .withHubProtocol(new MessagePackHubProtocol())
@@ -24,13 +30,16 @@ function boot() {
   connection.on('JS.Error', unhandledError);
 
   connection.start()
-    .then(() => {
+    .then(async () => {
       DotNet.attachDispatcher({
         beginInvokeDotNetFromJS: (callId, assemblyName, methodIdentifier, argsJson) => {
           connection.send('BeginInvokeDotNetFromJS', callId ? callId.toString() : null, assemblyName, methodIdentifier, argsJson);
         }
       });
 
+      // Ensure any embedded resources have been loaded before starting the app
+      await embeddedResourcesPromise;
+
       connection.send(
         'StartCircuit',
         uriHelperFunctions.getLocationHref(),

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Boot.WebAssembly.ts

@@ -7,6 +7,7 @@ import { renderBatch } from './Rendering/Renderer';
 import { RenderBatch } from './Rendering/RenderBatch/RenderBatch';
 import { SharedMemoryRenderBatch } from './Rendering/RenderBatch/SharedMemoryRenderBatch';
 import { Pointer } from './Platform/Platform';
+import { fetchBootConfigAsync, loadEmbeddedResourcesAsync } from './BootCommon';
 
 async function boot() {
   // Configure environment for execution under Mono WebAssembly with shared-memory rendering
@@ -16,11 +17,8 @@ async function boot() {
   };
 
   // Fetch the boot JSON file
-  // Later we might make the location of this configurable (e.g., as an attribute on the <script>
+  const bootConfig = await fetchBootConfigAsync();
-  // element that's importing this file), but currently there isn't a use case for that.
+  const embeddedResourcesPromise = loadEmbeddedResourcesAsync(bootConfig);
-  const bootConfigResponse = await fetch('_framework/blazor.boot.json');
-  const bootConfig: BootJsonData = await bootConfigResponse.json();
-  const embeddedResourcePromises = startLoadingEmbeddedResources(bootConfig);
 
   if (!bootConfig.linkerEnabled) {
     console.info('Blazor is running in dev mode without IL stripping. To make the bundle size significantly smaller, publish the application or see https://go.microsoft.com/fwlink/?linkid=870414');
@@ -38,44 +36,11 @@ async function boot() {
   }
 
   // Before we start running .NET code, be sure embedded content resources are all loaded
-  await Promise.all(embeddedResourcePromises)
+  await embeddedResourcesPromise;
 
   // Start up the application
   const mainAssemblyName = getAssemblyNameFromUrl(bootConfig.main);
   platform.callEntryPoint(mainAssemblyName, bootConfig.entryPoint, []);
 }
 
-function startLoadingEmbeddedResources(bootConfig: BootJsonData) {
-  const cssLoadingPromises = bootConfig.cssReferences.map(cssReference => {
-    const linkElement = document.createElement('link');
-    linkElement.rel = 'stylesheet';
-    linkElement.href = cssReference;
-    return loadResourceFromElement(linkElement);
-  });
-  const jsLoadingPromises = bootConfig.jsReferences.map(jsReference => {
-    const scriptElement = document.createElement('script');
-    scriptElement.src = jsReference;
-    return loadResourceFromElement(scriptElement);
-  });
-  return cssLoadingPromises.concat(jsLoadingPromises);
-}
-
-function loadResourceFromElement(element: HTMLElement) {
-  return new Promise((resolve, reject) => {
-    element.onload = resolve;
-    element.onerror = reject;
-    document.head.appendChild(element);
-  });
-}
-
-// Keep in sync with BootJsonData in Microsoft.AspNetCore.Blazor.Build
-interface BootJsonData {
-  main: string;
-  entryPoint: string;
-  assemblyReferences: string[];
-  cssReferences: string[];
-  jsReferences: string[];
-  linkerEnabled: boolean;
-}
-
 boot();

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/BootCommon.ts

@@ -0,0 +1,39 @@
+export async function fetchBootConfigAsync() {
+  // Later we might make the location of this configurable (e.g., as an attribute on the <script>
+  // element that's importing this file), but currently there isn't a use case for that.
+  const bootConfigResponse = await fetch('_framework/blazor.boot.json');
+  return bootConfigResponse.json() as Promise<BootJsonData>;
+}
+
+export function loadEmbeddedResourcesAsync(bootConfig: BootJsonData): Promise<any> {
+  const cssLoadingPromises = bootConfig.cssReferences.map(cssReference => {
+    const linkElement = document.createElement('link');
+    linkElement.rel = 'stylesheet';
+    linkElement.href = cssReference;
+    return loadResourceFromElement(linkElement);
+  });
+  const jsLoadingPromises = bootConfig.jsReferences.map(jsReference => {
+    const scriptElement = document.createElement('script');
+    scriptElement.src = jsReference;
+    return loadResourceFromElement(scriptElement);
+  });
+  return Promise.all(cssLoadingPromises.concat(jsLoadingPromises));
+}
+
+function loadResourceFromElement(element: HTMLElement) {
+  return new Promise((resolve, reject) => {
+    element.onload = resolve;
+    element.onerror = reject;
+    document.head.appendChild(element);
+  });
+}
+
+// Keep in sync with BootJsonData in Microsoft.AspNetCore.Blazor.Build
+interface BootJsonData {
+  main: string;
+  entryPoint: string;
+  assemblyReferences: string[];
+  cssReferences: string[];
+  jsReferences: string[];
+  linkerEnabled: boolean;
+}