Find environment from all component descriptors

and use it instead of relying on first component in blazor.web

Author: maraf

src/Components/Web.JS/src/Boot.WebAssembly.ts

@@ -6,7 +6,7 @@ import { Blazor } from './GlobalExports';
 import { shouldAutoStart } from './BootCommon';
 import { WebAssemblyStartOptions } from './Platform/WebAssemblyStartOptions';
 import { setWebAssemblyOptions, startWebAssembly } from './Boot.WebAssembly.Common';
-import { WebAssemblyComponentDescriptor, discoverComponents } from './Services/ComponentDescriptorDiscovery';
+import { WebAssemblyComponentDescriptor, discoverComponents, findWebAssemblyEnvironment } from './Services/ComponentDescriptorDiscovery';
 import { DotNet } from '@microsoft/dotnet-js-interop';
 import { InitialRootComponentsList } from './Services/InitialRootComponentsList';
 import { JSEventRegistry } from './Services/JSEventRegistry';
@@ -26,18 +26,7 @@ async function boot(options?: Partial<WebAssemblyStartOptions>): Promise<void> {
   const webAssemblyComponents = discoverComponents(document, 'webassembly') as WebAssemblyComponentDescriptor[];
 
   const components = new InitialRootComponentsList(webAssemblyComponents);
-  await startWebAssembly(components, findEnvironment(webAssemblyComponents));
-}
-
-function findEnvironment(webAssemblyComponents: WebAssemblyComponentDescriptor[]): string | undefined {
-  for (let index = 0; index < webAssemblyComponents.length; index++) {
-    const component = webAssemblyComponents[index];
-    if (component.environment) {
-      return component.environment;
-    }
-  }
-
-  return undefined;
+  await startWebAssembly(components, findWebAssemblyEnvironment(webAssemblyComponents));
 }
 
 Blazor.start = boot;

src/Components/Web.JS/src/Rendering/DomMerging/DomSync.ts

@@ -1,7 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-import { AutoComponentDescriptor, ComponentDescriptor, ServerComponentDescriptor, WebAssemblyComponentDescriptor, canMergeDescriptors, discoverComponents, mergeDescriptors } from '../../Services/ComponentDescriptorDiscovery';
+import { AutoComponentDescriptor, ComponentDescriptor, ServerComponentDescriptor, WebAssemblyComponentDescriptor, canMergeDescriptors, discoverComponents, findWebAssemblyEnvironment, mergeDescriptors } from '../../Services/ComponentDescriptorDiscovery';
 import { isInteractiveRootComponentElement } from '../BrowserRenderer';
 import { applyAnyDeferredValue } from '../DomSpecialPropertyUtil';
 import { LogicalElement, getLogicalChildrenArray, getLogicalNextSibling, getLogicalParent, getLogicalRootDescriptor, insertLogicalChild, insertLogicalChildBefore, isLogicalElement, toLogicalElement, toLogicalRootCommentElement } from '../LogicalElements';
@@ -13,6 +13,7 @@ let descriptorHandler: DescriptorHandler | null = null;
 
 export interface DescriptorHandler {
   registerComponent(descriptor: ComponentDescriptor): void;
+  setWebAssemblyEnvironment(webAssemblyEnvironment: string | undefined): void;
 }
 
 export function attachComponentDescriptorHandler(handler: DescriptorHandler) {
@@ -21,6 +22,8 @@ export function attachComponentDescriptorHandler(handler: DescriptorHandler) {
 
 export function registerAllComponentDescriptors(root: Node) {
   const descriptors = upgradeComponentCommentsToLogicalRootComments(root);
+  const webAssemblyEnvironment = findWebAssemblyEnvironment(descriptors);
+  descriptorHandler?.setWebAssemblyEnvironment(webAssemblyEnvironment);
 
   for (const descriptor of descriptors) {
     descriptorHandler?.registerComponent(descriptor);

src/Components/Web.JS/src/Services/ComponentDescriptorDiscovery.ts

@@ -16,6 +16,18 @@ const blazorServerStateCommentRegularExpression = /^\s*Blazor-Server-Component-S
 const blazorWebAssemblyStateCommentRegularExpression = /^\s*Blazor-WebAssembly-Component-State:(?<state>[a-zA-Z0-9+/=]+)$/;
 const blazorWebInitializerCommentRegularExpression = /^\s*Blazor-Web-Initializers:(?<initializers>[a-zA-Z0-9+/=]+)$/;
 
+export function findWebAssemblyEnvironment(components: ComponentDescriptor[]): string | undefined {
+  for (let index = 0; index < components.length; index++) {
+    const component = components[index];
+    const webAssemblyComponent = component as WebAssemblyComponentDescriptor;
+    if (webAssemblyComponent.environment) {
+      return webAssemblyComponent.environment;
+    }
+  }
+
+  return undefined;
+}
+
 export function discoverServerPersistedState(node: Node): string | null | undefined {
   return discoverBlazorComment(node, blazorServerStateCommentRegularExpression);
 }

src/Components/Web.JS/src/Services/WebRootComponentManager.ts

@@ -63,6 +63,8 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
 
   private _circuitInactivityTimeoutId: any;
 
+  private _webAssemblyEnvironment: string | undefined;
+
   // Implements RootComponentManager.
   // An empty array becuase all root components managed
   // by WebRootComponentManager are added and removed dynamically.
@@ -94,6 +96,10 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
     this.rootComponentsMayRequireRefresh();
   }
 
+  public setWebAssemblyEnvironment(webAssemblyEnvironment: string | undefined): void {
+    this._webAssemblyEnvironment = webAssemblyEnvironment;
+  }
+
   public registerComponent(descriptor: ComponentDescriptor) {
     if (this._seenDescriptors.has(descriptor)) {
       return;
@@ -132,7 +138,7 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
 
     setWaitForRootComponents();
 
-    const loadWebAssemblyPromise = loadWebAssemblyPlatformIfNotStarted(environment);
+    const loadWebAssemblyPromise = loadWebAssemblyPlatformIfNotStarted(environment ?? this._webAssemblyEnvironment);
     const bootConfig = await waitForBootConfigLoaded();
 
     if (maxParallelDownloadsOverride !== undefined) {
@@ -182,7 +188,7 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
     this.startLoadingWebAssemblyIfNotStarted(environment);
 
     if (!hasStartedWebAssembly()) {
-      await startWebAssembly(this, environment);
+      await startWebAssembly(this, environment ?? this._webAssemblyEnvironment);
     }
   }