Pass DOTNET_MODIFIABLE_ASSEMBLIES & __ASPNETCORE_BROWSER_TOOLS in WebAssembly options comment

Author: maraf

src/Components/Endpoints/src/DependencyInjection/RazorComponentsServiceCollectionExtensions.cs

@@ -71,7 +71,7 @@ public static IRazorComponentsBuilder AddRazorComponents(this IServiceCollection
         services.TryAddScoped<AuthenticationStateProvider, ServerAuthenticationStateProvider>();
         services.AddSupplyValueFromQueryProvider();
         services.TryAddCascadingValue(sp => sp.GetRequiredService<EndpointHtmlRenderer>().HttpContext);
-        services.TryAddScoped<WebAssemblyEnvironmentEmitter>();
+        services.TryAddScoped<WebAssemblySettingsEmitter>();
 
         services.TryAddScoped<ResourceCollectionProvider>();
 

src/Components/Endpoints/src/DependencyInjection/WebAssemblyEnvironmentEmitter.cs

@@ -0,0 +1,53 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.Extensions.Hosting;
+
+namespace Microsoft.AspNetCore.Components.Endpoints;
+
+internal record WebAssemblySettings(string EnvironmentName, Dictionary<string, string> EnvironmentVariables);
+
+internal class WebAssemblySettingsEmitter(IHostEnvironment hostEnvironment)
+{
+    private bool wasEmittedAlready;
+
+    private const string dotnetModifiableAssembliesName = "DOTNET_MODIFIABLE_ASSEMBLIES";
+    private const string aspnetcoreBrowserToolsName = "__ASPNETCORE_BROWSER_TOOLS";
+
+    private static readonly string? s_dotnetModifiableAssemblies = GetNonEmptyEnvironmentVariableValue(dotnetModifiableAssembliesName);
+    private static readonly string? s_aspnetcoreBrowserTools = GetNonEmptyEnvironmentVariableValue(aspnetcoreBrowserToolsName);
+
+    private static string? GetNonEmptyEnvironmentVariableValue(string name)
+        => Environment.GetEnvironmentVariable(name) is { Length: > 0 } value ? value : null;
+
+    public bool TryGetSettingsOnce([NotNullWhen(true)] out WebAssemblySettings? settings)
+    {
+        if (wasEmittedAlready)
+        {
+            settings = default;
+            return false;
+        }
+
+        var environmentVariables = new Dictionary<string, string>();
+
+        // DOTNET_MODIFIABLE_ASSEMBLIES is used by the runtime to initialize hot-reload specific environment variables and is configured
+        // by the launching process (dotnet-watch / Visual Studio).
+        // Always add the header if the environment variable is set, regardless of the kind of environment.
+        if (s_dotnetModifiableAssemblies != null)
+        {
+            environmentVariables[dotnetModifiableAssembliesName] = s_dotnetModifiableAssemblies;
+        }
+
+        // See https://github.com/dotnet/aspnetcore/issues/37357#issuecomment-941237000
+        // Translate the _ASPNETCORE_BROWSER_TOOLS environment configured by the browser tools agent in to a HTTP response header.
+        if (s_aspnetcoreBrowserTools != null)
+        {
+            environmentVariables[aspnetcoreBrowserToolsName] = s_aspnetcoreBrowserTools;
+        }
+
+        wasEmittedAlready = true;
+        settings = new (hostEnvironment.EnvironmentName, environmentVariables);
+        return true;
+    }
+}

src/Components/Endpoints/src/DependencyInjection/WebAssemblySettingsEmitter.cs

@@ -273,9 +273,10 @@ private void WriteComponentHtml(int componentId, TextWriter output, bool allowBo
 
             if (marker.Type is ComponentMarker.WebAssemblyMarkerType or ComponentMarker.AutoMarkerType)
             {
-                if (_httpContext.RequestServices.GetRequiredService<WebAssemblyEnvironmentEmitter>().TryGetEnvironmentOnce(out var environment))
+                if (_httpContext.RequestServices.GetRequiredService<WebAssemblySettingsEmitter>().TryGetSettingsOnce(out var settings))
                 {
-                    output.Write($"<!--Blazor-WebAssemblyEnvironment:{environment}-->");
+                    var settingsJson = JsonSerializer.Serialize(settings, ServerComponentSerializationSettings.JsonSerializationOptions);
+                    output.Write($"<!--Blazor-WebAssembly:{settingsJson}-->");
                 }
             }
 

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.Streaming.cs

@@ -11,7 +11,7 @@ import { SharedMemoryRenderBatch } from './Rendering/RenderBatch/SharedMemoryRen
 import { Pointer } from './Platform/Platform';
 import { WebAssemblyStartOptions } from './Platform/WebAssemblyStartOptions';
 import { addDispatchEventMiddleware } from './Rendering/WebRendererInteropMethods';
-import { WebAssemblyComponentDescriptor, discoverWebAssemblyPersistedState } from './Services/ComponentDescriptorDiscovery';
+import { WebAssemblyComponentDescriptor, WebAssemblyServerOptions, discoverWebAssemblyPersistedState } from './Services/ComponentDescriptorDiscovery';
 import { receiveDotNetDataStream } from './StreamingInterop';
 import { WebAssemblyComponentAttacher } from './Platform/WebAssemblyComponentAttacher';
 import { MonoConfig } from '@microsoft/dotnet-runtime';
@@ -68,23 +68,23 @@ export function setWebAssemblyOptions(initializersReady: Promise<Partial<WebAsse
   }
 }
 
-export function startWebAssembly(components: RootComponentManager<WebAssemblyComponentDescriptor>, environment: string | null | undefined): Promise<void> {
+export function startWebAssembly(components: RootComponentManager<WebAssemblyComponentDescriptor>, options: WebAssemblyServerOptions | undefined): Promise<void> {
   if (startPromise !== undefined) {
     throw new Error('Blazor WebAssembly has already started.');
   }
 
-  startPromise = new Promise(startCore.bind(null, components, environment));
+  startPromise = new Promise(startCore.bind(null, components, options));
 
   return startPromise;
 }
 
-async function startCore(components: RootComponentManager<WebAssemblyComponentDescriptor>, environment: string | null | undefined, resolve, _) {
+async function startCore(components: RootComponentManager<WebAssemblyComponentDescriptor>, options: WebAssemblyServerOptions | undefined, resolve, _) {
   if (inAuthRedirectIframe()) {
     // eslint-disable-next-line @typescript-eslint/no-empty-function
     await new Promise(() => { }); // See inAuthRedirectIframe for explanation
   }
 
-  const platformLoadPromise = loadWebAssemblyPlatformIfNotStarted(environment);
+  const platformLoadPromise = loadWebAssemblyPlatformIfNotStarted(options);
 
   addDispatchEventMiddleware((browserRendererId, eventHandlerId, continuation) => {
     // It's extremely unusual, but an event can be raised while we're in the middle of synchronously applying a
@@ -206,16 +206,19 @@ export function waitForBootConfigLoaded(): Promise<MonoConfig> {
   return bootConfigPromise;
 }
 
-export function loadWebAssemblyPlatformIfNotStarted(environment: string | null | undefined): Promise<void> {
+export function loadWebAssemblyPlatformIfNotStarted(serverOptions: WebAssemblyServerOptions | undefined): Promise<void> {
   platformLoadPromise ??= (async () => {
     await initializersPromise;
     const finalOptions = options ?? {};
     if (!finalOptions.environment) {
-      finalOptions.environment = environment ?? undefined;
+      finalOptions.environment = serverOptions?.environmentName ?? undefined;
     }
     const existingConfig = options?.configureRuntime;
     finalOptions.configureRuntime = (config) => {
       existingConfig?.(config);
+      if (serverOptions?.environmentVariables) {
+        config.withEnvironmentVariables(serverOptions.environmentVariables);
+      }
       if (waitForRootComponents) {
         config.withEnvironmentVariable('__BLAZOR_WEBASSEMBLY_WAIT_FOR_ROOT_COMPONENTS', 'true');
       }

src/Components/Web.JS/src/Boot.WebAssembly.Common.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, discoverWebAssemblyEnvironment } from './Services/ComponentDescriptorDiscovery';
+import { WebAssemblyComponentDescriptor, discoverComponents, discoverWebAssemblyOptions } from './Services/ComponentDescriptorDiscovery';
 import { DotNet } from '@microsoft/dotnet-js-interop';
 import { InitialRootComponentsList } from './Services/InitialRootComponentsList';
 import { JSEventRegistry } from './Services/JSEventRegistry';
@@ -24,10 +24,10 @@ async function boot(options?: Partial<WebAssemblyStartOptions>): Promise<void> {
 
   JSEventRegistry.create(Blazor);
   const webAssemblyComponents = discoverComponents(document, 'webassembly') as WebAssemblyComponentDescriptor[];
-  const webAssemblyEnvironment = discoverWebAssemblyEnvironment(document);
+  const webAssemblyOptions = discoverWebAssemblyOptions(document);
 
   const components = new InitialRootComponentsList(webAssemblyComponents);
-  await startWebAssembly(components, webAssemblyEnvironment);
+  await startWebAssembly(components, webAssemblyOptions);
 }
 
 Blazor.start = boot;

src/Components/Web.JS/src/Boot.WebAssembly.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, discoverWebAssemblyEnvironment, mergeDescriptors } from '../../Services/ComponentDescriptorDiscovery';
+import { AutoComponentDescriptor, ComponentDescriptor, ServerComponentDescriptor, WebAssemblyComponentDescriptor, WebAssemblyServerOptions, canMergeDescriptors, discoverComponents, discoverWebAssemblyOptions, 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';
@@ -13,7 +13,7 @@ let descriptorHandler: DescriptorHandler | null = null;
 
 export interface DescriptorHandler {
   registerComponent(descriptor: ComponentDescriptor): void;
-  setWebAssemblyEnvironment(webAssemblyEnvironment: string | null | undefined): void;
+  setWebAssemblyOptions(options: WebAssemblyServerOptions | undefined): void;
 }
 
 export function attachComponentDescriptorHandler(handler: DescriptorHandler) {
@@ -22,8 +22,8 @@ export function attachComponentDescriptorHandler(handler: DescriptorHandler) {
 
 export function registerAllComponentDescriptors(root: Node) {
   const descriptors = upgradeComponentCommentsToLogicalRootComments(root);
-  const webAssemblyEnvironment = discoverWebAssemblyEnvironment(root);
-  descriptorHandler?.setWebAssemblyEnvironment(webAssemblyEnvironment);
+  const webAssemblyOptions = discoverWebAssemblyOptions(root);
+  descriptorHandler?.setWebAssemblyOptions(webAssemblyOptions);
 
   for (const descriptor of descriptors) {
     descriptorHandler?.registerComponent(descriptor);

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

@@ -15,10 +15,15 @@ export function discoverComponents(root: Node, type: 'webassembly' | 'server' |
 const blazorServerStateCommentRegularExpression = /^\s*Blazor-Server-Component-State:(?<state>[a-zA-Z0-9+/=]+)$/;
 const blazorWebAssemblyStateCommentRegularExpression = /^\s*Blazor-WebAssembly-Component-State:(?<state>[a-zA-Z0-9+/=]+)$/;
 const blazorWebInitializerCommentRegularExpression = /^\s*Blazor-Web-Initializers:(?<initializers>[a-zA-Z0-9+/=]+)$/;
-const blazorWebAssemblyEnvironmentCommentRegularExpression = /^\s*Blazor-WebAssemblyEnvironment:(?<environment>[a-zA-Z0-9+/=]+)$/;
+const blazorWebAssemblyOptionsCommentRegularExpression = /^\s*Blazor-WebAssembly:[^{]*(?<options>.*)$/;
 
-export function discoverWebAssemblyEnvironment(root: Node): string | null | undefined {
-  return discoverBlazorComment(root, blazorWebAssemblyEnvironmentCommentRegularExpression, 'environment');
+export function discoverWebAssemblyOptions(root: Node): WebAssemblyServerOptions | undefined {
+  const optionsJson = discoverBlazorComment(root, blazorWebAssemblyOptionsCommentRegularExpression, 'options');
+  if (!optionsJson) {
+    return undefined;
+  }
+  const options = JSON.parse(optionsJson);
+  return options;
 }
 
 export function discoverServerPersistedState(node: Node): string | null | undefined {
@@ -344,6 +349,11 @@ export type ServerComponentDescriptor = ServerComponentMarker & DescriptorData;
 export type WebAssemblyComponentDescriptor = WebAssemblyComponentMarker & DescriptorData;
 export type AutoComponentDescriptor = AutoComponentMarker & DescriptorData;
 
+export type WebAssemblyServerOptions = {
+  environmentName: string,
+  environmentVariables: { [i: string]: string; }
+};
+
 type DescriptorData = {
   uniqueId: number;
   start: Comment;

src/Components/Web.JS/src/Services/ComponentDescriptorDiscovery.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 { ComponentDescriptor, ComponentMarker, descriptorToMarker } from './ComponentDescriptorDiscovery';
+import { ComponentDescriptor, ComponentMarker, descriptorToMarker, WebAssemblyServerOptions } from './ComponentDescriptorDiscovery';
 import { isRendererAttached, registerRendererAttachedListener } from '../Rendering/WebRendererInteropMethods';
 import { WebRendererId } from '../Rendering/WebRendererId';
 import { DescriptorHandler } from '../Rendering/DomMerging/DomSync';
@@ -63,7 +63,7 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
 
   private _circuitInactivityTimeoutId: any;
 
-  private _webAssemblyEnvironment: string | undefined;
+  private _webAssemblyOptions: WebAssemblyServerOptions | undefined;
 
   // Implements RootComponentManager.
   // An empty array becuase all root components managed
@@ -96,8 +96,8 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
     this.rootComponentsMayRequireRefresh();
   }
 
-  public setWebAssemblyEnvironment(webAssemblyEnvironment: string | undefined): void {
-    this._webAssemblyEnvironment = webAssemblyEnvironment;
+  public setWebAssemblyOptions(webAssemblyOptions: WebAssemblyServerOptions | undefined): void {
+    this._webAssemblyOptions = webAssemblyOptions;
   }
 
   public registerComponent(descriptor: ComponentDescriptor) {
@@ -138,7 +138,7 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
 
     setWaitForRootComponents();
 
-    const loadWebAssemblyPromise = loadWebAssemblyPlatformIfNotStarted(this._webAssemblyEnvironment);
+    const loadWebAssemblyPromise = loadWebAssemblyPlatformIfNotStarted(this._webAssemblyOptions);
     const bootConfig = await waitForBootConfigLoaded();
 
     if (maxParallelDownloadsOverride !== undefined) {
@@ -188,7 +188,7 @@ export class WebRootComponentManager implements DescriptorHandler, RootComponent
     this.startLoadingWebAssemblyIfNotStarted();
 
     if (!hasStartedWebAssembly()) {
-      await startWebAssembly(this, this._webAssemblyEnvironment);
+      await startWebAssembly(this, this._webAssemblyOptions);
     }
   }
 

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

@@ -59,7 +59,6 @@ public static RazorComponentsEndpointConventionBuilder AddInteractiveWebAssembly
         var descriptors = StaticAssetsEndpointDataSourceHelper.ResolveStaticAssetDescriptors(endpointBuilder, options.StaticAssetsManifestPath);
         if (descriptors != null && descriptors.Count > 0)
         {
-            ComponentWebAssemblyConventions.AddBlazorWebAssemblyConventions(descriptors, environment);
             return builder;
         }