Fix issues preventing hot reload for Blazor WASM (#31108)

* Configure DOTNET_MODIFIABLE_ASSEMBLIES=debug env variable
* Fixup broken reflection

Author: pranavkm

src/Components/Web.JS/dist/Release/blazor.server.js

@@ -22,6 +22,7 @@ export class BootConfigResult {
 export interface BootJsonData {
   readonly entryAssembly: string;
   readonly resources: ResourceGroups;
+  /** Gets a value that determines if this boot config was produced from a non-published build (i.e. dotnet build or dotnet run) */
   readonly debugBuild: boolean;
   readonly linkerEnabled: boolean;
   readonly cacheBootResources: boolean;

src/Components/Web.JS/src/Platform/BootConfig.ts

@@ -428,6 +428,11 @@ function createEmscriptenModuleInstance(resourceLoader: WebAssemblyResourceLoade
       timeZone = Intl.DateTimeFormat().resolvedOptions().timeZone;
     } catch { }
     MONO.mono_wasm_setenv("TZ", timeZone || 'UTC');
+    if (resourceLoader.bootConfig.debugBuild) {
+      // Configure the app to enable hot reload in Development.
+      MONO.mono_wasm_setenv('DOTNET_MODIFIABLE_ASSEMBLIES', 'debug');
+    }
+
     const load_runtime = cwrap('mono_wasm_load_runtime', null, ['string', 'number']);
     // -1 enables debugging with logging disabled. 0 disables debugging entirely.
     load_runtime(appBinDirName, hasDebuggingEnabled() ? -1 : 0);

src/Components/Web.JS/src/Platform/Mono/MonoPlatform.ts

@@ -60,7 +60,7 @@ public static void ApplyHotReloadDelta(string moduleId, byte[] metadataDelta, by
             }
 
             // Remove this once there's a runtime API to subscribe to.
-            typeof(ComponentBase).Assembly.GetType("Microsoft.AspNetCore.Components.HotReload.HotReloadManager")!.GetMethod("DeltaApplied", BindingFlags.NonPublic | BindingFlags.Static)!.Invoke(null, null);
+            typeof(ComponentBase).Assembly.GetType("Microsoft.AspNetCore.Components.HotReload.HotReloadManager")!.GetMethod("DeltaApplied", BindingFlags.Public | BindingFlags.Static)!.Invoke(null, null);
         }
     }
 }