fix(@angular/build): handle empty module case to avoid TypeError

Ensure that accessing the module after invalidation doesn't result in an empty module, which causes a `TypeError: ɵgetOrCreateAngularServerApp is not a function`.

Closes #29458

(cherry picked from commit 8e884a0)

Author: alan-agius4

packages/angular/build/src/builders/dev-server/vite-server.ts

@@ -501,35 +501,30 @@ async function invalidateUpdatedFiles(
   }
 
   // Invalidate any updated files
-  let destroyAngularServerAppCalled = false;
+  let serverApplicationChanged = false;
   for (const [file, record] of generatedFiles) {
     if (!record.updated) {
       continue;
     }
-    record.updated = false;
-
-    if (record.type === BuildOutputFileType.ServerApplication && !destroyAngularServerAppCalled) {
-      // Clear the server app cache
-      // This must be done before module invalidation.
-      const { ɵdestroyAngularServerApp } = (await server.ssrLoadModule('/main.server.mjs')) as {
-        ɵdestroyAngularServerApp: typeof destroyAngularServerApp;
-      };
-
-      ɵdestroyAngularServerApp();
-      destroyAngularServerAppCalled = true;
-    }
 
+    record.updated = false;
     updatedFiles.push(file);
+    serverApplicationChanged ||= record.type === BuildOutputFileType.ServerApplication;
 
     const updatedModules = server.moduleGraph.getModulesByFile(
       normalizePath(join(server.config.root, file)),
     );
     updatedModules?.forEach((m) => server.moduleGraph.invalidateModule(m));
   }
 
-  if (destroyAngularServerAppCalled) {
-    // Trigger module evaluation before reload to initiate dependency optimization.
-    await server.ssrLoadModule('/main.server.mjs');
+  if (serverApplicationChanged) {
+    // Clear the server app cache and
+    // trigger module evaluation before reload to initiate dependency optimization.
+    const { ɵdestroyAngularServerApp } = (await server.ssrLoadModule('/main.server.mjs')) as {
+      ɵdestroyAngularServerApp: typeof destroyAngularServerApp;
+    };
+
+    ɵdestroyAngularServerApp();
   }
 
   return updatedFiles;

packages/angular/build/src/tools/vite/middlewares/ssr-middleware.ts

@@ -40,6 +40,11 @@ export function createAngularSsrInternalMiddleware(
       const { writeResponseToNodeResponse, createWebRequestFromNodeRequest } =
         await loadEsmModule<typeof import('@angular/ssr/node')>('@angular/ssr/node');
 
+      // The following is necessary because accessing the module after invalidation may result in an empty module,
+      // which can trigger a `TypeError: ɵgetOrCreateAngularServerApp is not a function` error.
+      // TODO: look into why.
+      await server.ssrLoadModule('/main.server.mjs');
+
       const { ɵgetOrCreateAngularServerApp } = (await server.ssrLoadModule('/main.server.mjs')) as {
         ɵgetOrCreateAngularServerApp: typeof getOrCreateAngularServerApp;
       };