fix(server): add waitUntil to the server context in Fastify integration

.changeset/blue-pugs-provide.md

@@ -0,0 +1,8 @@
+---
+'@whatwg-node/server': patch
+---
+
+While calling `handleNodeRequest` or `handleNodeRequestAndResponse`, `waitUntil` is not added automatically as in `requestListener` for Node.js integration.
+This change adds `waitUntil` into the `serverContext` if not present.
+
+Fixes the issue with Fastify integration that uses the mentioned methods

packages/server/src/createServerAdapter.ts

@@ -133,17 +133,19 @@ function createServerAdapter<
 
   function waitUntil(promiseLike: PromiseLike<unknown>) {
     // Ensure that the disposable stack is created
-    ensureDisposableStack();
-    waitUntilPromises.add(promiseLike);
-    promiseLike.then(
-      () => {
-        waitUntilPromises.delete(promiseLike);
-      },
-      err => {
-        console.error(`Unexpected error while waiting: ${err.message || err}`);
-        waitUntilPromises.delete(promiseLike);
-      },
-    );
+    if (isPromise(promiseLike)) {
+      ensureDisposableStack();
+      waitUntilPromises.add(promiseLike);
+      promiseLike.then(
+        () => {
+          waitUntilPromises.delete(promiseLike);
+        },
+        err => {
+          console.error(`Unexpected error while waiting: ${err.message || err}`);
+          waitUntilPromises.delete(promiseLike);
+        },
+      );
+    }
   }
 
   if (options?.plugins != null) {
@@ -250,6 +252,10 @@ function createServerAdapter<
   // TODO: Remove this on the next major version
   function handleNodeRequest(nodeRequest: NodeRequest, ...ctx: Partial<TServerContext>[]) {
     const serverContext = ctx.length > 1 ? completeAssign(...ctx) : ctx[0] || {};
+    // Ensure `waitUntil` is available in the server context
+    if (!serverContext.waitUntil) {
+      serverContext.waitUntil = waitUntil;
+    }
     const request = normalizeNodeRequest(nodeRequest, fetchAPI);
     return handleRequest(request, serverContext);
   }

packages/server/test/fastify.spec.ts

@@ -212,6 +212,33 @@ describe('Fastify', () => {
           reqBody: 'TEST',
         });
       });
+
+      it('handles waitUntil', async () => {
+        const backgroundJob$ = createDeferredPromise<void>();
+        let backgroundJobDone = false;
+        backgroundJob$.promise.finally(() => {
+          backgroundJobDone = true;
+        });
+        serverAdapter = createServerAdapter((_request: Request, ctx) => {
+          ctx.waitUntil(backgroundJob$.promise);
+          return new Response('OK');
+        });
+        const res = await fastifyServer.inject({
+          url: '/mypath',
+        });
+        expect(res.body).toEqual('OK');
+        const dispose$ = Promise.resolve(serverAdapter.dispose());
+        let disposeDone = false;
+        dispose$.then(() => {
+          disposeDone = true;
+        });
+        expect(backgroundJobDone).toBe(false);
+        expect(disposeDone).toBe(false);
+        backgroundJob$.resolve();
+        await dispose$;
+        expect(backgroundJobDone).toBe(true);
+        expect(disposeDone).toBe(true);
+      });
     },
   );
 });