await flush

src/js/node/http.ts

@@ -1260,17 +1260,17 @@ function flushFirstWrite(self) {
     new Response(
       new ReadableStream({
         type: "direct",
-        pull: controller => {
+        pull: async controller => {
           self[controllerSymbol] = controller;
           if (firstWrite) {
             controller.write(firstWrite);
-            controller.flush(); // flush the first write
+            await controller.flush(); // flush the first write
           }
           firstWrite = undefined;
           if (!self[finishedSymbol]) {
             const { promise, resolve } = $newPromiseCapability(GlobalPromise);
             self[deferredSymbol] = resolve;
-            return promise;
+            return await promise;
           }
         },
       }),

test/js/node/http/node-http.test.ts

@@ -2477,7 +2477,10 @@ it("response body streaming is immediate (#13696)", async () => {
       // chunks before real-time streaming started working.
       expect(new Date().getTime() - Number.parseInt(decoder.decode(value).trimEnd(), 10)).toBeLessThan(acceptableDelay);
     }
+    // Verify that the correct number of chunks were sent (in case server
+    // decides to send no chunks at all).
     expect(receivedChunks).toEqual(totalChunks);
+    // Also verify the total size in case some data was lost.
     expect(receivedSize).toEqual(totalSize);
   } finally {
     server.close();