fix(ext/http): flush gzip streaming response (#23991)

This commit changes `gzip` compression in `Deno.serve` API to flush data
after each write. There's a slight performance regression, but provided
test shows a scenario that was not possible before.

---------

Co-authored-by: Divy Srivastava <dj.srivastava23@gmail.com>

ext/http/response_body.rs

@@ -394,7 +394,7 @@ impl PollFrame for GZipResponseStream {
         stm.compress(&[], &mut buf, flate2::FlushCompress::Finish)
       }
       ResponseStreamResult::NonEmptyBuf(mut input) => {
-        let res = stm.compress(&input, &mut buf, flate2::FlushCompress::None);
+        let res = stm.compress(&input, &mut buf, flate2::FlushCompress::Sync);
         let len_in = (stm.total_in() - start_in) as usize;
         debug_assert!(len_in <= input.len());
         this.crc.update(&input[..len_in]);

ext/node/polyfills/http.ts

@@ -671,6 +671,9 @@ class ClientRequest extends OutgoingMessage {
     (async () => {
       try {
         const res = await op_fetch_send(this._req.requestRid);
+        if (this._req.cancelHandleRid !== null) {
+          core.tryClose(this._req.cancelHandleRid);
+        }
         try {
           cb?.();
         } catch (_) {
@@ -709,10 +712,6 @@ class ClientRequest extends OutgoingMessage {
           Object.entries(res.headers).flat().length,
         );
 
-        if (this._req.cancelHandleRid !== null) {
-          core.tryClose(this._req.cancelHandleRid);
-        }
-
         if (incoming.upgrade) {
           if (this.listenerCount("upgrade") === 0) {
             // No listeners, so we got nothing to do

tests/unit/serve_test.ts

@@ -11,6 +11,7 @@ import {
   curlRequest,
   curlRequestWithStdErr,
   execCode,
+  execCode3,
   fail,
   tmpUnixSocketPath,
 } from "./test_util.ts";
@@ -3985,3 +3986,59 @@ Deno.test(
     assert(respText === "Internal Server Error");
   },
 );
+
+Deno.test(
+  {
+    permissions: { net: true, run: true, read: true },
+    ignore: Deno.build.os !== "linux",
+  },
+  async function gzipFlushResponseStream() {
+    const { promise, resolve } = Promise.withResolvers<void>();
+    const ac = new AbortController();
+
+    console.log("Starting server", servePort);
+    let timer: number | undefined = undefined;
+    let _controller;
+
+    const server = Deno.serve(
+      {
+        port: servePort,
+        onListen: onListen(resolve),
+        signal: ac.signal,
+      },
+      () => {
+        const body = new ReadableStream({
+          start(controller) {
+            timer = setInterval(() => {
+              const message = `It is ${new Date().toISOString()}\n`;
+              controller.enqueue(new TextEncoder().encode(message));
+            }, 1000);
+            _controller = controller;
+          },
+          cancel() {
+            if (timer !== undefined) {
+              clearInterval(timer);
+            }
+          },
+        });
+        return new Response(body, {
+          headers: {
+            "content-type": "text/plain",
+            "x-content-type-options": "nosniff",
+          },
+        });
+      },
+    );
+    await promise;
+    const e = await execCode3("/usr/bin/sh", [
+      "-c",
+      `curl --stderr - -N --compressed --no-progress-meter http://localhost:${servePort}`,
+    ]);
+    await e.waitStdoutText("It is ");
+    clearTimeout(timer);
+    _controller!.close();
+    await e.finished();
+    ac.abort();
+    await server.finished;
+  },
+);

tests/unit/test_util.ts

@@ -35,14 +35,9 @@ export function execCode(code: string): Promise<readonly [number, string]> {
   return execCode2(code).finished();
 }
 
-export function execCode2(code: string) {
-  const command = new Deno.Command(Deno.execPath(), {
-    args: [
-      "eval",
-      "--unstable",
-      "--no-check",
-      code,
-    ],
+export function execCode3(cmd: string, args: string[]) {
+  const command = new Deno.Command(cmd, {
+    args,
     stdout: "piped",
     stderr: "inherit",
   });
@@ -82,6 +77,10 @@ export function execCode2(code: string) {
   };
 }
 
+export function execCode2(code: string) {
+  return execCode3(Deno.execPath(), ["eval", "--unstable", "--no-check", code]);
+}
+
 export function tmpUnixSocketPath(): string {
   const folder = Deno.makeTempDirSync();
   return join(folder, "socket");