From ce1d668929a91da2dc204f6bcc53afd5173c0a33 Mon Sep 17 00:00:00 2001
From: Yoshiya Hinosawa <stibium121@gmail.com>
Date: Sun, 8 Sep 2024 12:22:18 +0900
Subject: [PATCH] fix(ext/node): delay accept() call 2 ticks in
 net.Server#listen (#25481)

A workaround for the issue #25480

`Deno.Listener` can't be closed synchronously after `accept()` is
called. This PR delays the `accept` call 2 ticks (The listener callback
is called 1 tick later. So the 1 tick delay is not enough), and makes
`net.Server` capable of being closed synchronously.

This unblocks `npm:detect-port` and `npm:portfinder`

closes #18301
closes #25175
---
 .../polyfills/internal_binding/tcp_wrap.ts    | 10 +++++++++-
 tests/unit_node/net_test.ts                   | 19 +++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/ext/node/polyfills/internal_binding/tcp_wrap.ts b/ext/node/polyfills/internal_binding/tcp_wrap.ts
index 9897bccd06d3da..4b57a7e1ecdf24 100644
--- a/ext/node/polyfills/internal_binding/tcp_wrap.ts
+++ b/ext/node/polyfills/internal_binding/tcp_wrap.ts
@@ -45,6 +45,7 @@ import {
   INITIAL_ACCEPT_BACKOFF_DELAY,
   MAX_ACCEPT_BACKOFF_DELAY,
 } from "ext:deno_node/internal_binding/_listen.ts";
+import { nextTick } from "ext:deno_node/_next_tick.ts";
 
 /** The type of TCP socket. */
 enum socketType {
@@ -228,7 +229,14 @@ export class TCP extends ConnectionWrap {
     this.#port = address.port;
 
     this.#listener = listener;
-    this.#accept();
+
+    // TODO(kt3k): Delays the accept() call 2 ticks. Deno.Listener can't be closed
+    // synchronously when accept() is called. By delaying the accept() call,
+    // the user can close the server synchronously in the callback of listen().
+    // This workaround enables `npm:detect-port` to work correctly.
+    // Remove these nextTick calls when the below issue resolved:
+    // https://github.com/denoland/deno/issues/25480
+    nextTick(nextTick, () => this.#accept());
 
     return 0;
   }
diff --git a/tests/unit_node/net_test.ts b/tests/unit_node/net_test.ts
index 708d06386caf38..8196874f301111 100644
--- a/tests/unit_node/net_test.ts
+++ b/tests/unit_node/net_test.ts
@@ -228,3 +228,22 @@ Deno.test("[node/net] BlockList doesn't leak resources", () => {
   blockList.addAddress("1.1.1.1");
   assert(blockList.check("1.1.1.1"));
 });
+
+Deno.test("[node/net] net.Server can listen on the same port immediately after it's closed", async () => {
+  const serverClosed = Promise.withResolvers<void>();
+  const server = net.createServer();
+  server.on("error", (e) => {
+    console.error(e);
+  });
+  server.listen(0, () => {
+    // deno-lint-ignore no-explicit-any
+    const { port } = server.address() as any;
+    server.close();
+    server.listen(port, () => {
+      server.close(() => {
+        serverClosed.resolve();
+      });
+    });
+  });
+  await serverClosed.promise;
+});