From 1f54ee08c67151303f17b5adcd1d3708df2d0fe1 Mon Sep 17 00:00:00 2001
From: Damien Arrachequesne <damien.arrachequesne@gmail.com>
Date: Wed, 18 Sep 2024 12:26:22 +0200
Subject: [PATCH] refactor(sio): simplify middleware execution

---
 packages/socket.io/lib/namespace.ts        | 12 ++++++------
 packages/socket.io/lib/parent-namespace.ts |  2 +-
 packages/socket.io/lib/socket.ts           |  9 +++++----
 3 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/packages/socket.io/lib/namespace.ts b/packages/socket.io/lib/namespace.ts
index 023b1f7f6a..27c71b22a8 100644
--- a/packages/socket.io/lib/namespace.ts
+++ b/packages/socket.io/lib/namespace.ts
@@ -150,8 +150,7 @@ export class Namespace<
     SocketData
   >;
 
-  /** @private */
-  _fns: Array<
+  protected _fns: Array<
     (
       socket: Socket<ListenEvents, EmitEvents, ServerSideEvents, SocketData>,
       next: (err?: ExtendedError) => void,
@@ -221,18 +220,19 @@ export class Namespace<
    */
   private run(
     socket: Socket<ListenEvents, EmitEvents, ServerSideEvents, SocketData>,
-    fn: (err: ExtendedError | null) => void,
+    fn: (err?: ExtendedError) => void,
   ) {
+    if (!this._fns) return fn();
+
     const fns = this._fns.slice(0);
-    if (!fns.length) return fn(null);
 
     function run(i: number) {
-      fns[i](socket, function (err) {
+      fns[i](socket, (err) => {
         // upon error, short-circuit
         if (err) return fn(err);
 
         // if no middleware left, summon callback
-        if (!fns[i + 1]) return fn(null);
+        if (!fns[i + 1]) return fn();
 
         // go on to next
         run(i + 1);
diff --git a/packages/socket.io/lib/parent-namespace.ts b/packages/socket.io/lib/parent-namespace.ts
index 9df17da279..6139b8e969 100644
--- a/packages/socket.io/lib/parent-namespace.ts
+++ b/packages/socket.io/lib/parent-namespace.ts
@@ -67,7 +67,7 @@ export class ParentNamespace<
   ): Namespace<ListenEvents, EmitEvents, ServerSideEvents, SocketData> {
     debug("creating child namespace %s", name);
     const namespace = new Namespace(this.server, name);
-    namespace._fns = this._fns.slice(0);
+    this._fns.forEach((fn) => namespace.use(fn));
     this.listeners("connect").forEach((listener) =>
       namespace.on("connect", listener),
     );
diff --git a/packages/socket.io/lib/socket.ts b/packages/socket.io/lib/socket.ts
index 0adc9fea79..bc31441382 100644
--- a/packages/socket.io/lib/socket.ts
+++ b/packages/socket.io/lib/socket.ts
@@ -961,17 +961,18 @@ export class Socket<
    * @param {Function} fn - last fn call in the middleware
    * @private
    */
-  private run(event: Event, fn: (err: Error | null) => void): void {
+  private run(event: Event, fn: (err?: Error) => void): void {
+    if (!this.fns.length) return fn();
+
     const fns = this.fns.slice(0);
-    if (!fns.length) return fn(null);
 
     function run(i: number) {
-      fns[i](event, function (err) {
+      fns[i](event, (err) => {
         // upon error, short-circuit
         if (err) return fn(err);
 
         // if no middleware left, summon callback
-        if (!fns[i + 1]) return fn(null);
+        if (!fns[i + 1]) return fn();
 
         // go on to next
         run(i + 1);