From cd32f02470d44d860479f9d483829a02c4321b53 Mon Sep 17 00:00:00 2001
From: Ankit Silwal <silwalankit27@gmail.com>
Date: Sun, 25 Oct 2026 23:52:42 +0530
Subject: [PATCH] Allow socketsJoin/socketsLeave/disconnectSockets to return
 Promise
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Update the return types of addSockets, delSockets, and
disconnectSockets in the base Adapter from void to void | Promise<void>
so adapters (like the Redis adapter) can return Promises that resolve
once all remote nodes have processed the operation.

Update BroadcastOperator's socketsJoin, socketsLeave, and
disconnectSockets to propagate the adapter's return value, enabling:
  await io.in(socketId).socketsJoin(room);

This is fully backward compatible — existing code that doesn't await
continues to work unchanged, while multi-server setups with async
adapters can now await to ensure ordering guarantees.

Related: socketio/socket.io#4734

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 .../socket.io-adapter/lib/in-memory-adapter.ts   | 15 ++++++++++++---
 packages/socket.io/lib/broadcast-operator.ts     | 16 ++++++++--------
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/packages/socket.io-adapter/lib/in-memory-adapter.ts b/packages/socket.io-adapter/lib/in-memory-adapter.ts
index cf178170e0..ee2a4d1a3f 100644
--- a/packages/socket.io-adapter/lib/in-memory-adapter.ts
+++ b/packages/socket.io-adapter/lib/in-memory-adapter.ts
@@ -300,7 +300,10 @@ export class Adapter extends EventEmitter {
    * @param opts - the filters to apply
    * @param rooms - the rooms to join
    */
-  public addSockets(opts: BroadcastOptions, rooms: Room[]): void {
+  public addSockets(
+    opts: BroadcastOptions,
+    rooms: Room[],
+  ): void | Promise<void> {
     this.apply(opts, (socket) => {
       socket.join(rooms);
     });
@@ -312,7 +315,10 @@ export class Adapter extends EventEmitter {
    * @param opts - the filters to apply
    * @param rooms - the rooms to leave
    */
-  public delSockets(opts: BroadcastOptions, rooms: Room[]): void {
+  public delSockets(
+    opts: BroadcastOptions,
+    rooms: Room[],
+  ): void | Promise<void> {
     this.apply(opts, (socket) => {
       rooms.forEach((room) => socket.leave(room));
     });
@@ -324,7 +330,10 @@ export class Adapter extends EventEmitter {
    * @param opts - the filters to apply
    * @param close - whether to close the underlying connection
    */
-  public disconnectSockets(opts: BroadcastOptions, close: boolean): void {
+  public disconnectSockets(
+    opts: BroadcastOptions,
+    close: boolean,
+  ): void | Promise<void> {
     this.apply(opts, (socket) => {
       socket.disconnect(close);
     });
diff --git a/packages/socket.io/lib/broadcast-operator.ts b/packages/socket.io/lib/broadcast-operator.ts
index ca7eccf2f4..ee32bb1ca6 100644
--- a/packages/socket.io/lib/broadcast-operator.ts
+++ b/packages/socket.io/lib/broadcast-operator.ts
@@ -413,8 +413,8 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
    *
    * @param room - a room, or an array of rooms
    */
-  public socketsJoin(room: Room | Room[]): void {
-    this.adapter.addSockets(
+  public socketsJoin(room: Room | Room[]): void | Promise<void> {
+    return this.adapter.addSockets(
       {
         rooms: this.rooms,
         except: this.exceptRooms,
@@ -438,8 +438,8 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
    *
    * @param room - a room, or an array of rooms
    */
-  public socketsLeave(room: Room | Room[]): void {
-    this.adapter.delSockets(
+  public socketsLeave(room: Room | Room[]): void | Promise<void> {
+    return this.adapter.delSockets(
       {
         rooms: this.rooms,
         except: this.exceptRooms,
@@ -463,8 +463,8 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
    *
    * @param close - whether to close the underlying connection
    */
-  public disconnectSockets(close: boolean = false): void {
-    this.adapter.disconnectSockets(
+  public disconnectSockets(close: boolean = false): void | Promise<void> {
+    return this.adapter.disconnectSockets(
       {
         rooms: this.rooms,
         except: this.exceptRooms,
@@ -554,7 +554,7 @@ export class RemoteSocket<EmitEvents extends EventsMap, SocketData>
    *
    * @param {String|Array} room - room or array of rooms
    */
-  public join(room: Room | Room[]): void {
+  public join(room: Room | Room[]): void | Promise<void> {
     return this.operator.socketsJoin(room);
   }
 
@@ -563,7 +563,7 @@ export class RemoteSocket<EmitEvents extends EventsMap, SocketData>
    *
    * @param {String} room
    */
-  public leave(room: Room): void {
+  public leave(room: Room): void | Promise<void> {
     return this.operator.socketsLeave(room);
   }