From 38ff4f8fd45e4f9124154e9bcfaaa9577b64c74f Mon Sep 17 00:00:00 2001
From: Sebastiaan Marynissen <sebastiaan.marynissen@gmail.com>
Date: Fri, 22 Oct 2021 19:09:00 +0200
Subject: [PATCH 1/2] fix: fix race conditions with dynamic namespaces (#4136)

---
 lib/client.ts     |  9 +++++++--
 lib/index.ts      |  7 ++++++-
 test/socket.io.ts | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/lib/client.ts b/lib/client.ts
index 268cfbd085..8dc02c1d02 100644
--- a/lib/client.ts
+++ b/lib/client.ts
@@ -113,10 +113,15 @@ export class Client<
       (
         dynamicNspName:
           | Namespace<ListenEvents, EmitEvents, ServerSideEvents>
-          | false
+          | false,
+        race: boolean = false
       ) => {
         if (dynamicNspName) {
-          debug("dynamic namespace %s was created", dynamicNspName);
+          if (race) {
+            debug("dynamic namespace %s already created", dynamicNspName);
+          } else {
+            debug("dynamic namespace %s was created", dynamicNspName);
+          }
           this.doConnect(name, auth);
         } else {
           debug("creation of namespace %s was denied", name);
diff --git a/lib/index.ts b/lib/index.ts
index 72c87ef677..d4505cc32a 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -188,7 +188,8 @@ export class Server<
     name: string,
     auth: { [key: string]: any },
     fn: (
-      nsp: Namespace<ListenEvents, EmitEvents, ServerSideEvents> | false
+      nsp: Namespace<ListenEvents, EmitEvents, ServerSideEvents> | false,
+      race?: boolean
     ) => void
   ): void {
     if (this.parentNsps.size === 0) return fn(false);
@@ -203,6 +204,10 @@ export class Server<
       nextFn.value(name, auth, (err, allow) => {
         if (err || !allow) {
           run();
+        } else if (this._nsps.has(name)) {
+          // See #4316. It's possible that in the meantime the namespace has
+          // already been created, so we'll have to handle this properly.
+          fn(this._nsps.get(name) as Namespace, true);
         } else {
           const namespace = this.parentNsps
             .get(nextFn.value)!
diff --git a/test/socket.io.ts b/test/socket.io.ts
index 4777796f89..74efb0e13a 100644
--- a/test/socket.io.ts
+++ b/test/socket.io.ts
@@ -998,6 +998,42 @@ describe("socket.io", () => {
           const socket = client(srv, "/dynamic-101");
         });
       });
+
+      it("should handle race conditions with dynamic namespaces (#4136)", (done) => {
+        const srv = createServer();
+        const sio = new Server(srv);
+        const counters = {
+          connected: 0,
+          created: 0,
+          events: 0,
+        };
+        sio.on("new_namespace", (namespace) => {
+          counters.created++;
+        });
+        srv.listen(() => {
+          const handler = () => {
+            if (++counters.events === 2) {
+              expect(counters.created).to.equal(1);
+              done();
+            }
+          };
+
+          sio
+            .of((name, query, next) => {
+              setTimeout(() => next(null, true), 50);
+            })
+            .on("connection", (socket) => {
+              if (++counters.connected === 2) {
+                sio.of("/dynamic-101").emit("message");
+              }
+            });
+
+          let one = client(srv, "/dynamic-101");
+          let two = client(srv, "/dynamic-101");
+          one.on("message", handler);
+          two.on("message", handler);
+        });
+      });
     });
   });
 

From d09de3d99549cf26713918c999c3a56a6b41983e Mon Sep 17 00:00:00 2001
From: Sebastiaan Marynissen <sebastiaan.marynissen@gmail.com>
Date: Sat, 23 Oct 2021 16:52:48 +0200
Subject: [PATCH 2/2] fix: avoid relying on `setTimeout()` in tests

---
 lib/index.ts      | 2 +-
 test/socket.io.ts | 8 +++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/index.ts b/lib/index.ts
index d4505cc32a..f38819195f 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -205,7 +205,7 @@ export class Server<
         if (err || !allow) {
           run();
         } else if (this._nsps.has(name)) {
-          // See #4316. It's possible that in the meantime the namespace has
+          // See #4136. It's possible that in the meantime the namespace has
           // already been created, so we'll have to handle this properly.
           fn(this._nsps.get(name) as Namespace, true);
         } else {
diff --git a/test/socket.io.ts b/test/socket.io.ts
index 74efb0e13a..63e7f1b830 100644
--- a/test/socket.io.ts
+++ b/test/socket.io.ts
@@ -15,6 +15,8 @@ import { io as ioc, Socket as ClientSocket } from "socket.io-client";
 import "./support/util";
 import "./utility-methods";
 
+type callback = (err: Error | null, success: boolean) => void;
+
 // Creates a socket.io client for the given server
 function client(srv, nsp?: string | object, opts?: object): ClientSocket {
   if ("object" == typeof nsp) {
@@ -1007,6 +1009,7 @@ describe("socket.io", () => {
           created: 0,
           events: 0,
         };
+        const buffer: callback[] = [];
         sio.on("new_namespace", (namespace) => {
           counters.created++;
         });
@@ -1020,7 +1023,10 @@ describe("socket.io", () => {
 
           sio
             .of((name, query, next) => {
-              setTimeout(() => next(null, true), 50);
+              buffer.push(next);
+              if (buffer.length === 2) {
+                buffer.forEach((next) => next(null, true));
+              }
             })
             .on("connection", (socket) => {
               if (++counters.connected === 2) {