From 8c080de19ed81278e95ecbe71466e256bb7f5bce Mon Sep 17 00:00:00 2001
From: Sebastiaan Marynissen <sebastiaan.marynissen@gmail.com>
Date: Tue, 2 Feb 2021 11:58:48 +0100
Subject: [PATCH] Exclude specific sockets when emitting

---
 lib/namespace.ts  | 18 ++++++++++++++
 lib/socket.ts     | 17 ++++++++++++-
 test/socket.io.ts | 63 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 97 insertions(+), 1 deletion(-)

diff --git a/lib/namespace.ts b/lib/namespace.ts
index 96b64d2aa7..4aa5abe646 100644
--- a/lib/namespace.ts
+++ b/lib/namespace.ts
@@ -29,6 +29,9 @@ export class Namespace extends EventEmitter {
   /** @private */
   _rooms: Set<Room> = new Set();
 
+  /** @private */
+  _except: Set<Room> = new Set();
+
   /** @private */
   _flags: any = {};
 
@@ -123,6 +126,18 @@ export class Namespace extends EventEmitter {
     return this;
   }
 
+  /**
+   * Excludes a room when emitting.
+   *
+   * @param name
+   * @return self
+   * @public
+   */
+  public except(name: Room): Namespace {
+    this._except.add(name);
+    return this;
+  }
+
   /**
    * Adds a new client.
    *
@@ -203,14 +218,17 @@ export class Namespace extends EventEmitter {
 
     const rooms = new Set(this._rooms);
     const flags = Object.assign({}, this._flags);
+    const except = new Set(this._except);
 
     // reset flags
     this._rooms.clear();
     this._flags = {};
+    this._except.clear();
 
     this.adapter.broadcast(packet, {
       rooms: rooms,
       flags: flags,
+      except: except,
     });
 
     return true;
diff --git a/lib/socket.ts b/lib/socket.ts
index 6662271bad..4719581f13 100644
--- a/lib/socket.ts
+++ b/lib/socket.ts
@@ -91,6 +91,7 @@ export class Socket extends EventEmitter {
   > = [];
   private flags: BroadcastFlags = {};
   private _rooms: Set<Room> = new Set();
+  private _except: Set<Room> = new Set();
   private _anyListeners?: Array<(...args: any[]) => void>;
 
   /**
@@ -165,14 +166,16 @@ export class Socket extends EventEmitter {
 
     const rooms = new Set(this._rooms);
     const flags = Object.assign({}, this.flags);
+    const except = new Set(this._except);
 
     // reset flags
     this._rooms.clear();
     this.flags = {};
+    this._except.clear();
 
     if (rooms.size || flags.broadcast) {
       this.adapter.broadcast(packet, {
-        except: new Set([this.id]),
+        except: new Set([this.id, ...except]),
         rooms: rooms,
         flags: flags,
       });
@@ -207,6 +210,18 @@ export class Socket extends EventEmitter {
     return this;
   }
 
+  /**
+   * Excludes a room when broadcasting.
+   *
+   * @param name
+   * @return self
+   * @public
+   */
+  public except(name: Room): Socket {
+    this._except.add(name);
+    return this;
+  }
+
   /**
    * Sends a `message` event.
    *
diff --git a/test/socket.io.ts b/test/socket.io.ts
index 15cb4f3b0c..8dae7ec45a 100644
--- a/test/socket.io.ts
+++ b/test/socket.io.ts
@@ -823,6 +823,35 @@ describe("socket.io", () => {
       });
     });
 
+    it("should exclude a specific socket when emitting", (done) => {
+      const srv = createServer();
+      const sio = new Server(srv);
+
+      const nsp = sio.of("/nsp");
+
+      srv.listen(() => {
+        const socket1 = client(srv, "/nsp");
+        const socket2 = client(srv, "/nsp");
+
+        socket2.on("a", () => {
+          done(new Error("not"));
+        });
+        socket1.on("a", () => {
+          done();
+        });
+
+        nsp.on("connection", (socket) => {
+          socket.on("id", (cb) => {
+            cb(socket.id);
+          });
+        });
+
+        socket2.emit("id", (id) => {
+          nsp.except(id).emit("a");
+        });
+      });
+    });
+
     describe("dynamic namespaces", () => {
       it("should allow connections to dynamic namespaces with a regex", (done) => {
         const srv = createServer();
@@ -2195,6 +2224,40 @@ describe("socket.io", () => {
         });
       });
     });
+
+    it("should exclude specific sockets when broadcasting", (done) => {
+      const srv = createServer();
+      const sio = new Server(srv);
+
+      srv.listen(() => {
+        const socket1 = client(srv, { multiplex: false });
+        const socket2 = client(srv, { multiplex: false });
+        const socket3 = client(srv, { multiplex: false });
+
+        socket2.on("a", () => {
+          done(new Error("not"));
+        });
+        socket3.on("a", () => {
+          done(new Error("not"));
+        });
+        socket1.on("a", () => {
+          done();
+        });
+
+        sio.on("connection", (socket) => {
+          socket.on("id", (cb) => {
+            cb(socket.id);
+          });
+          socket.on("exclude", (id) => {
+            socket.broadcast.except(id).emit("a");
+          });
+        });
+
+        socket2.emit("id", (id) => {
+          socket3.emit("exclude", id);
+        });
+      });
+    });
   });
 
   describe("middleware", () => {