feat: add support for catch-all listeners

Inspired from EventEmitter2 [1]

```js
io.on("connect", socket => {

  socket.onAny((event, ...args) => {});

  socket.prependAny((event, ...args) => {});

  socket.offAny(); // remove all listeners

  socket.offAny(listener);

  const listeners = socket.listenersAny();
});
```

Breaking change: the socket.use() method is removed

This method was introduced in [2] for the same feature (having a
catch-all listener), but there were two issues:

- the API is not very user-friendly, since the user has to know the structure of the packet argument
- it uses an ERROR packet, which is reserved for Namespace authentication issues (see [3])

[1]: https://github.com/EventEmitter2/EventEmitter2
[2]: #434
[3]: https://github.com/socketio/socket.io-protocol

lib/socket.ts

@@ -86,6 +86,7 @@ export class Socket extends EventEmitter {
   > = [];
   private flags: BroadcastFlags = {};
   private _rooms: Set<Room> = new Set();
+  private _anyListeners: Array<(...args: any[]) => void>;
 
   /**
    * Interface to a `Client` for a given `Namespace`.
@@ -335,7 +336,13 @@ export class Socket extends EventEmitter {
       args.push(this.ack(packet.id));
     }
 
-    this.dispatch(args);
+    if (this._anyListeners && this._anyListeners.length) {
+      const listeners = this._anyListeners.slice();
+      for (const listener of listeners) {
+        listener.apply(this, args);
+      }
+    }
+    super.emit.apply(this, args);
   }
 
   /**
@@ -502,86 +509,87 @@ export class Socket extends EventEmitter {
   }
 
   /**
-   * Dispatch incoming event to socket listeners.
+   * A reference to the request that originated the underlying Engine.IO Socket.
    *
-   * @param {Array} event - event that will get emitted
-   * @private
+   * @public
    */
-  private dispatch(event: Array<string>): void {
-    debug("dispatching an event %j", event);
-    this.run(event, err => {
-      process.nextTick(() => {
-        if (err) {
-          return this._error(err.message);
-        }
-        super.emit.apply(this, event);
-      });
-    });
+  public get request(): IncomingMessage {
+    return this.client.request;
   }
 
   /**
-   * Sets up socket middleware.
+   * A reference to the underlying Client transport connection (Engine.IO Socket object).
    *
-   * @param {Function} fn - middleware function (event, next)
-   * @return {Socket} self
    * @public
    */
-  public use(
-    fn: (event: Array<any>, next: (err: Error) => void) => void
-  ): Socket {
-    this.fns.push(fn);
-    return this;
+  public get conn() {
+    return this.client.conn;
   }
 
   /**
-   * Executes the middleware for an incoming event.
-   *
-   * @param {Array} event - event that will get emitted
-   * @param {Function} fn - last fn call in the middleware
-   * @private
+   * @public
    */
-  private run(event: Array<any>, fn: (err: Error) => void) {
-    const fns = this.fns.slice(0);
-    if (!fns.length) return fn(null);
-
-    function run(i) {
-      fns[i](event, function(err) {
-        // upon error, short-circuit
-        if (err) return fn(err);
-
-        // if no middleware left, summon callback
-        if (!fns[i + 1]) return fn(null);
-
-        // go on to next
-        run(i + 1);
-      });
-    }
+  public get rooms(): Set<Room> {
+    return this.adapter.socketRooms(this.id) || new Set();
+  }
 
-    run(0);
+  /**
+   * Adds a listener that will be fired when any event is emitted. The event name is passed as the first argument to the
+   * callback.
+   *
+   * @param listener
+   * @public
+   */
+  public onAny(listener: (...args: any[]) => void): Socket {
+    this._anyListeners = this._anyListeners || [];
+    this._anyListeners.push(listener);
+    return this;
   }
 
   /**
-   * A reference to the request that originated the underlying Engine.IO Socket.
+   * Adds a listener that will be fired when any event is emitted. The event name is passed as the first argument to the
+   * callback. The listener is added to the beginning of the listeners array.
    *
+   * @param listener
    * @public
    */
-  public get request(): IncomingMessage {
-    return this.client.request;
+  public prependAny(listener: (...args: any[]) => void): Socket {
+    this._anyListeners = this._anyListeners || [];
+    this._anyListeners.unshift(listener);
+    return this;
   }
 
   /**
-   * A reference to the underlying Client transport connection (Engine.IO Socket object).
+   * Removes the listener that will be fired when any event is emitted.
    *
+   * @param listener
    * @public
    */
-  public get conn() {
-    return this.client.conn;
+  public offAny(listener?: (...args: any[]) => void): Socket {
+    if (!this._anyListeners) {
+      return this;
+    }
+    if (listener) {
+      const listeners = this._anyListeners;
+      for (let i = 0; i < listeners.length; i++) {
+        if (listener === listeners[i]) {
+          listeners.splice(i, 1);
+          return this;
+        }
+      }
+    } else {
+      this._anyListeners = [];
+    }
+    return this;
   }
 
   /**
+   * Returns an array of listeners that are listening for any event that is specified. This array can be manipulated,
+   * e.g. to remove listeners.
+   *
    * @public
    */
-  public get rooms(): Set<Room> {
-    return this.adapter.socketRooms(this.id) || new Set();
+  public listenersAny() {
+    return this._anyListeners || [];
   }
 }

test/socket.io.ts

@@ -1719,6 +1719,78 @@ describe("socket.io", () => {
         });
       });
     });
+
+    describe("onAny", () => {
+      it("should call listener", done => {
+        const srv = createServer();
+        const sio = new Server(srv);
+
+        srv.listen(() => {
+          const socket = client(srv, { multiplex: false });
+
+          socket.emit("my-event", "123");
+
+          sio.on("connection", (socket: Socket) => {
+            socket.onAny((event, arg1) => {
+              expect(event).to.be("my-event");
+              expect(arg1).to.be("123");
+              done();
+            });
+          });
+        });
+      });
+
+      it("should prepend listener", done => {
+        const srv = createServer();
+        const sio = new Server(srv);
+
+        srv.listen(() => {
+          const socket = client(srv, { multiplex: false });
+
+          socket.emit("my-event", "123");
+
+          sio.on("connection", (socket: Socket) => {
+            let count = 0;
+
+            socket.onAny((event, arg1) => {
+              expect(count).to.be(2);
+              done();
+            });
+
+            socket.prependAny(() => {
+              expect(count++).to.be(1);
+            });
+
+            socket.prependAny(() => {
+              expect(count++).to.be(0);
+            });
+          });
+        });
+      });
+
+      it("should remove listener", done => {
+        const srv = createServer();
+        const sio = new Server(srv);
+
+        srv.listen(() => {
+          const socket = client(srv, { multiplex: false });
+
+          socket.emit("my-event", "123");
+
+          sio.on("connection", (socket: Socket) => {
+            const fail = () => done(new Error("fail"));
+
+            socket.onAny(fail);
+            socket.offAny(fail);
+            expect(socket.listenersAny.length).to.be(0);
+
+            socket.onAny(() => {
+              done();
+            });
+          });
+        });
+      });
+    });
   });
 
   describe("messaging many", () => {
@@ -2226,69 +2298,4 @@ describe("socket.io", () => {
       });
     });
   });
-
-  describe("socket middleware", () => {
-    const { Socket } = require("../dist/socket");
-
-    it("should call functions", done => {
-      const srv = createServer();
-      const sio = new Server(srv);
-      let run = 0;
-
-      srv.listen(() => {
-        const socket = client(srv, { multiplex: false });
-
-        socket.emit("join", "woot");
-
-        sio.on("connection", socket => {
-          socket.use((event, next) => {
-            expect(event).to.eql(["join", "woot"]);
-            event.unshift("wrap");
-            run++;
-            next();
-          });
-          socket.use((event, next) => {
-            expect(event).to.eql(["wrap", "join", "woot"]);
-            run++;
-            next();
-          });
-          socket.on("wrap", (data1, data2) => {
-            expect(data1).to.be("join");
-            expect(data2).to.be("woot");
-            expect(run).to.be(2);
-            done();
-          });
-        });
-      });
-    });
-
-    it("should pass errors", done => {
-      const srv = createServer();
-      const sio = new Server(srv);
-
-      srv.listen(() => {
-        const clientSocket = client(srv, { multiplex: false });
-
-        clientSocket.emit("join", "woot");
-
-        clientSocket.on("error", err => {
-          expect(err).to.be("Authentication error");
-          done();
-        });
-
-        sio.on("connection", socket => {
-          socket.use((event, next) => {
-            next(new Error("Authentication error"));
-          });
-          socket.use((event, next) => {
-            done(new Error("nope"));
-          });
-
-          socket.on("join", () => {
-            done(new Error("nope"));
-          });
-        });
-      });
-    });
-  });
 });