feat: throw upon reserved event names

These events cannot be used by the end users, because they are part of
the Socket.IO public API, so using them will now throw an error
explicitly.

Related: socketio/socket.io@f7ed81e

Author: darrachequesne

build/socket.js

@@ -12,25 +12,19 @@ const component_bind_1 = __importDefault(require("component-bind"));
 const has_binary2_1 = __importDefault(require("has-binary2"));
 const debug = require("debug")("socket.io-client:socket");
 /**
- * Internal events (blacklisted).
+ * Internal events.
  * These events can't be emitted by the user.
  *
  * @api private
  */
-const events = {
+const RESERVED_EVENTS = {
     connect: 1,
-    connect_error: 1,
-    connect_timeout: 1,
-    connecting: 1,
     disconnect: 1,
+    disconnecting: 1,
     error: 1,
-    reconnect: 1,
-    reconnect_attempt: 1,
-    reconnect_failed: 1,
-    reconnect_error: 1,
-    reconnecting: 1,
-    ping: 1,
-    pong: 1,
+    // EventEmitter reserved events: https://nodejs.org/api/events.html#events_event_newlistener
+    newListener: 1,
+    removeListener: 1,
 };
 class Socket extends component_emitter_1.default {
     /**
@@ -88,7 +82,7 @@ class Socket extends component_emitter_1.default {
             this.io.open(); // ensure open
         if ("open" === this.io.readyState)
             this.onopen();
-        this.emit("connecting");
+        super.emit("connecting");
         return this;
     }
     connect() {
@@ -99,7 +93,7 @@ class Socket extends component_emitter_1.default {
             this.io.open(); // ensure open
         if ("open" === this.io.readyState)
             this.onopen();
-        this.emit("connecting");
+        super.emit("connecting");
         return this;
     }
     /**
@@ -123,9 +117,8 @@ class Socket extends component_emitter_1.default {
      * @api public
      */
     emit(ev) {
-        if (events.hasOwnProperty(ev)) {
-            super.emit.apply(this, arguments);
-            return this;
+        if (RESERVED_EVENTS.hasOwnProperty(ev)) {
+            throw new Error('"' + ev + '" is a reserved event name');
         }
         const args = to_array_1.default(arguments);
         const packet = {
@@ -294,7 +287,7 @@ class Socket extends component_emitter_1.default {
         this.id = id;
         this.connected = true;
         this.disconnected = false;
-        this.emit("connect");
+        super.emit("connect");
         this.emitBuffered();
     }
     /**

lib/socket.ts

@@ -9,26 +9,20 @@ import { Manager } from "./manager";
 const debug = require("debug")("socket.io-client:socket");
 
 /**
- * Internal events (blacklisted).
+ * Internal events.
  * These events can't be emitted by the user.
  *
  * @api private
  */
 
-const events = {
+const RESERVED_EVENTS = {
   connect: 1,
-  connect_error: 1,
-  connect_timeout: 1,
-  connecting: 1,
   disconnect: 1,
+  disconnecting: 1,
   error: 1,
-  reconnect: 1,
-  reconnect_attempt: 1,
-  reconnect_failed: 1,
-  reconnect_error: 1,
-  reconnecting: 1,
-  ping: 1,
-  pong: 1,
+  // EventEmitter reserved events: https://nodejs.org/api/events.html#events_event_newlistener
+  newListener: 1,
+  removeListener: 1,
 };
 
 export class Socket extends Emitter {
@@ -97,7 +91,7 @@ export class Socket extends Emitter {
     this.subEvents();
     if (!this.io.reconnecting) this.io.open(); // ensure open
     if ("open" === this.io.readyState) this.onopen();
-    this.emit("connecting");
+    super.emit("connecting");
     return this;
   }
 
@@ -107,7 +101,7 @@ export class Socket extends Emitter {
     this.subEvents();
     if (!this.io.reconnecting) this.io.open(); // ensure open
     if ("open" === this.io.readyState) this.onopen();
-    this.emit("connecting");
+    super.emit("connecting");
     return this;
   }
 
@@ -133,9 +127,8 @@ export class Socket extends Emitter {
    * @api public
    */
   emit(ev) {
-    if (events.hasOwnProperty(ev)) {
-      super.emit.apply(this, arguments);
-      return this;
+    if (RESERVED_EVENTS.hasOwnProperty(ev)) {
+      throw new Error('"' + ev + '" is a reserved event name');
     }
 
     const args = toArray(arguments);
@@ -324,7 +317,7 @@ export class Socket extends Emitter {
     this.id = id;
     this.connected = true;
     this.disconnected = false;
-    this.emit("connect");
+    super.emit("connect");
     this.emitBuffered();
   }
 

test/socket.js

@@ -182,4 +182,12 @@ describe("socket", function () {
       done();
     });
   });
+
+  it("should throw on reserved event", () => {
+    const socket = io("/no", { forceNew: true });
+
+    expect(() => socket.emit("disconnecting", "goodbye")).to.throwException(
+      /"disconnecting" is a reserved event name/
+    );
+  });
 });