fix(node/events): Accept only functions as listener arguments

node/_tools/config.json

@@ -10,6 +10,7 @@
       "test-assert.js",
       "test-assert-async.js",
       "test-assert-fail.js",
+      "test-event-emitter-invalid-listener.js",
       "test-event-emitter-listener-count.js"
     ]
   },

node/_tools/suites/parallel/test-event-emitter-invalid-listener.js

@@ -0,0 +1,27 @@
+// deno-fmt-ignore-file
+// deno-lint-ignore-file
+
+// Copyright Joyent and Node contributors. All rights reserved. MIT license.
+// Taken from Node 15.5.1
+// This file is automatically generated by "node/_tools/setup.ts". Do not modify this file manually
+
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const EventEmitter = require('events');
+
+const eventsMethods = ['on', 'once', 'removeListener', 'prependOnceListener'];
+
+// Verify that the listener must be a function for events methods
+for (const method of eventsMethods) {
+  assert.throws(() => {
+    const ee = new EventEmitter();
+    ee[method]('foo', null);
+  }, {
+    code: 'ERR_INVALID_ARG_TYPE',
+    name: 'TypeError',
+    message: 'The "listener" argument must be of type function. ' +
+             'Received null'
+  }, `event.${method}('foo', null) should throw the proper error`);
+}

node/events.ts

@@ -23,6 +23,7 @@
 
 import { validateIntegerRange } from "./_utils.ts";
 import { assert } from "../_util/assert.ts";
+import { ERR_INVALID_ARG_TYPE } from "./_errors.ts";
 
 // deno-lint-ignore no-explicit-any
 export type GenericFunction = (...args: any[]) => any;
@@ -76,6 +77,7 @@ export class EventEmitter {
     listener: GenericFunction | WrappedFunction,
     prepend: boolean,
   ): this {
+    this.checkListenerArgument(listener);
     this.emit("newListener", eventName, listener);
     if (this._events.has(eventName)) {
       const listeners = this._events.get(eventName) as Array<
@@ -256,6 +258,7 @@ export class EventEmitter {
     eventName: string | symbol,
     listener: GenericFunction,
   ): WrappedFunction {
+    this.checkListenerArgument(listener);
     const wrapper = function (
       this: {
         eventName: string | symbol;
@@ -348,6 +351,7 @@ export class EventEmitter {
     eventName: string | symbol,
     listener: GenericFunction,
   ): this {
+    this.checkListenerArgument(listener);
     if (this._events.has(eventName)) {
       const arr:
         | Array<GenericFunction | WrappedFunction>
@@ -556,6 +560,12 @@ export class EventEmitter {
       iterator.return();
     }
   }
+
+  private checkListenerArgument(listener: unknown): void {
+    if (typeof listener !== "function") {
+      throw new ERR_INVALID_ARG_TYPE("listener", "function", listener);
+    }
+  }
 }
 
 export default Object.assign(EventEmitter, { EventEmitter });