events: migrate to internal/errors

PR-URL: nodejs/node#15623
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/errors.md

@@ -1251,6 +1251,12 @@ buffer.
 
 Used when a string that contains unescaped characters was received.
 
+<a id="ERR_UNHANDLED_ERROR"></a>
+### ERR_UNHANDLED_ERROR
+
+Used when an unhandled "error" occurs (for instance, when an `'error'` event
+is emitted by an `EventEmitter` but an `'error'` handler is not registered).
+
 <a id="ERR_UNKNOWN_ENCODING"></a>
 ### ERR_UNKNOWN_ENCODING
 

lib/events.js

@@ -41,6 +41,13 @@ EventEmitter.prototype._maxListeners = undefined;
 // added to it. This is a useful default which helps finding memory leaks.
 var defaultMaxListeners = 10;
 
+var errors;
+function lazyErrors() {
+  if (errors === undefined)
+    errors = require('internal/errors');
+  return errors;
+}
+
 Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
   enumerable: true,
   get: function() {
@@ -52,8 +59,10 @@ Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
     console;
     // check whether the input is a positive number (whose value is zero or
     // greater and not a NaN).
-    if (typeof arg !== 'number' || arg < 0 || arg !== arg)
-      throw new TypeError('"defaultMaxListeners" must be a positive number');
+    if (typeof arg !== 'number' || arg < 0 || arg !== arg) {
+      const errors = lazyErrors();
+      throw new errors.TypeError('ERR_OUT_OF_RANGE', 'defaultMaxListeners');
+    }
     defaultMaxListeners = arg;
   }
 });
@@ -79,8 +88,10 @@ EventEmitter.init = function() {
 // Obviously not all Emitters should be limited to 10. This function allows
 // that to be increased. Set to zero for unlimited.
 EventEmitter.prototype.setMaxListeners = function setMaxListeners(n) {
-  if (typeof n !== 'number' || n < 0 || isNaN(n))
-    throw new TypeError('"n" argument must be a positive number');
+  if (typeof n !== 'number' || n < 0 || isNaN(n)) {
+    const errors = lazyErrors();
+    throw new errors.TypeError('ERR_OUT_OF_RANGE', 'n');
+  }
   this._maxListeners = n;
   return this;
 };
@@ -170,8 +181,10 @@ EventEmitter.prototype.emit = function emit(type) {
     if (arguments.length > 1)
       er = arguments[1];
     if (domain) {
-      if (!er)
-        er = new Error('Unhandled "error" event');
+      if (!er) {
+        const errors = lazyErrors();
+        er = new errors.Error('ERR_UNHANDLED_ERROR');
+      }
       if (typeof er === 'object' && er !== null) {
         er.domainEmitter = this;
         er.domain = domain;
@@ -182,7 +195,8 @@ EventEmitter.prototype.emit = function emit(type) {
       throw er; // Unhandled 'error' event
     } else {
       // At least give some kind of context to the user
-      const err = new Error('Unhandled "error" event. (' + er + ')');
+      const errors = lazyErrors();
+      const err = new errors.Error('ERR_UNHANDLED_ERROR', er);
       err.context = er;
       throw err;
     }
@@ -234,8 +248,10 @@ function _addListener(target, type, listener, prepend) {
   var events;
   var existing;
 
-  if (typeof listener !== 'function')
-    throw new TypeError('"listener" argument must be a function');
+  if (typeof listener !== 'function') {
+    const errors = lazyErrors();
+    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'listener', 'function');
+  }
 
   events = target._events;
   if (!events) {
@@ -278,6 +294,7 @@ function _addListener(target, type, listener, prepend) {
       m = $getMaxListeners(target);
       if (m && m > 0 && existing.length > m) {
         existing.warned = true;
+        // No error code for this since it is a Warning
         const w = new Error('Possible EventEmitter memory leak detected. ' +
                             `${existing.length} ${String(type)} listeners ` +
                             'added. Use emitter.setMaxListeners() to ' +
@@ -337,16 +354,21 @@ function _onceWrap(target, type, listener) {
 }
 
 EventEmitter.prototype.once = function once(type, listener) {
-  if (typeof listener !== 'function')
-    throw new TypeError('"listener" argument must be a function');
+  if (typeof listener !== 'function') {
+    const errors = lazyErrors();
+    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'listener', 'function');
+  }
   this.on(type, _onceWrap(this, type, listener));
   return this;
 };
 
 EventEmitter.prototype.prependOnceListener =
     function prependOnceListener(type, listener) {
-      if (typeof listener !== 'function')
-        throw new TypeError('"listener" argument must be a function');
+      if (typeof listener !== 'function') {
+        const errors = lazyErrors();
+        throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'listener',
+                                   'function');
+      }
       this.prependListener(type, _onceWrap(this, type, listener));
       return this;
     };
@@ -356,8 +378,11 @@ EventEmitter.prototype.removeListener =
     function removeListener(type, listener) {
       var list, events, position, i, originalListener;
 
-      if (typeof listener !== 'function')
-        throw new TypeError('"listener" argument must be a function');
+      if (typeof listener !== 'function') {
+        const errors = lazyErrors();
+        throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'listener',
+                                   'function');
+      }
 
       events = this._events;
       if (!events)

lib/internal/errors.js

@@ -327,6 +327,12 @@ E('ERR_TRANSFORM_WITH_LENGTH_0',
   'Calling transform done when writableState.length != 0');
 E('ERR_UNESCAPED_CHARACTERS',
   (name) => `${name} contains unescaped characters`);
+E('ERR_UNHANDLED_ERROR',
+  (err) => {
+    const msg = 'Unhandled error.';
+    if (err === undefined) return msg;
+    return `${msg} (${err})`;
+  });
 E('ERR_UNKNOWN_ENCODING', 'Unknown encoding: %s');
 E('ERR_UNKNOWN_FILE_EXTENSION', 'Unknown file extension: %s');
 E('ERR_UNKNOWN_MODULE_FORMAT', 'Unknown module format: %s');

test/parallel/test-event-emitter-add-listeners.js

@@ -86,8 +86,11 @@ const EventEmitter = require('events');
 }
 
 // Verify that the listener must be a function
-assert.throws(() => {
+common.expectsError(() => {
   const ee = new EventEmitter();
-
   ee.on('foo', null);
-}, /^TypeError: "listener" argument must be a function$/);
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+  type: TypeError,
+  message: 'The "listener" argument must be of type function'
+});

test/parallel/test-event-emitter-errors.js

@@ -1,14 +1,23 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const EventEmitter = require('events');
-const assert = require('assert');
 
 const EE = new EventEmitter();
 
-assert.throws(() => {
-  EE.emit('error', 'Accepts a string');
-}, /^Error: Unhandled "error" event\. \(Accepts a string\)$/);
+common.expectsError(
+  () => EE.emit('error', 'Accepts a string'),
+  {
+    code: 'ERR_UNHANDLED_ERROR',
+    type: Error,
+    message: 'Unhandled error. (Accepts a string)'
+  }
+);
 
-assert.throws(() => {
-  EE.emit('error', { message: 'Error!' });
-}, /^Error: Unhandled "error" event\. \(\[object Object\]\)$/);
+common.expectsError(
+  () => EE.emit('error', { message: 'Error!' }),
+  {
+    code: 'ERR_UNHANDLED_ERROR',
+    type: Error,
+    message: 'Unhandled error. ([object Object])'
+  }
+);

test/parallel/test-event-emitter-max-listeners.js

@@ -21,7 +21,6 @@
 
 'use strict';
 const common = require('../common');
-const assert = require('assert');
 const events = require('events');
 const e = new events.EventEmitter();
 
@@ -31,12 +30,25 @@ e.on('maxListeners', common.mustCall());
 e.setMaxListeners(42);
 
 const throwsObjs = [NaN, -1, 'and even this'];
-const maxError = /^TypeError: "n" argument must be a positive number$/;
-const defError = /^TypeError: "defaultMaxListeners" must be a positive number$/;
 
 for (const obj of throwsObjs) {
-  assert.throws(() => e.setMaxListeners(obj), maxError);
-  assert.throws(() => events.defaultMaxListeners = obj, defError);
+  common.expectsError(
+    () => e.setMaxListeners(obj),
+    {
+      code: 'ERR_OUT_OF_RANGE',
+      type: TypeError,
+      message: 'The "n" argument is out of range'
+    }
+  );
+
+  common.expectsError(
+    () => events.defaultMaxListeners = obj,
+    {
+      code: 'ERR_OUT_OF_RANGE',
+      type: TypeError,
+      message: 'The "defaultMaxListeners" argument is out of range'
+    }
+  );
 }
 
 e.emit('maxListeners');

test/parallel/test-event-emitter-once.js

@@ -50,11 +50,15 @@ e.once('e', common.mustCall());
 e.emit('e');
 
 // Verify that the listener must be a function
-assert.throws(() => {
+common.expectsError(() => {
   const ee = new EventEmitter();
 
   ee.once('foo', null);
-}, /^TypeError: "listener" argument must be a function$/);
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+  type: TypeError,
+  message: 'The "listener" argument must be of type function'
+});
 
 {
   // once() has different code paths based on the number of arguments being

test/parallel/test-event-emitter-prepend.js

@@ -19,11 +19,15 @@ myEE.prependOnceListener('foo',
 myEE.emit('foo');
 
 // Verify that the listener must be a function
-assert.throws(() => {
+common.expectsError(() => {
   const ee = new EventEmitter();
 
   ee.prependOnceListener('foo', null);
-}, /^TypeError: "listener" argument must be a function$/);
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+  type: TypeError,
+  message: 'The "listener" argument must be of type function'
+});
 
 // Test fallback if prependListener is undefined.
 const stream = require('stream');

test/parallel/test-event-emitter-remove-listeners.js

@@ -144,11 +144,15 @@ function listener2() {}
 }
 
 // Verify that the removed listener must be a function
-assert.throws(() => {
+common.expectsError(() => {
   const ee = new EventEmitter();
 
   ee.removeListener('foo', null);
-}, /^TypeError: "listener" argument must be a function$/);
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+  type: TypeError,
+  message: 'The "listener" argument must be of type function'
+});
 
 {
   const ee = new EventEmitter();