[v9.x backport] PRs: 17403, 17456 and 17588

lib/domain.js

@@ -31,11 +31,6 @@ const EventEmitter = require('events');
 const errors = require('internal/errors');
 const { createHook } = require('async_hooks');
 
-// communicate with events module, but don't require that
-// module to have to load this one, since this module has
-// a few side effects.
-EventEmitter.usingDomains = true;
-
 // overwrite process.domain with a getter/setter that will allow for more
 // effective optimizations
 var _domain = [null];
@@ -387,3 +382,52 @@ Domain.prototype.bind = function(cb) {
 
   return runBound;
 };
+
+// Override EventEmitter methods to make it domain-aware.
+EventEmitter.usingDomains = true;
+
+const eventInit = EventEmitter.init;
+EventEmitter.init = function() {
+  this.domain = null;
+  if (exports.active && !(this instanceof exports.Domain)) {
+    this.domain = exports.active;
+  }
+
+  return eventInit.call(this);
+};
+
+const eventEmit = EventEmitter.prototype.emit;
+EventEmitter.prototype.emit = function emit(...args) {
+  const domain = this.domain;
+
+  const type = args[0];
+  const shouldEmitError = type === 'error' &&
+                          this.listenerCount(type) > 0;
+
+  // Just call original `emit` if current EE instance has `error`
+  // handler, there's no active domain or this is process
+  if (shouldEmitError || domain === null || domain === undefined ||
+      this === process) {
+    return Reflect.apply(eventEmit, this, args);
+  }
+
+  if (type === 'error') {
+    const er = args.length > 1 && args[1] ?
+      args[1] : new errors.Error('ERR_UNHANDLED_ERROR');
+
+    if (typeof er === 'object') {
+      er.domainEmitter = this;
+      er.domain = domain;
+      er.domainThrown = false;
+    }
+
+    domain.emit('error', er);
+    return false;
+  }
+
+  domain.enter();
+  const ret = Reflect.apply(eventEmit, this, args);
+  domain.exit();
+
+  return ret;
+};

lib/events.js

@@ -21,7 +21,6 @@
 
 'use strict';
 
-var domain;
 var spliceOne;
 
 function EventEmitter() {
@@ -32,9 +31,6 @@ module.exports = EventEmitter;
 // Backwards-compat with node 0.10.x
 EventEmitter.EventEmitter = EventEmitter;
 
-EventEmitter.usingDomains = false;
-
-EventEmitter.prototype.domain = undefined;
 EventEmitter.prototype._events = undefined;
 EventEmitter.prototype._eventsCount = 0;
 EventEmitter.prototype._maxListeners = undefined;
@@ -67,14 +63,6 @@ Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
 });
 
 EventEmitter.init = function() {
-  this.domain = null;
-  if (EventEmitter.usingDomains) {
-    // if there is an active domain, then attach to it.
-    domain = domain || require('domain');
-    if (domain.active && !(this instanceof domain.Domain)) {
-      this.domain = domain.active;
-    }
-  }
 
   if (this._events === undefined ||
       this._events === Object.getPrototypeOf(this)._events) {
@@ -115,59 +103,35 @@ EventEmitter.prototype.emit = function emit(type, ...args) {
   else if (!doError)
     return false;
 
-  const domain = this.domain;
-
   // If there is no 'error' event listener then throw.
   if (doError) {
     let er;
     if (args.length > 0)
       er = args[0];
-    if (domain !== null && domain !== undefined) {
-      if (!er) {
-        const errors = lazyErrors();
-        er = new errors.Error('ERR_UNHANDLED_ERROR');
-      }
-      if (typeof er === 'object' && er !== null) {
-        er.domainEmitter = this;
-        er.domain = domain;
-        er.domainThrown = false;
-      }
-      domain.emit('error', er);
-    } else if (er instanceof Error) {
+    if (er instanceof Error) {
       throw er; // Unhandled 'error' event
-    } else {
-      // At least give some kind of context to the user
-      const errors = lazyErrors();
-      const err = new errors.Error('ERR_UNHANDLED_ERROR', er);
-      err.context = er;
-      throw err;
     }
-    return false;
+    // At least give some kind of context to the user
+    const errors = lazyErrors();
+    const err = new errors.Error('ERR_UNHANDLED_ERROR', er);
+    err.context = er;
+    throw err;
   }
 
   const handler = events[type];
 
   if (handler === undefined)
     return false;
 
-  let needDomainExit = false;
-  if (domain !== null && domain !== undefined && this !== process) {
-    domain.enter();
-    needDomainExit = true;
-  }
-
   if (typeof handler === 'function') {
-    handler.apply(this, args);
+    Reflect.apply(handler, this, args);
   } else {
     const len = handler.length;
     const listeners = arrayClone(handler, len);
     for (var i = 0; i < len; ++i)
-      listeners[i].apply(this, args);
+      Reflect.apply(listeners[i], this, args);
   }
 
-  if (needDomainExit)
-    domain.exit();
-
   return true;
 };
 
@@ -252,7 +216,7 @@ function onceWrapper(...args) {
   if (!this.fired) {
     this.target.removeListener(this.type, this.wrapFn);
     this.fired = true;
-    this.listener.apply(this.target, args);
+    Reflect.apply(this.listener, this.target, args);
   }
 }
 

test/parallel/test-domain-ee-error-listener.js

@@ -0,0 +1,20 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const domain = require('domain').create();
+const EventEmitter = require('events');
+
+domain.on('error', common.mustNotCall());
+
+const ee = new EventEmitter();
+
+const plainObject = { justAn: 'object' };
+ee.once('error', common.mustCall((err) => {
+  assert.deepStrictEqual(err, plainObject);
+}));
+ee.emit('error', plainObject);
+
+const err = new Error('test error');
+ee.once('error', common.expectsError(err));
+ee.emit('error', err);