events: onceWrapper returns target value

PR-URL: #25818
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/events.js

@@ -274,7 +274,7 @@ function onceWrapper(...args) {
   if (!this.fired) {
     this.target.removeListener(this.type, this.wrapFn);
     this.fired = true;
-    Reflect.apply(this.listener, this.target, args);
+    return Reflect.apply(this.listener, this.target, args);
   }
 }
 

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

@@ -27,6 +27,12 @@ const events = require('events');
 
 function listener() {}
 function listener2() {}
+function listener3() {
+  return 0;
+}
+function listener4() {
+  return 1;
+}
 
 {
   const ee = new events.EventEmitter();
@@ -101,3 +107,15 @@ function listener2() {}
   assert.strictEqual(wrappedListeners.length, 2);
   assert.strictEqual(wrappedListeners[1].listener, listener);
 }
+
+{
+  const ee = new events.EventEmitter();
+  ee.once('foo', listener3);
+  ee.on('foo', listener4);
+  const rawListeners = ee.rawListeners('foo');
+  assert.strictEqual(rawListeners.length, 2);
+  assert.strictEqual(rawListeners[0](), 0);
+  const rawListener = ee.rawListeners('foo');
+  assert.strictEqual(rawListener.length, 1);
+  assert.strictEqual(rawListener[0](), 1);
+}