console: don't attach unnecessary error handlers

A noop error handler is attached to the console's stream on write. The handler is then immediately removed after the write. This commit skips adding the error handler if one already exists. PR-URL: #27691 Fixes: #27687 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de> Reviewed-By: Gus Caplan <me@gus.host> Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
nodejs · cjihrig · May 16, 2019 · May 14, 2019 · May 16, 2019 · cca375f4af235ed7e7f763b2e35532ae843a5854
commit cca375f4af235ed7e7f763b2e35532ae843a5854
diff --git a/lib/internal/console/constructor.js b/lib/internal/console/constructor.js
@@ -231,7 +231,8 @@ Console.prototype[kWriteToConsole] = function(streamSymbol, string) {
   // handle both situations.
   try {
     // Add and later remove a noop error handler to catch synchronous errors.
-    stream.once('error', noop);
+    if (stream.listenerCount('error') === 0)
+      stream.once('error', noop);
 
     stream.write(string, errorHandler);
   } catch (e) {

diff --git a/test/parallel/test-worker-console-listeners.js b/test/parallel/test-worker-console-listeners.js
@@ -0,0 +1,16 @@
+'use strict';
+const common = require('../common');
+const { Worker, isMainThread } = require('worker_threads');
+const EventEmitter = require('events');
+
+if (isMainThread) {
+  process.on('warning', common.mustNotCall('unexpected warning'));
+
+  for (let i = 0; i < EventEmitter.defaultMaxListeners; ++i) {
+    const worker = new Worker(__filename);
+
+    worker.on('exit', common.mustCall(() => {
+      console.log('a'); // This console.log() is part of the test.
+    }));
+  }
+}