console: avoid adding infinite error listeners

mcollina · gibfahn · commit 9df1e8f10e6a · 2017-11-08T15:41:55.000Z
If the console destination is a unix pipe (net.Socket), write() is async. If the destination is broken, we are adding an 'error' event listener to avoid a process crash. This PR makes sure that we are adding that listener only once. Fixes: #16767 PR-URL: #16770 Fixes: #16767 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Anatoli Papirovski <apapirovski@mac.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
diff --git a/lib/console.js b/lib/console.js
@@ -82,7 +82,10 @@ function createWriteErrorHandler(stream) {
       // an `error` event. Adding a `once` listener will keep that error
       // from becoming an uncaught exception, but since the handler is
       // removed after the event, non-console.* writes won&rsquo;t be affected.
-      stream.once('error', noop);
+      // we are only adding noop if there is no one else listening for 'error'
+      if (stream.listenerCount('error') === 0) {
+        stream.on('error', noop);
+      }
     }
   };
 }
diff --git a/test/parallel/test-console-log-stdio-broken-dest.js b/test/parallel/test-console-log-stdio-broken-dest.js
@@ -0,0 +1,24 @@
+'use strict';
+
+const common = require('../common');
+const { Writable } = require('stream');
+const { Console } = require('console');
+const { EventEmitter } = require('events');
+
+const stream = new Writable({
+  write(chunk, enc, cb) {
+    cb();
+  },
+  writev(chunks, cb) {
+    setTimeout(cb, 10, new Error('kaboom'));
+  }
+});
+const myConsole = new Console(stream, stream);
+
+process.on('warning', common.mustNotCall);
+
+stream.cork();
+for (let i = 0; i < EventEmitter.defaultMaxListeners + 1; i++) {
+  myConsole.log('a message');
+}
+stream.uncork();

Original file line number	Diff line number	Diff line change
`@@ -82,7 +82,10 @@ function createWriteErrorHandler(stream) {`
`82`	`82`	// an `error` event. Adding a `once` listener will keep that error
`83`	`83`	`// from becoming an uncaught exception, but since the handler is`
`84`	`84`	`// removed after the event, non-console.* writes won’t be affected.`
`85`		`- stream.once('error', noop);`
	`85`	`+ // we are only adding noop if there is no one else listening for 'error'`
	`86`	`+ if (stream.listenerCount('error') === 0) {`
	`87`	`+ stream.on('error', noop);`
	`88`	`+ }`
`86`	`89`	`}`
`87`	`90`	`};`
`88`	`91`	`}`