console: do not emit error events

Fixes: #831
Fixes: #947
Ref: #9470
PR-URL: #9744
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>

Author: addaleax

lib/console.js

@@ -2,9 +2,9 @@
 
 const util = require('util');
 
-function Console(stdout, stderr) {
+function Console(stdout, stderr, ignoreErrors = true) {
   if (!(this instanceof Console)) {
-    return new Console(stdout, stderr);
+    return new Console(stdout, stderr, ignoreErrors);
   }
   if (!stdout || typeof stdout.write !== 'function') {
     throw new TypeError('Console expects a writable stream instance');
@@ -24,8 +24,14 @@ function Console(stdout, stderr) {
   Object.defineProperty(this, '_stdout', prop);
   prop.value = stderr;
   Object.defineProperty(this, '_stderr', prop);
+  prop.value = ignoreErrors;
+  Object.defineProperty(this, '_ignoreErrors', prop);
   prop.value = new Map();
   Object.defineProperty(this, '_times', prop);
+  prop.value = createWriteErrorHandler(stdout);
+  Object.defineProperty(this, '_stdoutErrorHandler', prop);
+  prop.value = createWriteErrorHandler(stderr);
+  Object.defineProperty(this, '_stderrErrorHandler', prop);
 
   // bind the prototype functions to this Console instance
   var keys = Object.keys(Console.prototype);
@@ -35,20 +41,60 @@ function Console(stdout, stderr) {
   }
 }
 
+// Make a function that can serve as the callback passed to `stream.write()`.
+function createWriteErrorHandler(stream) {
+  return (err) => {
+    // This conditional evaluates to true if and only if there was an error
+    // that was not already emitted (which happens when the _write callback
+    // is invoked asynchronously).
+    if (err && !stream._writableState.errorEmitted) {
+      // If there was an error, it will be emitted on `stream` as
+      // 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’t be affected.
+      stream.once('error', noop);
+    }
+  };
+}
+
+function write(ignoreErrors, stream, string, errorhandler) {
+  if (!ignoreErrors) return stream.write(string);
+
+  // There may be an error occurring synchronously (e.g. for files or TTYs
+  // on POSIX systems) or asynchronously (e.g. pipes on POSIX systems), so
+  // handle both situations.
+  try {
+    // Add and later remove a noop error handler to catch synchronous errors.
+    stream.once('error', noop);
+
+    stream.write(string, errorhandler);
+  } catch (e) {
+    // Sorry, there’s no proper way to pass along the error here.
+  } finally {
+    stream.removeListener('error', noop);
+  }
+}
+
 
 // As of v8 5.0.71.32, the combination of rest param, template string
 // and .apply(null, args) benchmarks consistently faster than using
 // the spread operator when calling util.format.
 Console.prototype.log = function log(...args) {
-  this._stdout.write(`${util.format.apply(null, args)}\n`);
+  write(this._ignoreErrors,
+        this._stdout,
+        `${util.format.apply(null, args)}\n`,
+        this._stdoutErrorHandler);
 };
 
 
 Console.prototype.info = Console.prototype.log;
 
 
 Console.prototype.warn = function warn(...args) {
-  this._stderr.write(`${util.format.apply(null, args)}\n`);
+  write(this._ignoreErrors,
+        this._stderr,
+        `${util.format.apply(null, args)}\n`,
+        this._stderrErrorHandler);
 };
 
 
@@ -57,7 +103,7 @@ Console.prototype.error = Console.prototype.warn;
 
 Console.prototype.dir = function dir(object, options) {
   options = Object.assign({customInspect: false}, options);
-  this._stdout.write(`${util.inspect(object, options)}\n`);
+  write(this._ignoreErrors, this._stdout, `${util.inspect(object, options)}\n`);
 };
 
 
@@ -99,3 +145,5 @@ Console.prototype.assert = function assert(expression, ...args) {
 
 module.exports = new Console(process.stdout, process.stderr);
 module.exports.Console = Console;
+
+function noop() {}

test/parallel/test-console-async-write-error.js

@@ -0,0 +1,17 @@
+'use strict';
+const common = require('../common');
+const { Console } = require('console');
+const { Writable } = require('stream');
+const assert = require('assert');
+
+const out = new Writable({
+  write: common.mustCall((chunk, enc, callback) => {
+    process.nextTick(callback, new Error('foobar'));
+  })
+});
+
+const c = new Console(out, out, true);
+
+assert.doesNotThrow(() => {
+  c.log('abc');
+});

test/parallel/test-console-sync-write-error.js

@@ -0,0 +1,47 @@
+'use strict';
+const common = require('../common');
+const { Console } = require('console');
+const { Writable } = require('stream');
+const assert = require('assert');
+
+{
+  const out = new Writable({
+    write: common.mustCall((chunk, enc, callback) => {
+      callback(new Error('foobar'));
+    })
+  });
+
+  const c = new Console(out, out, true);
+
+  assert.doesNotThrow(() => {
+    c.log('abc');
+  });
+}
+
+{
+  const out = new Writable({
+    write: common.mustCall((chunk, enc, callback) => {
+      throw new Error('foobar');
+    })
+  });
+
+  const c = new Console(out, out, true);
+
+  assert.doesNotThrow(() => {
+    c.log('abc');
+  });
+}
+
+{
+  const out = new Writable({
+    write: common.mustCall((chunk, enc, callback) => {
+      setImmediate(() => callback(new Error('foobar')));
+    })
+  });
+
+  const c = new Console(out, out, true);
+
+  assert.doesNotThrow(() => {
+    c.log('abc');
+  });
+}