Fix unhandled rejection handling (#2390)

* Fix unhandled rejection handlers

* Fix unhandled rejection handlers

* Fix typo

lib/winston.js

@@ -135,6 +135,17 @@ Object.defineProperty(exports, 'exceptions', {
   }
 });
 
+/**
+ * Define getter for `rejections` which replaces `handleRejections` and
+ * `unhandleRejections`.
+ * @type {Object}
+ */
+Object.defineProperty(exports, 'rejections', {
+  get() {
+    return defaultLogger.rejections;
+  }
+});
+
 /**
  * Define getters / setters for appropriate properties of the default logger
  * which need to be exposed by winston.

lib/winston/rejection-handler.js

@@ -12,7 +12,7 @@ const asyncForEach = require('async/forEach');
 const debug = require('@dabh/diagnostics')('winston:rejection');
 const once = require('one-time');
 const stackTrace = require('stack-trace');
-const ExceptionStream = require('./exception-stream');
+const RejectionStream = require('./rejection-stream');
 
 /**
  * Object for handling unhandledRejection events.
@@ -88,7 +88,7 @@ module.exports = class RejectionHandler {
         err && err.stack || '  No stack trace'
       ].join('\n'),
       stack: err && err.stack,
-      exception: true,
+      rejection: true,
       date: new Date().toString(),
       process: this.getProcessInfo(),
       os: this.getOsInfo(),
@@ -151,7 +151,7 @@ module.exports = class RejectionHandler {
   _addHandler(handler) {
     if (!this.handlers.has(handler)) {
       handler.handleRejections = true;
-      const wrapper = new ExceptionStream(handler);
+      const wrapper = new RejectionStream(handler);
       this.handlers.set(handler, wrapper);
       this.logger.pipe(wrapper);
     }

lib/winston/rejection-stream.js

@@ -0,0 +1,52 @@
+/**
+ * rejection-stream.js: TODO: add file header handler.
+ *
+ * (C) 2010 Charlie Robbins
+ * MIT LICENCE
+ */
+
+'use strict';
+
+const { Writable } = require('readable-stream');
+
+/**
+ * TODO: add class description.
+ * @type {RejectionStream}
+ * @extends {Writable}
+ */
+module.exports = class RejectionStream extends Writable {
+  /**
+   * Constructor function for the RejectionStream responsible for wrapping a
+   * TransportStream; only allowing writes of `info` objects with
+   * `info.rejection` set to true.
+   * @param {!TransportStream} transport - Stream to filter to rejections
+   */
+  constructor(transport) {
+    super({ objectMode: true });
+
+    if (!transport) {
+      throw new Error('RejectionStream requires a TransportStream instance.');
+    }
+
+    this.handleRejections = true;
+    this.transport = transport;
+  }
+
+  /**
+   * Writes the info object to our transport instance if (and only if) the
+   * `rejection` property is set on the info.
+   * @param {mixed} info - TODO: add param description.
+   * @param {mixed} enc - TODO: add param description.
+   * @param {mixed} callback - TODO: add param description.
+   * @returns {mixed} - TODO: add return description.
+   * @private
+   */
+  _write(info, enc, callback) {
+    if (info.rejection) {
+      return this.transport.log(info, callback);
+    }
+
+    callback();
+    return true;
+  }
+};