Greatly simplify drain mechanism based on PR feedback and testing

lib/winston/transports/file.js

@@ -18,12 +18,6 @@ const debug = require('diagnostics')('winston:file');
 const os = require('os');
 const tailFile = require('../tail-file');
 
-/**
- * Simple no-op function.
- * @returns {undefined}
- */
-function noop() {}
-
 /**
  * Transport for outputting to a local log file.
  * @type {File}
@@ -88,8 +82,6 @@ module.exports = class File extends TransportStream {
     this._size = 0;
     this._pendingSize = 0;
     this._created = 0;
-    this._drain = false;
-    this._next = noop;
     this._opening = false;
 
     this.open();
@@ -101,7 +93,7 @@ module.exports = class File extends TransportStream {
    * @param {Function} callback - TODO: add param description.
    * @returns {undefined}
    */
-  log(info, callback = noop) {
+  log(info, callback = () => {}) {
     // Remark: (jcrugzz) What is necessary about this callback(null, true) now
     // when thinking about 3.x? Should silent be handled in the base
     // TransportStream _write method?
@@ -142,23 +134,6 @@ module.exports = class File extends TransportStream {
       this._endStream(() => this._rotateFile());
     }
 
-    if (this._drain) {
-      this._stream.once('drain', () => {
-        this._drain = false;
-        this.log(info, callback);
-      });
-      return;
-    }
-
-    const written = this._stream.write(output, logged.bind(this));
-    if (written === false) {
-      this._drain = true;
-      this._stream.once('drain', () => {
-        this._drain = false;
-        callback();
-      });
-    }
-
     // Keep track of the pending bytes being written while files are opening
     // in order to properly rotate the PassThrough this._stream when the file
     // eventually does open.
@@ -169,11 +144,15 @@ module.exports = class File extends TransportStream {
       this.rotatedWhileOpening = true;
     }
 
-    debug('written', written, this._drain);
-    if (written) {
+    const written = this._stream.write(output, logged.bind(this));
+    if (!written) {
+      this._stream.once('drain', callback);
+    } else {
       callback(); // eslint-disable-line callback-return
     }
 
+    debug('written', written);
+
     return written;
   }