fix: File Transport not flush when logger.end() invoked

lib/winston/transports/file.js

@@ -87,6 +87,7 @@ module.exports = class File extends TransportStream {
     this._created = 0;
     this._drain = false;
     this._opening = false;
+    this._destOpened = false;
     this._ending = false;
 
     if (this.dirname) this._createLogDirIfNotExist(this.dirname);
@@ -522,8 +523,8 @@ module.exports = class File extends TransportStream {
    */
   _endStream(callback = () => {}) {
     if (this._dest) {
-      this._stream.unpipe(this._dest);
       this._dest.end(() => {
+        this._stream.unpipe(this._dest);
         this._cleanupStream(this._dest);
         callback();
       });
@@ -532,6 +533,32 @@ module.exports = class File extends TransportStream {
     }
   }
 
+  /**
+   * To fix issue https://github.com/winstonjs/winston/issues/228
+   * @private
+   * @param {function} cb Delaying the 'finish' event until callback is called
+   * @returns {undefined}
+   */
+  _waitStreamsCreatedButNotPiped(cb) {
+    if (this._destOpened) {
+      return cb();
+    }
+
+    this.once('startPipe', () => {
+      this._dest.once('finish', () => {
+        cb();
+      });
+
+      this.close(() => {
+        this._endStream();
+      });
+    });
+  }
+
+  _final(cb) {
+    this._waitStreamsCreatedButNotPiped(cb);
+  }
+
   /**
    * Returns the WritableStream for the active file on this instance. If we
    * should gzip the file then a zlib stream is returned.
@@ -549,8 +576,10 @@ module.exports = class File extends TransportStream {
       .on('close', () => debug('close', dest.path, dest.bytesWritten))
       .on('open', () => {
         debug('file open ok', fullpath);
+        this._destOpened = true;
         this.emit('open', fullpath);
         source.pipe(dest);
+        this.emit('startPipe');
 
         // If rotation occured during the open operation then we immediately
         // start writing to a new PassThrough, begin opening the next file