[fix] support to create log directory if it doesn't exist for file transport (#1556)

* feat: support to create log dir if it doesn't exist for file transport

* test: add test cases

Author: adoyle-h

lib/winston/transports/file.js

@@ -66,6 +66,7 @@ module.exports = class File extends TransportStream {
       console.warn('options.stream will be removed in winston@4. Use winston.transports.Stream');
       throwIf('stream', 'filename', 'maxsize');
       this._dest = this._stream.pipe(this._setupStream(options.stream));
+      this.dirname = path.dirname(this._dest.path);
       // We need to listen for drain events when write() returns false. This
       // can make node mad at times.
     } else {
@@ -88,6 +89,7 @@ module.exports = class File extends TransportStream {
     this._opening = false;
     this._ending = false;
 
+    if (this.dirname) this._createLogDirIfNotExist(this.dirname);
     this.open();
   }
 
@@ -685,4 +687,12 @@ module.exports = class File extends TransportStream {
       );
     });
   }
+
+  _createLogDirIfNotExist(dirPath) {
+    /* eslint-disable no-sync */
+    if (!fs.existsSync(dirPath)) {
+      fs.mkdirSync(dirPath, { recursive: true });
+    }
+    /* eslint-enable no-sync */
+  }
 };

test/transports/file-create-dir-test.js

@@ -0,0 +1,43 @@
+'use strict';
+
+const fs = require('fs');
+const assert = require('assert');
+const path = require('path');
+const winston = require('../../lib/winston');
+
+/* eslint-disable no-sync */
+
+describe('winston/transports/file/createLogDir', function () {
+  const logDir = path.resolve(__dirname, '../fixtures/temp_logs');
+
+  beforeEach(function () {
+    fs.rmdirSync(logDir);
+  });
+
+  it('should create directory if it does not exist', function () {
+    winston.createLogger({
+      transports: [
+        new winston.transports.File({
+          filename: path.join(logDir, 'file.log')
+        })
+      ]
+    });
+
+    assert(fs.existsSync(logDir));
+  });
+
+  it('should create directory if it does not exist when write to the stream', function () {
+    const streamfile = path.join(logDir, 'simple-stream.log');
+    const stream = fs.createWriteStream(streamfile);
+
+    winston.createLogger({
+      transports: [
+        new winston.transports.File({
+          stream: stream
+        })
+      ]
+    });
+
+    assert(fs.existsSync(logDir));
+  });
+});