Alternative fix for #1501 (#1539)

* [wip fix] Assume message is the empty string when level-helper methods are invoked with no arguments.

* [fix] Add test for #1501.

Author: indexzero

lib/winston/create-logger.js

@@ -57,6 +57,12 @@ class DerivedLogger extends Logger {
           return this;
         }
 
+        // When provided nothing assume the empty string
+        if (args.length === 0) {
+          this.log(level, '');
+          return this;
+        }
+
         // Otherwise build argument list which could potentially conform to
         // either:
         // . v3 API: log(obj)

test/logger.test.js

@@ -281,6 +281,25 @@ describe('Logger (levels)', function () {
     done();
   });
 
+  it('.<level>()', function (done) {
+    var logger = helpers.createLogger(function (info) {
+      assume(info).is.an('object');
+      assume(info.level).equals('info');
+      assume(info.message).is.a('string');
+      assume(info[MESSAGE]).is.a('string');
+      assume(info.message).equals('');
+      assume(info[MESSAGE]).equals(JSON.stringify({
+        level: 'info',
+        message: ''
+      }));
+
+      done();
+    });
+
+    logger.info();
+    logger.info('');
+  });
+
   it('default levels', function (done) {
     var logger = winston.createLogger();
     var expected = { message: 'foo', level: 'debug' };