Always decycle objects before cloning (#977)

- Fixes #862 
- Fixes #474 
- Fixes #914

lib/winston/common.js

@@ -77,15 +77,10 @@ exports.longestElement = function (xs) {
 // i.e. JSON objects that are either literals or objects (no Arrays, etc)
 //
 exports.clone = function (obj) {
-  //
-  // We only need to clone reference types (Object)
-  //
-  var copy = {};
-
   if (obj instanceof Error) {
     // With potential custom Error objects, this might not be exactly correct,
     // but probably close-enough for purposes of this lib.
-    copy = { message: obj.message };
+    var copy = { message: obj.message };
     Object.getOwnPropertyNames(obj).forEach(function (key) {
       copy[key] = obj[key];
     });
@@ -99,6 +94,15 @@ exports.clone = function (obj) {
     return new Date(obj.getTime());
   }
 
+  return clone(cycle.decycle(obj));
+};
+
+function clone(obj) {
+  //
+  // We only need to clone reference types (Object)
+  //
+  var copy = {};
+
   for (var i in obj) {
     if (Array.isArray(obj[i])) {
       copy[i] = obj[i].slice(0);
@@ -115,7 +119,7 @@ exports.clone = function (obj) {
   }
 
   return copy;
-};
+}
 
 //
 // ### function log (options)
@@ -140,7 +144,7 @@ exports.log = function (options) {
       timestamp   = options.timestamp ? timestampFn() : null,
       showLevel   = options.showLevel === undefined ? true : options.showLevel,
       meta        = options.meta !== null && options.meta !== undefined && !(options.meta instanceof Error)
-        ? exports.clone(cycle.decycle(options.meta))
+        ? exports.clone(options.meta)
         : options.meta || null,
       output;