[Winston 2.x] Decycle circular Error instances (#1307)

* Adds support for Error instances with circular references

* Bumps version to 2.5.0

* Removes superfluous line break

* Update package.json

lib/winston/common.js

@@ -85,7 +85,7 @@ exports.clone = function (obj) {
       copy[key] = obj[key];
     });
 
-    return copy;
+    return cycle.decycle(copy);
   }
   else if (!(obj instanceof Object)) {
     return obj;
@@ -145,7 +145,7 @@ exports.log = function (options) {
         : exports.timestamp,
       timestamp   = options.timestamp ? timestampFn() : null,
       showLevel   = options.showLevel === undefined ? true : options.showLevel,
-      meta        = options.meta !== null && options.meta !== undefined && !(options.meta instanceof Error)
+      meta        = options.meta !== null && options.meta !== undefined
         ? exports.clone(options.meta)
         : options.meta || null,
       output;
@@ -244,10 +244,6 @@ exports.log = function (options) {
     : options.message;
 
   if (meta !== null && meta !== undefined) {
-    if (meta && meta instanceof Error && meta.stack) {
-      meta = meta.stack;
-    }
-
     if (typeof meta !== 'object') {
       output += ' ' + meta;
     }

test/helpers.js

@@ -194,6 +194,23 @@ helpers.testLevels = function (levels, transport, assertMsg, assertFn) {
   circmetadatatest[assertMsg] = assertFn;
   tests['when passed circular metadata'] = circmetadatatest;
 
+  var circerror = new Error("message!");
+  var foo = {};
+  var circerrordatatest;
+
+  foo.bar = foo;
+  circerror.foo = foo;
+  circerror.stack = 'Some stacktrace';
+
+  circerrordatatest = {
+    topic: function () {
+      transport.log('info', 'test message', circerror, this.callback.bind(this, null));
+    }
+  };
+
+  circerrordatatest[assertMsg] = assertFn;
+  tests['when passed circular error as metadata'] = circerrordatatest;
+
   return tests;
 };