[fix] Properly handle JSON.stringify errors (#84)

JSON.stringify method throws when passed a circular object.

index.js

@@ -113,6 +113,8 @@ exports.Decoder = Decoder;
 
 function Encoder() {}
 
+var ERROR_PACKET = exports.ERROR + '"encode error"';
+
 /**
  * Encode a packet as a single string if non-binary, or as a
  * buffer sequence, depending on packet type.
@@ -128,8 +130,7 @@ Encoder.prototype.encode = function(obj, callback){
 
   if (exports.BINARY_EVENT === obj.type || exports.BINARY_ACK === obj.type) {
     encodeAsBinary(obj, callback);
-  }
-  else {
+  } else {
     var encoding = encodeAsString(obj);
     callback([encoding]);
   }
@@ -166,13 +167,26 @@ function encodeAsString(obj) {
 
   // json data
   if (null != obj.data) {
-    str += JSON.stringify(obj.data);
+    var payload = tryStringify(obj.data);
+    if (payload !== false) {
+      str += payload;
+    } else {
+      return ERROR_PACKET;
+    }
   }
 
   debug('encoded %j as %s', obj, str);
   return str;
 }
 
+function tryStringify(str) {
+  try {
+    return JSON.stringify(str);
+  } catch(e){
+    return false;
+  }
+}
+
 /**
  * Encode packet as 'buffer sequence' by removing blobs, and
  * deconstructing packet into object with placeholders and

test/parser.js

@@ -1,8 +1,6 @@
 var parser = require('../index.js');
 var expect = require('expect.js');
 var helpers = require('./helpers.js');
-var encode = parser.encode;
-var decode = parser.decode;
 
 describe('parser', function(){
 
@@ -61,6 +59,24 @@ describe('parser', function(){
     });
   });
 
+  it('properly handles circular objects', function() {
+    var a = {};
+    a.b = a;
+
+    var data = {
+      type: parser.EVENT,
+      data: a,
+      id: 1,
+      nsp: '/'
+    }
+
+    var encoder = new parser.Encoder();
+
+    encoder.encode(data, function(encodedPackets) {
+      expect(encodedPackets[0]).to.be('4"encode error"');
+    });
+  });
+
   it('decodes a bad binary packet', function(){
     try {
       var decoder = new parser.Decoder();