fix: throw upon invalid payload format

An invalid packet was previously parsed as an ERROR packet, which was
then ignored because it didn't contain any 'nsp' (namespace) field.

This behavior was wrong because:

- it means the other side is sending invalid payloads, so the
connection must be closed right away

- ERROR packets are meant for namespace authentication failures

Parsing an invalid payload will now throw an error, which must be
caught by the caller.

Closes #86

lib/index.ts

@@ -257,15 +257,15 @@ export class Decoder extends Emitter {
    * @param {String} str
    * @return {Object} packet
    */
-  private decodeString(str) {
+  private decodeString(str): Packet {
     let i = 0;
     // look up type
     const p: any = {
       type: Number(str.charAt(0)),
     };
 
     if (null == exports.types[p.type]) {
-      return error("unknown packet type " + p.type);
+      throw new Error("unknown packet type " + p.type);
     }
 
     // look up attachments if type binary
@@ -316,7 +316,7 @@ export class Decoder extends Emitter {
       if (isPayloadValid) {
         p.data = payload;
       } else {
-        return error("invalid payload");
+        throw new Error("invalid payload");
       }
     }
 
@@ -386,10 +386,3 @@ class BinaryReconstructor {
     this.buffers = [];
   }
 }
-
-function error(msg) {
-  return {
-    type: exports.ERROR,
-    data: "parser error: " + msg,
-  };
-}

test/parser.js

@@ -86,12 +86,8 @@ describe('parser', function(){
     }
   });
 
-  it('returns an error packet on parsing error', function(done){
-    var decoder = new parser.Decoder();
-    decoder.on('decoded', function(packet) {
-      expect(packet).to.eql({ type: 4, data: 'parser error: invalid payload' });
-      done();
-    });
-    decoder.add('442["some","data"');
+  it('throw an error upon parsing error', () => {
+    expect(() => new parser.Decoder().add('442["some","data"')).to.throwException(/^invalid payload$/);
+    expect(() => new parser.Decoder().add('999')).to.throwException(/^unknown packet type 9$/);
   });
 });