include standard claims from payload. closes #196

sign.js

@@ -93,10 +93,12 @@ module.exports = function(payload, secretOrPrivateKey, options, callback) {
 
   Object.keys(options_to_payload).forEach(function (key) {
     var claim = options_to_payload[key];
-    if (typeof options[key] !== 'undefined' && typeof payload[claim] !== 'undefined') {
-      throw new Error('Bad "options.' + key + '" option. The payload already has an "' + claim + '" property.');
+    if (typeof options[key] !== 'undefined') {
+      if (typeof payload[claim] !== 'undefined') {
+        throw new Error('Bad "options.' + key + '" option. The payload already has an "' + claim + '" property.');
+      }
+      payload[claim] = options[key];
     }
-    payload[claim] = options[key];
   });
 
   var encoding = options.encoding || 'utf8';

test/issue_196.tests.js

@@ -0,0 +1,15 @@
+var expect = require('chai').expect;
+var jwt = require('./..');
+var atob = require('atob');
+
+describe('issue 196', function () {
+  function b64_to_utf8 (str) {
+    return decodeURIComponent(escape(atob( str )));
+  }
+
+  it('should use issuer provided in payload.iss', function () {
+    var token = jwt.sign({ iss: 'foo' }, 'shhhhh');
+    var decoded_issuer = JSON.parse(b64_to_utf8(token.split('.')[1])).iss;
+    expect(decoded_issuer).to.equal('foo');
+  });
+});