[fix] Handle the username and password properties

Update the value of the `auth` property when the `username` or
`password` property is set.

Refs: #213 (comment)

index.js

@@ -459,15 +459,16 @@ function set(part, value, fn) {
       }
       break;
 
+    case 'username':
+    case 'password':
+      url[part] = encodeURIComponent(value);
+      break;
+
     case 'auth':
       var splits = value.split(':');
       url.username = splits[0];
       url.password = splits.length === 2 ? splits[1] : '';
       url[part] = value;
-      break;
-
-    default:
-      url[part] = value;
   }
 
   for (var i = 0; i < rules.length; i++) {
@@ -476,6 +477,8 @@ function set(part, value, fn) {
     if (ins[4]) url[ins[1]] = url[ins[1]].toLowerCase();
   }
 
+  url.auth = url.password ? url.username +':'+ url.password : url.username;
+
   url.origin = url.protocol !== 'file:' && isSpecial(url.protocol) && url.host
     ? url.protocol +'//'+ url.host
     : 'null';

test/test.js

@@ -1046,6 +1046,62 @@ describe('url-parse', function () {
       assume(data.href).equals('mailto:alice@atlanta.com');
     });
 
+    it('updates auth when updating username', function() {
+      var data = parse('https://example.com');
+
+      assume(data.set('username', 'foo')).equals(data);
+      assume(data.username).equals('foo');
+      assume(data.auth).equals('foo')
+      assume(data.href).equals('https://foo@example.com/');
+
+      data.set('username', '');
+
+      assume(data.username).equals('');
+      assume(data.auth).equals('')
+      assume(data.href).equals('https://example.com/');
+
+      data.set('username', 'foo:');
+
+      assume(data.username).equals('foo%3A');
+      assume(data.auth).equals('foo%3A')
+      assume(data.href).equals('https://foo%3A@example.com/');
+
+      data = parse('https://foo:bar@example.com')
+      data.set('username', 'baz');
+
+      assume(data.username).equals('baz');
+      assume(data.auth).equals('baz:bar')
+      assume(data.href).equals('https://baz:bar@example.com/');
+    });
+
+    it('updates auth when updating password', function() {
+      var data = parse('https://example.com');
+
+      assume(data.set('password', 'foo')).equals(data);
+      assume(data.password).equals('foo');
+      assume(data.auth).equals(':foo')
+      assume(data.href).equals('https://:foo@example.com/');
+
+      data.set('password', '');
+
+      assume(data.password).equals('');
+      assume(data.auth).equals('')
+      assume(data.href).equals('https://example.com/');
+
+      data.set('password', ':foo@');
+
+      assume(data.password).equals('%3Afoo%40');
+      assume(data.auth).equals(':%3Afoo%40')
+      assume(data.href).equals('https://:%3Afoo%40@example.com/');
+
+      data = parse('https://foo:bar@example.com')
+      data.set('password', 'baz');
+
+      assume(data.password).equals('baz');
+      assume(data.auth).equals('foo:baz')
+      assume(data.href).equals('https://foo:baz@example.com/');
+    });
+
     it('updates username and password when updating auth', function() {
       var data = parse('https://example.com');