fix(build): handle relative paths with missing authority

closes #387

src/URI.js

@@ -669,19 +669,21 @@
 
   URI.build = function(parts) {
     var t = '';
+    var requireAbsolutePath = false
 
     if (parts.protocol) {
       t += parts.protocol + ':';
     }
 
     if (!parts.urn && (t || parts.hostname)) {
       t += '//';
+      requireAbsolutePath = true
     }
 
     t += (URI.buildAuthority(parts) || '');
 
     if (typeof parts.path === 'string') {
-      if (parts.path.charAt(0) !== '/' && typeof parts.hostname === 'string') {
+      if (parts.path.charAt(0) !== '/' && requireAbsolutePath) {
         t += '/';
       }
 

test/test.js

@@ -234,6 +234,16 @@
     })(t);
   }
 
+  module('serializing');
+  test('scheme and relative path', function() {
+    var u = new URI('')
+      .protocol('food')
+      .path('test/file.csv')
+      .toString()
+
+    equal(u.toString(), 'food:///test/file.csv', 'relative-path with scheme but no authority');
+  });
+
   module('mutating basics');
   test('protocol', function() {
     var u = new URI('http://example.org/foo.html');

test/urls.js

@@ -629,6 +629,54 @@ var urls = [{
       idn: false,
       punycode: false
     }
+  }, {
+    name: 'missing authority',
+    url: 'food:///test/file.csv',
+    parts: {
+      protocol: 'food',
+      username: null,
+      password: null,
+      hostname: null,
+      port: null,
+      path: '/test/file.csv',
+      query: null,
+      fragment: null
+    },
+    accessors: {
+      protocol: 'food',
+      username: '',
+      password: '',
+      port: '',
+      path: '/test/file.csv',
+      query: '',
+      fragment: '',
+      resource: '/test/file.csv',
+      authority: '',
+      origin: '',
+      userinfo: '',
+      subdomain: '',
+      domain: '',
+      tld: '',
+      directory: '/test',
+      filename: 'file.csv',
+      suffix: 'csv',
+      hash: '',
+      search: '',
+      host: '',
+      hostname: ''
+    },
+    is: {
+      urn: false,
+      url: true,
+      relative: true,
+      name: false,
+      sld: false,
+      ip: false,
+      ip4: false,
+      ip6: false,
+      idn: false,
+      punycode: false
+    }
   }, {
     name: 'IPv4',
     url: 'http://user:[email protected]:123/some/directory/file.html?query=string#fragment',