Support for relative dependencies for define().

Note that this implementation is a little naive; it completely ignores
the id given to define, and always assumes that URLs will be relative
to the script's document. That will not work for vulcanized bundles.
Separate PR for that.

src/lib/module.html

@@ -44,15 +44,21 @@
       dependencies = Array.isArray(id) ? id : [];
     }
 
+    var inferredId = _inferModuleId();
     if (typeof id !== 'string') {
-      id = _inferModuleId();
+      id = inferredId;
+    }
+    if (id.indexOf('\\') !== -1) {
+      throw new TypeError('Please use / as module path delimiters');
     }
 
     if (id in _modules) {
       throw new Error('The module "' + id + '" has already been defined');
     }
 
-    _modules[id] = _withDependencies(dependencies, factory);
+    // TODO(nevir): This is naive; doesn't support the vulcanize case.
+    var base = inferredId.match(/^(.*?)[^\/]*$/)[1];
+    _modules[id] = _withDependencies(base, dependencies, factory);
     return _modules[id];
   }
   // Semi-private. We expose this for tests & introspection.
@@ -66,23 +72,25 @@
 
   // Utility
 
-  // TODO(nevir): Temporary for anonymous module ids until we determine them via
-  // current script URL.
-  var _anonymousModuleCount = 0;
-
   /** @return {string} A module id inferred from the current document/import. */
   function _inferModuleId() {
-    return '__anonymous_' + _anonymousModuleCount++ + '__';
+    var doc = document.currentScript && document.currentScript.ownerDocument || document;
+    if (!doc.baseURI) {
+      throw new Error('Unable to determine a module id: No baseURI for the document');
+    }
+    return doc.baseURI;
   }
 
   /**
    * Calls `factory` with the exported values of `dependencies`.
    *
+   * @param {string} base
    * @param {Array<string>} dependencies
    * @param {function(...*)} factory
    */
-  function _withDependencies(dependencies, factory) {
+  function _withDependencies(base, dependencies, factory) {
     var modules = dependencies.map(function(id) {
+      id = _resolveRelativeId(base, id);
       if (!(id in _modules)) {
         throw new ReferenceError('The module "' + id + '" has not been loaded');
       }
@@ -91,6 +99,34 @@
     return factory.apply(null, modules);
   }
 
+  /**
+   * @param {string} base The module path/URI that acts as the relative base.
+   * @param {string} id The module ID that should be relatively resolved.
+   * @return {string} The expanded module ID.
+   */
+  function _resolveRelativeId(base, id) {
+    if (id[0] !== '.') return id;
+    // We need to be careful to only process the path of URLs.
+    var match  = base.match(/^([^\/]*\/\/[^\/]+\/)?(.*?)\/?$/);
+    var prefix = match[1] || '';
+    // We start with the base, and then mutate it into the final path.
+    var terms   = match[2] ? match[2].split('/') : [];
+    var idTerms = id.match(/^\/?(.*?)\/?$/)[1].split('/');
+
+    for (var i = 0; i < idTerms.length; i++) {
+      var idTerm = idTerms[i];
+      if (idTerm === '.') {
+        continue;
+      } else if (idTerm === '..') {
+        terms.pop();
+      } else {
+        terms.push(idTerm);
+      }
+    }
+
+    return prefix + terms.join('/');
+  }
+
   // Exports
 
   scope.define = define;
@@ -111,6 +147,5 @@
     define(dependencies, factory);
   };
 
-
 })(this);
 </script>

test/assets/modules/one.html

@@ -0,0 +1,19 @@
+<!--
+@license
+Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
+
+<link rel="import" href="../../../src/lib/module.html">
+
+<script>
+
+define(function() {
+  return 'module 1';
+});
+
+</script>

test/assets/modules/sub/three.html

@@ -0,0 +1,19 @@
+<!--
+@license
+Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
+
+<link rel="import" href="../../../../src/lib/module.html">
+
+<script>
+
+define(function() {
+  return 'module 3';
+});
+
+</script>

test/assets/modules/two.html

@@ -0,0 +1,25 @@
+<!--
+@license
+Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
+
+<link rel="import" href="../../../src/lib/module.html">
+<link rel="import" href="one.html">
+<link rel="import" href="sub/three.html">
+
+<script>
+
+define(['./one.html', './sub/three.html'], function(one, three) {
+  return {
+    one:   one,
+    me:   'module 2',
+    three: three,
+  };
+});
+
+</script>

test/unit/module.html

@@ -14,6 +14,8 @@
   <script src="../../../webcomponentsjs/webcomponents-lite.js"></script>
   <script src="../../../web-component-tester/browser.js"></script>
   <link rel="import" href="../../src/lib/module.html">
+  <link rel="import" href="../assets/modules/one.html">
+  <link rel="import" href="../assets/modules/two.html">
 </head>
 <body>
 
@@ -22,7 +24,11 @@
   suite('define()', function() {
 
     beforeEach(function() {
-      for (var key in define._modules) { delete define._modules[key]; };
+      for (var key in define._modules) {
+        if (/\/assets\/modules\//.test(key)) continue;
+        delete define._modules[key];
+      }
+
       define('a', function() { return 'module A'; });
       define('b', function() { return 'module B'; });
     });
@@ -86,6 +92,26 @@
       }, Error, /"a".*defined/i);
     });
 
+    suite('relative dependencies', function() {
+
+      test('loads modules relative to the current', function(done) {
+        define(['../assets/modules/one.html'], function(one) {
+          assert.equal(one, 'module 1');
+          done();
+        });
+      });
+
+      test('loads relative modules transitively', function(done) {
+        define(['../assets/modules/two.html'], function(two) {
+          assert.equal(two.one,   'module 1');
+          assert.equal(two.me,    'module 2');
+          assert.equal(two.three, 'module 3');
+          done();
+        });
+      });
+
+    });
+
   });
 
 </script>