Ensure that Sizzle loads properly in RequireJS or CommonJS environments.

[close prototypejs#203]

Author: Andrew Dupont

vendor/sizzle/selector_engine.js

@@ -1,6 +1,45 @@
 Prototype._original_property = window.Sizzle;
+
+;(function () {
+  function fakeDefine(fn) {
+    Prototype._actual_sizzle = fn();
+  }
+  fakeDefine.amd = true;
+  
+  if (typeof define !== 'undefined' && define.amd) {
+    // RequireJS is loaded. We need to pretend to be `define` while Sizzle
+    // runs.
+    Prototype._original_define = define;
+    Prototype._actual_sizzle = null;
+    window.define = fakeDefine;
+  }
+})();
+
 //= require "repository/dist/sizzle"
 
+;(function() {
+  if (typeof Sizzle !== 'undefined') {
+    // Sizzle was properly defined.
+    return;
+  }
+  
+  if (typeof define !== 'undefined' && define.amd) {
+    // RequireJS.
+    // We should find Sizzle where we put it. And we need to restore the original `define`.
+    window.Sizzle = Prototype._actual_sizzle;
+    window.define = Prototype._original_define;
+    delete Prototype._actual_sizzle;
+    delete Prototype._original_define;
+    // TODO: Should we make our own `define` call here?
+  } else if (typeof module !== 'undefined' && module.exports) {
+    // Sizzle saw that it's in a CommonJS environment and attached itself to
+    // `module.exports` instead.
+    window.Sizzle = module.exports;
+    // Reset `module.exports`.
+    module.exports = {};
+  }
+})();
+
 ;(function(engine) {
   var extendElements = Prototype.Selector.extendElements;