perf($controller): cache the later constructor

Author: jbedard

src/ng/controller.js

@@ -104,9 +104,13 @@ function $ControllerProvider() {
         //
         // This feature is not intended for use by applications, and is thus not documented
         // publicly.
-        var Constructor = function() {};
-        Constructor.prototype = (isArray(expression) ?
-          expression[expression.length - 1] : expression).prototype;
+        // http://jsperf.com/create-constructor/2
+        constructor = isArray(expression) ? expression[expression.length - 1] : expression;
+        var Constructor = constructor.$$Constructor;
+        if (!Constructor) {
+          Constructor = constructor.$$Constructor = function Constructor() {};
+          Constructor.prototype = constructor.prototype;
+        }
         instance = new Constructor();
 
         if (identifier) {

test/ng/controllerSpec.js

@@ -157,4 +157,38 @@ describe('$controller', function() {
 
     });
   });
+
+  describe('ctrl later', function() {
+    it('should return a delayed constructor instance', function() {
+      function Ctrl() {
+        this.prop = 123;
+      }
+      Ctrl.prop = 123;
+      Ctrl.prototype.foobar = Ctrl.foobar = function() { return this.prop; };
+
+      var setup = $controller(Ctrl, {}, true);
+      var instance = setup.instance;
+
+      expect(Object.getPrototypeOf(instance)).toBe(Ctrl.prototype);
+      expect(instance.foobar()).not.toBeDefined();
+
+      setup();
+      expect(instance.foobar()).toBe(123);
+      instance.prop = 456;
+      expect(instance.foobar()).toBe(456);
+    });
+
+    it('should work with inherited constructors', function() {
+      function Parent() {}
+      function Child() {}
+      Child.prototype = new Parent();
+
+      var parent  = $controller(Parent, {}, true).instance;
+      var parent2 = $controller(Parent, {}, true).instance;
+      var child   = $controller(Child, {}, true).instance;
+
+      expect(parent.constructor).toBe(parent2.constructor, "should reuse the base controller");
+      expect(Object.getPrototypeOf(child)).toBe(Child.prototype);
+    });
+  });
 });