fix ($compile): keep prototype properties for template URL directives

Previously, if a directive definition object was defined with methods like `compile`
provided on the prototype rather than the instance, the Angular compiler failed
to use these methods when the directive had a `templateURL`. This change ensures
that these prototypical methods are not lost.

This enables developers to define their directives using "classes" such as
in CoffeeScript or ES6.

Closes #10926

Author: hannahhoward

src/ng/compile.js

@@ -2155,8 +2155,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
           afterTemplateChildLinkFn,
           beforeTemplateCompileNode = $compileNode[0],
           origAsyncDirective = directives.shift(),
-          // The fact that we have to copy and patch the directive seems wrong!
-          derivedSyncDirective = extend({}, origAsyncDirective, {
+          derivedSyncDirective = inherit(origAsyncDirective, {
             templateUrl: null, transclude: null, replace: null, $$originalDirective: origAsyncDirective
           }),
           templateUrl = (isFunction(origAsyncDirective.templateUrl))

test/ng/compileSpec.js

@@ -1109,6 +1109,29 @@ describe('$compile', function() {
             expect(element.find('p').text()).toBe('Hello, world!');
           });
         });
+
+        it('should keep prototype properties on directive', function() {
+          module(function() {
+            function DirectiveClass() {
+              this.restrict = 'E';
+              this.template = "<p>{{value}}</p>";
+            }
+
+            DirectiveClass.prototype.compile = function() {
+              return function(scope, element, attrs) {
+                scope.value = "Test Value";
+              };
+            };
+
+            directive('templateUrlWithPrototype', valueFn(new DirectiveClass()));
+          });
+
+          inject(function($compile, $rootScope) {
+            element = $compile('<template-url-with-prototype><template-url-with-prototype>')($rootScope);
+            $rootScope.$digest();
+            expect(element.find("p")[0].innerHTML).toEqual("Test Value");
+          });
+        });
       });
 
 
@@ -2028,6 +2051,32 @@ describe('$compile', function() {
           });
         });
 
+        it('should keep prototype properties on sync version of async directive', function() {
+          module(function() {
+            function DirectiveClass() {
+              this.restrict = 'E';
+              this.templateUrl = "test.html";
+            }
+
+            DirectiveClass.prototype.compile = function() {
+              return function(scope, element, attrs) {
+                scope.value = "Test Value";
+              };
+            };
+
+            directive('templateUrlWithPrototype', valueFn(new DirectiveClass()));
+          });
+
+          inject(function($compile, $rootScope, $httpBackend) {
+            $httpBackend.whenGET('test.html').
+              respond('<p>{{value}}</p>');
+            element = $compile('<template-url-with-prototype><template-url-with-prototype>')($rootScope);
+            $httpBackend.flush();
+            $rootScope.$digest();
+            expect(element.find("p")[0].innerHTML).toEqual("Test Value");
+          });
+        });
+
       });