feat($compile): call $ngOnInit on directive controllers after controller construction

This enables option three of #13510 (comment)
by allowing the creator of directive controllers using ES6 classes to have a hook
that is called when the bindings are definitely available.

Moreover this will help solve the problem of accessing `require`d controllers
from controller instances without resorting to wiring up in a `link` function.
See #5893

Author: petebacondarwin

src/ng/compile.js

@@ -1072,7 +1072,8 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
         transclude: options.transclude,
         scope: {},
         bindToController: options.bindings || {},
-        restrict: 'E'
+        restrict: 'E',
+        require: options.require
       };
     }
 
@@ -2388,6 +2389,13 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
           }
         }
 
+        // Trigger the `$onInit` method on all controllers that have one
+        forEach(elementControllers, function(controller) {
+          if (isFunction(controller.instance.$onInit)) {
+            controller.instance.$onInit();
+          }
+        });
+
         // PRELINKING
         for (i = 0, ii = preLinkFns.length; i < ii; i++) {
           linkFn = preLinkFns[i];

test/ng/compileSpec.js

@@ -4929,6 +4929,32 @@ describe('$compile', function() {
       });
     });
 
+    it('should call `controller.$onInit`, if provided after all the controllers have been constructed', function() {
+
+      function Controller1($element) { this.id = 1; this.element = $element; }
+      Controller1.prototype.$onInit = jasmine.createSpy('$onInit').andCallFake(function() {
+        expect(this.element.controller('d1').id).toEqual(1);
+        expect(this.element.controller('d2').id).toEqual(2);
+      });
+
+      function Controller2($element) { this.id = 2; this.element = $element; }
+      Controller2.prototype.$onInit = jasmine.createSpy('$onInit').andCallFake(function() {
+        expect(this.element.controller('d1').id).toEqual(1);
+        expect(this.element.controller('d2').id).toEqual(2);
+      });
+
+      angular.module('my', [])
+        .directive('d1', function() { return { controller: Controller1 }; })
+        .directive('d2', function() { return { controller: Controller2 }; });
+
+      module('my');
+      inject(function($compile, $rootScope) {
+        element = $compile('<div d1 d2></div>')($rootScope);
+        expect(Controller1.prototype.$onInit).toHaveBeenCalledOnce();
+        expect(Controller2.prototype.$onInit).toHaveBeenCalledOnce();
+      });
+    });
+
     describe('should not overwrite @-bound property each digest when not present', function() {
       it('when creating new scope', function() {
         module(function($compileProvider) {