feat($compile): backport $doCheck

Backuport ngDoCheck from Angular 2.

Closes #14656

Author: zbjornson

src/ng/compile.js

@@ -300,6 +300,12 @@
  *   `changesObj` is a hash whose keys are the names of the bound properties that have changed, and the values are an
  *   object of the form `{ currentValue, previousValue, isFirstChange() }`. Use this hook to trigger updates within a
  *   component such as cloning the bound value to prevent accidental mutation of the outer value.
+ * * `$doCheck()` - Called on each turn of the digest cycle. Provides an opportunity to detect and act on
+ *   changes. Any actions that you wish to take in response to the changes that you detect must be
+ *   invoked from this hook; implementing this has no effect on when `$onChanges` is called. For example, this hook
+ *   could be useful if you wish to perform a deep equality check, or to check a Date object, changes to which would not
+ *   be detected by Angular's change detector and thus not trigger `$onChanges`. This hook is invoked with no arguments;
+ *   if detecting changes, you must store the previous value(s) for comparison to the current values.
  * * `$onDestroy()` - Called on a controller when its containing scope is destroyed. Use this hook for releasing
  *   external resources, watches and event handlers. Note that components have their `$onDestroy()` hooks called in
  *   the same order as the `$scope.$broadcast` events are triggered, which is top down. This means that parent
@@ -2512,6 +2518,12 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
               $exceptionHandler(e);
             }
           }
+          if (isFunction(controllerInstance.$doCheck)) {
+            controllerInstance.$doCheck();
+          }
+          if (isFunction(controllerInstance.$doCheck)) {
+            controllerInstance.$doCheck();
+          }
           if (isFunction(controllerInstance.$onDestroy)) {
             controllerScope.$on('$destroy', function callOnDestroyHook() {
               controllerInstance.$onDestroy();
@@ -3158,7 +3170,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
       forEach(bindings, function initializeBinding(definition, scopeName) {
         var attrName = definition.attrName,
         optional = definition.optional,
-        mode = definition.mode, // @, =, or &
+        mode = definition.mode, // @, =, <, or &
         lastValue,
         parentGet, parentSet, compare, removeWatch;
 
@@ -3270,6 +3282,11 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
         }
       });
 
+      if (isFunction(destination.$doCheck)) {
+        var doCheckWatch = scope.$watch(triggerDoCheckHook);
+        removeWatchCollection.push(doCheckWatch);
+      }
+
       function recordChanges(key, currentValue, previousValue) {
         if (isFunction(destination.$onChanges) && currentValue !== previousValue) {
           // If we have not already scheduled the top level onChangesQueue handler then do so now
@@ -3297,6 +3314,10 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
         changes = undefined;
       }
 
+      function triggerDoCheckHook() {
+        destination.$doCheck();
+      }
+
       return {
         initialChanges: initialChanges,
         removeWatches: removeWatchCollection.length && function removeWatches() {

test/ng/compileSpec.js

@@ -3816,6 +3816,51 @@ describe('$compile', function() {
       });
     });
 
+    describe('$doCheck', function() {
+      it('should call `$doCheck`, if provided, for each digest cycle, after $onChanges and $onInit', function() {
+        var log = [];
+
+        function TestController() { }
+        TestController.prototype.$doCheck = function() { log.push('$doCheck'); };
+        TestController.prototype.$onChanges = function() { log.push('$onChanges'); };
+        TestController.prototype.$onInit = function() { log.push('$onInit'); };
+
+        angular.module('my', [])
+          .component('dcc', {
+            controller: TestController,
+            bindings: { 'prop1': '<' }
+          });
+
+        module('my');
+        inject(function($compile, $rootScope) {
+          element = $compile('<dcc prop1="val"></dcc>')($rootScope);
+          expect(log).toEqual([
+            '$onChanges',
+            '$onInit',
+            '$doCheck'
+          ]);
+
+          // Clear log
+          log = [];
+
+          $rootScope.$apply();
+          expect(log).toEqual([
+            '$doCheck',
+            '$doCheck'
+          ]);
+
+          // Clear log
+          log = [];
+
+          $rootScope.$apply('val = 2');
+          expect(log).toEqual([
+            '$doCheck',
+            '$onChanges',
+            '$doCheck'
+          ]);
+        });
+      });
+    });
 
     describe('$onChanges', function() {