fix(paging): garbage collect parent $watchers

- Garbage collect parent $watchers on $destroy

Closes #5276

src/pagination/pagination.js

@@ -12,10 +12,10 @@ angular.module('ui.bootstrap.pagination', ['ui.bootstrap.paging'])
   uibPaging.create(this, $scope, $attrs);
 
   if ($attrs.maxSize) {
-    $scope.$parent.$watch($parse($attrs.maxSize), function(value) {
+    ctrl._watchers.push($scope.$parent.$watch($parse($attrs.maxSize), function(value) {
       maxSize = parseInt(value, 10);
       ctrl.render();
-    });
+    }));
   }
 
   // Create page object used in template

src/paging/paging.js

@@ -8,6 +8,7 @@ angular.module('ui.bootstrap.paging', [])
     create: function(ctrl, $scope, $attrs) {
       ctrl.setNumPages = $attrs.numPages ? $parse($attrs.numPages).assign : angular.noop;
       ctrl.ngModelCtrl = { $setViewValue: angular.noop }; // nullModelCtrl
+      ctrl._watchers = [];
 
       ctrl.init = function(ngModelCtrl, config) {
         ctrl.ngModelCtrl = ngModelCtrl;
@@ -18,11 +19,11 @@ angular.module('ui.bootstrap.paging', [])
         };
 
         if ($attrs.itemsPerPage) {
-          $scope.$parent.$watch($parse($attrs.itemsPerPage), function(value) {
+          ctrl._watchers.push($scope.$parent.$watch($parse($attrs.itemsPerPage), function(value) {
             ctrl.itemsPerPage = parseInt(value, 10);
             $scope.totalPages = ctrl.calculateTotalPages();
             ctrl.updatePage();
-          });
+          }));
         } else {
           ctrl.itemsPerPage = config.itemsPerPage;
         }
@@ -80,6 +81,12 @@ angular.module('ui.bootstrap.paging', [])
           ctrl.ngModelCtrl.$render();
         }
       };
+
+      $scope.$on('$destroy', function() {
+        while (ctrl._watchers.length) {
+          ctrl._watchers.shift()();
+        }
+      });
     }
   };
 }]);

src/paging/test/paging.spec.js

@@ -253,4 +253,18 @@ describe('paging factory', function() {
       expect(ctrl.ngModelCtrl.$render).toHaveBeenCalled();
     });
   });
+
+  describe('gc', function() {
+    it('should clear watchers', function() {
+      var watcher1 = jasmine.createSpy('watcher1'),
+        watcher2 = jasmine.createSpy('watcher2');
+      ctrl._watchers = [watcher1, watcher2];
+
+      $scope.$destroy();
+
+      expect(ctrl._watchers.length).toBe(0);
+      expect(watcher1).toHaveBeenCalled();
+      expect(watcher2).toHaveBeenCalled();
+    });
+  });
 });