fix($animate): ensure that animateable directives cancel expired leave animations

If enter -> leave -> enter -> leave occurs then the first leave animation will
animate alongside the second. This causes the very first DOM node (the view in ngView
for example) to animate at the same time as the most recent DOM node which ends
up being an undesired effect. This fix takes care of this issue.

Closes #5886

src/ng/directive/ngIf.js

@@ -84,7 +84,7 @@ var ngIfDirective = ['$animate', function($animate) {
     restrict: 'A',
     $$tlb: true,
     link: function ($scope, $element, $attr, ctrl, $transclude) {
-        var block, childScope;
+        var block, childScope, previousElements;
         $scope.$watch($attr.ngIf, function ngIfWatchAction(value) {
 
           if (toBoolean(value)) {
@@ -102,14 +102,19 @@ var ngIfDirective = ['$animate', function($animate) {
               });
             }
           } else {
-
-            if (childScope) {
+            if(previousElements) {
+              previousElements.remove();
+              previousElements = null;
+            }
+            if(childScope) {
               childScope.$destroy();
               childScope = null;
             }
-
-            if (block) {
-              $animate.leave(getBlockElements(block.clone));
+            if(block) {
+              previousElements = getBlockElements(block.clone);
+              $animate.leave(previousElements, function() {
+                previousElements = null;
+              });
               block = null;
             }
           }

src/ng/directive/ngInclude.js

@@ -177,15 +177,23 @@ var ngIncludeDirective = ['$http', '$templateCache', '$anchorScroll', '$animate'
       return function(scope, $element, $attr, ctrl, $transclude) {
         var changeCounter = 0,
             currentScope,
+            previousElement,
             currentElement;
 
         var cleanupLastIncludeContent = function() {
-          if (currentScope) {
+          if(previousElement) {
+            previousElement.remove();
+            previousElement = null;
+          }
+          if(currentScope) {
             currentScope.$destroy();
             currentScope = null;
           }
           if(currentElement) {
-            $animate.leave(currentElement);
+            $animate.leave(currentElement, function() {
+              previousElement = null;
+            });
+            previousElement = currentElement;
             currentElement = null;
           }
         };

src/ng/directive/ngSwitch.js

@@ -138,12 +138,31 @@ var ngSwitchDirective = ['$animate', function($animate) {
       var watchExpr = attr.ngSwitch || attr.on,
           selectedTranscludes,
           selectedElements,
+          previousElements,
           selectedScopes = [];
 
       scope.$watch(watchExpr, function ngSwitchWatchAction(value) {
-        for (var i= 0, ii=selectedScopes.length; i<ii; i++) {
-          selectedScopes[i].$destroy();
-          $animate.leave(selectedElements[i]);
+        var i, ii = selectedScopes.length;
+        if(ii > 0) {
+          if(previousElements) {
+            for (i = 0; i < ii; i++) {
+              previousElements[i].remove();
+            }
+            previousElements = null;
+          }
+
+          previousElements = [];
+          for (i= 0; i<ii; i++) {
+            var selected = selectedElements[i];
+            selectedScopes[i].$destroy();
+            previousElements[i] = selected;
+            $animate.leave(selected, function() {
+              previousElements.splice(i, 1);
+              if(previousElements.length === 0) {
+                previousElements = null;
+              }
+            });
+          }
         }
 
         selectedElements = [];

src/ngAnimate/animate.js

@@ -764,6 +764,27 @@ angular.module('ngAnimate', ['ng'])
           return;
         }
 
+        if(animationEvent == 'leave') {
+          //there's no need to ever remove the listener since the element
+          //will be removed (destroyed) after the leave animation ends or
+          //is cancelled midway
+          element.one('$destroy', function(e) {
+            var element = angular.element(this);
+            var state = element.data(NG_ANIMATE_STATE) || {};
+            var activeLeaveAnimation = state.active['ng-leave'];
+            if(activeLeaveAnimation) {
+              var animations = activeLeaveAnimation.animations;
+
+              //if the before animation is completed then the element will be
+              //removed shortly after so there is no need to cancel the animation
+              if(!animations[0].beforeComplete) {
+                cancelAnimations(animations);
+                cleanup(element, 'ng-leave');
+              }
+            }
+          });
+        }
+
         //the ng-animate class does nothing, but it's here to allow for
         //parent animations to find and cancel child animations when needed
         element.addClass(NG_ANIMATE_CLASS_NAME);

src/ngRoute/directive/ngView.js

@@ -189,6 +189,7 @@ function ngViewFactory(   $route,   $anchorScroll,   $animate) {
     link: function(scope, $element, attr, ctrl, $transclude) {
         var currentScope,
             currentElement,
+            previousElement,
             autoScrollExp = attr.autoscroll,
             onloadExp = attr.onload || '';
 
@@ -196,12 +197,19 @@ function ngViewFactory(   $route,   $anchorScroll,   $animate) {
         update();
 
         function cleanupLastView() {
-          if (currentScope) {
+          if(previousElement) {
+            previousElement.remove();
+            previousElement = null;
+          }
+          if(currentScope) {
             currentScope.$destroy();
             currentScope = null;
           }
           if(currentElement) {
-            $animate.leave(currentElement);
+            $animate.leave(currentElement, function() {
+              previousElement = null;
+            });
+            previousElement = currentElement;
             currentElement = null;
           }
         }

test/ng/directive/ngIfSpec.js

@@ -277,4 +277,42 @@ describe('ngIf animations', function () {
       expect(element.children().length).toBe(0);
   }));
 
+  it('should destroy the previous leave animation if a new one takes place', function() {
+    module(function($provide) {
+      $provide.value('$animate', {
+        enabled : function() { return true; },
+        leave : function() {
+          //DOM operation left blank
+        },
+        enter : function(element, parent) {
+          parent.append(element);
+        }
+      });
+    });
+    inject(function ($compile, $rootScope, $animate) {
+      var item;
+      var $scope = $rootScope.$new();
+      element = $compile(html(
+        '<div>' +
+          '<div ng-if="value">Yo</div>' +
+        '</div>'
+      ))($scope);
+
+      $scope.$apply('value = true');
+
+      var destroyed, inner = element.children(0);
+      inner.on('$destroy', function() {
+        destroyed = true;
+      });
+
+      $scope.$apply('value = false');
+
+      $scope.$apply('value = true');
+
+      $scope.$apply('value = false');
+
+      expect(destroyed).toBe(true);
+    });
+  });
+
 });

test/ng/directive/ngIncludeSpec.js

@@ -663,4 +663,44 @@ describe('ngInclude animations', function() {
       expect(itemA).not.toEqual(itemB);
   }));
 
+  it('should destroy the previous leave animation if a new one takes place', function() {
+    module(function($provide) {
+      $provide.value('$animate', {
+        enabled : function() { return true; },
+        leave : function() {
+          //DOM operation left blank
+        },
+        enter : function(element, parent, after) {
+          angular.element(after).after(element);
+        }
+      });
+    });
+    inject(function ($compile, $rootScope, $animate, $templateCache) {
+      var item;
+      var $scope = $rootScope.$new();
+      element = $compile(html(
+        '<div>' +
+          '<div ng-include="inc">Yo</div>' +
+        '</div>'
+      ))($scope);
+
+      $templateCache.put('one', [200, '<div>one</div>', {}]);
+      $templateCache.put('two', [200, '<div>two</div>', {}]);
+
+      $scope.$apply('inc = "one"');
+
+      var destroyed, inner = element.children(0);
+      inner.on('$destroy', function() {
+        destroyed = true;
+      });
+
+      $scope.$apply('inc = "two"');
+
+      $scope.$apply('inc = "one"');
+
+      $scope.$apply('inc = "two"');
+
+      expect(destroyed).toBe(true);
+    });
+  });
 });

test/ng/directive/ngSwitchSpec.js

@@ -293,4 +293,42 @@ describe('ngSwitch animations', function() {
       expect(item.element.text()).toBe('three');
   }));
 
+  it('should destroy the previous leave animation if a new one takes place', function() {
+    module(function($provide) {
+      $provide.value('$animate', {
+        enabled : function() { return true; },
+        leave : function() {
+          //DOM operation left blank
+        },
+        enter : function(element, parent, after) {
+          angular.element(after).after(element);
+        }
+      });
+    });
+    inject(function ($compile, $rootScope, $animate, $templateCache) {
+      var item;
+      var $scope = $rootScope.$new();
+      element = $compile(html(
+        '<div ng-switch="inc">' +
+          '<div ng-switch-when="one">one</div>' +
+          '<div ng-switch-when="two">two</div>' +
+        '</div>'
+      ))($scope);
+
+      $scope.$apply('inc = "one"');
+
+      var destroyed, inner = element.children(0);
+      inner.on('$destroy', function() {
+        destroyed = true;
+      });
+
+      $scope.$apply('inc = "two"');
+
+      $scope.$apply('inc = "one"');
+
+      $scope.$apply('inc = "two"');
+
+      expect(destroyed).toBe(true);
+    });
+  });
 });

test/ngAnimate/animateSpec.js

@@ -3335,5 +3335,40 @@ describe("ngAnimate", function() {
         expect(cancelReflowCallback).toHaveBeenCalled();
       });
     });
+
+    it('should immediately close off a leave animation if the element is removed from the DOM', function() {
+      var stat;
+      module(function($animateProvider) {
+        $animateProvider.register('.going', function() {
+          return {
+            leave : function() {
+              //left blank so it hangs
+              stat = 'leaving';
+              return function(cancelled) {
+                stat = cancelled && 'gone';
+              };
+            }
+          };
+        });
+      });
+      inject(function($sniffer, $compile, $rootScope, $rootElement, $animate, $timeout) {
+
+        $animate.enabled(true);
+
+        var element = $compile('<div id="parentGuy"></div>')($rootScope);
+        var child = $compile('<div class="going"></div>')($rootScope);
+        $rootElement.append(element);
+        element.append(child);
+
+        $animate.leave(child);
+        $rootScope.$digest();
+
+        expect(stat).toBe('leaving');
+
+        child.remove();
+
+        expect(stat).toBe('gone');
+      });
+    });
   });
 });

test/ngRoute/directive/ngViewSpec.js

@@ -833,6 +833,50 @@ describe('ngView animations', function() {
           }
         });
       });
+
+      it('should destroy the previous leave animation if a new one takes place', function() {
+        module(function($provide) {
+          $provide.value('$animate', {
+            enabled : function() { return true; },
+            leave : function() {
+              //DOM operation left blank
+            },
+            enter : function(element, parent, after) {
+              angular.element(after).after(element);
+            }
+          });
+        });
+        inject(function ($compile, $rootScope, $animate, $location) {
+          var item;
+          var $scope = $rootScope.$new();
+          element = $compile(html(
+            '<div>' +
+              '<div ng-view></div>' +
+            '</div>'
+          ))($scope);
+
+          $scope.$apply('value = true');
+
+          $location.path('/bar');
+          $rootScope.$digest();
+
+          var destroyed, inner = element.children(0);
+          inner.on('$destroy', function() {
+            destroyed = true;
+          });
+
+          $location.path('/foo');
+          $rootScope.$digest();
+
+          $location.path('/bar');
+          $rootScope.$digest();
+
+          $location.path('/bar');
+          $rootScope.$digest();
+
+          expect(destroyed).toBe(true);
+        });
+      });
     });