fix(ngAnimate): always apply a preparation reflow for CSS-based animations

It's unpredictable sometimes to ensure that a browser triggers a reflow
for an animation. Prior to this patch, reflows would be applied
carefully in between parent/child DOM structure, but that doesn't seem
to be enough for animations that contain complex CSS styling rules.

Closes angular#12553
Closes angular#12554
Closes angular#12267

Author: matsko

src/ngAnimate/animateQueue.js

@@ -67,9 +67,9 @@ var $$AnimateQueueProvider = ['$animateProvider', function($animateProvider) {
   });
 
   this.$get = ['$$rAF', '$rootScope', '$rootElement', '$document', '$$body', '$$HashMap',
-               '$$animation', '$$AnimateRunner', '$templateRequest', '$$jqLite',
+               '$$animation', '$$AnimateRunner', '$templateRequest', '$$jqLite', '$$forceReflow',
        function($$rAF,   $rootScope,   $rootElement,   $document,   $$body,   $$HashMap,
-                $$animation,   $$AnimateRunner,   $templateRequest,   $$jqLite) {
+                $$animation,   $$AnimateRunner,   $templateRequest,   $$jqLite,   $$forceReflow) {
 
     var activeAnimationsLookup = new $$HashMap();
     var disabledElementsLookup = new $$HashMap();
@@ -443,6 +443,7 @@ var $$AnimateQueueProvider = ['$animateProvider', function($animateProvider) {
 
         markElementAnimationState(element, RUNNING_STATE);
         var realRunner = $$animation(element, event, animationDetails.options, function(e) {
+          $$forceReflow();
           blockTransitions(getDomNode(e), false);
         });
 

src/ngAnimate/animation.js

@@ -19,8 +19,8 @@ var $$AnimationProvider = ['$animateProvider', function($animateProvider) {
     return element.data(RUNNER_STORAGE_KEY);
   }
 
-  this.$get = ['$$jqLite', '$rootScope', '$injector', '$$AnimateRunner', '$$HashMap', '$$forceReflow',
-       function($$jqLite,   $rootScope,   $injector,   $$AnimateRunner,   $$HashMap,   $$forceReflow) {
+  this.$get = ['$$jqLite', '$rootScope', '$injector', '$$AnimateRunner', '$$HashMap',
+       function($$jqLite,   $rootScope,   $injector,   $$AnimateRunner,   $$HashMap) {
 
     var animationQueue = [];
     var applyAnimationClasses = applyAnimationClassesFactory($$jqLite);
@@ -91,11 +91,8 @@ var $$AnimationProvider = ['$animateProvider', function($animateProvider) {
             result = result.concat(row);
             row = [];
           }
-          row.push({
-            fn: entry.fn,
-            terminal: entry.children.length === 0
-          });
-          entry.children.forEach(function(childEntry) {
+          row.push(entry.fn);
+          forEach(entry.children, function(childEntry) {
             nextLevelEntries++;
             queue.push(childEntry);
           });
@@ -105,17 +102,7 @@ var $$AnimationProvider = ['$animateProvider', function($animateProvider) {
         if (row.length) {
           result = result.concat(row);
         }
-
-        var terminalAnimations = [];
-        var parentAnimations = [];
-        forEach(result, function(result) {
-          if (result.terminal) {
-            terminalAnimations.push(result.fn);
-          } else {
-            parentAnimations.push(result.fn);
-          }
-        });
-        return [parentAnimations, terminalAnimations];
+        return result;
       }
     }
 
@@ -224,27 +211,9 @@ var $$AnimationProvider = ['$animateProvider', function($animateProvider) {
         });
 
         // we need to sort each of the animations in order of parent to child
-        // relationships. This ensures that the child classes are applied at the
-        // right time.
-        var anim = sortAnimations(toBeSortedAnimations);
-        var finalLevel = anim.length - 1;
-
-        // sortAnimations will return two lists of animations. The first list
-        // is all of the parent animations that are likely class-based and the
-        // second list is a collection of the rest. Before we run the second
-        // list we must ensure that atleast one reflow has been passed such that
-        // the preparation classes (ng-enter, class-add, etc...) have been applied
-        // to their associated element.
-        if (anim[0].length) {
-          forEach(anim[0], function(triggerAnimation) {
-            $$forceReflow();
-            triggerAnimation();
-          });
-        } else {
-          $$forceReflow();
-        }
-
-        forEach(anim[1], function(triggerAnimation) {
+        // relationships. This ensures that the parent to child classes are
+        // applied at the right time.
+        forEach(sortAnimations(toBeSortedAnimations), function(triggerAnimation) {
           triggerAnimation();
         });
       });

test/ngAnimate/integrationSpec.js

@@ -249,7 +249,7 @@ describe('ngAnimate integration tests', function() {
       expect(child).not.toHaveClass('expand-add');
     }));
 
-    it('should only issue a reflow for each parent CSS class change that contains ready-to-fire child animations', function() {
+    it('should issue a reflow for each element animation on all DOM levels', function() {
       module('ngAnimateMock');
       inject(function($animate, $compile, $rootScope, $rootElement, $$rAF, $document) {
         element = jqLite(
@@ -273,11 +273,13 @@ describe('ngAnimate integration tests', function() {
         $rootScope.items = [1,2,3,4,5,6,7,8,9,10];
 
         $rootScope.$digest();
-        expect($animate.reflows).toBe(2);
+
+        // 2 parents + 10 items = 12
+        expect($animate.reflows).toBe(12);
       });
     });
 
-    it('should issue a reflow for each parent class-based animation that contains active child animations', function() {
+    it('should issue a reflow for each element and also its children', function() {
       module('ngAnimateMock');
       inject(function($animate, $compile, $rootScope, $rootElement, $$rAF, $document) {
         element = jqLite(
@@ -302,37 +304,9 @@ describe('ngAnimate integration tests', function() {
 
         $rootScope.exp = true;
         $rootScope.$digest();
-        expect($animate.reflows).toBe(2);
-      });
-    });
-
-    it('should only issue one reflow for class-based animations if none of them have children with queued animations', function() {
-      module('ngAnimateMock');
-      inject(function($animate, $compile, $rootScope, $rootElement, $$rAF, $document) {
-        element = jqLite(
-          '<div ng-class="{one:exp}">' +
-             '<div ng-if="exp2"></div>' +
-          '</div>' +
-          '<div ng-class="{two:exp}">' +
-             '<div ng-if="exp2"></div>' +
-          '</div>' +
-          '<div ng-class="{three:exp}"></div>'
-        );
 
-        $rootElement.append(element);
-        jqLite($document[0].body).append($rootElement);
-
-        $compile(element)($rootScope);
-        $rootScope.$digest();
-        expect($animate.reflows).toBe(0);
-
-        $rootScope.exp = true;
-        $rootScope.$digest();
-        expect($animate.reflows).toBe(1);
-
-        $rootScope.exp2 = true;
-        $rootScope.$digest();
-        expect($animate.reflows).toBe(2);
+        // there is one element's expression in there that is false
+        expect($animate.reflows).toBe(6);
       });
     });
 
@@ -356,7 +330,7 @@ describe('ngAnimate integration tests', function() {
         $rootScope.items = [1,2,3,4,5,6,7,8,9,10];
         $rootScope.$digest();
 
-        expect($animate.reflows).toBe(1);
+        expect($animate.reflows).toBe(10);
       });
     });
   });