refactor(accordion): use ngAnimate for animations

- Deprecate collapse module
  Consider removing it after transition module is deprecated as well.

Author: chrisirhc

src/accordion/accordion.js

@@ -1,4 +1,4 @@
-angular.module('ui.bootstrap.accordion', ['ui.bootstrap.collapse'])
+angular.module('ui.bootstrap.accordion', [])
 
 .constant('accordionConfig', {
   closeOthers: true
@@ -129,4 +129,64 @@ angular.module('ui.bootstrap.accordion', ['ui.bootstrap.collapse'])
       });
     }
   };
-});
+})
+
+/**
+ * Animations based on addition and removal of `in` class
+ * This requires the bootstrap classes to be present in order to take advantage
+ * of the animation classes.
+ */
+.animation('.panel-collapse', function () {
+  return {
+    beforeAddClass: function (element, className, done) {
+      if (className == 'in') {
+        element
+          .removeClass('collapse')
+          .addClass('collapsing')
+          .css({height: '0'});
+      }
+      done();
+    },
+    addClass: function (element, className, done) {
+      if (className == 'in') {
+        element
+          .css({height: element[0].scrollHeight + 'px'})
+          .removeClass('collapsing')
+          // FIXME awaiting: https://github.com/angular/angular.js/pull/5984
+          .on('$animate:close', function closeFn() {
+            element
+              .css({height: 'auto'});
+            element.off('$animate:close', closeFn);
+          });
+      }
+      done();
+    },
+    beforeRemoveClass: function (element, className, done) {
+      if (className == 'in') {
+        element
+          // initially all panel collapse have the collapse class, this removal
+          // prevents the animation from jumping to collapsed state
+          .removeClass('collapse')
+          .addClass('collapsing')
+          .css({height: element[0].scrollHeight + 'px'});
+      }
+      done();
+    },
+    removeClass: function (element, className, done) {
+      if (className == 'in') {
+        element
+          .css({height: '0'})
+          .removeClass('collapsing')
+          // FIXME awaiting: https://github.com/angular/angular.js/pull/5984
+          .on('$animate:close', function closeFn() {
+            element
+              .addClass('collapse');
+            element.off('$animate:close', closeFn);
+          });
+      }
+      done();
+    }
+  };
+})
+
+;

src/accordion/test/accordion.spec.js

@@ -265,8 +265,8 @@ describe('accordion', function () {
       });
 
       it('should have visible panel body when the group with isOpen set to true', function () {
-        expect(findGroupBody(0)[0].clientHeight).not.toBe(0);
-        expect(findGroupBody(1)[0].clientHeight).toBe(0);
+        expect(findGroupBody(0)).toHaveClass('in');
+        expect(findGroupBody(1)).not.toHaveClass('in');
       });
     });
 

src/collapse/collapse.js

@@ -1,3 +1,6 @@
+/**
+ * @deprecated Switching over to using ngAnimate for animations
+ */
 angular.module('ui.bootstrap.collapse', ['ui.bootstrap.transition'])
 
   .directive('collapse', ['$transition', function ($transition) {

template/accordion/accordion-group.html

@@ -4,7 +4,7 @@ <h4 class="panel-title">
       <a class="accordion-toggle" ng-click="toggleOpen()" accordion-transclude="heading"><span ng-class="{'text-muted': isDisabled}">{{heading}}</span></a>
     </h4>
   </div>
-  <div class="panel-collapse" collapse="!isOpen">
+  <div class="panel-collapse collapse" ng-class="{in: isOpen}">
 	  <div class="panel-body" ng-transclude></div>
   </div>
 </div>