fix(ngAnimateChildren): make it compatible with ngIf

Previously, ngAnimateChildren would set the data on the element
in an $observe listener, which means the data was available after one digest happend.
This is too late when the element is animated immediately after compilation, as happens with ngIf.
Now the data is also set right in the linking function.

Fixes #13865
Closes #13876

Author: Narretz

src/ngAnimate/animateChildrenDirective.js

@@ -1,15 +1,22 @@
 'use strict';
 
-var $$AnimateChildrenDirective = [function() {
-  return function(scope, element, attrs) {
-    var val = attrs.ngAnimateChildren;
-    if (angular.isString(val) && val.length === 0) { //empty attribute
-      element.data(NG_ANIMATE_CHILDREN_DATA, true);
-    } else {
-      attrs.$observe('ngAnimateChildren', function(value) {
+var $$AnimateChildrenDirective = ['$interpolate', function($interpolate) {
+  return {
+    link: function(scope, element, attrs) {
+      var val = attrs.ngAnimateChildren;
+      if (angular.isString(val) && val.length === 0) { //empty attribute
+        element.data(NG_ANIMATE_CHILDREN_DATA, true);
+      } else {
+        // Interpolate and set the value, so that it is available to
+        // animations that run right after compilation
+        setData($interpolate(attrs.ngAnimateChildren)(scope));
+        attrs.$observe('ngAnimateChildren', setData);
+      }
+
+      function setData(value) {
         value = value === 'on' || value === 'true';
         element.data(NG_ANIMATE_CHILDREN_DATA, value);
-      });
+      }
     }
   };
 }];

test/ngAnimate/animateSpec.js

@@ -1492,6 +1492,22 @@ describe("animations", function() {
       dealoc(element);
       dealoc(child);
     }));
+
+    it('should respect the value if the directive is on an element with ngIf',
+      inject(function($animate, $rootScope, $rootElement, $compile) {
+
+      parent.attr('ng-animate-children', 'true');
+      parent.attr('ng-if', 'true');
+      element.attr('ng-if', 'true');
+
+      $rootElement.append(parent);
+      parent.append(element);
+
+      $compile(parent)($rootScope);
+      $rootScope.$digest();
+
+      expect(captureLog.length).toBe(2);
+    }));
   });
 
   describe('.pin()', function() {