fix(transcluding component factory): allow removing components that have no content to transclude

Author: chirayuk

lib/core_dom/transcluding_component_factory.dart

@@ -32,14 +32,16 @@ class ContentPort {
 
   content(dom.Element elt) {
     var hash = elt.hashCode;
-    var beginComment = new dom.Comment("content $hash");
+    var beginComment = null;
 
     if (_childNodes.isNotEmpty) {
+      beginComment = new dom.Comment("content $hash");
       elt.parent.insertBefore(beginComment, elt);
       elt.parent.insertAllBefore(_childNodes, elt);
       elt.parent.insertBefore(new dom.Comment("end-content $hash"), elt);
       _childNodes = [];
     }
+
     elt.remove();
     return beginComment;
   }
@@ -48,6 +50,10 @@ class ContentPort {
     // Search for endComment and extract everything in between.
     // TODO optimize -- there may be a better way of pulling out nodes.
 
+    if (_beginComment == null) {
+      return;
+    }
+
     var endCommentText = "end-${_beginComment.text}";
 
     var next;

test/core_dom/compiler_spec.dart

@@ -348,6 +348,14 @@ void main() {
         expect(element).toHaveText('And jump');
       }));
 
+      it('should safely remove transcluding components that transclude no content', async(() {
+        _.rootScope.context['flag'] = true;
+        _.compile('<div ng-if=flag><simple></simple></div>');
+        microLeap(); _.rootScope.apply();
+        _.rootScope.context['flag'] = false;
+        microLeap(); _.rootScope.apply();
+      }));
+
       it('should store ElementProbe with Elements', async(() {
         _.compile('<div><simple>innerText</simple></div>');
         microLeap();