Issues adding source code to a custom DSL file programatically - dsl

Question

I currently have a xtext grammar that looks like the following :
Features:
'feature' name = ID
'{'(
('action' '{' action+=Actions (',' action+=Actions)* '}')? &
('dependencies' '{' dependencies = Dependencies '}')? &
('children' '{' children = Children '}')?
)'}'
;
What I want to do with this is add an action to an already existing source file programatically, for that I am using the IUnitOfWork.Void class that I subclass for easier implementation , it currently looks like this (the meaningful part of it) :
final XtextEditor editor = (XtextEditor)sourcepart;
final IXtextDocument document = editor.getDocument();
document.modify(new IUnitOfWork.Void<XtextResource>(){
public void process (XtextResource resource) throws Exception {
IParseResult parseResult = resource.getParseResult();
if(parseResult ==null)
return;
CompositeNode rootNode=(CompositeNode) parseResult.getRootNode();
LeafNode node = (LeafNode)NodeModelUtils.findLeafNodeAtOffset(rootNode, 0);
EObject object =NodeModelUtils.findActualSemanticObjectFor(node);
Through this I traverse the tree of the model and get to my Features object to which I want to add an action to (this is done through a pop up menu in a custom Tree View I'm implementing)
Here's my problem : whenever I want to add an action it screws up the way the tags are placed in the source file , and by that I mean that instead of :
action {
act1.set (foo),
act2.set (bar),
act3.set (baz),
act4.set (booze) //where this is the new action that I add
}
it will add it as
action {
act1.set (foo),
act2.set (bar),
act3.set (baz)
}
action {
act4.set(booze)
}
And this is illegal by the rules of my grammar, and I'm not allowed to change the way it should be written. (I am allowed to make small changes to the way the rules are implemented, but would really want to avoid it as it would mean a whole new amount of work to reimplement other things that depend on them)
I've tried :
adding it directly through Features.getAction().add(*the new action);
copying the items in the list into an array with the toArray() method so as to avoid referencing, adding my action to the array, clearing the list then adding all the elements again one by one
creating an entirely new Features object and setting everything in it to be the same as the currently edited one then replacing the feature with the new one
And I'm out of ideas after that. The frustrating part is that the 3rd method worked for a different kind of object in my grammar and had no errors there.
How could I make this work ?

Answer 1

this is a bug in xtext. (can you please file a ticket?)
as a workaround you may use the following
Features:
'feature' name = ID
'{'(
('action' '{' actionList=ActionList '}')? &
('dependencies' '{' dependencies = Dependencies '}')? &
('children' '{' children = Children '}')?
)'}';
ActionList:
(action+=Action (',' action+=Action)*)
;