enabledwhen without using property tester class

Question

I have a tree created using TreeViewer. I want to disable a menu item say "Expand All" when user right clicks on the last tree item (i.e., tree item does not have a child). Using PropertyTester i am able to achieve this. plugin.xml code:

<enabledWhen>
   <with
     variable="selection">
     <iterate
            ifEmpty="false">
            <instanceof
                    value="com.xxx.automation.touchstone.model.GUIObject">
            </instanceof>
     </iterate>
     <test
            forcePluginActivation="true"
            property="com.xxx.automation.touchstone.testers.GUIObjects.canExpandAll"
            value="true">
     </test>
   </with>
</enabledWhen>

I want to know if we can achieve the same without using property tester class. I mean using ContentProvider's hasChildren method within the plugin xml .

Thoughts