Eclipse RCP dynamic MenuContribution hide and unhide with CoreExpression - eclipse

Question

I'm trying currently to add a visibleWhen condition for a MenuContribution in my Eclipse RCP application. We've different versions of our app and we've differentiate them with a IClientConfiguration interface/service which works more or less as feature toggles.
Depending on witch app-$version.product is called different implementations of the configuration will part of the app.
However.. get to the current situation: We've a menu which is defined in a common fragment.e4xmi and I would like to hide one menu depending on the configuration. For that I've added the toggle isAdminMenuActive(). I've hoped that I can create a CoreExpression and using (somehow) the return value of this service. But unfortunately I can't get this to work by now.
What I tried was the following:
fragment.e4xmi:
<elements xsi:type="menu:MenuContribution" xmi:id="_ZuL6oA4IEeqbk5lJVdc6WQ" elementId="com.example.client.menucontribution.administration" parentId="com.example.product.main.menu">
<children xsi:type="menu:Menu" xmi:id="_ngOY4LOMEemRpJf6BiOdqQ" elementId="com.example.client.menu.administration" label="%UI.general.administration">
<visibleWhen xsi:type="ui:CoreExpression" xmi:id="_rrmcQA4lEeqbk5lJVdc6WQ" coreExpressionId="com.example.client.configuration.adminMenuActiveExpression"/>
<children xsi:type="menu:HandledMenuItem" xmi:id="_B4RqsLONEemRpJf6BiOdqQ" elementId="com.example.client.menuitem.action.administration" label="%UI.action" tooltip="%UI.action" command="_XnSp8LOPEemRpJf6BiOdqQ"/>
</children>
</elements>
plugin.xml
<extension
point="org.eclipse.core.expressions.definitions">
<definition
id="com.example.client.configuration.adminMenuActiveExpression">
<with variable="com.example.client.configuration.adminMenuActive">
<equals
value="true">
</equals>
</with>
</definition>
</extension>
Startapp.java
#PostConstruct
public void init(IEclipseContext context) {
context.set(com.example.client.configuration.adminMenuActive,
configuration.isAdminMenuActive().toString());
}
The current behaviour is that the menu is never shown no matter which configuration is loaded. I've tried if the variable is added to the IEclipseContext and this happens very early in the start up phase of the application. Currently I've no idea what's wrong.

Answer 1

Rather than using a core expression in the fragment.e4xmi you can use an 'Imperative Expression'. You do this by changing the 'Visible-When Expression' in the fragment editor.
An imperative expression specifies a Java class which is called directly making it easier to access your code. The method tagged with #Evaluate is called to evaluate the expression. Maybe something like:
#Evaluate
public boolean evaluate(#Named("com.example.client.configuration.adminMenuActive") String active)
{
return Boolean.valueOf(active);
}
Using this makes it much easier to see what is happening.