Deleting Ecore Inheritance Edges

[glsp-bot]

I am currently working on this Issue. From my understanding the handling of deleting inheritance Edges needs to be different from references, since inhertitance in ecore is represented by the eSuperTypes tag in an EClassifier. My question would be wheter or not the DeleteOperationHandler is applicable here? Does the deletion of an inhertance trigger this handler or another one? Currently there seems to be no way to get the source classifier from the elementId in the DeleteOperationHanlder.

```public class EcoreDeleteOperationHandler extends DeleteOperationHandler {
    @Override
    protected boolean delete(String elementId, GModelIndex index, GraphicalModelState graphicalModelState) {

        super.delete(elementId, index, graphicalModelState);
        EcoreModelState modelState = EcoreModelState.getModelState(graphicalModelState);

        modelState.getIndex().getSemantic(elementId).ifPresent(element -> {
            if(element instanceof EReference && ((EReference) element).getEOpposite() != null) {
                EcoreUtil.delete(((EReference) element).getEOpposite());
                modelState.getIndex().getBidirectionalReferences().remove(EcoreEdgeUtil.getStringId((EReference)element));
            }
        });
        modelState.getIndex().getSemantic(elementId).ifPresent(EcoreUtil::remove);
        modelState.getIndex().getNotation(elementId).ifPresent(EcoreUtil::remove);
        return true;
    }

}```

original thread by simongraband

[tortmayr]

Yes the DeleteOperationHandler should be applicable here but I think that inheritance edges are ignored in the current implementation because they have no semantic element counterpart. (hence modelState.getIndex().getSemantic(elementId) will always be empty for inheritance edges)

[tortmayr]

(Without having a detailed look at the code) I think delete method should be adapted to cover this corner case

[tortmayr]

A solution for this could look somewhat like this:

[tortmayr]

If modelState.getIndex().getSemantic(elementId) is present execute the current functionality.

[tortmayr]

but if the semantic element is absent we have to check if this is an inheritance edge.

[tortmayr]

For this I would use modelState.getIndex() to retrieve the corresponding GmodelElement for the given 'elementId'. And check if the GModelElement has the inheritance type.

[tortmayr]

If so the source and target id of the edge have to be mapped to the semantic elements and then the inheritance can be removed there

[glsp-bot]

[simongraband]

I still have 2 questions about this. Currently i am not quite sure how i can get the GModelElement from the modelState.getIndex() and from what element is the elementID in the action? Is it from the Edge itself or from the source of the Edge?

[tortmayr]

The elementId is the id of the edge itself. You could use modelState.getIndex(). findElementByClass(elementId,GEdge.class) to retrieve the corresponding GElement

[glsp-bot]

[simongraband]

I tried the approach you described above:

```modelState.getIndex().getSemantic(elementId).ifPresentOrElse(element -> {
      if (element instanceof EReference && ((EReference) element).getEOpposite() != null) {
            EcoreUtil.delete(((EReference) element).getEOpposite());
            modelState.getIndex().getBidirectionalReferences()
                    .remove(EcoreEdgeUtil.getStringId((EReference) element));
      }
}, () -> {
       if(elementId.equals(Types.INHERITANCE)){
             modelState.getIndex().findElementByClass(elementId, GEdge.class).ifPresent(edge ->{
                 modelState.getIndex().getSemantic(edge.getSourceId(), EClass.class).ifPresent(source ->{
                        EClass target = modelState.getIndex().getSemantic(edge.getSourceId(), EClass.class).get();
                        source.getESuperTypes().remove(target);
                        modelState.getIndex().remove(edge);
                  });;
              });
        }
});```

However it is not working, Theia notices that something is changing, but neither the Editor nor the Ecore file remove the inheritance/the ESuperTypes.

Did i forget something here? If i just delete the ESuperType Attribute in the Ecore file it works, which should be what source.getESuperTypes().remove(target) does right?

EDIT: I just realized that elementId.equals(Types.INHERITANCE) doesnt make any sense and that i would need the elementTypeId instead. Is there a way to get the elementTypeId? The Code also does not work if i remove the if-statement.

[tortmayr]

EClass target = modelState.getIndex().getSemantic(edge.getSourceId(), EClass.class).get()

[tortmayr]

Shouldn't this be ...getSemantic(edge.getTargetId()...?

[tortmayr]

And for checking the element type id I'd suggest to move the if statement inside of the first if present clause

[tortmayr]

modelState.getIndex().findElementByClass(elementId, GEdge.class).ifPresent(edge ->{ if (edge.getType().equals(Types.INHERITANCE)){...

[glsp-bot]

[simongraband]

Sure... i changed it however it still doesn´t work. I debugged it and it seems like it isn´t able to find the GEdge for the elementId, since the debugger is jumping the whole block.

[glsp-bot]

[simongraband]

It seems like the elementId is the ID of the sourceClass. I tested this, and the same id is send when i delete the SourceClass and the Node. Is this intended?

[tortmayr]

That's definitly not intended. According to https://github.com/eclipsesource/ecore-glsp/blob/master/server/org.eclipse.emfcloud.ecore.glsp/src/main/java/org/eclipse/emfcloud/ecore/glsp/gmodel/GModelFactory.java#L199 the elementId should be sourceId+'_'+targetId.

[glsp-bot]

[simongraband]

I think that inheritance edges are never added to the GModelFactory in the first place. See here: https://github.com/eclipsesource/ecore-glsp/blob/de808d766176a9567d39cc3d25c8b818831bebd5/server/org.eclipse.emfcloud.ecore.glsp/src/main/java/org/eclipse/emfcloud/ecore/glsp/operationhandler/CreateEcoreEdgeOperationHandler.java#L63

[glsp-bot]

[simongraband]

As far as i understand it, currently inheritance edges are rendered when the ESuperType is set. However, this prevents us from storing the postition of the inheritance, since there is no semantic element for it. Furthermore it cannot be deleted, since the Edge is not found in the index, because it is not stored there. The Second Issue could be worked around by just looking up the sourceId from the name of the deleted element, but this will still not allow us to store the position.
So the question would be what is the cleanest way for storing the inheritance edges in the index, without 'breaking' the rules of Ecore, since in Ecore its only described via the ESuperClass-Attribute, right?

[tortmayr]

The position is stored in the notation element and not the semantic element. And there should definitively be a corresponding notation element for each inheritance edge. The edge should be in the index as well so looks like there is a bug in the creation process of inheritance edges.

[tortmayr]

Could you push you current state so that I can have a look at the code?

[glsp-bot]

[simongraband]

Here is my current state: https://github.com/simongraband/ecore-glsp/tree/inheritanceFix-103