Re: [henshin-user] Issue with (and fix for) EGraph.copy

[Steffen Zschaler <steffen.zschaler@xxxxxxxxx>]

Thanks, Daniel.

I have thought about this a little more and have realised that perhaps there's a more general issue here. There may well be other metamodels with such "non-standard" implementations, which consequently would require specialised copiers, too. As a result, it might even make sense to allow the copier to be externally configured somehow perhaps through some sort of factory method in EGraphImpl with a default implementation producing the result that is currently hard-coded in EGraphImpl.copy. So

public class EGraphImpl extends LinkedHashSet<EObject> implements EGraph {
	...
	public EGraph copy(Map<EObject, EObject> copies) {
		if (copies==null) {
			Copier copier = createGraphCopier();
			copier.copyAll(getRoots());
			copier.copyReferences();
			copies = copier;
		}
		...
	}
	
	/**
	 * Create an instance of {@link EcoreUtil.Copier} that can be used to copy the elements in this graph.
	 * By default produces a copier that can handle standard metamodels and Ecore instances. If your models 
	 * need special treatment when copying, override this method. In particular, make sure that all model 
	 * elements that can be found in the source model have an image in the copier map after copying.
	 */
	protected Copier createGraphCopier() {
		if (packages.contains(EcorePackage.eINSTANCE)) {
			return new EcoreCopier();
		} else {
			return new Copier();
		}

	}
	...

Best regards,

Steffen

On 25/09/2017 09:45, Daniel Strüber wrote:

Hi Steffen,

thanks! What you describe makes sense. Therefore, I have modified EGraphImpl.copy() to use your copier in case that the EGraph contains instances from Ecore: [1] https://git.eclipse.org/r/#/c/105679/

Best regards,
Daniel

Am 21.09.2017 um 12:39 schrieb Steffen Zschaler:

Hi,

I've been trying to run some transformations over meta-models (i.e., instances of Ecore). As part of this, I needed to copy EGraphs and used EGraph.copy. This crashed with an NPE.

I did some digging and found out that the reason is that there is an issue with how EcoreUtil.Copier works and how types and generic types are handled in Ecore. Details here: https://stackoverflow.com/questions/46323548/copying-egenerictype-instances-with-ecoreutil-copier As a result, when calling EGraph.copy (null), in some cases the code can then not find copies of the EGenericType instances in the resulting map and adding them to the new graph crashes.

I have written a slightly extended version of EcoreUtil.Copier which I attach. I have so far used this like in the code below, but was wondering whether there's an interest to include this directly into Henshin instead.

// Given a graph graph1 with some Ecore instances in it
EcoreCopier copier = new EcoreCopier();
copier.copyAll(graph1.getRoots());
copier.copyReferences();

EGraph graph2 = graph1.copy(copier);

Best regards,

Steffen

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Dr. rer. nat. Steffen Zschaler AHEA
Senior Lecturer

King's College London
Department of Informatics

Email szschaler@xxxxxxx
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