Match only based on Event-B names and qualified references, not EMF IDs

We don't care about generic EMF objects, only about EventBElement
(right..?). This noticeably improves performance when saving (almost
twice as fast for a medium-sized machine with 30 invariants).

org.eventb.texteditor.feature/feature.xml

@@ -9,6 +9,7 @@
    <description>
       A text editor for the Rodin platform to edit Event-B models
 --- Release History ---
+3.6.0 - Improved performance when saving larger files.
 3.5.1 - Fix "Empty label" error when adding a variant to a machine
 3.5.0 - Compatibility with EventB-EMF 7.0.0 - fixes CamilleX dependency conflict. Fixed OOM error when top-level end keyword is missing.
 3.4.1 - Internal updates to the build process - no visible changes.

org.eventb.texttools/src/org/eventb/texttools/diffmerge/EventBEObjectMatcher.java

@@ -12,10 +12,7 @@ import org.eclipse.emf.compare.Comparison;
 import org.eclipse.emf.compare.Match;
 import org.eclipse.emf.compare.match.eobject.IEObjectMatcher;
 import org.eclipse.emf.ecore.EObject;
-import org.eclipse.emf.ecore.InternalEObject;
-import org.eclipse.emf.ecore.resource.Resource;
-import org.eclipse.emf.ecore.util.EcoreUtil;
-import org.eclipse.emf.ecore.xmi.XMIResource;
+import org.eventb.emf.core.EventBElement;
 import org.eventb.emf.core.EventBNamed;
 import org.eventb.emf.core.machine.Variant;
 
@@ -76,7 +73,8 @@ public class EventBEObjectMatcher implements IEObjectMatcher {
 			return false;
 		}
 		/*
-		 * Only one variant may exist in a model, so two variants are a match
+		 * Only one variant may exist in a model, so two variants are a match.
+		 * TODO Rodin now allows multiple variants per model, but Camille doesn't support that properly yet...
 		 */
 		if (left instanceof Variant) {
 			assert candidate instanceof Variant;
@@ -84,51 +82,33 @@ public class EventBEObjectMatcher implements IEObjectMatcher {
 		}
 
 		/*
-		 * Improve matching for event b named objects with same name
+		 * Match named elements based on only their name and not their fully qualified reference,
+		 * so that renaming a component doesn't cause mismatches for all the elements in it.
 		 */
 		if (left instanceof EventBNamed) {
 			assert candidate instanceof EventBNamed;
 			EventBNamed l = (EventBNamed) left;
 			EventBNamed c = (EventBNamed) candidate;
 
-			if (l.getName().equals(c.getName())) {
-				return true;
-			}
+			return l.getName().equals(c.getName());
 		}
 
 		/*
-		 * rely on emf identifiers after the event-b specific code
+		 * Match unnamed objects based on their fully qualified reference,
+		 * which includes a unique ID generated by Event-B EMF.
 		 */
-		String idLeft = getEMFId(left);
-		if (idLeft == null) {
-			return false;
+		if (left instanceof EventBElement) {
+			assert candidate instanceof EventBElement;
+			EventBElement l = (EventBElement)left;
+			EventBElement c = (EventBElement)candidate;
+			return l.getReference().equals(c.getReference());
 		}
-		String idCandidate = getEMFId(candidate);
-		return idLeft.equals(idCandidate);
+
+		return false;
 	}
 
 	private static boolean areSameType(final EObject obj1, final EObject obj2) {
 		return obj1 != null && obj2 != null
 				&& obj1.eClass().equals(obj2.eClass());
 	}
-
-	private static String getEMFId(EObject eObject) {
-		final String identifier;
-		if (eObject.eIsProxy()) {
-			identifier = ((InternalEObject) eObject).eProxyURI().fragment();
-		} else {
-			String functionalId = EcoreUtil.getID(eObject);
-			if (functionalId != null) {
-				identifier = functionalId;
-			} else {
-				final Resource eObjectResource = eObject.eResource();
-				if (eObjectResource instanceof XMIResource) {
-					identifier = ((XMIResource) eObjectResource).getID(eObject);
-				} else {
-					identifier = null;
-				}
-			}
-		}
-		return identifier;
-	}
 }