[5617] Fix duplication of an element to a mono valued containment

Bug: #5617
Signed-off-by: Arthur Daussy <arthur.daussy@obeo.fr>

Author: adaussy

CHANGELOG.adoc

@@ -27,6 +27,7 @@
 
 - https://github.com/eclipse-sirius/sirius-web/issues/5491[#5491] [test] Add missing module in tsconfig for the playwright package
 - https://github.com/eclipse-sirius/sirius-web/issues/5627[#5627] [sirius-web] Fix the duplication of an element with incoming non changeable references
+- https://github.com/eclipse-sirius/sirius-web/issues/5617[#5617] [sirius-web] Fix duplication of an element to a mono valued containment feature while updating incoming reference.
 
 
 === New Features

packages/sirius-web/backend/sirius-web-application/src/main/java/org/eclipse/sirius/web/application/views/explorer/services/DefaultObjectDuplicator.java

@@ -65,22 +65,22 @@ public IStatus duplicateObject(IEditingContext editingContext, EObject objectToD
                     .filter(reference -> containmentFeature.equals(reference.getName()))
                     .findFirst();
 
-            Optional<Object> optionalDuplicatedObject = Optional.empty();
+            Optional<EObject> optionalDuplicatedObject = Optional.empty();
 
             if (optionalEReference.isPresent()) {
                 if (this.canFeatureBeSet(containerEObject, optionalEReference.get())) {
-                    optionalDuplicatedObject = this.duplicateObject(objectToDuplicate, settings)
-                            .flatMap(eObject -> this.addOrSetEObjet(optionalEditingDomain.get(), eObject, containerEObject, optionalEReference.get()));
-                    if (optionalDuplicatedObject.isPresent()) {
+                    optionalDuplicatedObject = this.duplicateObject(objectToDuplicate, settings);
+                    optionalDuplicatedObject.ifPresent(eObject -> this.addOrSetEObjet(optionalEditingDomain.get(), eObject, containerEObject, optionalEReference.get()));
+                    if (optionalDuplicatedObject.isPresent() && optionalDuplicatedObject.get().eContainer() != null) {
                         result = new Success(ChangeKind.SEMANTIC_CHANGE, Map.of(IObjectDuplicator.NEW_OBJECT, optionalDuplicatedObject.get()));
                     }
                 } else {
                     result = new Failure(this.messageService.upperBoundaryReached(objectToDuplicate.eClass().getName(), containmentFeature));
                 }
             }
 
-            if (settings.updateIncomingReferences() && optionalDuplicatedObject.isPresent() && optionalDuplicatedObject.get() instanceof EObject duplicatedEObject) {
-                this.updateIncomingReferences(duplicatedEObject, objectToDuplicate);
+            if (settings.updateIncomingReferences() && optionalDuplicatedObject.isPresent()) {
+                this.updateIncomingReferences(optionalDuplicatedObject.get(), objectToDuplicate);
             }
         }
         return result;
@@ -111,18 +111,15 @@ private void updateIncomingReferences(EObject duplicatedEObject, EObject objectT
                 });
     }
 
-    private Optional<Object> addOrSetEObjet(EditingDomain editingDomain, EObject duplicatedObject, EObject container, EReference eReference) {
+    private void addOrSetEObjet(EditingDomain editingDomain, EObject duplicatedObject, EObject container, EReference eReference) {
         Command command;
         if (eReference.isMany()) {
             command = new AddCommand(editingDomain, container, eReference, List.of(duplicatedObject));
         } else {
             command = new SetCommand(editingDomain, container, eReference, duplicatedObject);
         }
         editingDomain.getCommandStack().execute(command);
-        if (command.getResult().size() == 1) {
-            return Optional.of(command.getResult().iterator().next());
-        }
-        return Optional.empty();
+
     }
 
     private Optional<EObject> duplicateObject(EObject eObjectToDuplicate, DuplicationSettings settings) {