[fix] Start and Done prevent succession removal when removed

Start and Done special actions break the automatic cleanup of succession
edge when they are deleted from the diagram.

+ Avoid creation of Dependency edge tool on those actions.

Bug: eclipse-syson#269
Signed-off-by: Jerome Gout <jerome.gout@obeosoft.com>

backend/services/syson-services/src/main/java/org/eclipse/syson/services/RelatedElementsSwitch.java

@@ -13,6 +13,7 @@
 package org.eclipse.syson.services;
 
 import java.util.HashSet;
+import java.util.List;
 import java.util.Objects;
 import java.util.Set;
 
@@ -116,8 +117,7 @@ public Set<EObject> caseSuccession(Succession object) {
         if (this.eStructuralFeature.equals(SysmlPackage.eINSTANCE.getRelationship_Target())
                 || this.eStructuralFeature.equals(SysmlPackage.eINSTANCE.getRelationship_Source())) {
             // Handle the case where the succession source or target has already been deleted
-            if ((!object.getSource().isEmpty() && object.getSource().get(0).getOwner() == null)
-                    || (!object.getTarget().isEmpty() && object.getTarget().get(0).getOwner() == null)) {
+            if (this.hasBeenAlreadyDeleted(object.getSource()) || this.hasBeenAlreadyDeleted(object.getTarget())) {
                 return relatedElements;
             }
             relatedElements.add(object);
@@ -133,4 +133,8 @@ public Set<EObject> caseSuccession(Succession object) {
         }
         return relatedElements;
     }
+
+    private boolean hasBeenAlreadyDeleted(List<Element> ends) {
+        return !ends.isEmpty() && !(ends.get(0) instanceof Membership) && ends.get(0).getOwner() == null;
+    }
 }

backend/views/syson-diagram-common-view/src/main/java/org/eclipse/syson/diagram/common/view/services/ViewEdgeToolSwitch.java

@@ -23,6 +23,7 @@
 import org.eclipse.sirius.components.view.diagram.EdgeTool;
 import org.eclipse.sirius.components.view.diagram.NodeDescription;
 import org.eclipse.syson.diagram.common.view.nodes.DoneActionNodeDescriptionProvider;
+import org.eclipse.syson.diagram.common.view.nodes.StartActionNodeDescriptionProvider;
 import org.eclipse.syson.sysml.AcceptActionUsage;
 import org.eclipse.syson.sysml.ActionUsage;
 import org.eclipse.syson.sysml.AllocationUsage;
@@ -255,10 +256,15 @@ public List<EdgeTool> caseStateUsage(StateUsage object) {
     @Override
     public List<EdgeTool> caseUsage(Usage object) {
         var edgeTools = new ArrayList<EdgeTool>();
-        edgeTools.add(this.edgeToolService.createDependencyEdgeTool(this.allNodeDescriptions));
+        // special actions (such as Start or Done) should not be considered to create edges.
+        var targetDescriptions = this.allNodeDescriptions.stream()
+                .filter(nodeDesc -> !this.nameGenerator.getNodeName(StartActionNodeDescriptionProvider.START_ACTION_NAME).equals(nodeDesc.getName()) &&
+                        !this.nameGenerator.getNodeName(DoneActionNodeDescriptionProvider.DONE_ACTION_NAME).equals(nodeDesc.getName()))
+                .toList();
+        edgeTools.add(this.edgeToolService.createDependencyEdgeTool(targetDescriptions));
         edgeTools.add(this.edgeToolService.createRedefinitionEdgeTool(List.of(this.nodeDescription)));
         edgeTools.add(this.edgeToolService.createSubsettingEdgeTool(List.of(this.nodeDescription)));
-        edgeTools.add(this.edgeToolService.createAllocateEdgeTool(this.allNodeDescriptions));
+        edgeTools.add(this.edgeToolService.createAllocateEdgeTool(targetDescriptions));
         var definitionNodeDescription = this.edgeToolService.getNodeDescription(this.edgeToolService.getDefinitionFromUsage(object));
         if (definitionNodeDescription.isPresent()) {
             edgeTools.add(this.edgeToolService.createFeatureTypingEdgeTool(List.of(definitionNodeDescription.get())));