[2369] Forbid subclassify an EnumerationDefinition by another one

CHANGELOG.adoc

@@ -42,6 +42,7 @@ In any case, it is strongly recommended to back up your data before proceeding w
 - https://github.com/eclipse-syson/syson/issues/2399[#2399] [details] Fix the _Typed by_ selection dialog so a `Usage` can only be typed by its corresponding `Definition` kind.
 - https://github.com/eclipse-syson/syson/issues/2407[#2407] [diagrams] Fix the nested composition edge tool label on `ConcernUsage` graphical nodes in _General View_ diagrams.
 It is now _Become nested Concern_ instead of _Become nested Requirement_.
+- https://github.com/eclipse-syson/syson/issues/2369[#2369] [diagrams] Remove the _New Subclassification_ edge tool from `EnumerationDefinition` graphical nodes, which cannot subclassify another `EnumerationDefinition`.
 - https://github.com/eclipse-syson/syson/issues/2388[#2388] [search] Fix concurrent creation of SysML model search indices.
 - https://github.com/eclipse-syson/syson/issues/2397[#2397] [metamodel] Fix the resolution of the ends of a connector so the ends declared with the `end` keyword inside a connection body are taken into account.
 Following KerML, where `endFeature` is defined as the owned features having `isEnd = true`, the ends owned through a plain `FeatureMembership` are now collected as well, and not only those owned through an `EndFeatureMembership`.

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

@@ -178,7 +178,10 @@ public List<EdgeTool> caseDefinition(Definition object) {
         addAttributeAsNestedOfDefinition.forEach(nodeDesc -> edgeTools.add(this.edgeToolService.createAddAsNestedEdgeTool(nodeDesc)));
 
         edgeTools.add(this.edgeToolService.createDependencyEdgeTool(this.allNodeDescriptions));
-        edgeTools.add(this.edgeToolService.createSubclassificationEdgeTool(List.of(this.nodeDescription)));
+        // SysML forbids an EnumerationDefinition from subclassifying another EnumerationDefinition.
+        if (!SysmlPackage.eINSTANCE.getEnumerationDefinition().isInstance(object)) {
+            edgeTools.add(this.edgeToolService.createSubclassificationEdgeTool(List.of(this.nodeDescription)));
+        }
         return edgeTools;
     }
 

backend/views/syson-diagram-common-view/src/test/java/org/eclipse/syson/diagram/common/view/services/ViewEdgeToolSwitchTest.java

@@ -0,0 +1,86 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Obeo.
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.syson.diagram.common.view.services;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.eclipse.emf.ecore.EClass;
+import org.eclipse.sirius.components.view.builder.generated.diagram.DiagramBuilders;
+import org.eclipse.sirius.components.view.diagram.EdgeTool;
+import org.eclipse.sirius.components.view.diagram.NodeDescription;
+import org.eclipse.syson.sysml.SysmlPackage;
+import org.eclipse.syson.util.DescriptionNameGenerator;
+import org.eclipse.syson.util.SysMLMetamodelHelper;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests for {@link ViewEdgeToolSwitch}.
+ *
+ * @author arichard
+ */
+public class ViewEdgeToolSwitchTest {
+
+    private final DescriptionNameGenerator descriptionNameGenerator = new DescriptionNameGenerator("test");
+
+    @Test
+    @DisplayName("GIVEN an EnumerationDefinition, WHEN its edge tools are created, THEN the New Subclassification tool is not available")
+    void enumerationDefinitionDoesNotProvideSubclassificationEdgeTool() {
+        var nodeDescription = this.createNodeDescription(SysmlPackage.eINSTANCE.getEnumerationDefinition());
+
+        var edgeTools = this.createEdgeToolSwitch(nodeDescription).doSwitch(SysmlPackage.eINSTANCE.getEnumerationDefinition());
+
+        assertThat(edgeTools)
+                .extracting(EdgeTool::getName)
+                .doesNotContain(this.descriptionNameGenerator.getCreationToolName(SysmlPackage.eINSTANCE.getSubclassification()));
+    }
+
+    @Test
+    @DisplayName("GIVEN a PartDefinition, WHEN its edge tools are created, THEN the New Subclassification tool is available")
+    void partDefinitionProvidesSubclassificationEdgeTool() {
+        var nodeDescription = this.createNodeDescription(SysmlPackage.eINSTANCE.getPartDefinition());
+
+        var edgeTools = this.createEdgeToolSwitch(nodeDescription).doSwitch(SysmlPackage.eINSTANCE.getPartDefinition());
+
+        assertThat(edgeTools)
+                .extracting(EdgeTool::getName)
+                .contains(this.descriptionNameGenerator.getCreationToolName(SysmlPackage.eINSTANCE.getSubclassification()));
+    }
+
+    /**
+     * Creates the edge tool switch to test with the given node description.
+     *
+     * @param nodeDescription
+     *            the node description represented by the switch
+     * @return the configured edge tool switch
+     */
+    private ViewEdgeToolSwitch createEdgeToolSwitch(NodeDescription nodeDescription) {
+        return new ViewEdgeToolSwitch(nodeDescription, List.of(nodeDescription), this.descriptionNameGenerator);
+    }
+
+    /**
+     * Creates a minimal node description for an EClass.
+     *
+     * @param eClass
+     *            the EClass represented by the node description
+     * @return the node description for the given EClass
+     */
+    private NodeDescription createNodeDescription(EClass eClass) {
+        return new DiagramBuilders().newNodeDescription()
+                .name(eClass.getName())
+                .domainType(SysMLMetamodelHelper.buildQualifiedName(eClass))
+                .build();
+    }
+}

doc/content/modules/user-manual/pages/release-notes/2026.9.0.adoc

@@ -86,6 +86,7 @@ It is now _Become nested Concern_ instead of _Become nested Requirement_.
 ** Fix the ends of the connections whose ends are declared with the `end` keyword inside the body of the connection, which were not resolved.
 Those connections were missing their source and their target, and were therefore never displayed as edges.
 ** Replace the name of the _New Perform action_ tool to _New Perform Action_ to be consistent with other tools.
+** Remove the _New Subclassification_ edge tool from `EnumerationDefinition` graphical nodes, which cannot subclassify another `EnumerationDefinition`.
 
 * In all views: