[1876] Fix potential NPE when trying to delete some elements from the Explorer

CHANGELOG.adoc

@@ -54,6 +54,7 @@ This fix ensure that imported models containing, for example, a top-level `Libra
 - https://github.com/eclipse-syson/syson/issues/1852[#1852] [diagrams] Do not propose the _Duplicate Element_ node action on elements which do not support it.
 - https://github.com/eclipse-syson/syson/issues/1857[#1857] [diagrams] Fix an issue where existing graphical node could disappear when new graphical node was created.
 - https://github.com/eclipse-syson/syson/issues/1865[#1865] [explorer] Fix focus loss on some characters in the _New object from text_ modal.
+- https://github.com/eclipse-syson/syson/issues/1876[#1876] [explorer] Fix potential NPE when trying to delete elements with associated `EAnnotations` from the _Explorer_.
 
 === Improvements
 

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

@@ -57,6 +57,11 @@ public Set<EObject> caseElement(Element object) {
         return Set.of();
     }
 
+    @Override
+    public Set<EObject> defaultCase(EObject object) {
+        return Set.of();
+    }
+
     @Override
     public Set<EObject> caseAnnotation(Annotation object) {
         Set<EObject> relatedElements = new HashSet<>();

backend/services/syson-services/src/test/java/org/eclipse/syson/services/DeleteServiceTest.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2024, 2025 Obeo.
+ * Copyright (c) 2024, 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
@@ -15,9 +15,12 @@
 import static org.assertj.core.api.Assertions.assertThat;
 
 import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.ecore.EAnnotation;
+import org.eclipse.emf.ecore.EcoreFactory;
 import org.eclipse.emf.ecore.impl.EPackageRegistryImpl;
 import org.eclipse.emf.ecore.resource.Resource;
 import org.eclipse.emf.ecore.resource.impl.ResourceSetImpl;
+import org.eclipse.emf.ecore.util.ECrossReferenceAdapter;
 import org.eclipse.sirius.emfjson.resource.JsonResourceFactoryImpl;
 import org.eclipse.syson.sysml.SysmlFactory;
 import org.eclipse.syson.sysml.SysmlPackage;
@@ -98,4 +101,21 @@ void testMembershipExpose() {
         assertThat(view1.getExposedElement()).isEmpty();
 
     }
+
+    @DisplayName("GIVEN a SysML element with and EMF EAnnotation, WHEN it is deleted, THEN the deletion completes without error")
+    @Test
+    void testDeleteSysMLElementWithEAnnotation() {
+        var pkg1 = SysmlFactory.eINSTANCE.createPackage();
+        pkg1.setDeclaredName("Pkg1");
+        this.resource.getContents().add(pkg1);
+
+        EAnnotation annotation = EcoreFactory.eINSTANCE.createEAnnotation();
+        pkg1.getEAnnotations().add(annotation);
+
+        this.resource.getResourceSet().eAdapters().add(new ECrossReferenceAdapter());
+
+        assertThat(this.resource.getContents()).hasSize(1).contains(pkg1);
+        this.deleteService.deleteFromModel(pkg1);
+        assertThat(this.resource.getContents()).isEmpty();
+    }
 }

integration-tests-playwright/playwright/e2e/diagram_node_creation.spec.ts

@@ -41,7 +41,7 @@ test.describe('diagram - general view', () => {
     await page.getByTestId('tool-New Part Definition').click();
     diagram.expectNumberOfTopNodes(1);
     // Create Port
-    const partDefinitionNode = new PlaywrightNode(page, 'PartDefinition1', 'List');
+    let partDefinitionNode = new PlaywrightNode(page, 'PartDefinition1', 'List');
     await expect(partDefinitionNode.nodeLocator).toBeAttached();
     await partDefinitionNode.openPalette();
     await page.getByTestId('toolSection-Structure').click();
@@ -56,6 +56,8 @@ test.describe('diagram - general view', () => {
     await expect(portNode.nodeLocator).toBeAttached();
     diagram.expectNumberOfTopNodes(3);
     // The port can be displayed as a list item
+    partDefinitionNode = new PlaywrightNode(page, 'PartDefinition1', 'List');
+    await expect(partDefinitionNode.nodeLocator).toBeAttached();
     await partDefinitionNode.click();
     await partDefinitionNode.revealElement('ports');
     const portsListNode = new PlaywrightNode(page, 'ports', 'List');

scripts/check-coverage.jsh

@@ -53,7 +53,7 @@ var moduleCoverageData = List.of(
   new ModuleCoverage("syson-sysml-validation", 99.0),
   new ModuleCoverage("syson-table-requirements-view", 77.0),
   new ModuleCoverage("syson-table-services", 100.0),
-  new ModuleCoverage("syson-tree-explorer-view", 88.0),
+  new ModuleCoverage("syson-tree-explorer-view", 87.0),
   new ModuleCoverage("syson-tree-services", 82.0)
 );