[2133] Fix NPE in Related Elements view

Since #2032, `self` is a single element, not a list.

Bug: #2133
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
Signed-off-by: Axel RICHARD <axel.richard@obeo.fr>

CHANGELOG.adoc

@@ -35,6 +35,7 @@ An absent/empty candidates expression now simply means the widget is empty.
 - https://github.com/eclipse-sirius/sirius-components/issues/2067[#2064] [view] Enable completion support and other text field customizations for custom widgets
 - https://github.com/eclipse-sirius/sirius-components/issues/2092[#2092] [form] Fix support for help expressions on the _FlexboxContainer_ widget
 - https://github.com/eclipse-sirius/sirius-components/issues/2088[#2088] [tree] Fix initial value of the tree filter bar
+- https://github.com/eclipse-sirius/sirius-components/issues/2133[#2133] [workbench] Fix NPE in Related Elements view
 
 === New Features
 

integration-tests/cypress/e2e/project/edit/related-elements-view.cy.js

@@ -0,0 +1,42 @@
+/*******************************************************************************
+ * Copyright (c) 2023 Obeo.
+ * This program and the accompanying materials
+ * are made available under the erms 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
+ *******************************************************************************/
+
+/**
+ * This test suite will be used to validate the proper lifecycle of our application.
+ *
+ * For that, we will open and close in various ways several representations and we will evaluate if we have
+ * the proper number of representations and if they behave properly.
+ */
+describe('/projects/:projectId/edit - Related ELements View', () => {
+  beforeEach(() => {
+    cy.deleteAllProjects();
+    cy.createProject('Cypress Project').then((res) => {
+      const projectId = res.body.data.createProject.project.id;
+      cy.wrap(projectId).as('projectId');
+      const robot_flow_id = 'c26b6086-b444-3ee6-b8cd-9a4fde5956a7';
+
+      cy.createDocument(projectId, robot_flow_id, 'robot').then(() => {
+        cy.visit(`/projects/${projectId}/edit`);
+      });
+    });
+  });
+
+  it('can open the related elements view', function () {
+    cy.getByTestId('robot').dblclick();
+    cy.getByTestId('Robot').dblclick();
+    cy.getByTestId('viewselector-Related Elements').click();
+    cy.getByTestId('view-Related Elements').within(() => {
+      cy.getByTestId('form').should('exist');
+    });
+  });
+});

packages/sirius-web/backend/sirius-web-services/src/main/java/org/eclipse/sirius/web/services/relatedelements/DefaultRelatedElementsDescriptionProvider.java

@@ -62,9 +62,6 @@ public FormDescription getFormDescription() {
 
         // @formatter:off
         Function<VariableManager, String> targetObjectIdProvider = variableManager -> variableManager.get(VariableManager.SELF, Object.class)
-                .filter(self -> self instanceof List<?>)
-                .map(self -> (List<?>) self)
-                .flatMap(self -> self.stream().findFirst())
                 .map(this.objectService::getId)
                 .orElse(null);