[2194] Properly report feedback messages while moving elements in GV

CHANGELOG.adoc

@@ -17,6 +17,7 @@
 === Improvements
 
 - https://github.com/eclipse-syson/syson/issues/2198[#2198] [diagrams] Improve diagram-to-diagram drag and drop to support dropping multiple graphical nodes at once, leveraging Sirius Web's `droppedNodes` and `droppedElements` variables.
+- https://github.com/eclipse-syson/syson/issues/2194[#2194] [diagrams] Properly report feedback messages to user when using _ISysMLMoveElementService_.
 
 === New features
 

backend/application/syson-application/src/test/java/org/eclipse/syson/application/controllers/diagrams/general/view/GVForbiddenMoveTests.java

@@ -0,0 +1,178 @@
+/*******************************************************************************
+ * 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.application.controllers.diagrams.general.view;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+import static org.eclipse.sirius.components.diagrams.tests.DiagramEventPayloadConsumer.assertRefreshedDiagramThat;
+
+import com.jayway.jsonpath.Configuration;
+import com.jayway.jsonpath.DocumentContext;
+import com.jayway.jsonpath.JsonPath;
+import com.jayway.jsonpath.TypeRef;
+import com.jayway.jsonpath.spi.json.JacksonJsonProvider;
+import com.jayway.jsonpath.spi.mapper.JacksonMappingProvider;
+
+import java.time.Duration;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Consumer;
+
+import org.eclipse.sirius.components.collaborative.diagrams.dto.DiagramEventInput;
+import org.eclipse.sirius.components.collaborative.diagrams.dto.DiagramRefreshedEventPayload;
+import org.eclipse.sirius.components.collaborative.diagrams.dto.DropNodesInput;
+import org.eclipse.sirius.components.diagrams.Diagram;
+import org.eclipse.sirius.components.diagrams.events.ReconnectEdgeKind;
+import org.eclipse.sirius.components.diagrams.layoutdata.Position;
+import org.eclipse.sirius.components.graphql.tests.api.GraphQLResult;
+import org.eclipse.sirius.components.representations.Message;
+import org.eclipse.sirius.components.representations.MessageLevel;
+import org.eclipse.sirius.web.tests.services.api.IGivenInitialServerState;
+import org.eclipse.syson.AbstractIntegrationTests;
+import org.eclipse.syson.GivenSysONServer;
+import org.eclipse.syson.application.controllers.diagrams.checkers.CheckDiagramElementCount;
+import org.eclipse.syson.application.controllers.diagrams.testers.DropNodesWithMessageMutationRunner;
+import org.eclipse.syson.application.controllers.diagrams.testers.EdgeReconnectionTester;
+import org.eclipse.syson.application.data.GVWithReadOnlyNodesProjectData;
+import org.eclipse.syson.services.diagrams.DiagramComparator;
+import org.eclipse.syson.services.diagrams.api.IGivenDiagramSubscription;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.transaction.annotation.Transactional;
+
+import reactor.core.publisher.Flux;
+import reactor.test.StepVerifier;
+
+/**
+ * Tests the feedback messages returned after forbidden move or edge reconnection resulting in a move operation.
+ *
+ * @author Arthur Daussy
+ */
+@Transactional
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+public class GVForbiddenMoveTests extends AbstractIntegrationTests {
+
+    @Autowired
+    private IGivenInitialServerState givenInitialServerState;
+
+    @Autowired
+    private IGivenDiagramSubscription givenDiagramSubscription;
+
+    @Autowired
+    private EdgeReconnectionTester edgeReconnectionTester;
+
+    @Autowired
+    private DropNodesWithMessageMutationRunner dropRunner;
+
+    @Autowired
+    private DiagramComparator diagramComparator;
+
+    @BeforeEach
+    public void setUp() {
+        this.givenInitialServerState.initialize();
+    }
+
+    @DisplayName("GIVEN composite edge, WHEN when reconnecting to a read only source, THEN no new edge is created and a feedback message is reported")
+    @GivenSysONServer({ GVWithReadOnlyNodesProjectData.SCRIPT_PATH })
+    @Test
+    public void reconnectCompositeEdgeSourceToReadOnlyObject() {
+        var flux = this.givenSubscriptionToDiagram(GVWithReadOnlyNodesProjectData.EDITING_CONTEXT_ID);
+
+        AtomicReference<Diagram> diagram = new AtomicReference<>();
+        Consumer<Object> initialDiagramContentConsumer = assertRefreshedDiagramThat(diagram::set);
+
+        Runnable reconnectEdgeRunnable = this.buildReconnectRunnable(
+                GVWithReadOnlyNodesProjectData.GraphicalIds.PART_ID,
+                ReconnectEdgeKind.SOURCE,
+                diagram,
+                List.of(new Message("Unable to move part2 in Part: Unable to move a Element to a read only Element", MessageLevel.WARNING)));
+
+        Consumer<Object> newEdgeConsumer = assertRefreshedDiagramThat(newDiagram -> {
+            new CheckDiagramElementCount(this.diagramComparator)
+                    .hasNewEdgeCount(0)
+                    .check(diagram.get(), newDiagram, true);
+        });
+
+        StepVerifier.create(flux)
+                .consumeNextWith(initialDiagramContentConsumer)
+                .then(reconnectEdgeRunnable)
+                .consumeNextWith(newEdgeConsumer)
+                .thenCancel()
+                .verify(Duration.ofSeconds(10));
+
+    }
+
+    @DisplayName("GIVEN a part and a read only package, WHEN when dropping the part on the read only package, THEN the drop should be prevented and a feedback message should be sent")
+    @GivenSysONServer({ GVWithReadOnlyNodesProjectData.SCRIPT_PATH })
+    @Test
+    public void moveElementToReadOnlyElement() {
+        var flux = this.givenSubscriptionToDiagram(GVWithReadOnlyNodesProjectData.EDITING_CONTEXT_ID);
+
+        AtomicReference<Diagram> diagram = new AtomicReference<>();
+        Consumer<Object> initialDiagramContentConsumer = assertRefreshedDiagramThat(diagram::set);
+
+        Runnable dropPartOnPartsRunnable = () -> {
+            GraphQLResult response = this.dropRunner.run(new DropNodesInput(UUID.randomUUID(),
+                    GVWithReadOnlyNodesProjectData.EDITING_CONTEXT_ID,
+                    GVWithReadOnlyNodesProjectData.GraphicalIds.DIAGRAM_ID,
+                    List.of(GVWithReadOnlyNodesProjectData.GraphicalIds.PART1_ID),
+                    GVWithReadOnlyNodesProjectData.GraphicalIds.PARTS_PKG_ID,
+                    List.of(new Position(0, 0))));
+
+            assertThat(this.readDropNodesMessages(response.data()))
+                    .isEqualTo(List.of(new Message("Unable to move part1 in Parts: Unable to move a Element to a read only Element", MessageLevel.WARNING)));
+        };
+        Consumer<Object> newEdgeConsumer = assertRefreshedDiagramThat(newDiagram -> {
+            new CheckDiagramElementCount(this.diagramComparator)
+                    .hasNewEdgeCount(0)
+                    .hasNewNodeCount(0)
+                    .check(diagram.get(), newDiagram, true);
+        });
+
+        StepVerifier.create(flux)
+                .consumeNextWith(initialDiagramContentConsumer)
+                .then(dropPartOnPartsRunnable)
+                .consumeNextWith(newEdgeConsumer)
+                .thenCancel()
+                .verify(Duration.ofSeconds(10));
+
+    }
+
+    private List<Message> readDropNodesMessages(String responseData) {
+        Configuration conf = Configuration.builder()
+                .jsonProvider(new JacksonJsonProvider())
+                .mappingProvider(new JacksonMappingProvider())
+                .build();
+        DocumentContext ctx = JsonPath.using(conf).parse(responseData);
+        return ctx.read("$.data.dropNodes.messages", new TypeRef<List<Message>>() {
+        });
+    }
+
+    private Runnable buildReconnectRunnable(String newTarget, ReconnectEdgeKind reconnectionKind, AtomicReference<Diagram> diagram, List<Message> expectedMessages) {
+        return () ->
+                assertThat(
+                        this.edgeReconnectionTester.reconnectEdge(GVWithReadOnlyNodesProjectData.EDITING_CONTEXT_ID,
+                                diagram,
+                                GVWithReadOnlyNodesProjectData.GraphicalIds.NESTED_USAGE_EDGE,
+                                newTarget,
+                                reconnectionKind)).isEqualTo(expectedMessages);
+    }
+
+    private Flux<DiagramRefreshedEventPayload> givenSubscriptionToDiagram(String editingContextId) {
+        var diagramEventInput = new DiagramEventInput(UUID.randomUUID(), editingContextId, GVWithReadOnlyNodesProjectData.GraphicalIds.DIAGRAM_ID);
+        return this.givenDiagramSubscription.subscribe(diagramEventInput);
+    }
+}

backend/application/syson-application/src/test/java/org/eclipse/syson/application/controllers/diagrams/testers/DropNodesWithMessageMutationRunner.java

@@ -0,0 +1,60 @@
+/*******************************************************************************
+ * 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.application.controllers.diagrams.testers;
+
+import java.util.Objects;
+
+import org.eclipse.sirius.components.collaborative.diagrams.dto.DropNodesInput;
+import org.eclipse.sirius.components.graphql.tests.api.GraphQLResult;
+import org.eclipse.sirius.components.graphql.tests.api.IGraphQLRequestor;
+import org.eclipse.sirius.components.graphql.tests.api.IMutationRunner;
+import org.springframework.stereotype.Service;
+/**
+ * Same as {@link org.eclipse.sirius.components.diagrams.tests.graphql.DropNodesMutationRunner} but with feedback messages.
+ *
+ * @author Arthur Daussy
+ */
+@Service
+public class DropNodesWithMessageMutationRunner implements IMutationRunner<DropNodesInput> {
+    private static final String DROP_NODE_MUTATION = """
+            mutation dropNodes($input: DropNodesInput!) {
+              dropNodes(input: $input) {
+                __typename
+                ... on SuccessPayload {
+                  messages {
+                    body
+                    level
+                  }
+                }
+                ... on ErrorPayload {
+                  message
+                  messages {
+                    body
+                    level
+                  }
+                }
+              }
+            }
+            """;
+
+    private final IGraphQLRequestor graphQLRequestor;
+
+    public DropNodesWithMessageMutationRunner(IGraphQLRequestor graphQLRequestor) {
+        this.graphQLRequestor = Objects.requireNonNull(graphQLRequestor);
+    }
+
+    @Override
+    public GraphQLResult run(DropNodesInput input) {
+        return this.graphQLRequestor.execute(DROP_NODE_MUTATION, input);
+    }
+}

backend/application/syson-application/src/test/java/org/eclipse/syson/application/controllers/diagrams/testers/EdgeReconnectionTester.java

@@ -14,8 +14,14 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import com.jayway.jsonpath.Configuration;
+import com.jayway.jsonpath.DocumentContext;
 import com.jayway.jsonpath.JsonPath;
+import com.jayway.jsonpath.TypeRef;
+import com.jayway.jsonpath.spi.json.JacksonJsonProvider;
+import com.jayway.jsonpath.spi.mapper.JacksonMappingProvider;
 
+import java.util.List;
 import java.util.UUID;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -24,6 +30,7 @@
 import org.eclipse.sirius.components.diagrams.Diagram;
 import org.eclipse.sirius.components.diagrams.events.ReconnectEdgeKind;
 import org.eclipse.sirius.components.diagrams.tests.graphql.ReconnectEdgeMutationRunner;
+import org.eclipse.sirius.components.representations.Message;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 
@@ -38,7 +45,7 @@ public class EdgeReconnectionTester {
     @Autowired
     private ReconnectEdgeMutationRunner reconnectEdgeMutationRunner;
 
-    public void reconnectEdge(String projectId, AtomicReference<Diagram> diagram, String edgeId, String newEdgeEnd, ReconnectEdgeKind reconnectEdgeKind) {
+    public List<Message> reconnectEdge(String projectId, AtomicReference<Diagram> diagram, String edgeId, String newEdgeEnd, ReconnectEdgeKind reconnectEdgeKind) {
         var reconnectEdgeInput = new ReconnectEdgeInput(
                 UUID.randomUUID(),
                 projectId,
@@ -51,6 +58,16 @@ public void reconnectEdge(String projectId, AtomicReference<Diagram> diagram, St
         var createEdgeResult = this.reconnectEdgeMutationRunner.run(reconnectEdgeInput);
         var typename = JsonPath.read(createEdgeResult.data(), "$.data.reconnectEdge.__typename");
         assertThat(typename).isEqualTo(SuccessPayload.class.getSimpleName());
+
+        // Return feedback messages
+        Configuration conf = Configuration.builder()
+                .jsonProvider(new JacksonJsonProvider())
+                .mappingProvider(new JacksonMappingProvider())
+                .build();
+        DocumentContext ctx = JsonPath.using(conf).parse(createEdgeResult.data());
+        return ctx.read("$.data.reconnectEdge.messages", new TypeRef<List<Message>>() {
+        });
+
     }
 
 }

backend/application/syson-application/src/test/java/org/eclipse/syson/application/data/GVWithReadOnlyNodesProjectData.java

@@ -0,0 +1,44 @@
+/*******************************************************************************
+ * 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.application.data;
+
+/**
+ * Project data for project "SysMLv2-WithReadOnlyNode".
+ *
+ * @author Arthur Daussy
+ */
+public class GVWithReadOnlyNodesProjectData {
+
+    public static final String SCRIPT_PATH = "/scripts/database-content/SysMLv2-WithReadOnlyNode.sql";
+
+    public static final String EDITING_CONTEXT_ID = "6e261505-a9ee-49df-8695-20c43a748d51";
+
+    /**
+     * Ids of graphical elements.
+     */
+    public static final class GraphicalIds {
+
+        public static final String DIAGRAM_ID = "032613cb-2bbb-41be-857a-2687a3901b91";
+
+        public static final String PART_ID = "d4c076f3-8158-39e5-849d-39ab4e6e9e1a";
+
+        public static final String PART1_ID = "7b744096-f831-3aa8-8728-c2f61bc52f73";
+
+        public static final String PARTS_PAR_ID = "34c0a2e2-6bf4-3e76-8cf6-8bbaea855a3a";
+
+        public static final String PARTS_PKG_ID = "592ab045-03de-3f13-9812-5541588848c8";
+
+        public static final String NESTED_USAGE_EDGE = "5755ae43-957a-3513-b64a-cc2776759a7b";
+
+    }
+}