[2105] Display textual representation of expressions in the Explorer

Bug: #2105
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>

Author: pcdavid

CHANGELOG.adoc

@@ -32,6 +32,7 @@ As a result, the following GraphQL mutations have been removed `exposeRequiremen
 
 === Improvements
 
+- https://github.com/eclipse-syson/syson/issues/2105[#2105] [explorer] In the _Explorer_ view, `Expression` elements now display their full textual representation
 
 === New features
 

backend/application/syson-application/src/test/java/org/eclipse/syson/application/controller/explorer/view/SysONExplorerTests.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2025 Obeo.
+ * Copyright (c) 2025, 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
@@ -42,6 +42,8 @@ public static final class GraphicalIds {
      */
     public static final class SemanticIds {
 
+        public static final String DOCUMENT_ID = "26a78eef-bfa1-4de0-9d0a-c1f86a1b97d5";
+
         public static final String PACKAGE_1_ID = "2264f62c-b223-4b9b-ae41-96dc2ba0070e";
 
         public static final String A0_ID = "82a2fa10-e736-4c3e-b27a-e94f76d7456d";

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

@@ -282,7 +282,6 @@ public static <T extends EObject> List<T> getAncestors(Class<T> type, EObject ob
      */
     public static <T extends EObject> Optional<T> getFirstAncestor(Class<T> type, EObject object, Predicate<EObject> ancestorPredicate) {
         var current = object;
-        List<T> results = new ArrayList<>();
         while (current != null) {
             if (type.isInstance(current) && (ancestorPredicate == null || ancestorPredicate.test(current))) {
                 return Optional.of((T) current);

backend/metamodel/syson-sysml-metamodel/src/main/java/org/eclipse/syson/sysml/helper/EMFUtils.java

@@ -38,8 +38,13 @@
 import org.eclipse.sirius.web.domain.boundedcontexts.representationdata.RepresentationMetadata;
 import org.eclipse.sirius.web.domain.boundedcontexts.representationdata.services.api.IRepresentationMetadataSearchService;
 import org.eclipse.syson.sysml.Element;
+import org.eclipse.syson.sysml.Expression;
 import org.eclipse.syson.sysml.Type;
+import org.eclipse.syson.sysml.Usage;
 import org.eclipse.syson.sysml.ViewUsage;
+import org.eclipse.syson.sysml.textual.SysMLElementSerializer;
+import org.eclipse.syson.sysml.textual.SysMLSerializingOptions;
+import org.eclipse.syson.sysml.textual.utils.FileNameDeresolver;
 import org.eclipse.syson.sysml.util.ElementUtil;
 import org.eclipse.syson.tree.explorer.fragments.KerMLStandardLibraryDirectory;
 import org.eclipse.syson.tree.explorer.fragments.LibrariesDirectory;
@@ -148,6 +153,8 @@ public String getLabel(Object self) {
         String label = "";
         if (self instanceof ISysONExplorerFragment fragment) {
             label = fragment.getLabel();
+        } else if (self instanceof Expression expression && !(self instanceof Usage)) {
+            label = this.getValueExpressionTextualRepresentation(expression);
         } else if (self instanceof Type type) {
             String name = type.getName();
             if (name != null) {
@@ -159,6 +166,25 @@ public String getLabel(Object self) {
         return label;
     }
 
+    private String getValueExpressionTextualRepresentation(Expression value) {
+        String result = "";
+        if (value != null) {
+            SysMLSerializingOptions options = new SysMLSerializingOptions.Builder()
+                    .lineSeparator("\n")
+                    .nameDeresolver(new FileNameDeresolver())
+                    .indentation("\t")
+                    .needEscapeCharacter(false)
+                    .build();
+            String textualFormat = new SysMLElementSerializer(options, s -> {
+                // Do nothing for now
+            }).doSwitch(value);
+            if (textualFormat != null) {
+                result = textualFormat;
+            }
+        }
+        return result;
+    }
+
     private String getFallbackLabel(Object self) {
         StyledString styledLabel = this.labelService.getStyledLabel(self);
         if (styledLabel != null) {

backend/services/syson-tree-services/src/main/java/org/eclipse/syson/tree/explorer/services/SysONDefaultExplorerServices.java

@@ -25,6 +25,12 @@
 ** Add tools to create timeslices and snapshots, available on `OccurrenceUsage`, `ItemUsage`, and `PartUsage` graphical nodes.
 These tools leverage a selection dialog to either create a specific timeslice/snapshot graphical node or, if no selection is made, default to a timeslice/snapshot `OccurrenceUsage` graphical node.
 
+* In the _Explorer_ view:
+
+** `Expression` elements now display their full textual representation:
+
+image::explorer-expression-text.png[Expression textual representation]
+
 == Technical details
 
 * For technical details on this {product} release (including breaking changes), please refer to https://github.com/eclipse-syson/syson/blob/main/CHANGELOG.adoc[changelog].