Resolve #3490853 "Fix revision overview"

Closes #3490853

src/Controller/VersionHistoryTrait.php

+<?php
+
+namespace Drupal\wse\Controller;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Render\Element;
+
+/**
+ * Provides helper methods for the revision overview controllers.
+ */
+trait VersionHistoryTrait {
+
+  /**
+   * Adds information about each revision's workspace.
+   *
+   * @param array $build
+   *   The render array from the version history controller.
+   * @param \Drupal\Core\Entity\EntityInterface $entity
+   *   The entity object.
+   * @param array|null $revisions
+   *   (optional) An array of revisions that are displayed in the table.
+   */
+  protected function alterRevisionsTable(array &$build, EntityInterface $entity, ?array $revisions = NULL): void {
+    // Add a column to show the workspace in which a revision has been created.
+    $keys = Element::children($build);
+    if (!$revisions) {
+      $revisions = \Drupal::entityTypeManager()
+        ->getStorage($entity->getEntityTypeId())
+        ->loadMultipleRevisions($keys);
+    }
+
+    $field_name = $entity->getEntityType()->getRevisionMetadataKey('workspace');
+    foreach ($keys as $key) {
+      $revision = current($revisions);
+
+      $label = '';
+      if ($workspace = $revision->get($field_name)->entity) {
+        $label = $workspace->access('view label') ? $workspace->label() : $this->t('- Restricted access -');
+      }
+
+      // Insert the workspace label column.
+      if (isset($build[$key]['data'])) {
+        $build[$key]['data']['workspace'] = ['data' => $label];
+      }
+      elseif (isset($build[$key][0])) {
+        $build[$key]['workspace'] = ['data' => $label];
+      }
+      else {
+        $build[$key]['workspace'] = ['#markup' => $label];
+      }
+
+      next($revisions);
+    }
+  }
+
+}