Issue #3450267: Add support for Preview Draft Content

src/Form/NodeEditForm.php

@@ -25,13 +25,15 @@ class NodeEditForm extends NodeForm {
    * Overridden to store the root parent entity.
    */
   public function buildForm(array $form, FormStateInterface $form_state) {
+    // Calculate if preview | latest published revision.
+    $this->calculateNodeEntity($form, $form_state);
+    // Build the form.
     $form = parent::buildForm($form, $form_state);
-    $node = $this->calculateNodeEntity($form, $form_state);
 
+    // Hide Preview button.
+    $form['actions']['preview']['#access'] = $this->isLatestRevision();
     // Hide Delete button.
     $form['actions']['delete']['#access'] = FALSE;
-    // Hide advanced tab.
-    $form['advanced']['#attributes']['class'][] = 'visually-hidden';
     // Add ajax callback to submit button.
     $form['actions']['submit']['#ajax']['callback'] = '::ajaxSubmit';
     // @todo static::ajaxSubmit() requires data-drupal-selector to be the same

src/FormEditTrait.php

@@ -9,6 +9,23 @@ namespace Drupal\visual_editor;
  */
 trait FormEditTrait {
 
+  /**
+   * Stores the isLatestRevision status.
+   *
+   * @var bool
+   */
+  protected $isLatestRevision = FALSE;
+
+  /**
+   * Get the isLatestRevision status.
+   *
+   * @return bool
+   *   The isLatestRevision status.
+   */
+  public function isLatestRevision() {
+    return $this->isLatestRevision;
+  }
+
   /**
    * Sets the entity for sidebar edit form.
    *
@@ -17,19 +34,43 @@ trait FormEditTrait {
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The form state object.
    *
-   * @return \Drupal\Core\Entity\ContentEntityInterface
-   *   The node object to return.
+   * @return void
+   *   Return nothing.
    */
   public function calculateNodeEntity(&$form, &$form_state) {
+    // Check if the entity is not the latest published revision.
+    $entity = $form_state->getFormObject()->getEntity();
+    // Set the isLatestRevision status.
+    $this->isLatestRevision = $entity->isLatestRevision();
+
+    // If not the latest revision, load the latest revision.
+    if (!$entity->isLatestRevision()) {
+      $revisionId = $this->entityTypeManager
+        ->getStorage('node')
+        ->getLatestRevisionId($entity->id());
+
+      $node = $this->entityTypeManager
+        ->getStorage('node')
+        ->loadRevision($revisionId);
+
+      $form_state->getFormObject()->setEntity($node);
+      $form_state->setRebuild();
+
+      $this->entity = $node;
+      return;
+    }
+
+    // Check if the form is in preview mode.
     $query = \Drupal::request()->query;
-    $is_preview = $query->has('preview') && $query->get('preview') == 'true';
+    $isPreview = $query->has('preview') && $query->get('preview') == 'true';
 
     // Try to restore from temp store, this must be done before calling
     // parent::form().
     $store = $this->tempStoreFactory->get('node_preview');
-    $node_uuid = $form_state->getFormObject()->getEntity()->uuid();
+    $uuid = $form_state->getFormObject()->getEntity()->uuid();
+    $preview = $store->get($uuid);
 
-    if ($is_preview && !$form_state->isRebuilding() && $node_uuid && $preview = $store->get($node_uuid)) {
+    if ($isPreview && !$form_state->isRebuilding() && $uuid && $preview) {
       /** @var \Drupal\Core\Form\FormStateInterface $preview */
       $form_state->setStorage($preview->getStorage());
       $form_state->setUserInput($preview->getUserInput());
@@ -46,14 +87,10 @@ trait FormEditTrait {
       $this->entity->in_preview = NULL;
 
       $form_state->set('has_been_previewed', TRUE);
-
-      return $this->entity;
-    }
-    else {
-      $this->entity = $form_state->getFormObject()->getEntity();
-      return $form_state->getFormObject()->getEntity();
+      return;
     }
 
+    $this->entity = $form_state->getFormObject()->getEntity();
   }
 
 }