Issue #3470570: Unable to save text format without enabling Markdown filter

Closes #3470570

src/Form/ParserConfigurationForm.php

@@ -176,6 +176,9 @@ class ParserConfigurationForm extends FormBase implements FilterAwareInterface,
    *   When an invalid parser or no parser is provided.
    */
   public function processSubform(array &$element, FormStateInterface $form_state, array &$complete_form) {
+    $filters = $form_state->getValue('filters');
+    $is_active = $filters['markdown']['status'] ?? NULL;
+
     // Keep track of subform parents for the validation and submit handlers.
     $form_state->set('markdownSubformParents', ($parents = isset($element['#parents']) ? $element['#parents'] : []));
     $form_state->set('markdownSubformArrayParents', $element['#array_parents']);
@@ -222,14 +225,16 @@ class ParserConfigurationForm extends FormBase implements FilterAwareInterface,
       ],
     ]);
 
-    // Build vertical tabs that parser and extensions will go into.
-    $element['ajax']['vertical_tabs'] = [
-      '#type' => 'vertical_tabs',
-      '#parents' => array_merge($parents, ['vertical_tabs']),
-    ];
+    if ($is_active) {
+      // Build vertical tabs that parser and extensions will go into.
+      $element['ajax']['vertical_tabs'] = [
+        '#type' => 'vertical_tabs',
+        '#parents' => array_merge($parents, ['vertical_tabs']),
+      ];
 
-    // Determine the group that details should be referencing for vertical tabs.
-    $form_state->set('markdownGroup', ($group = implode('][', array_merge($parents, ['vertical_tabs']))));
+      // Determine the group that details should be referencing for vertical tabs.
+      $form_state->set('markdownGroup', ($group = implode('][', array_merge($parents, ['vertical_tabs']))));
+    }
 
     // Create a subform state.
     $subform_state = SubformState::createForSubform($element, $complete_form, $form_state);