ISTWCMS-5866 Prevent URL aliases being created for reserved paths

uw_cfg_common.module

@@ -851,7 +851,14 @@ function uw_cfg_common_form_alter(array &$form, FormStateInterface $form_state,
   }
 
   // Ensure that we are on a UW content type node.
-  if (preg_match('/node_uw.*add_form/', $form_id) || preg_match('/node_uw.*edit_form/', $form_id)) {
+  if (
+    preg_match('/node_uw.*add_form/', $form_id) ||
+    preg_match('/node_uw.*edit_form/', $form_id) ||
+    preg_match('/node_uw.*_form/', $form_id)
+  ) {
+
+    // Add custom validation for alias.
+    $form['#validate'][] = '_uw_cfg_common_alias_validate';
 
     // Ensure that the node has metatag information.
     if (isset($form['field_uw_meta_tags'])) {
@@ -931,6 +938,40 @@ function uw_cfg_common_form_alter(array &$form, FormStateInterface $form_state,
   }
 }
 
+/**
+ * Validates submission values for alias on nodes.
+ */
+function _uw_cfg_common_alias_validate(array &$form, FormStateInterface $form_state): void {
+
+  // List of urls which should not be repeat in alias.
+  $urls = [
+    'blog',
+    'events',
+    'news',
+    'projects',
+    'profiles',
+    'contacts',
+    'service',
+    'opportunities',
+    'user',
+    'users',
+  ];
+
+  $values = $form_state->getValues();
+  $alias = $values['path'][0]['alias'];
+  $alias = str_replace('/', '', $alias);
+
+  // Check if the alias exists if yes, sets error.
+  if (
+    in_array($alias, $urls) ||
+    $alias == '/' ||
+    preg_match('/^\/?admin\/.*/', $values['path'][0]['alias'])
+  ) {
+    // Set an error message if alias exists.
+    $form_state->setError($form['path']['widget'][0], t('@url cannot be an alias', ['@url' => $alias]));
+  }
+}
+
 /**
  * Implements hook_field_widget_WIDGET_TYPE_form_alter().
  */