Issue #3277987 by smulvih2: Add common book page template fix to starterkit

Author: smulvihill

starterkits/wxt/THEMENAME.theme

@@ -7,6 +7,8 @@
  * Place your custom PHP code in this file.
  */
 
+use Drupal\node\NodeInterface;
+
 /**
  * Implements hook_theme_suggestions_HOOK_alter().
  */
@@ -17,3 +19,33 @@ function THEMENAME_theme_suggestions_block_alter(&$suggestions, $variables) {
     $suggestion = str_replace('THEMENAME_', 'wxt_bootstrap_', $suggestion);
   }
 }
+
+/**
+ * Implements hook_theme_suggestions_HOOK_alter().
+ */
+function THEMENAME_theme_suggestions_page_alter(array &$suggestions, array $variables) {
+  $moduleHandler = \Drupal::service('module_handler');
+
+  if ($moduleHandler->moduleExists('wxt_ext_book')) {
+    $node = \Drupal::routeMatch()->getParameter('node');
+
+    if ($node instanceof NodeInterface) {
+      if (!empty($node->book) && $node->book['bid'] != 0) {
+        /** @var \Drupal\wxt_library\LibraryService $wxt */
+        $wxt = \Drupal::service('wxt_library.service_wxt');
+        $wxt_active = $wxt->getLibraryName();
+
+        if ($node->book['bid'] == $node->id()) {
+          // Theme book index page
+          $suggestions[] = $variables['theme_hook_original'] . '__book_index';
+          $suggestions[] = $variables['theme_hook_original'] . '__' . $wxt_active . '__book_index';
+        }
+        else {
+          // Theme book child page
+          $suggestions[] = $variables['theme_hook_original'] . '__book_page';
+          $suggestions[] = $variables['theme_hook_original'] . '__' . $wxt_active . '__book_page';
+        }
+      }
+    }
+  }
+}