Issue #2056879 by martin107, Outi, ioskevich, Cottser: Improve twig_* vars...

Issue #2056879 by martin107, Outi, ioskevich, Cottser: Improve twig_* vars DOCs in settings.php and make Twig debug markup require a cache clear.

core/themes/engines/twig/twig.engine

@@ -6,7 +6,6 @@
  */
 
 use Drupal\Core\Extension\Extension;
-use Drupal\Component\Utility\Settings;
 
 /**
  * Implements hook_theme().
@@ -46,13 +45,14 @@ function twig_init(Extension $theme) {
  *   The output generated by the template, plus any debug information.
  */
 function twig_render_template($template_file, $variables) {
+  $twig_service = \Drupal::service('twig');
   $output = array(
     'debug_prefix'    => '',
     'debug_info'      => '',
-    'rendered_markup' => \Drupal::service('twig')->loadTemplate($template_file)->render($variables),
+    'rendered_markup' => $twig_service->loadTemplate($template_file)->render($variables),
     'debug_suffix'    => '',
   );
-  if (Settings::get('twig_debug', FALSE)) {
+  if ($twig_service->isDebug()) {
     $output['debug_prefix'] .= "\n\n<!-- THEME DEBUG -->";
     $output['debug_prefix'] .= "\n<!-- CALL: _theme('{$variables['theme_hook_original']}') -->";
     // If there are theme suggestions, reverse the array so more specific

sites/default/default.settings.php

@@ -289,6 +289,9 @@
  * - Twig templates are automatically recompiled whenever the source code
  *   changes (see twig_auto_reload below).
  *
+ * Note: changes to this setting will only take effect once the cache is
+ * cleared.
+ *
  * For more information about debugging Twig templates, see
  * http://drupal.org/node/1906392.
  *
@@ -303,6 +306,9 @@
  * you don't provide a value for twig_auto_reload, it will be determined based
  * on the value of twig_debug.
  *
+ * Note: changes to this setting will only take effect once the cache is
+ * cleared.
+ *
  * Not recommended in production environments (Default: NULL).
  */
 # $settings['twig_auto_reload'] = TRUE;
@@ -315,6 +321,9 @@
  * from source each time they are used. In most cases the twig_auto_reload
  * setting above should be enabled rather than disabling the Twig cache.
  *
+ * Note: changes to this setting will only take effect once the cache is
+ * cleared.
+ *
  * Not recommended in production environments (Default: TRUE).
  */
 # $settings['twig_cache'] = FALSE;