Issue #1898454 by c4rl, gnuget, Hydra, mr.baileys, Sean Charles, joelpittet:...

Issue #1898454 by c4rl, gnuget, Hydra, mr.baileys, Sean Charles, joelpittet: system.module - Convert PHPTemplate templates to Twig.

core/modules/system/system.module

@@ -2683,16 +2683,16 @@ function system_preprocess_block(&$variables) {
 }
 
 /**
- * Implements hook_preprocess_HOOK() for system-plugin-ui-form.tpl.php.
+ * Prepares variables for system plugin UI form templates.
  *
- * The $variables array contains the following arguments:
- * - $form
- */
+ * Default template: system-plugin-ui-form.html.twig.
+ *
+ * @param array $variables
+ *   An associative array containing:
+ *   - form: The plugin form elements.
+*/
 function template_preprocess_system_plugin_ui_form(&$variables) {
   drupal_add_css(drupal_get_path('module', 'system') . '/system.plugin.ui.css');
-  $variables['left'] = drupal_render($variables['form']['left']);
-  $variables['right'] = drupal_render($variables['form']['right']);
-  $variables['form_submit'] = drupal_render_children($variables['form']);
 }
 
 /**

core/modules/system/templates/system-plugin-ui-form.tpl.php → core/modules/system/templates/system-plugin-ui-form.html.twig

-<?php
-
+{#
 /**
  * @file
  * Default theme implementation to configure blocks.
  *
  * Available variables:
- * - $left: Any form array elements that should appear in the left hand column.
- * - $right: Any form array elements that should appear in the right hand column.
- * - $form_submit: Form submit button.
+ * - form: The form elements which contains:
+ *   - left: Form elements that appear in the left column.
+ *   - right: Form elements that appear in the right column.
  *
- * @see template_preprocess_block_library_form()
- * @see theme_block_library_form()
+ * @see template_preprocess()
+ * @see template_preprocess_system_plugin_ui_form()
  *
  * @ingroup themeable
  */
-?>
+#}
 <div id="block-library" class="container">
   <div class="left-col">
     <div class="inside">
-      <?php print $left; ?>
+      {{ form.left }}
     </div>
   </div>
   <div class="right-col">
     <div class="inside">
-      <?php print $right; ?>
+      {{ form.right }}
     </div>
   </div>
-  <?php if ($form_submit) { ?>
-  <div class="bottom-bar"><?php print $form_submit; ?></div>
-  <?php } ?>
+  {% if form -%}
+    <div class="bottom-bar">{{ form }}</div>
+  {%- endif -%}
 </div>