Issue #1963420 by jibran: Improve DX when writing style plugins by adding a...

Issue #1963420 by jibran: Improve DX when writing style plugins by adding a groupingTheme variable .

core/modules/views/lib/Drupal/views/Plugin/views/style/StylePluginBase.php

@@ -82,6 +82,18 @@ abstract class StylePluginBase extends PluginBase {
     */
   protected $rendered_fields;
 
+  /**
+   * The theme function used to render the grouping set.
+   *
+   * Plugins may override this attribute if they wish to use some other theme
+   * function to render the grouping set.
+   *
+   * @var string
+   *
+   * @see StylePluginBase::render_grouping_sets()
+   */
+  protected $groupingTheme = 'views_view_grouping';
+
   /**
    * Overrides \Drupal\views\Plugin\views\PluginBase::init().
    *
@@ -445,7 +457,7 @@ function render() {
    */
   function render_grouping_sets($sets, $level = 0) {
     $output = array();
-    $theme_functions = views_theme_functions('views_view_grouping', $this->view, $this->view->display_handler->display);
+    $theme_functions = views_theme_functions($this->groupingTheme, $this->view, $this->view->display_handler->display);
     foreach ($sets as $set) {
       $row = reset($set['rows']);
       // Render as a grouping set.