Issue #1937968 by ACF: Convert statistics's system_config_form() to SystemConfigFormBase.

core/modules/statistics/lib/Drupal/statistics/StatisticsSettingsForm.php

+<?php
+/**
+ * @file
+ * Contains \Drupal\statistics\StatisticsSettingsForm.
+ */
+
+namespace Drupal\statistics;
+
+use Drupal\system\SystemConfigFormBase;
+use Drupal\Core\Config\ConfigFactory;
+use Drupal\Core\Extension\ModuleHandler;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Configure statistics settings for this site.
+ */
+class StatisticsSettingsForm extends SystemConfigFormBase {
+
+  /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandler
+   */
+  protected $moduleHandler;
+
+  /**
+   * Constructs a \Drupal\user\StatisticsSettingsForm object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactory $config_factory
+   *   The factory for configuration objects.
+   * @param \Drupal\Core\Extension\ModuleHandler $module_handler
+   *   The module handler.
+   */
+  public function __construct(ConfigFactory $config_factory, ModuleHandler $module_handler) {
+    $this->configFactory = $config_factory;
+    $this->moduleHandler = $module_handler;
+  }
+
+  /**
+   * Implements \Drupal\Core\ControllerInterface::create().
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('config.factory'),
+      $container->get('module_handler')
+    );
+  }
+
+  /**
+   * Implements \Drupal\Core\Form\FormInterface::getFormID().
+   */
+  public function getFormID() {
+    return 'statistics_settings_form';
+  }
+
+  /**
+   * Implements \Drupal\Core\Form\FormInterface::buildForm().
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $config = $this->configFactory->get('statistics.settings');
+
+    // Content counter settings.
+    $form['content'] = array(
+      '#type' => 'details',
+      '#title' => t('Content viewing counter settings'),
+    );
+    $form['content']['statistics_count_content_views'] = array(
+      '#type' => 'checkbox',
+      '#title' => t('Count content views'),
+      '#default_value' => $config->get('count_content_views'),
+      '#description' => t('Increment a counter each time content is viewed.'),
+    );
+
+    return parent::buildForm($form, $form_state);
+  }
+
+  /**
+   * Implements \Drupal\Core\Form\FormInterface::submitForm().
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $this->configFactory->get('statistics.settings')
+      ->set('count_content_views', $form_state['values']['statistics_count_content_views'])
+      ->save();
+
+    // The popular statistics block is dependent on these settings, so clear the
+    // block plugin definitions cache.
+    if ($this->moduleHandler->moduleExists('block')) {
+      drupal_container()->get('plugin.manager.block')->clearCachedDefinitions();
+    }
+
+    parent::submitForm($form, $form_state);
+  }
+
+}

core/modules/statistics/statistics.admin.inc

-<?php
-
-/**
- * @file
- * Admin page callbacks for the Statistics module.
- */
-
-use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
-
-/**
- * Form constructor for the statistics administration form.
- *
- * @ingroup forms
- * @see statistics_settings_form_submit().
- */
-function statistics_settings_form($form, &$form_state) {
-  $config = config('statistics.settings');
-
-  // Content counter settings.
-  $form['content'] = array(
-    '#type' => 'details',
-    '#title' => t('Content viewing counter settings'),
-  );
-  $form['content']['statistics_count_content_views'] = array(
-    '#type' => 'checkbox',
-    '#title' => t('Count content views'),
-    '#default_value' => $config->get('count_content_views'),
-    '#description' => t('Increment a counter each time content is viewed.'),
-  );
-
-  return system_config_form($form, $form_state);
-}
-
-/**
- * Form submission handler for statistics_settings_form().
- */
-function statistics_settings_form_submit($form, &$form_state) {
-  config('statistics.settings')
-    ->set('count_content_views', $form_state['values']['statistics_count_content_views'])
-    ->save();
-  // The popular statistics block is dependent on these settings, so clear the
-  // block plugin definitions cache.
-  if (module_exists('block')) {
-    drupal_container()->get('plugin.manager.block')->clearCachedDefinitions();
-  }
-}

core/modules/statistics/statistics.module

@@ -79,10 +79,8 @@ function statistics_menu() {
   $items['admin/config/system/statistics'] = array(
     'title' => 'Statistics',
     'description' => 'Control details about what and how your site logs content statistics.',
-    'page callback' => 'drupal_get_form',
-    'page arguments' => array('statistics_settings_form'),
+    'route_name' => 'statistics_settings',
     'access arguments' => array('administer statistics'),
-    'file' => 'statistics.admin.inc',
     'weight' => -15,
   );
   return $items;

core/modules/statistics/statistics.routing.yml

+statistics_settings:
+  pattern: '/admin/config/system/statistics'
+  defaults:
+    _form: 'Drupal\statistics\StatisticsSettingsForm'
+  requirements:
+    _permission: 'administer statistics'