Extend MaxAgeCheck to support http_cache_control

Closes #3424019

src/Plugin/Purge/DiagnosticCheck/MaxAgeCheck.php

@@ -3,6 +3,7 @@
 namespace Drupal\purge\Plugin\Purge\DiagnosticCheck;
 
 use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
@@ -25,11 +26,20 @@ class MaxAgeCheck extends DiagnosticCheckBase implements DiagnosticCheckInterfac
    */
   protected $config;
 
+  /**
+   * The module handler service.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
   /**
    * Construct a MaxAgeCheck object.
    *
    * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
    *   The factory for configuration objects.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler service.
    * @param array $configuration
    *   A configuration array containing information about the plugin instance.
    * @param string $plugin_id
@@ -37,9 +47,10 @@ class MaxAgeCheck extends DiagnosticCheckBase implements DiagnosticCheckInterfac
    * @param mixed $plugin_definition
    *   The plugin implementation definition.
    */
-  final public function __construct(ConfigFactoryInterface $config_factory, array $configuration, $plugin_id, $plugin_definition) {
+  final public function __construct(ConfigFactoryInterface $config_factory, ModuleHandlerInterface $module_handler, array $configuration, $plugin_id, $plugin_definition) {
     parent::__construct($configuration, $plugin_id, $plugin_definition);
-    $this->config = $config_factory->get('system.performance');
+    $this->config = $config_factory;
+    $this->moduleHandler = $module_handler;
   }
 
   /**
@@ -48,6 +59,7 @@ class MaxAgeCheck extends DiagnosticCheckBase implements DiagnosticCheckInterfac
   public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
     return new static(
       $container->get('config.factory'),
+      $container->get('module_handler'),
       $configuration,
       $plugin_id,
       $plugin_definition
@@ -58,7 +70,14 @@ class MaxAgeCheck extends DiagnosticCheckBase implements DiagnosticCheckInterfac
    * {@inheritdoc}
    */
   public function run() {
-    $max_age = $this->config->get('cache.page.max_age');
+    // Avoid to get false positive when "s-maxage" is enabled
+    // by http_cache_control.
+    if ($this->moduleHandler->moduleExists('http_cache_control')) {
+      $max_age = $this->config->get('http_cache_control.settings')->get('cache.http.s_maxage');
+    }
+    else {
+      $max_age = $this->config->get('system.performance')->get('cache.page.max_age');
+    }
     $this->value = $this->valueTranslatable($max_age);
     if ($max_age === 0) {
       $this->recommendation = $this->t("Your site instructs external caching systems not to cache anything. Not only does this make cache invalidation futile, it is also a great danger to your website as any form of traffic can bring it down quickly!");