Issue #2671988 by Wim Leers: Add SessionExistsCacheContext ('session.exists')

core/core.services.yml

@@ -55,6 +55,11 @@ services:
     arguments: ['@request_stack']
     tags:
       - { name: cache.context}
+  cache_context.session.exists:
+    class: Drupal\Core\Cache\Context\SessionExistsCacheContext
+    arguments: ['@session_configuration', '@request_stack']
+    tags:
+      - { name: cache.context}
   cache_context.request_format:
     class: Drupal\Core\Cache\Context\RequestFormatCacheContext
     arguments: ['@request_stack']

core/lib/Drupal/Core/Cache/Context/SessionExistsCacheContext.php

@@ -0,0 +1,69 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Cache\Context\SessionExistsCacheContext.
+ */
+
+namespace Drupal\Core\Cache\Context;
+
+use Drupal\Core\Cache\CacheableMetadata;
+use Drupal\Core\Session\SessionConfigurationInterface;
+use Symfony\Component\HttpFoundation\RequestStack;
+
+/**
+ * Defines the SessionExistsCacheContext service, for "session or not" caching.
+ *
+ * Cache context ID: 'session.exists'.
+ */
+class SessionExistsCacheContext implements CacheContextInterface {
+
+  /**
+   * The session configuration.
+   *
+   * @var \Drupal\Core\Session\SessionConfigurationInterface
+   */
+  protected $sessionConfiguration;
+
+  /**
+   * The request stack.
+   *
+   * @var \Symfony\Component\HttpFoundation\RequestStack
+   */
+  protected $requestStack;
+
+  /**
+   * Constructs a new SessionExistsCacheContext class.
+   *
+   * @param \Drupal\Core\Session\SessionConfigurationInterface $session_configuration
+   *   The session configuration.
+   * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
+   *   The request stack.
+   */
+  public function __construct(SessionConfigurationInterface $session_configuration, RequestStack $request_stack) {
+    $this->sessionConfiguration = $session_configuration;
+    $this->requestStack = $request_stack;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getLabel() {
+    return t('Session exists');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getContext() {
+    return $this->sessionConfiguration->hasSession($this->requestStack->getCurrentRequest()) ? '1' : '0';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheableMetadata() {
+    return new CacheableMetadata();
+  }
+
+}

core/modules/system/src/Tests/Cache/SessionExistsCacheContextTest.php

@@ -0,0 +1,71 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Cache\SessionExistsCacheContextTest.
+ */
+
+namespace Drupal\system\Tests\Cache;
+
+use Drupal\Core\Url;
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Tests the 'session.exists' cache context service.
+ *
+ * @group Cache
+ */
+class SessionExistsCacheContextTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['session_exists_cache_context_test'];
+
+  /**
+   * Tests \Drupal\Core\Cache\Context\SessionExistsCacheContext::getContext().
+   */
+  public function testCacheContext() {
+    $this->dumpHeaders = TRUE;
+
+    // 1. No session (anonymous).
+    $this->assertSessionCookieOnClient(FALSE);
+    $this->drupalGet(Url::fromRoute('<front>'));
+    $this->assertSessionCookieOnClient(FALSE);
+    $this->assertRaw('Session does not exist!');
+    $this->assertRaw('[session.exists]=0');
+
+    // 2. Session (authenticated).
+    $this->assertSessionCookieOnClient(FALSE);
+    $this->drupalLogin($this->rootUser);
+    $this->assertSessionCookieOnClient(TRUE);
+    $this->assertRaw('Session exists!');
+    $this->assertRaw('[session.exists]=1');
+    $this->drupalLogout();
+    $this->assertSessionCookieOnClient(FALSE);
+    $this->assertRaw('Session does not exist!');
+    $this->assertRaw('[session.exists]=0');
+
+    // 3. Session (anonymous).
+    $this->assertSessionCookieOnClient(FALSE);
+    $this->drupalGet(Url::fromRoute('<front>', [], ['query' => ['trigger_session' => 1]]));
+    $this->assertSessionCookieOnClient(TRUE);
+    $this->assertRaw('Session does not exist!');
+    $this->assertRaw('[session.exists]=0');
+    $this->drupalGet(Url::fromRoute('<front>'));
+    $this->assertSessionCookieOnClient(TRUE);
+    $this->assertRaw('Session exists!');
+    $this->assertRaw('[session.exists]=1');
+  }
+
+  /**
+   * Asserts whether a session cookie is present on the client or not.
+   */
+  function assertSessionCookieOnClient($expected_present) {
+    $non_deleted_cookies = array_filter($this->cookies, function ($item) { return $item['value'] !== 'deleted'; });
+    $this->assertEqual($expected_present, isset($non_deleted_cookies[$this->getSessionName()]), 'Session cookie exists.');
+  }
+
+}

core/modules/system/tests/modules/session_exists_cache_context_test/session_exists_cache_context_test.info.yml

@@ -0,0 +1,6 @@
+name: 'session.exists cache context test'
+type: module
+description: 'Support module for session.exists cache context testing.'
+package: Testing
+version: VERSION
+core: 8.x

core/modules/system/tests/modules/session_exists_cache_context_test/session_exists_cache_context_test.module

@@ -0,0 +1,24 @@
+<?php
+
+/**
+ * Implements hook_page_top().
+ */
+function session_exists_cache_context_test_page_top(array &$page_top) {
+  // Ensure this hook is invoked on every page load.
+  $page_top['#cache']['max-age'] = 0;
+
+  $request = \Drupal::request();
+  $session_exists = \Drupal::service('session_configuration')->hasSession($request);
+  $page_top['session_exists_cache_context_test'] = [
+    'label' => [
+      '#markup' => '<p>' . ($session_exists ? 'Session exists!' : 'Session does not exist!') . '</p>',
+    ],
+    'cache_context_value' => [
+      '#markup' => '<code>[session.exists]=' . \Drupal::service('cache_context.session.exists')->getContext() . '</code>',
+    ],
+  ];
+
+  if (\Drupal::request()->query->get('trigger_session')) {
+    $_SESSION['session_exists_cache_context_test'] = TRUE;
+  }
+}