Issue #2416831 by cilefen, vasi, tadityar, Noe_, lauriii, akalata, JeroenT, Cottser, davidhernandez: Add an active_theme twig function

core/core.services.yml

@@ -1323,6 +1323,7 @@ services:
       - { name: twig.extension, priority: 100 }
     calls:
       - [setGenerators, ['@url_generator']]
+      - [setThemeManager, ['@theme.manager']]
   # @todo Figure out what to do about debugging functions.
   # @see https://www.drupal.org/node/1804998
   twig.extension.debug:

core/lib/Drupal/Core/Template/TwigExtension.php

@@ -15,6 +15,7 @@ namespace Drupal\Core\Template;
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Render\RendererInterface;
 use Drupal\Core\Routing\UrlGeneratorInterface;
+use Drupal\Core\Theme\ThemeManagerInterface;
 use Drupal\Core\Url;
 
 /**
@@ -40,6 +41,13 @@ class TwigExtension extends \Twig_Extension {
    */
   protected $renderer;
 
+  /**
+   * The theme manager.
+   *
+   * @var \Drupal\Core\Theme\ThemeManagerInterface
+   */
+  protected $themeManager;
+
   /**
    * Constructs \Drupal\Core\Template\TwigExtension.
    *
@@ -63,11 +71,24 @@ class TwigExtension extends \Twig_Extension {
     return $this;
   }
 
+  /**
+   * Sets the theme manager.
+   *
+   * @param \Drupal\Core\Theme\ThemeManagerInterface $theme_manager
+   *   The theme manager.
+   *
+   * @return $this
+   */
+  public function setThemeManager(ThemeManagerInterface $theme_manager) {
+    $this->themeManager = $theme_manager;
+    return $this;
+  }
+
   /**
    * {@inheritdoc}
    */
   public function getFunctions() {
-    return array(
+    return [
       // This function will receive a renderable array, if an array is detected.
       new \Twig_SimpleFunction('render_var', array($this, 'renderVar')),
       // The url and path function are defined in close parallel to those found
@@ -77,8 +98,9 @@ class TwigExtension extends \Twig_Extension {
       new \Twig_SimpleFunction('url_from_path', array($this, 'getUrlFromPath'), array('is_safe_callback' => array($this, 'isUrlGenerationSafe'))),
       new \Twig_SimpleFunction('link', array($this, 'getLink')),
       new \Twig_SimpleFunction('file_url', 'file_create_url'),
-      new \Twig_SimpleFunction('attach_library', array($this, 'attachLibrary'))
-    );
+      new \Twig_SimpleFunction('attach_library', [$this, 'attachLibrary']),
+      new \Twig_SimpleFunction('active_theme', [$this, 'getActiveTheme']),
+    ];
   }
 
   /**
@@ -246,6 +268,16 @@ class TwigExtension extends \Twig_Extension {
     return $build;
   }
 
+  /**
+   * Gets the name of the active theme.
+   *
+   * @return string
+   *   The name of the active theme.
+   */
+  public function getActiveTheme() {
+    return $this->themeManager->getActiveTheme()->getName();
+  }
+
   /**
    * Determines at compile time whether the generated URL will be safe.
    *

core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php

@@ -72,4 +72,31 @@ class TwigExtensionTest extends UnitTestCase {
     );
   }
 
+  /**
+   * Tests the active_theme function.
+   */
+  public function testActiveTheme() {
+    $renderer = $this->getMock('\Drupal\Core\Render\RendererInterface');
+    $extension = new TwigExtension($renderer);
+    $theme_manager = $this->getMock('\Drupal\Core\Theme\ThemeManagerInterface');
+    $active_theme = $this->getMockBuilder('\Drupal\Core\Theme\ActiveTheme')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $active_theme
+      ->expects($this->once())
+      ->method('getName')
+      ->willReturn('test_theme');
+    $theme_manager
+      ->expects($this->once())
+      ->method('getActiveTheme')
+      ->willReturn($active_theme);
+    $extension->setThemeManager($theme_manager);
+
+    $loader = new \Twig_Loader_String();
+    $twig = new \Twig_Environment($loader);
+    $twig->addExtension($extension);
+    $result = $twig->render('{{ active_theme() }}');
+    $this->assertEquals('test_theme', $result);
+  }
+
 }