Update to Drupal 8.0.0-rc3. For more information, see https://www.drupal.org/node/2608078

core/tests/Drupal/KernelTests/Core/Theme/TwigMarkupInterfaceTest.php

@@ -0,0 +1,112 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\KernelTests\Core\Theme\ThemeRenderAndAutoescapeTest.
+ */
+
+namespace Drupal\KernelTests\Core\Theme;
+
+use Drupal\Component\Render\FormattableMarkup;
+use Drupal\Component\Render\MarkupInterface;
+use Drupal\Component\Render\MarkupTrait;
+use Drupal\Core\GeneratedLink;
+use Drupal\Core\Render\RenderContext;
+use Drupal\Core\Render\Markup;
+use Drupal\Core\Site\Settings;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests Twig with MarkupInterface objects.
+ *
+ * @group Theme
+ */
+class TwigMarkupInterfaceTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = [
+    'language'
+  ];
+
+  /**
+   * @dataProvider providerTestMarkupInterfaceEmpty
+   */
+  public function testMarkupInterfaceEmpty($expected, $variable) {
+    $this->assertEquals($expected, $this->renderObjectWithTwig($variable));
+  }
+
+  /**
+   * Provide test examples.
+   */
+  public function providerTestMarkupInterfaceEmpty() {
+    return [
+      'empty TranslatableMarkup' => ['', new TranslatableMarkup('')],
+      'non-empty TranslatableMarkup' => ['<span>test</span>', new TranslatableMarkup('test')],
+      'empty FormattableMarkup' => ['', new FormattableMarkup('', ['@foo' => 'bar'])],
+      'non-empty FormattableMarkup' => ['<span>bar</span>', new FormattableMarkup('@foo', ['@foo' => 'bar'])],
+      'non-empty Markup' => ['<span>test</span>', Markup::create('test')],
+      'empty GeneratedLink' => ['', new GeneratedLink()],
+      'non-empty GeneratedLink' => ['<span><a hef="http://www.example.com">test</a></span>', (new GeneratedLink())->setGeneratedLink('<a hef="http://www.example.com">test</a>')],
+      // Test objects that do not implement \Countable.
+      'empty SafeMarkupTestMarkup' => ['<span></span>', SafeMarkupTestMarkup::create('')],
+      'non-empty SafeMarkupTestMarkup' => ['<span>test</span>', SafeMarkupTestMarkup::create('test')],
+    ];
+  }
+
+  /**
+   * Tests behaviour if a string is translated to become an empty string.
+   */
+  public function testEmptyTranslation() {
+    $settings = Settings::getAll();
+    $settings['locale_custom_strings_en'] = ['' => ['test' => '']];
+    // Recreate the settings static.
+    new Settings($settings);
+
+    $variable = new TranslatableMarkup('test');
+    $this->assertEquals('', $this->renderObjectWithTwig($variable));
+
+    $variable = new TranslatableMarkup('test', [], ['langcode' => 'de']);
+    $this->assertEquals('<span>test</span>', $this->renderObjectWithTwig($variable));
+  }
+
+  /**
+   * @return \Drupal\Component\Render\MarkupInterface
+   *   The rendered HTML.
+   */
+  protected function renderObjectWithTwig($variable) {
+    /** @var \Drupal\Core\Render\RendererInterface $renderer */
+    $renderer = \Drupal::service('renderer');
+    $context = new RenderContext();
+    return $renderer->executeInRenderContext($context, function () use ($renderer, $variable) {
+      $elements = [
+        '#type' => 'inline_template',
+        '#template' => '{%- if variable is not empty -%}<span>{{ variable }}</span>{%- endif -%}',
+        '#context' => array('variable' => $variable),
+      ];
+      return $renderer->render($elements);
+    });
+  }
+
+}
+
+/**
+ * Implements MarkupInterface without implementing \Countable
+ */
+class SafeMarkupTestMarkup implements MarkupInterface {
+  use MarkupTrait;
+
+  /**
+   * Overrides MarkupTrait::create() to allow creation with empty strings.
+   */
+  public static function create($string) {
+    $object = new static();
+    $object->string = $string;
+    return $object;
+  }
+
+}