Issue #2881981 by foxtrotcharlie, Vidushi Mehta, vakulrai, Mile23, larowlan, dawehner, heddn: Mitigate Extension dependency on DRUPAL_ROOT

core/lib/Drupal/Core/Extension/Extension.php

@@ -185,7 +185,7 @@ class Extension implements \Serializable {
   public function unserialize($data) {
     $data = unserialize($data);
     // Get the app root from the container.
-    $this->root = DRUPAL_ROOT;
+    $this->root = \Drupal::hasService('app.root') ? \Drupal::root() : DRUPAL_ROOT;
     $this->type = $data['type'];
     $this->pathname = $data['pathname'];
     $this->filename = $data['filename'];

core/tests/Drupal/Tests/Core/Extension/ExtensionUnserializedServiceAppRootUsageTest.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace Drupal\Tests\Core\Extension;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\Core\Extension\Extension;
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+
+/**
+ * Tests preferred use of service application root over DRUPAL_ROOT.
+ *
+ * @coversDefaultClass \Drupal\Core\Extension\Extension
+ * @group Extension
+ */
+class ExtensionUnserializedServiceAppRootUsageTest extends UnitTestCase {
+
+  /**
+   * Tests that the Extension class unserialize method uses the preferred root.
+   *
+   * When the Extension unserialize method is called on serialized Extension
+   * object data, test that the Extension object's root property is set to the
+   * container's app.root and not the DRUPAL_ROOT constant if the service
+   * container app.root is available.
+   *
+   * @covers ::unserialize
+   */
+  public function testServiceAppRouteUsage() {
+    // The assumption of our test is that DRUPAL_ROOT is not defined.
+    $this->assertFalse(defined('DRUPAL_ROOT'), 'Constant DRUPAL_ROOT is defined.');
+    $container = new ContainerBuilder();
+    // Set a dummy container app.root to test against.
+    $container->set('app.root', '/dummy/app/root');
+    \Drupal::setContainer($container);
+    // Instantiate an Extension object for testing unserialization.
+    $extension = new Extension($container->get('app.root'), 'module', 'core/modules/system/system.info.yml', 'system.module');
+    $data = $extension->serialize();
+    $extension->unserialize($data);
+    $this->assertEquals('/dummy/app/root', $this->readAttribute($extension, 'root'));
+  }
+
+}