Issue #2804391 by Jo Fitzgerald, Berdir, amateescu, gaurav.kapoor, arunkumark,...

    elseif ($scheme === 'entity') {

      list($entity_type, $entity_id) = explode('/', substr($uri, 7), 2);

      // Show the 'entity:' URI as the entity autocomplete would.

      $entity_manager = \Drupal::entityManager();

      if ($entity_manager->getDefinition($entity_type, FALSE) && $entity = \Drupal::entityManager()->getStorage($entity_type)->load($entity_id)) {

      // @todo Support entity types other than 'node'. Will be fixed in

      //    https://www.drupal.org/node/2423093.

      if ($entity_type == 'node' && $entity = \Drupal::entityTypeManager()->getStorage($entity_type)->load($entity_id)) {

        $displayable_string = EntityAutocomplete::getEntityLabels([$entity]);

      }

    }

use Drupal\entity_test\Entity\EntityTest;

use Drupal\field\Entity\FieldConfig;

use Drupal\link\LinkItemInterface;

use Drupal\node\NodeInterface;

use Drupal\Tests\BrowserTestBase;

use Drupal\field\Entity\FieldStorageConfig;

    // Create a node to test the link widget.

    $node = $this->drupalCreateNode();

    // Create an entity with restricted view access.

    $entity_test_no_label_access = EntityTest::create([

      'name' => 'forbid_access',

    ]);

    $entity_test_no_label_access->save();

    $restricted_node = $this->drupalCreateNode(['status' => NodeInterface::NOT_PUBLISHED]);

    // Define some valid URLs (keys are the entered values, values are the

    // strings displayed to the user).

      // Entity URI displayed as ER autocomplete value when displayed in a form.

      'entity:node/1' => $node->label() . ' (1)',

      // URI for an entity that exists, but is not accessible by the user.

      'entity:entity_test/' . $entity_test_no_label_access->id() => '- Restricted access - (' . $entity_test_no_label_access->id() . ')',

      'entity:node/' . $restricted_node->id() => '- Restricted access - (' . $restricted_node->id() . ')',

      // URI for an entity that doesn't exist, but with a valid ID.

      'entity:user/999999' => 'entity:user/999999',

    ];

    }

  }

  /**

   * Tests editing a link to a non-node entity.

   */

  public function testEditNonNodeEntityLink() {

    $entity_type_manager = \Drupal::entityTypeManager();

    $entity_test_storage = $entity_type_manager->getStorage('entity_test');

    // Create a field with settings to validate.

    $this->fieldStorage = FieldStorageConfig::create([

      'field_name' => 'field_link',

      'entity_type' => 'entity_test',

      'type' => 'link',

      'cardinality' => 1,

    ]);

    $this->fieldStorage->save();

    FieldConfig::create([

      'field_storage' => $this->fieldStorage,

      'label' => 'Read more about this entity',

      'bundle' => 'entity_test',

      'settings' => [

        'title' => DRUPAL_OPTIONAL,

      ],

    ])->save();

    $entity_type_manager

      ->getStorage('entity_form_display')

      ->load('entity_test.entity_test.default')

      ->setComponent('field_link', [

        'type' => 'link_default',

      ])

      ->save();

    // Create a node and a test entity to have a possibly valid reference for

    // both. Create another test entity that references the first test entity.

    $entity_test_link = $entity_test_storage->create(['name' => 'correct link target']);

    $entity_test_link->save();

    $node = $this->drupalCreateNode(['wrong link target']);

    $correct_link = 'entity:entity_test/' . $entity_test_link->id();

    $entity_test = $entity_test_storage->create([

      'name' => 'correct link target',

      'field_link' => $correct_link,

    ]);

    $entity_test->save();

    // Edit the entity and save it, verify the correct link is kept and not

    // changed to point to a node. Currently, widget does not support non-node

    // autocomplete and therefore must show the link unaltered.

    $this->drupalGet($entity_test->toUrl('edit-form'));

    $this->assertSession()->fieldValueEquals('field_link[0][uri]', $correct_link);

    $this->drupalPostForm(NULL, [], 'Save');

    $entity_test_storage->resetCache();

    $entity_test = $entity_test_storage->load($entity_test->id());

    $this->assertEquals($correct_link, $entity_test->get('field_link')->uri);

  }

  /**

   * Renders a test_entity and returns the output.

   *