Issue #2650910 by drpal, Anishnirmal, markdorison, Tom Robert, psend,...

      // Update all contextual links placeholders whose HTML is cached.

      var uncachedIDs = _.filter(ids, function initIfCached(contextualID) {

        var html = storage.getItem('Drupal.contextual.' + contextualID);

        if (html !== null) {

        if (html && html.length) {

          // Initialize after the current execution cycle, to make the AJAX

          // request for retrieving the uncached contextual links as soon as

          // possible, but also to ensure that other Drupal behaviors have had

<?php

namespace Drupal\Tests\contextual\FunctionalJavascript;

use Drupal\FunctionalJavascriptTests\JavascriptTestBase;

use Drupal\user\Entity\Role;

/**

 * Tests the UI for correct contextual links.

 *

 * @group contextual

 */

class ContextualLinksTest extends JavascriptTestBase {

  /**

   * {@inheritdoc}

   */

  public static $modules = ['block', 'contextual'];

  /**

   * {@inheritdoc}

   */

  protected function setUp() {

    parent::setUp();

    $this->placeBlock('system_branding_block', ['id' => 'branding']);

  }

  /**

   * Tests the visibility of contextual links.

   */

  public function testContextualLinksVisibility() {

    $this->drupalLogin($this->drupalCreateUser([

      'access contextual links'

    ]));

    $this->drupalGet('user');

    $contextualLinks = $this->assertSession()->waitForElement('css', '.contextual button');

    $this->assertEmpty($contextualLinks);

    // Ensure visibility remains correct after cached paged load.

    $this->drupalGet('user');

    $contextualLinks = $this->assertSession()->waitForElement('css', '.contextual button');

    $this->assertEmpty($contextualLinks);

    // Grant permissions to use contextual links on blocks.

    $this->grantPermissions(Role::load(Role::AUTHENTICATED_ID), [

      'access contextual links',

      'administer blocks',

    ]);

    $this->drupalGet('user');

    $contextualLinks = $this->assertSession()->waitForElement('css', '.contextual button');

    $this->assertNotEmpty($contextualLinks);

    // Ensure visibility remains correct after cached paged load.

    $this->drupalGet('user');

    $contextualLinks = $this->assertSession()->waitForElement('css', '.contextual button');

    $this->assertNotEmpty($contextualLinks);

  }

}