Issue #3165010 by dpi, acbramley, tim.plunkett, larowlan: Using the layout...

      '#value' => $this->t('Discard changes'),

      '#submit' => ['::redirectOnSubmit'],

      '#redirect' => 'discard_changes',

      // Discard is not dependent on form input.

      '#limit_validation_errors' => [],

    ];

    // @todo This button should be conditionally displayed, see

    //   https://www.drupal.org/node/2917777.

<?php

namespace Drupal\Tests\layout_builder\Functional;

use Drupal\Core\Entity\Entity\EntityFormDisplay;

use Drupal\Core\Entity\Entity\EntityFormMode;

use Drupal\entity_test\Entity\EntityTest;

use Drupal\field\Entity\FieldConfig;

use Drupal\field\Entity\FieldStorageConfig;

use Drupal\layout_builder\Entity\LayoutBuilderEntityViewDisplay;

use Drupal\Tests\BrowserTestBase;

/**

 * Tests Layout Builder forms.

 *

 * @group layout_builder

 */

class LayoutBuilderFormModeTest extends BrowserTestBase {

  /**

   * {@inheritdoc}

   */

  protected static $modules = [

    'field',

    'entity_test',

    'layout_builder',

  ];

  /**

   * {@inheritdoc}

   */

  protected $defaultTheme = 'classy';

  /**

   * {@inheritdoc}

   */

  protected function setUp(): void {

    parent::setUp();

    // Set up a field with a validation constraint.

    $field_storage = FieldStorageConfig::create([

      'field_name' => 'foo',

      'entity_type' => 'entity_test',

      'type' => 'string',

    ]);

    $field_storage->save();

    FieldConfig::create([

      'field_storage' => $field_storage,

      'bundle' => 'entity_test',

      // Expecting required value.

      'required' => TRUE,

    ])->save();

    // Enable layout builder custom layouts.

    LayoutBuilderEntityViewDisplay::create([

      'targetEntityType' => 'entity_test',

      'bundle' => 'entity_test',

      'mode' => 'default',

      'status' => TRUE,

    ])

      ->enable()

      ->enableLayoutBuilder()

      ->setOverridable()

      ->save();

    // Add the form mode and show the field with a constraint.

    EntityFormMode::create([

      'id' => 'entity_test.layout_builder',

      'targetEntityType' => 'entity_test',

    ])->save();

    EntityFormDisplay::create([

      'targetEntityType' => 'entity_test',

      'bundle' => 'entity_test',

      'mode' => 'layout_builder',

      'status' => TRUE,

    ])

      ->setComponent('foo', [

        'type' => 'string_textfield',

      ])

      ->save();

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

      'view test entity',

      'configure any layout',

      'configure all entity_test entity_test layout overrides',

    ]));

    EntityTest::create()->setName($this->randomMachineName())->save();

  }

  /**

   * Tests that the 'Discard changes' button skips validation and ignores input.

   */

  public function testDiscardValidation() {

    $page = $this->getSession()->getPage();

    $assert_session = $this->assertSession();

    // When submitting the form normally, a validation error should be shown.

    $this->drupalGet('entity_test/1/layout');

    $assert_session->fieldExists('foo[0][value]');

    $assert_session->elementAttributeContains('named', ['field', 'foo[0][value]'], 'required', 'required');

    $page->pressButton('Save layout');

    $assert_session->pageTextContains('foo field is required.');

    // When Discarding changes, a validation error will not be shown.

    // Reload the form for fresh state.

    $this->drupalGet('entity_test/1/layout');

    $page->pressButton('Discard changes');

    $assert_session->pageTextNotContains('foo field is required.');

    $assert_session->addressEquals('entity_test/1/layout/discard-changes');

    // Submit the form to ensure no invalid form state retained.

    $page->pressButton('Confirm');

    $assert_session->pageTextContains('The changes to the layout have been discarded.');

  }

}