Issue #3272273 by mxh: Add a form context stack

type: module

name: "Context Stack Form"

description: "Provides a context stack for objects that belong to forms."

core_version_requirement: ^9 || ^10

package: Other

dependencies:

  - context_stack:context_stack

<?php

/**

 * @file

 * The Context Stack Form module file.

 */

use Drupal\context_stack\ContextStackFactory;

use Drupal\context_stack\Plugin\Context\GenericEntityContext;

use Drupal\Core\Cache\CacheableMetadata;

use Drupal\Core\Entity\EntityFormInterface;

use Drupal\Core\Entity\EntityInterface;

use Drupal\Core\Form\FormStateInterface;

/**

 * Implements hook_form_alter().

 */

function context_stack_form_form_alter(&$form, FormStateInterface $form_state) {

  $form_object = $form_state->getFormObject();

  $entities = [];

  foreach ($form as $entry) {

    if (($entry instanceof EntityInterface) && !isset($entities[$entry->getEntityTypeId()])) {

      $entities[$entry->getEntityTypeId()] = $entry;

    }

  }

  if ($form_object instanceof EntityFormInterface) {

    $entity = $form_object->getEntity();

    if (!isset($entities[$entity->getEntityTypeId()])) {

      $entities[$entity->getEntityTypeId()] = $entity;

    }

  }

  if (empty($entities)) {

    return;

  }

  $collection = ContextStackFactory::get()->createCollection();

  foreach ($entities as $entity_type_id => $entity) {

    $collection->addContext(GenericEntityContext::fromEntity($entity, $entity->getEntityType()->getLabel()), $entity_type_id);

  }

  $form['#context_stack']['form'] = $collection;

  // Add cacheability from the context stack to the render array. This is done

  // by temporarily adding the collection to the stack, fetch its calculated

  // metadata, then remove it so the render system would render every entity

  // one-by-one, using the current context that is being pushed via pre-render.

  /** @var \Drupal\context_stack\ContextStackInterface $context_stack */

  $context_stack = \Drupal::service('context_stack.form');

  $context_stack->push(clone $collection);

  CacheableMetadata::createFromRenderArray($form)

    ->addCacheableDependency($context_stack)

    ->applyTo($form);

  $context_stack->pop();

  // Add the pre-render callback that will push the current context into the

  // context stack. The post-render callback is responsible for removing the

  // added context collection from the stack afterwards.

  $form['#pre_render'][] = [

    '\Drupal\context_stack_form\Render\FormStack',

    'preRender',

  ];

  $form['#post_render'][] = [

    '\Drupal\context_stack_form\Render\FormStack',

    'postRender',

  ];

}

/**

 * Implements hook_inline_entity_form_entity_form_alter().

 *

 * This hook is only available when inline_entity_form is installed.

 */

function context_stack_form_inline_entity_form_entity_form_alter(&$form, FormStateInterface $form_state) {

  context_stack_form_form_alter($form, $form_state);

}

services:

  context_stack.form:

    class: Drupal\context_stack\ContextStack

    factory: ['@context_stack.factory', createStack]

    arguments: [form]

    tags:

      - { name: context_stack }

<?php

namespace Drupal\context_stack_form\Render;

use Drupal\Core\Security\TrustedCallbackInterface;

/**

 * Trusted callbacks for pushing entities into the "form" stack.

 */

final class FormStack implements TrustedCallbackInterface {

  /**

   * Pre render callback to add form entities to the stack.

   *

   * @param array $element

   *   The render element.

   *

   * @return array

   *   The (preprocessed) render element.

   */

  public static function preRender(array $element) {

    if (!empty($element['#context_stack']['form'])) {

      /** @var \Drupal\context_stack\ContextCollectionInterface $collection */

      $collection = $element['#context_stack']['form'];

      /** @var \Drupal\context_stack\ContextStackInterface $context_stack */

      $context_stack = \Drupal::service('context_stack.form');

      if (!$collection->getParent() && $collection !== $context_stack->current()) {

        $context_stack->push($collection);

      }

      unset($element['#context_stack']['form']);

    }

    return $element;

  }

  /**

   * Post render callback to pop form entities off the stack.

   *

   * @param mixed $children

   *   The result of rendering the children.

   * @param mixed $element

   *   The element as render array.

   *

   * @return mixed

   *   The post-processed result.

   */

  public static function postRender($children, $element) {

    if (!empty($element['#context_stack']['form'])) {

      $collection = $element['#context_stack']['form'];

      /** @var \Drupal\context_stack\ContextStackInterface $context_stack */

      $context_stack = \Drupal::service('context_stack.form');

      while ($collection !== $context_stack->pop() && $context_stack->current());

    }

    return $children;

  }

  /**

   * {@inheritdoc}

   */

  public static function trustedCallbacks() {

    return ['preRender', 'postRender'];

  }

}