EntityFormBuilder.php

<?php

namespace Drupal\Core\Entity;

use Drupal\Core\Form\FormBuilderInterface;
use Drupal\Core\Form\FormState;

/**
 * Builds entity forms.
 */
class EntityFormBuilder implements EntityFormBuilderInterface {
    
    /**
     * The entity type manager service.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The form builder.
     *
     * @var \Drupal\Core\Form\FormBuilderInterface
     */
    protected $formBuilder;
    
    /**
     * Constructs a new EntityFormBuilder.
     *
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager service.
     * @param \Drupal\Core\Form\FormBuilderInterface $form_builder
     *   The form builder.
     */
    public function __construct(EntityTypeManagerInterface $entity_type_manager, FormBuilderInterface $form_builder) {
        $this->entityTypeManager = $entity_type_manager;
        $this->formBuilder = $form_builder;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getForm(EntityInterface $entity, $operation = 'default', array $form_state_additions = []) {
        $form_object = $this->entityTypeManager
            ->getFormObject($entity->getEntityTypeId(), $operation);
        $form_object->setEntity($entity);
        $form_state = (new FormState())->setFormState($form_state_additions);
        return $this->formBuilder
            ->buildForm($form_object, $form_state);
    }

}