How do I programmatically generate an entity form?

Question

I need to programmatically generate the entity form for my custom entity - basically get the same output that happens when you call

\Drupal::formBuilder()->getForm('form namespace')

When I try to do that with my entity form I get the error:

Call to a member function getEntityTypeId() on null in Drupal\Core\Entity\EntityForm->getBaseFormId() (line 77 of core/lib/Drupal/Core/Entity/EntityForm.php).

Really stumped on how to proceed.

---

Here's an obfuscated version of code I'm using

Entity Definition:

/**
 * Defines the My Entity entity.
 *
 * @ingroup my_module
 *
 * @ContentEntityType(
 *   id = "my_entity",
 *   label = @Translation("My Entity"),
 *   handlers = {
 *     "view_builder" = "Drupal\Core\Entity\EntityViewBuilder",
 *     "list_builder" = "Drupal\my_module\MyEntityListBuilder",
 *     "views_data" = "Drupal\my_module\Entity\MyEntityViewsData",
 *     "translation" = "Drupal\my_module\MyEntityTranslationHandler",
 *
 *     "form" = {
 *       "default" = "Drupal\my_module\Form\MyEntityForm",
 *       "add" = "Drupal\my_module\Form\MyEntityForm",
 *       "edit" = "Drupal\my_module\Form\MyEntityForm",
 *       "delete" = "Drupal\my_module\Form\MyEntityDeleteForm",
 *     },
 *     "access" = "Drupal\my_module\MyEntityAccessControlHandler",
 *     "route_provider" = {
 *       "html" = "Drupal\my_module\MyEntityHtmlRouteProvider",
 *     },
 *   },
 *   base_table = "my_entity",
 *   data_table = "my_entity_field_data",
 *   translatable = TRUE,
 *   admin_permission = "administer as my_entity entities",
 *   entity_keys = {
 *     "id" = "id",
 *     "label" = "name",
 *     "uuid" = "uuid",
 *     "uid" = "user_id",
 *     "langcode" = "langcode",
 *     "status" = "status",
 *   },
 *   links = {
 *     "canonical" = "/admin/structure/my_entity/{my_entity}",
 *     "add-form" = "/admin/structure/my_entity/add",
 *     "edit-form" = "/admin/structure/my_entity/{my_entity}/edit",
 *     "delete-form" = "/admin/structure/my_entity/{my_entity}/delete",
 *     "collection" = "/admin/structure/my_entity",
 *   },
 *   field_ui_base_route = "my_entity.settings",
 *   constraints = {
 *     "CustomContraint" = {}
 *   }
 * )
 */
class MyEntity extends ContentEntityBase implements MyEntityInterface {

Form namespace

namespace Drupal\my_module\Form;

use Drupal\Core\Entity\ContentEntityForm;
use Drupal\Core\Form\FormStateInterface;

/**
 * Form controller for My Entity edit forms.
 *
 * @ingroup my_module
 */
class MyEntityForm extends ContentEntityForm {

---

Okay, so this is what I've found so far. User oknate's answer partially works; I also had to add a dummy function to my container form class to get around a callback error, which looked like this:

 public function processForm($element, FormStateInterface $form_state, $form)
  {
    return $element;
  }

This is probably not the right way to do this, but it does result in a form object that will render in another form.

Answer 1

You can use the entity form builder service. I was able to load the user form this way (with $entity being the current user):

$entity = User::load($uid);
$user_form = \Drupal::service('entity.form_builder')->getForm($entity, 'default');

If you want to get the user register form (which is basically an entity form without a saved entity), you can just use the create method on your entity class before passing it to the form:

$entity = User::create();
$user_form = \Drupal::service('entity.form_builder')->getForm($entity, 'default');

Answer 2

Entity forms don't work without an entity. If you want an empty form then use a newly created entity instance. You can use this example from the node entity:

/**
 * Provides the node submission form.
 *
 * @param \Drupal\node\NodeTypeInterface $node_type
 *   The node type entity for the node.
 *
 * @return array
 *   A node submission form.
 */
public function add(NodeTypeInterface $node_type) {
  $node = $this->entityManager()->getStorage('node')->create(array(
    'type' => $node_type->id(),
  ));

  $form = $this->entityFormBuilder()->getForm($node);

  return $form;
}

The entity form builder is injected in the controller base class. So usually you use a controller to build entity forms.

When creating a node you need to define a bundle (content type), for which the entity form will be built. If your entity has no bundles you can use an empty array.

---

Comments

Comments need more work, because they are attached to an entity field.

Example how to build a form for the comment field of a node:

$comment = $this->entityTypeManager()->getStorage('comment')->create([
  'entity_type' => 'node',
  'entity_id' => $node->id(),
  'field_name' => 'comment',
]);
$build = $this->entityFormBuilder()->getForm($comment);

Or the same outside of a controller without injected services:

$comment = \Drupal::entityTypeManager()->getStorage('comment')->create([
  'entity_type' => 'node',
  'entity_id' => $node->id(),
  'field_name' => 'comment',
]);
$build = \Drupal::service('entity.form_builder')->getForm($comment);

Answer 3

Just to clarify, the below code does work for me in Drupal 8.2.x:

$form = \Drupal::formBuilder()->getForm(Drupal\user\Form\UserLoginForm::class);