Programmatically create a comment form for a node

Question

I'm trying to port a theme from Drupal 6 to Drupal 8, and I find code like the following.

$edit = array();
$edit['nid'] = $node->nid;
$form = drupal_get_form('comment_form', $edit));

How do I load the form in Drupal 8? I get the following error:

Fatal error: Call to a member function getEntityTypeId() on null in /www/site/core/lib/Drupal/Core/Entity/EntityForm.php on line 77

The line causing the error is the following one:

\Drupal::formBuilder()->getForm('Drupal\comment\CommentForm');

I can't work out how to pass the node object to the form builder. How can I do it?

Answer 1

kiamlaluno's solution didn't work for me. This did:

$values = array(
    'entity_type'  => 'node',
    'entity_id'    => $node->id(),
    'field_name'   => 'comment',
    'comment_type' => 'comment',
    'pid' => NULL,
);

$comment = \Drupal::entityTypeManager()->getStorage('comment')->create($values);
$formHTML  = \Drupal::service('entity.form_builder')->getForm($comment);

Answer 2

FormBuilder::getForm() doesn't accept just a single argument; it accepts additional arguments that are passed to the functions called by FormBuilder::getForm(), including the unique form constructor function. These values are available to implementations of hook_form_alter() and hook_form_FORM_ID_alter() as $form_state->getBuildInfo()['args'].

To build an entity form, though, Drupal core uses the entity.form_builder service instead of form_builder. The following is the code used in CommentLazyBuilders::renderForm() to build the comment form.

$values = [
  'entity_type' => $commented_entity_type_id,
  'entity_id' => $commented_entity_id,
  'field_name' => $field_name,
  'comment_type' => $comment_type_id,
  'pid' => NULL,
];
$comment = $this->entityTypeManager->getStorage('comment')
  ->create($values);

return $this->entityFormBuilder->getForm($comment);

EntityFormBuilder::getForm() accepts two arguments more; the second one is the operation to be done on the entity. Passing 'delete' as second argument, the code would obtain the form to delete the entity.

Answer 3

Example in core using lazy builder approach to make it work properly with caching per permission

http://cgit.drupalcode.org/drupal/tree/core/modules/comment/src/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php#n194