How do I get multiple references from the autocomplete?

Question

I am using the following form element.

$form['group']['one'] = array(
    '#type' => 'entity_autocomplete',
    '#title' => t('Tags'),
    '#target_type' => 'user',
);

I submit values similar to the following ones.

user00 (0), user01 (1), user02 (2), user0x (3)

What I receive from the form is the following:

one = 3

It only picks up the last ID.

How can I get all the references entered in the form element? How does the form element handle the references to not existing entities?

Answer 1

The comma is used to separate multiple references, but looking at the code in Name::valueForm() I would say the form element needs to use a property more.

  $form['value'] = array(
    '#type' => 'entity_autocomplete',
    '#title' => $this->t('Usernames'),
    '#description' => $this->t('Enter a comma separated list of user names.'),
    '#target_type' => 'user',
    '#tags' => TRUE,
    '#default_value' => $default_value,
    '#process_default_value' => $this->isExposed(),
  );

Settings #tags to TRUE makes the the form element accept multiple values.

The format of the values assigned to the form element is evident in EntityAutocomplete::validateEntityAutocomplete() (its validation handler), which uses this code.

  $input_values = $element['#tags'] ? Tags::explode($element['#value']) : array($element['#value']);

  foreach ($input_values as $input) {
    $match = static::extractEntityIdFromAutocompleteInput($input);
    if ($match === NULL) {
      // Try to get a match from the input string when the user didn't use
      // the autocomplete but filled in a value manually.
      $match = static::matchEntityByTitle($handler, $input, $element, $form_state, !$autocreate);
    }

    if ($match !== NULL) {
      $value[] = array(
        'target_id' => $match,
      );
    }
    elseif ($autocreate) {
      /** @var \Drupal\Core\Entity\EntityReferenceSelection\SelectionWithAutocreateInterface $handler */
      // Auto-create item. See an example of how this is handled in
      // \Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem::presave().
      $value[] = array(
        'entity' => $handler->createNewEntity($element['#target_type'], $element['#autocreate']['bundle'], $input, $element['#autocreate']['uid']),
      );
    }

The form element value is an array of item whose target_id key is an object of the requested entity.

(From that code, it is also clear that #tags makes the form element accepts multiple references separated by commas.)

As for the using reference that aren't found, you can decide what the autocomplete does by setting #validate_reference: If you set it to TRUE, and #autocreate is not set to TRUE, the autocomplete will accept only existing references.