[Drupal 8] Inline entity form - Single value does not work

Yep ! I confirm this !! Inline_entity_form work only in multiple value mode.

I'll take a look this. I suspect a problem in retrieving form elements.

OK !! It's "normal"

The function formElement() is not set in InlineEntityFormSingle class.

  /**
   * {@inheritdoc}
   */
  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
    $ief_id = $this->fieldDefinition;

    return $element;
  }

I think this issue join this https://www.drupal.org/node/2489230.

Because the contents of the form will be the same in the end. It does not just have the opportunity to set a higher value 1 in the setting of the widget. And this is already the case in the configuration

 * @FieldWidget(
 *   id = "inline_entity_form_single",
 *   label = @Translation("Inline entity form - Single value"),
 *   field_types = {
 *     "entity_reference"
 *   },
 *   settings = {
 *     "allow_existing" = FALSE,
 *     "match_operator" = "CONTAINS",
 *     "delete_references" = FALSE,
 *     "override_labels" = FALSE,
 *     "label_singular" = "",
 *     "label_plural" = ""
 *   },
 *   multiple_values = false <------ See this
 * )

The final definition of the elements will be the same as multiple I think. (Feel free to tell me if I'm wrong).

--------Test------
Apply the test patch file in this issue, Singlewidget does works.

Conclusion !

It is not the fix for this issue, but an example. We must define what should be displayed in the single case or not . Single and Multiple define whether have the same form Elements or if the configuration widget which prevents add more items ?

It takes little thinking be if two widgets are still useful in the sense that with multiple it is possible to make a widget set has one value, it becomes a single one ... Make widget also solves the issue of refactoring that I ' I propose to the other end and simplifies the structure !

I wait your reactions :)

Reload the patch with last version of IEF.

Close the benefit of a more suitable outcome @see https://www.drupal.org/node/2491527#comment-9940087

I need you brutzelspeck :)

Thanks for your job .