[1.0.0-alpha3] Field formatters compatibility with Layout Builder

Work done, but let's do more tests before MR

Jean,

There may be something wrong with the custom IconFormatter::validateSettings() method:

  public function validateSettings(array $element, FormStateInterface $form_state, &$complete_form): void {
    $values = $form_state->getValues();
    $name = $this->fieldDefinition->getName();

    $settings = $values['fields'][$name]['settings_edit_form']['settings'] ?? [];
    unset($settings['icon_settings']);

    // @todo do we need configuration validation of plugin form?
    $form_state->setValueForElement($element, $settings);
  }

$values['fields'][$name]['settings_edit_form']['settings'] seems to mimic the form structure of manage display, so the formatter settings are not saved in layout builder.

If I remove the call to validateSettings:

    $elements['icon_settings'] = [
      '#type' => 'hidden',
      '#element_validate' => [
        [$this, 'validateSettings'],
      ],
    ];

the settings are not saved in neither Manage Display nor Layotu Builder.

I don't know which change to make. Do you have an idea?

Field formatter must be tesetd with Manage Dispaly, Layout Builder, and Views.

Fixed for Icon formatter in Layout builder, but can not make it work for Link with Icon as sample values do not populate the icon.

And for now I didn't find hot to do it.

Link formatter issue created.

Is it possible to avoid doing such condition which is limited to "Manage display" and "Layout builder":?

    // Field UI "MAnage display" page.
    if (isset($values['fields'][$name]['settings_edit_form']['settings'])) {
      $settings = $values['fields'][$name]['settings_edit_form']['settings'];
    }
    // Layout builder UI.
    elseif (isset($values['settings']['formatter']['settings'])) {
      $settings = $values['settings']['formatter']['settings'];
    }

I am afraid the plugin will not work with Views and any other config entity from Drupal contrib leveraging this plugin type