Third Party Settings in Drupal

There would be instances where modules would need to include configurations or settings to configuration entities that are defined by other modules. Usually, this would be through altering the forms and implementing some hooks when operations are done to these entities (hook_*_presave(), hook_*_insert(), etc). Drupal 8 now has ThirdPartySettingsInterface which allows developers to include additional configurations associated to objects which implement this interface - ConfigEntityInterface.

Altering the Form

The form still needs to be altered and set the default values using getThirdPartySetting(). This is an example for a block configuration entity.

/**
 * Implements hook_form_alter().
 */
function strict_panda_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
  if ($form_id !== 'block_form') {
    return;
  }

  $block = $form_state->getFormObject()->getEntity();

  $third_party_settings = $block->getThirdPartySettings('strict_panda');

  $form['third_party_settings']['strict_panda']['name'] = [
    '#type' => 'textfield',
    '#title' => t('Name'),
    '#default_value' => $third_party_settings['name'],
  ];

  $form['third_party_settings']['strict_panda']['description'] = [
    '#type' => 'text_format',
    '#title' => t('Description'),
    '#format' => $third_party_settings['description']['format'],
    '#default_value' => $third_party_settings['description']['value'],
  ];
}

Simply including third_party_settings in the form tree automatically sets the third party settings for the configuration entity upon submission.

Appending a callback in the #entity_builders array can also be used when setting third party settings with the use of setThirdPartySetting().

Adding the Schema

Schema can optionally be added as well.

block.block.*.third_party.strict_panda:
  type: mapping
  label: 'Strict panda settings'
  mapping:
    name:
      type: string
      label: 'Name'
    description:
      type: boolean
      label: 'Description'