I have a custom plugin type and annotation. The purpose of it is so people can develop their own clients for an API integration, and tell the system which plugin to use to perform these actions. I am able to load all defined plugins and add their sub forms on the main settings configuration form page I have implemented.

When the form submits, I can see the values go through to the appropriate plugin, but the values are not persisted nor in the database. I'm having trouble figuring out how to get this to save.

    $clients = $form_state->getValue('connections');

    if (!empty($clients)) {
      foreach ($clients as $key => $client) {
        $instance = $this->clientPluginManager->createInstance($key, []);
        $client_form_state = SubformState::createForSubform($form['connections'][$key], $form, $form_state);
        $instance->submitConfigurationForm($form['connections'][$key], $client_form_state);

    parent::submitForm($form, $form_state);

In the plugin:

   * {@inheritdoc}
  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {

   * {@inheritdoc}
  public function setConfiguration(array $configuration) {
    $this->configuration = NestedArray::mergeDeep($this->defaultConfiguration(), $configuration);

In my module (from looking around at other modules):

  type: config_entity
  label: 'Default client configuration'
      type: string
      label: 'The client API key.'
      type: string
      label: 'The hostname or base URI of the API.'

  type: mymodule.default_client_configuration

I am not entirely certain how the schema should be set. Do I also have to create a custom config entity class definition too? How does configuration make it from the form into config state?

  • You don't have to, if the user can only choose one plugin to configure you could use simple configuration. You can store plugin configuration wherever you want, an instantiated plugin doesn't know from where it gets the configuration. In general, though, most configurable plugins have a custom config entity class to configure multiple plugins and then you use the entire infrastructure including add, edit and delete forms in an entity collection page to manage those.
    – 4uk4
    Feb 14, 2023 at 9:21

1 Answer 1


To clarify the comment, it's true that instantiated plugins don't know from where they get the configuration, but you can add a method to the plugin manager to determine plugin id and configuration to instantiate with $this->createInstance().

To answer the question

How to create configurable plugins under a plugin manager?

with a minimal code example:


  public function getInstance(array $options) {
    $settings = $this->configFactory->get('mymodule.settings');
    $plugin_id = $settings->get('default_client.plugin_id');
    $configuration = $settings->get('default_client.configuration');
    if ($plugin_id) {
      return $this->createInstance($plugin_id, $configuration);

A plugin by the way is not a form class. Even if it looks like this with build and submit methods, those are not fully working form functions. They are called by the corresponding methods of the parent form. The form instance is not the same as the plugin instance and the configuration is not saved to the database. You can do this in the parent form and by setting #tree you can usually submit the form structure as it is.

  • Sure, the plugin has interfaces that make it configurable, which grant those methods. I was taking inspiration from modules like Search API or Facets where backend connectors can have more than one way to connect to it (Solr) or multiple add ons with a common interface (Facet), and then part of a large form UI. Is there an example of this in core?
    – Kevin
    Feb 14, 2023 at 14:27
  • I couldn't find an example in core. But you need to define only a minimal UI in the module settings form. Discover the installed plugins and populate a select list. If the selected plugin needs specific form fields you could load them via Ajax and then submit the entire module settings form including the plugin configuration.
    – 4uk4
    Feb 14, 2023 at 15:54
  • I see - and its up to them to get the config namespace right as a config_object in their implementation, and there it is.
    – Kevin
    Feb 14, 2023 at 16:15

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