Settings not present in patterns layouts

Is it not possible to use preprocess for your use case. Do you use it with layout builder?

I think it is not a good idea to set a pattern class because the settings should work with other possible pattern implementations.

We are facing the same issue, using Drupal 8.8.1

When using ui_patterns_settings with display suite enabled, the settings appear correctly on the pattern template.

Steps to reproduce:
- Enable ds, ui_patterns_ds, ui_patterns_settings.
- Create settings for a pattern and use them (in my case on a paragraph view mode)
- Render the entity. Use kint() inside the template to access the variables. The settings appear and are directly usable (i.e. if I have a setting called textfieldw with a vale of "test", I receive a 'textfield' -> 'test' and can render {{ textfield }} )

But if you uninstall display suite, you face a settings-less render array: the same textfield setting is set to NULL.

If you set a few breakpoints you can check that src/Element/PatternSettings::processSettings() works with layout builder and display suite but it won't work on the default (core) case.

      $settings = isset($element['#settings']) ? $element['#settings'] : []; // ALWAYS EMPTY
      // Handling display suite pattern.
      if (empty($settings)) {
        $settings = isset($element['#ds_configuration']['layout']['settings']['pattern']['settings']) ? $element['#ds_configuration']['layout']['settings']['pattern']['settings'] : [];
      }
      // Handling layout builder.
      if (empty($settings) && isset($element['#layout'])) {
        /** @var \Drupal\ui_patterns_layout_builder\Plugin\Layout\PatternLayoutBuilder $layout */
        $layout = $element['#layout'];
        $configuration = $layout->getConfiguration();
        $settings = isset($configuration['pattern']['settings']) ? $configuration['pattern']['settings'] : [];
      }

Unlike the DS and Layout Builder cases, $settings = isset($element['#settings']) ? $element['#settings'] : []; returns an empty array as $element['#settings'] is not populated. So, when you are not using DS or Layout Builder, you are left with an empty $settings

The patch on #2 corrects this. I think it should be applied, because the module should be usable with Drupal's core.

@idiaz.roncero So which module do you use to apply a layout to your entity when you disabled ds. core/field_layout ?

Core's Field Layout and Layout Discovery. Sorry, forgot to mention that.

I did some tests. The patch works fine with other implementations. Thanks!