Tidy Instance methods

4 proposals to simplify Instance entity.

Rename ::getCurrentState()

"Current state" of a concept from the State Manager era of the project, before the move to revisionable entities.

Everywhere else, we use ::getSources(), so let's do the same here.

Add ::getBuildable()?

When I have added the buildable field in Instance entity, I was initially against exposing it to the public interface because it was an implementation detail, internal to the entity.

However, after a few months, it seems it not the case, and are overusing FieldableEntityInterface::get() to load the plugin.

Twice in InstanceListBuilder:

    /** @var \Drupal\display_builder\Plugin\Field\FieldType\PluginItem $item */
    $item = $instance->get('buildable')->first();
    /** @var \Drupal\display_builder\DisplayBuildableInterface $buildable */
    $buildable = $item->getInstance();
    $type = $buildable->label() ?? '-';

    /** @var \Drupal\display_builder\Plugin\Field\FieldType\PluginItem $field */
    $field = $entity->get('buildable')->first();
    /** @var \Drupal\display_builder\DisplayBuildableInterface $buildable */
    $buildable = $field->getInstance()

Once in ApiPreviewController:

    /** @var \Drupal\display_builder\Plugin\Field\FieldType\PluginItem|null $item */
    $item = $instance->get('buildable')->first();
    /** @var \Drupal\display_builder\DisplayBuildableInterface|null $buildable */
    $buildable = $item?->getInstance();
    $path = $buildable?->getPreviewPagePath();

Once in StateButtons

    /** @var \Drupal\display_builder\Plugin\Field\FieldType\PluginItem|null $item */
    $item = $instance->get('buildable')->first();
    /** @var \Drupal\display_builder\DisplayBuildableInterface|null $buildable */
    $buildable = $item?->getInstance();

    if ($buildable instanceof DisplayBuildableOverrideInterface) {
      return !empty($buildable->getSources());

Once in ProfileViewBuilder:

$buildable_id = $builder->get('buildable')->first()->get('plugin_id')->getValue() ?? '';

So, let's add a ::getBuildable() public method.

Do we keep ::getProfile(), ::getRuntimeContexts(), ::getAvailableContexts() ?

Remove ::getPathIndex()?

It seems it is used only in tests: InstanceTest, InstanceHistoryTest, & InstanceMoveToSlotTest

Remove Instance::refreshContexts()

While working on #3618072: Placeholders and real render, in Canvas and Preview, we asked ourselves why do we have Instance::refreshContexts()? Is it a leftover of previous architecture (before the buildable plugins) ?

There is nothing related to, or own by, the instance data in this method. Once #3544026: Cardinality constraints for slots wil lbe merged, it will seem the logic can be moved to EntityView, alongside ::markSampleEntity().