TestWithConstraints.php

<?php

namespace Drupal\media_test_source\Plugin\media\Source;

use Drupal\media\MediaSourceEntityConstraintsInterface;
use Drupal\media\MediaSourceFieldConstraintsInterface;

/**
 * Provides generic media type.
 *
 * @MediaSource(
 *   id = "test_constraints",
 *   label = @Translation("Test source with constraints"),
 *   description = @Translation("Test media source that provides constraints."),
 *   allowed_field_types = {"string_long"},
 * )
 */
class TestWithConstraints extends Test implements MediaSourceEntityConstraintsInterface, MediaSourceFieldConstraintsInterface {
    
    /**
     * {@inheritdoc}
     */
    public function getEntityConstraints() {
        return \Drupal::state()->get('media_source_test_entity_constraints', []);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getSourceFieldConstraints() {
        return \Drupal::state()->get('media_source_test_field_constraints', []);
    }

}