Issue #2504995 by Xano: Component DefaultFactory relies on core's concept of plugin providers

core/lib/Drupal/Component/Plugin/Factory/DefaultFactory.php

@@ -88,7 +88,7 @@ public static function getPluginClass($plugin_id, $plugin_definition = NULL, $re
     }
 
     if ($required_interface && !is_subclass_of($plugin_definition['class'], $required_interface)) {
-      throw new PluginException(sprintf('Plugin "%s" (%s) in %s should implement interface %s.', $plugin_id, $plugin_definition['class'], $plugin_definition['provider'], $required_interface));
+      throw new PluginException(sprintf('Plugin "%s" (%s) must implement interface %s.', $plugin_id, $plugin_definition['class'], $required_interface));
     }
 
     return $class;

core/tests/Drupal/Tests/Component/Plugin/DefaultFactoryTest.php

@@ -60,7 +60,7 @@ public function testGetPluginClassWithInterface() {
    * Tests getPluginClass() with a required interface but no implementation.
    *
    * @expectedException \Drupal\Component\Plugin\Exception\PluginException
-   * @expectedExceptionMessage Plugin "cherry" (Drupal\plugin_test\Plugin\plugin_test\fruit\Kale) in core should implement interface \Drupal\plugin_test\Plugin\plugin_test\fruit\FruitInterface.
+   * @expectedExceptionMessage Plugin "cherry" (Drupal\plugin_test\Plugin\plugin_test\fruit\Kale) must implement interface \Drupal\plugin_test\Plugin\plugin_test\fruit\FruitInterface.
    */
   public function testGetPluginClassWithInterfaceAndInvalidClass() {
     $plugin_class = 'Drupal\plugin_test\Plugin\plugin_test\fruit\Kale';

core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php

@@ -251,7 +251,7 @@ public function testCreateInstanceWithJustValidInterfaces() {
    * @covers ::createInstance
    *
    * @expectedException \Drupal\Component\Plugin\Exception\PluginException
-   * @expectedExceptionMessage Plugin "kale" (Drupal\plugin_test\Plugin\plugin_test\fruit\Kale) in plugin_test should implement interface \Drupal\plugin_test\Plugin\plugin_test\fruit\FruitInterface
+   * @expectedExceptionMessage Plugin "kale" (Drupal\plugin_test\Plugin\plugin_test\fruit\Kale) must implement interface \Drupal\plugin_test\Plugin\plugin_test\fruit\FruitInterface
    */
   public function testCreateInstanceWithInvalidInterfaces() {
     $module_handler = $this->getMock('Drupal\Core\Extension\ModuleHandlerInterface');