[DI] Handle invalid bundle configuration class

Author: ro0NL

CHANGELOG.md

@@ -9,6 +9,7 @@ CHANGELOG
  * added support for service's decorators autowiring
  * deprecated the `TypedReference::canBeAutoregistered()` and  `TypedReference::getRequiringClass()` methods
  * environment variables are validated when used in extension configuration
+ * deprecated support for auto-discovered extension configuration class which does not implement `ConfigurationInterface`
 
 4.0.0
 -----

Extension/Extension.php

@@ -82,11 +82,23 @@ public function getConfiguration(array $config, ContainerBuilder $container)
         $class = get_class($this);
         $class = substr_replace($class, '\Configuration', strrpos($class, '\\'));
         $class = $container->getReflectionClass($class);
-        $constructor = $class ? $class->getConstructor() : null;
 
-        if ($class && (!$constructor || !$constructor->getNumberOfRequiredParameters())) {
+        if (!$class) {
+            return null;
+        }
+
+        if (!$class->implementsInterface(ConfigurationInterface::class)) {
+            @trigger_error(sprintf('Not implementing "%s" in the extension configuration class "%s" is deprecated since Symfony 4.1.', ConfigurationInterface::class, $class->getName()), E_USER_DEPRECATED);
+            //throw new LogicException(sprintf('The extension configuration class "%s" must implement "%s".', $class->getName(), ConfigurationInterface::class));
+
+            return null;
+        }
+
+        if (!($constructor = $class->getConstructor()) || !$constructor->getNumberOfRequiredParameters()) {
             return $class->newInstance();
         }
+
+        return null;
     }
 
     final protected function processConfiguration(ConfigurationInterface $configuration, array $configs)