Display a nice error message if the form/serializer component is missing.

Author: derrabus

DependencyInjection/FrameworkExtension.php

@@ -171,6 +171,10 @@ public function load(array $configs, ContainerBuilder $container)
         }
 
         if ($this->isConfigEnabled($container, $config['form'])) {
+            if (!class_exists('Symfony\Component\Form\Form')) {
+                throw new LogicException('Form support cannot be enabled as the Form component is not installed.');
+            }
+
             $this->formConfigEnabled = true;
             $this->registerFormConfiguration($config, $container, $loader);
             $config['validation']['enabled'] = true;
@@ -216,6 +220,10 @@ public function load(array $configs, ContainerBuilder $container)
         $this->registerPropertyAccessConfiguration($config['property_access'], $container, $loader);
 
         if ($this->isConfigEnabled($container, $config['serializer'])) {
+            if (!class_exists('Symfony\Component\Serializer\Serializer')) {
+                throw new LogicException('Serializer support cannot be enabled as the Serializer component is not installed.');
+            }
+
             $this->registerSerializerConfiguration($config['serializer'], $container, $loader);
         }