MAGETWO-94819: Swatch validation breaks the whole attribute form

-- fix merge conflict

Author: fascinosum

app/code/Magento/Catalog/Controller/Adminhtml/Product/Attribute/Validate.php

@@ -8,15 +8,18 @@
 namespace Magento\Catalog\Controller\Adminhtml\Product\Attribute;
 
 use Magento\Catalog\Model\Product\Attribute\Option\OptionsDataSerializer;
+use Magento\Framework\App\Action\HttpGetActionInterface;
+use Magento\Framework\App\Action\HttpPostActionInterface as HttpPostActionInterface;
 use Magento\Framework\App\ObjectManager;
 use Magento\Framework\DataObject;
+use Magento\Catalog\Controller\Adminhtml\Product\Attribute as AttributeAction;
 
 /**
  * Product attribute validate controller.
  *
  * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
  */
-class Validate extends \Magento\Catalog\Controller\Adminhtml\Product\Attribute
+class Validate extends AttributeAction implements HttpGetActionInterface, HttpPostActionInterface
 {
     const DEFAULT_MESSAGE_KEY = 'message';
 

dev/tests/integration/testsuite/Magento/Swatches/Controller/Adminhtml/Product/AttributeTest.php

@@ -7,6 +7,8 @@
 
 namespace Magento\Swatches\Controller\Adminhtml\Product;
 
+use Magento\Framework\App\Request\Http as HttpRequest;
+use Magento\Framework\Data\Form\FormKey;
 use Magento\Framework\Exception\LocalizedException;
 
 /**
@@ -17,6 +19,21 @@
  */
 class AttributeTest extends \Magento\TestFramework\TestCase\AbstractBackendController
 {
+    /**
+     * @var FormKey
+     */
+    private $formKey;
+
+    /**
+     * @inheritDoc
+     */
+    protected function setUp()
+    {
+        parent::setUp();
+
+        $this->formKey = $this->_objectManager->get(FormKey::class);
+    }
+
     /**
      * Generate random hex color.
      *
@@ -116,6 +133,7 @@ private function getAttributePreset() : array
     {
         return [
             'form_key' => 'XxtpPYjm2YPYUlAt',
+            'serialized_options' => '[]',
             'frontend_label' => [
                 0 => 'asdasd',
                 1 => '',
@@ -178,7 +196,9 @@ public function testLargeOptionsDataSet(
         int $expectedOptionsCount,
         array $expectedLabels
     ) : void {
+        $this->getRequest()->setMethod(HttpRequest::METHOD_POST);
         $this->getRequest()->setPostValue($attributeData);
+        $this->getRequest()->setPostValue('form_key', $this->formKey->getFormKey());
         $this->dispatch('backend/catalog/product_attribute/save');
         $entityTypeId = $this->_objectManager->create(
             \Magento\Eav\Model\Entity::class