MAGETWO-69430: Magento allows to save not valid data using config:set command

Author: shiftedreality

app/code/Magento/Config/Console/Command/ConfigSet/LockProcessor.php

@@ -8,6 +8,7 @@
 use Magento\Config\App\Config\Type\System;
 use Magento\Config\Model\PreparedValueFactory;
 use Magento\Framework\App\Config\ConfigPathResolver;
+use Magento\Framework\App\Config\Value;
 use Magento\Framework\App\DeploymentConfig;
 use Magento\Framework\Config\File\ConfigFilePool;
 use Magento\Framework\Exception\CouldNotSaveException;
@@ -79,19 +80,27 @@ public function process($path, $value, $scope, $scopeCode)
             $configPath = $this->configPathResolver->resolve($path, $scope, $scopeCode, System::CONFIG_TYPE);
             $backendModel = $this->preparedValueFactory->create($path, $value, $scope, $scopeCode);
 
-            /**
-             * Temporary solution until Magento introduce unified interface
-             * for storing system configuration into database and configuration files.
-             */
-            $backendModel->validateBeforeSave();
-            $backendModel->beforeSave();
+            if ($backendModel instanceof Value) {
+                /**
+                 * Temporary solution until Magento introduce unified interface
+                 * for storing system configuration into database and configuration files.
+                 */
+                $backendModel->validateBeforeSave();
+                $backendModel->beforeSave();
 
-            $this->deploymentConfigWriter->saveConfig(
-                [ConfigFilePool::APP_ENV => $this->arrayManager->set($configPath, [], $backendModel->getValue())],
-                false
-            );
+                $value = $backendModel->getValue();
 
-            $backendModel->afterSave();
+                $backendModel->afterSave();
+
+                /**
+                 * Because FS does not support transactions,
+                 * we'll write value just after all validations are triggered.
+                 */
+                $this->deploymentConfigWriter->saveConfig(
+                    [ConfigFilePool::APP_ENV => $this->arrayManager->set($configPath, [], $value)],
+                    false
+                );
+            }
         } catch (\Exception $exception) {
             throw new CouldNotSaveException(__('%1', $exception->getMessage()), $exception);
         }

app/code/Magento/Config/Test/Unit/Console/Command/ConfigSet/LockProcessorTest.php

@@ -206,10 +206,10 @@ public function testCustomException()
             ->willReturn($this->valueMock);
         $this->arrayManagerMock->expects($this->never())
             ->method('set');
-        $this->valueMock->expects($this->never())
+        $this->valueMock->expects($this->once())
             ->method('getValue');
         $this->valueMock->expects($this->once())
-            ->method('validateBeforeSave')
+            ->method('afterSave')
             ->willThrowException(new \Exception('Invalid values'));
         $this->deploymentConfigWriterMock->expects($this->never())
             ->method('saveConfig');