MAGETWO-72860: Fix default values not being properly loaded for ArraySerialized fields - for 2.2

Author: viktym

app/code/Magento/Config/Block/System/Config/Form.php

@@ -425,24 +425,10 @@ private function getFieldData(\Magento\Config\Model\Config\Structure\Element\Fie
         if ($placeholderValue) {
             $data = $placeholderValue;
         }
+
         if ($data === null) {
-            if (array_key_exists($path, $this->_configData)) {
-                $data = $this->_configData[$path];
-
-                if ($field->hasBackendModel()) {
-                    $backendModel = $field->getBackendModel();
-                    $backendModel->setPath($path)
-                        ->setValue($data)
-                        ->setWebsite($this->getWebsiteCode())
-                        ->setStore($this->getStoreCode())
-                        ->afterLoad();
-                    $data = $backendModel->getValue();
-                }
-            } elseif ($field->getConfigPath() !== null) {
-                $data = $this->getConfigValue($field->getConfigPath());
-            } else {
-                $data = $this->getConfigValue($path);
-            }
+            $path = $field->getConfigPath() !== null ? $field->getConfigPath() : $path;
+            $data = $this->getConfigValue($path);
         }
 
         return $data;

app/code/Magento/Config/Model/Config/Backend/Serialized.php

@@ -5,14 +5,15 @@
  */
 namespace Magento\Config\Model\Config\Backend;
 
+use Magento\Framework\App\Config\Data\ProcessorInterface;
 use Magento\Framework\App\ObjectManager;
 use Magento\Framework\Serialize\Serializer\Json;
 
 /**
  * @api
  * @since 100.0.2
  */
-class Serialized extends \Magento\Framework\App\Config\Value
+class Serialized extends \Magento\Framework\App\Config\Value implements ProcessorInterface
 {
     /**
      * @var Json
@@ -67,4 +68,12 @@ public function beforeSave()
         parent::beforeSave();
         return $this;
     }
+
+    /**
+     * @inheritdoc
+     */
+    public function processValue($value)
+    {
+        return empty($value) ? '' : $this->serializer->unserialize($value);
+    }
 }

app/code/Magento/Config/Test/Unit/Block/System/Config/FormTest.php

@@ -543,12 +543,12 @@ public function initFieldsDataProvider()
         return [
             [
                 ['section1/group1/field1' => 'some_value'],
-                false,
-                null,
+                'some_value',
+                'section1/group1/field1',
                 false,
                 'some_value',
                 null,
-                1,
+                0,
                 false,
                 false,
                 false

dev/tests/integration/testsuite/Magento/Config/Block/System/Config/FieldArray.php

@@ -0,0 +1,34 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Config\Block\System\Config;
+
+use Magento\Config\Block\System\Config\Form\Field\FieldArray\AbstractFieldArray;
+
+/**
+ * Backend system config array field renderer for integration test.
+ */
+class FieldArray extends AbstractFieldArray
+{
+    /**
+     * @inheritdoc
+     */
+    protected function _toHtml()
+    {
+        $value = '';
+        $element = $this->getElement();
+        if ($element->getValue() && is_array($element->getValue())) {
+            $value = implode('|', $element->getValue());
+        }
+
+        return sprintf(
+            '<input id="%s" name="%s" value="%s" />',
+            $element->getId(),
+            $element->getName(),
+            $value
+        );
+    }
+}