Fix mass product update with group min cart qty

Resolves warning when using the product edit mass-action after configuring
global group cart min qty

Fixes #17592

Author: pmclain

app/code/Magento/Catalog/Block/Adminhtml/Product/Edit/Action/Attribute/Tab/Inventory.php

@@ -5,6 +5,8 @@
  */
 namespace Magento\Catalog\Block\Adminhtml\Product\Edit\Action\Attribute\Tab;
 
+use Magento\Customer\Api\Data\GroupInterface;
+
 /**
  * Products mass update inventory tab
  *
@@ -29,6 +31,11 @@ class Inventory extends \Magento\Backend\Block\Widget implements \Magento\Backen
      */
     protected $disabledFields = [];
 
+    /**
+     * @var \Magento\Framework\Serialize\SerializerInterface
+     */
+    private $serializer;
+
     /**
      * @param \Magento\Backend\Block\Template\Context $context
      * @param \Magento\CatalogInventory\Model\Source\Backorders $backorders
@@ -39,10 +46,13 @@ public function __construct(
         \Magento\Backend\Block\Template\Context $context,
         \Magento\CatalogInventory\Model\Source\Backorders $backorders,
         \Magento\CatalogInventory\Api\StockConfigurationInterface $stockConfiguration,
-        array $data = []
+        array $data = [],
+        \Magento\Framework\Serialize\SerializerInterface $serializer = null
     ) {
         $this->_backorders = $backorders;
         $this->stockConfiguration = $stockConfiguration;
+        $this->serializer = $serializer ?? \Magento\Framework\App\ObjectManager::getInstance()
+            ->get(\Magento\Framework\Serialize\SerializerInterface::class);
         parent::__construct($context, $data);
     }
 
@@ -88,6 +98,21 @@ public function getDefaultConfigValue($field)
         return $this->stockConfiguration->getDefaultConfigValue($field);
     }
 
+    /**
+     * Returns min_sale_qty configuration for the ALL Customer Group
+     * @return int
+     */
+    public function getDefaultMinSaleQty()
+    {
+        $default = $this->stockConfiguration->getDefaultConfigValue('min_sale_qty');
+        if (!is_numeric($default)) {
+            $default = $this->serializer->unserialize($default);
+            $default = isset($default[GroupInterface::CUST_GROUP_ALL]) ? $default[GroupInterface::CUST_GROUP_ALL] : 1;
+        }
+
+        return (int) $default;
+    }
+
     /**
      * Tab settings
      *

app/code/Magento/Catalog/Test/Unit/Block/Adminhtml/Product/Edit/Action/Attribute/Tab/InventoryTest.php

@@ -5,6 +5,8 @@
  */
 namespace Magento\Catalog\Test\Unit\Block\Adminhtml\Product\Edit\Action\Attribute\Tab;
 
+use Magento\Customer\Api\Data\GroupInterface;
+
 /**
  * Class InventoryTest
  */
@@ -68,7 +70,8 @@ protected function setUp()
             [
                 'context' => $this->contextMock,
                 'backorders' => $this->backordersMock,
-                'stockConfiguration' => $this->stockConfigurationMock
+                'stockConfiguration' => $this->stockConfigurationMock,
+                'serializer' => new \Magento\Framework\Serialize\Serializer\Json(),
             ]
         );
     }
@@ -126,6 +129,32 @@ public function testGetDefaultConfigValue()
         $this->assertEquals('return-value', $this->inventory->getDefaultConfigValue('field-name'));
     }
 
+    /**
+     * @dataProvider getDefaultMinSaleQtyDataProvider
+     * @param string $expected
+     * @param string $default
+     */
+    public function testGetDefaultMinSaleQty($expected, $default)
+    {
+        $this->stockConfigurationMock->method('getDefaultConfigValue')->willReturn($default);
+        $this->assertEquals($expected, $this->inventory->getDefaultMinSaleQty());
+    }
+
+    public function getDefaultMinSaleQtyDataProvider()
+    {
+        return [
+            'single-default-value' => [
+                22, '22'
+            ],
+            'no-default-for-all-group' => [
+                1, json_encode(['12' => '111'])
+            ],
+            'default-for-all-group' => [
+                5, json_encode(['12' => '111', GroupInterface::CUST_GROUP_ALL => '5'])
+            ]
+        ];
+    }
+
     /**
      * Run test getTabLabel method
      *

app/code/Magento/Catalog/view/adminhtml/templates/catalog/product/edit/action/inventory.phtml

@@ -132,7 +132,7 @@
                     <div class="field">
                         <input type="text" class="input-text validate-number" id="inventory_min_sale_qty"
                                name="<?= /* @escapeNotVerified */ $block->getFieldSuffix() ?>[min_sale_qty]"
-                               value="<?= /* @escapeNotVerified */ $block->getDefaultConfigValue('min_sale_qty') * 1 ?>"
+                               value="<?= /* @escapeNotVerified */ $block->getDefaultMinSaleQty() * 1 ?>"
                                disabled="disabled"/>
                     </div>
                     <div class="field choice">