Prevent Default Source/Stock to be deleted

app/code/Magento/InventoryCatalog/Plugin/Model/StockRepositoryPlugin.php

@@ -0,0 +1,47 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\InventoryCatalog\Plugin\Model;
+
+use Magento\Framework\Exception\CouldNotDeleteException;
+use Magento\InventoryApi\Api\StockRepositoryInterface;
+use Magento\InventoryCatalog\Api\DefaultStockProviderInterface;
+
+/**
+ * Class provide Before Plugin on StockRepositoryInterface::deleteByItem to prevent default stock could be deleted
+ */
+class StockRepositoryPlugin
+{
+    /**
+     * @var DefaultStockProviderInterface
+     */
+    private $defaultStockProvider;
+
+    /**
+     * @param DefaultStockProviderInterface $defaultStockProvider
+     */
+    public function __construct(DefaultStockProviderInterface $defaultStockProvider)
+    {
+        $this->defaultStockProvider = $defaultStockProvider;
+    }
+
+    /**
+     * Prevent default source to be deleted
+     *
+     * @param StockRepositoryInterface $subject
+     * @param int $stockId
+     *
+     * @return void
+     * @throws CouldNotDeleteException
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function beforeDeleteById(StockRepositoryInterface $subject, int $stockId)
+    {
+        if ($stockId === $this->defaultStockProvider->getId()) {
+            throw new CouldNotDeleteException(__('Default Stock could not be deleted.'));
+        }
+    }
+}

app/code/Magento/InventoryCatalog/Test/Api/StockRepository/CouldNotDeleteDefaultStockExceptionTest.php

@@ -0,0 +1,69 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\InventoryCatalog\Test\Api\StockRepository;
+
+use Magento\Framework\Webapi\Exception;
+use Magento\Framework\Webapi\Rest\Request;
+use Magento\TestFramework\TestCase\WebapiAbstract;
+use Magento\TestFramework\Helper\Bootstrap;
+use Magento\InventoryCatalog\Api\DefaultStockProviderInterface;
+
+/**
+ * Class CouldNotDeleteDefaultStockExceptionTest
+ */
+class CouldNotDeleteDefaultStockExceptionTest extends WebapiAbstract
+{
+    /**
+     * @var DefaultStockProviderInterface
+     */
+    private $defaultStockProvider;
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function setUp()
+    {
+        parent::setUp();
+        $this->defaultStockProvider = Bootstrap::getObjectManager()->get(DefaultStockProviderInterface::class);
+    }
+
+    /**
+     * Test that default Stock could not be deleted
+     *
+     * @throws \Exception
+     */
+    public function testCouldNotDeleteException()
+    {
+        $serviceInfo = [
+            'rest' => [
+                'resourcePath' => '/V1/inventory/stock/' . $this->defaultStockProvider->getId(),
+                'httpMethod' => Request::HTTP_METHOD_DELETE,
+            ],
+            'soap' => [
+                'service' => 'inventoryApiStockRepositoryV1',
+                'operation' => 'inventoryApiStockRepositoryV1DeleteById',
+            ],
+        ];
+        $expectedMessage = 'Default Stock could not be deleted.';
+        try {
+            (TESTS_WEB_API_ADAPTER == self::ADAPTER_REST) ? $this->_webApiCall($serviceInfo) :
+                $this->_webApiCall($serviceInfo, ['stockId' => $this->defaultStockProvider->getId()]);
+            $this->fail('Expected throwing exception');
+        } catch (\Exception $e) {
+            if (TESTS_WEB_API_ADAPTER == self::ADAPTER_REST) {
+                $errorData = $this->processRestExceptionResult($e);
+                self::assertEquals($expectedMessage, $errorData['message']);
+                self::assertEquals(Exception::HTTP_BAD_REQUEST, $e->getCode());
+            } elseif (TESTS_WEB_API_ADAPTER == self::ADAPTER_SOAP) {
+                $this->assertInstanceOf('SoapFault', $e);
+                $this->checkSoapFault($e, $expectedMessage, 'env:Sender');
+            } else {
+                throw $e;
+            }
+        }
+    }
+}

app/code/Magento/InventoryCatalog/Ui/Component/Control/Stock/DeleteButton.php

@@ -0,0 +1,62 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\InventoryCatalog\Ui\Component\Control\Stock;
+
+use Magento\Backend\Ui\Component\Control\DeleteButton as StockDeleteButton;
+use Magento\Framework\View\Element\UiComponent\Control\ButtonProviderInterface;
+use Magento\InventoryApi\Api\Data\StockInterface;
+use Magento\InventoryCatalog\Api\DefaultStockProviderInterface;
+use Magento\Framework\App\RequestInterface;
+
+/**
+ * Represents delete button with pre-configured options
+ * Provide an ability to show delete button only when stock id is not default
+ */
+class DeleteButton implements ButtonProviderInterface
+{
+    /**
+     * @var StockDeleteButton
+     */
+    private $deleteButton;
+
+    /**
+     * @var DefaultStockProviderInterface
+     */
+    private $defaultStockProvider;
+
+    /**
+     * @var RequestInterface
+     */
+    private $request;
+
+    /**
+     * @param StockDeleteButton $deleteButton
+     * @param DefaultStockProviderInterface $defaultStockProvider
+     * @param RequestInterface $request
+     */
+    public function __construct(
+        StockDeleteButton $deleteButton,
+        DefaultStockProviderInterface $defaultStockProvider,
+        RequestInterface $request
+    ) {
+        $this->deleteButton = $deleteButton;
+        $this->defaultStockProvider = $defaultStockProvider;
+        $this->request = $request;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getButtonData()
+    {
+        if ((int)$this->request->getParam(StockInterface::STOCK_ID) === $this->defaultStockProvider->getId()) {
+            return [];
+        }
+
+        return $this->deleteButton->getButtonData();
+    }
+}

app/code/Magento/InventoryCatalog/etc/adminhtml/di.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0"?>
+<!--
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
+    <type name="Magento\InventoryCatalog\Ui\Component\Control\Stock\DeleteButton">
+        <arguments>
+            <argument name="deleteButton" xsi:type="object">Magento\Inventory\Ui\Component\Control\Stock\DeleteButton</argument>
+        </arguments>
+    </type>
+</config>

app/code/Magento/InventoryCatalog/etc/di.xml

@@ -8,4 +8,7 @@
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
     <preference for="Magento\InventoryCatalog\Api\DefaultStockProviderInterface" type="Magento\InventoryCatalog\Model\DefaultStockProvider"/>
     <preference for="Magento\InventoryCatalog\Api\DefaultSourceProviderInterface" type="Magento\InventoryCatalog\Model\DefaultSourceProvider"/>
+    <type name="Magento\InventoryApi\Api\StockRepositoryInterface">
+        <plugin name="prevent_default_stock_deletion" type="Magento\InventoryCatalog\Plugin\Model\StockRepositoryPlugin" sortOrder="1"/>
+    </type>
 </config>

app/code/Magento/InventoryCatalog/view/adminhtml/ui_component/inventory_stock_form.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+-->
+<form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
+    <settings>
+        <buttons>
+            <button name="delete" class="Magento\InventoryCatalog\Ui\Component\Control\Stock\DeleteButton"/>
+        </buttons>
+    </settings>
+</form>