Merge pull request #3735 from magento-mpi/port-97898

Fixed issues:
- [MAGETWO-97898](https://jira.corp.magento.com/browse/MAGETWO-97898) [Magento Cloud] Store switcher URL redirects to the same store

app/code/Magento/Store/Model/StoreResolver/Website.php

@@ -45,8 +45,10 @@ public function getAllowedStoreIds($scopeCode)
         $stores = [];
         $website = $scopeCode ? $this->websiteRepository->get($scopeCode) : $this->websiteRepository->getDefault();
         foreach ($this->storeRepository->getList() as $store) {
-            if ($store->isActive() && $store->getWebsiteId() == $website->getId()) {
-                $stores[] = $store->getId();
+            if ($store->isActive()) {
+                if (!$scopeCode || ($store->getWebsiteId() === $website->getId())) {
+                    $stores[] = $store->getId();
+                }
             }
         }
         return $stores;

dev/tests/integration/testsuite/Magento/Store/Model/StoreResolver/WebsiteTest.php

@@ -0,0 +1,62 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Store\Model\StoreResolver;
+
+use Magento\TestFramework\Helper\Bootstrap;
+
+class WebsiteTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @var Website
+     */
+    private $reader;
+
+    protected function setUp()
+    {
+        $this->reader = Bootstrap::getObjectManager()->create(Website::class);
+    }
+
+    /**
+     * Tests retrieving of stores id by passed scope.
+     *
+     * @param string|null $scopeCode website code
+     * @param int $storesCount
+     * @magentoDataFixture Magento/Store/_files/second_website_with_two_stores.php
+     * @magentoDbIsolation disabled
+     * @magentoAppIsolation enabled
+     * @dataProvider scopeDataProvider
+     */
+    public function testGetAllowedStoreIds($scopeCode, $storesCount)
+    {
+        $this->assertCount($storesCount, $this->reader->getAllowedStoreIds($scopeCode));
+    }
+
+    /**
+     * Provides scopes and corresponding count of resolved stores.
+     *
+     * @return array
+     */
+    public function scopeDataProvider(): array
+    {
+        return [
+            [null, 4],
+            ['test', 2]
+        ];
+    }
+
+    /**
+     * Tests retrieving of stores id by passing incorrect scope.
+     *
+     * @expectedException \Magento\Framework\Exception\NoSuchEntityException
+     * @expectedExceptionMessage The website with code not_exists that was requested wasn't found.
+     */
+    public function testIncorrectScope()
+    {
+        $this->reader->getAllowedStoreIds('not_exists');
+    }
+}