Prefix dropdown in checkout doesn't select empty value by default if required

app/code/Magento/Customer/Model/Options.php

@@ -97,12 +97,14 @@ private function prepareNamePrefixSuffixOptions($options, $isOptional = false)
         if (empty($options)) {
             return false;
         }
+
         $result = [];
-        $options = array_filter(explode(';', $options));
+        $options = explode(';', $options);
         foreach ($options as $value) {
-            $value = $this->escaper->escapeHtml(trim($value));
+            $value = $this->escaper->escapeHtml(trim($value)) ?: ' ';
             $result[$value] = $value;
         }
+
         if ($isOptional && trim(current($options))) {
             $result = array_merge([' ' => ' '], $result);
         }

dev/tests/integration/testsuite/Magento/Customer/Model/OptionsTest.php

@@ -0,0 +1,156 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+declare(strict_types=1);
+
+namespace Magento\Customer\Model;
+
+use Magento\Config\Model\Config\Source\Nooptreq;
+use Magento\Customer\Helper\Address;
+use Magento\Framework\App\Config\MutableScopeConfigInterface;
+use Magento\Framework\ObjectManagerInterface;
+use Magento\Store\Model\ScopeInterface;
+use Magento\TestFramework\Helper\Bootstrap;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Test for \Magento\Customer\Model\Options.
+ * @magentoDbIsolation enabled
+ */
+class OptionsTest extends TestCase
+{
+    private const XML_PATH_SUFFIX_SHOW = 'customer/address/suffix_show';
+    private const XML_PATH_SUFFIX_OPTIONS = 'customer/address/suffix_options';
+    private const XML_PATH_PREFIX_SHOW = 'customer/address/prefix_show';
+    private const XML_PATH_PREFIX_OPTIONS = 'customer/address/prefix_options';
+
+    /**
+     * @var Options
+     */
+    private $model;
+
+    /**
+     * @var ObjectManagerInterface
+     */
+    private $objectManager;
+
+    /**
+     * @inheritdoc
+     */
+    protected function setUp(): void
+    {
+        $this->objectManager = Bootstrap::getObjectManager();
+        $this->model = $this->objectManager->create(Options::class);
+    }
+
+    /**
+     * Test suffix and prefix options
+     *
+     * @dataProvider optionsDataProvider
+     *
+     * @param string $optionType
+     * @param array $showOptionConfig
+     * @param array $optionValuesConfig
+     * @param array $expectedOptions
+     * @return void
+     */
+    public function testOptions(
+        string $optionType,
+        array $showOptionConfig,
+        array $optionValuesConfig,
+        array $expectedOptions
+    ): void {
+        $this->setConfig($showOptionConfig);
+        $this->setConfig($optionValuesConfig);
+
+        /** @var array $options */
+        $options = $optionType === 'prefix'
+            ? $this->model->getNamePrefixOptions()
+            : $this->model->getNameSuffixOptions();
+
+        $this->assertEquals($expectedOptions, $options);
+    }
+
+    /**
+     * Set config param
+     *
+     * @param array $data
+     * @param string|null $scopeType
+     * @param string|null $scopeCode
+     * @return void
+     */
+    private function setConfig(
+        array $data,
+        ?string $scopeType = ScopeInterface::SCOPE_STORE,
+        ?string $scopeCode = 'default'
+    ): void {
+        $path = array_key_first($data);
+        $this->objectManager->get(MutableScopeConfigInterface::class)
+            ->setValue($path, $data[$path], $scopeType, $scopeCode);
+    }
+
+    /**
+     * DataProvider for testOptions()
+     *
+     * @return array
+     */
+    public function optionsDataProvider(): array
+    {
+        $optionPrefixName = 'prefix';
+        $optionSuffixName = 'suffix';
+        $optionValues = 'v1;v2';
+        $optionValuesWithBlank = ';v1;v2';
+        $expectedValuesWithBlank = [' ' => ' ', 'v1' => 'v1', 'v2' => 'v2'];
+        $expectedValues = ['v1' => 'v1', 'v2' => 'v2'];
+
+        return [
+            'prefix_required_with_blank_option' => [
+                $optionPrefixName,
+                [self::XML_PATH_PREFIX_SHOW => Nooptreq::VALUE_REQUIRED],
+                [self::XML_PATH_PREFIX_OPTIONS => $optionValuesWithBlank],
+                $expectedValuesWithBlank,
+            ],
+            'prefix_required' => [
+                $optionPrefixName,
+                [self::XML_PATH_PREFIX_SHOW => Nooptreq::VALUE_REQUIRED],
+                [self::XML_PATH_PREFIX_OPTIONS => $optionValues],
+                $expectedValues,
+            ],
+            'prefix_optional' => [
+                $optionPrefixName,
+                [self::XML_PATH_PREFIX_SHOW => Nooptreq::VALUE_OPTIONAL],
+                [self::XML_PATH_PREFIX_OPTIONS => $optionValues],
+                $expectedValuesWithBlank,
+            ],
+            'suffix_optional' => [
+                $optionSuffixName,
+                [self::XML_PATH_SUFFIX_SHOW => Nooptreq::VALUE_OPTIONAL],
+                [self::XML_PATH_SUFFIX_OPTIONS => $optionValues],
+                $expectedValuesWithBlank,
+            ],
+            'suffix_optional_with_blank_option' => [
+                $optionSuffixName,
+                [self::XML_PATH_SUFFIX_SHOW => Nooptreq::VALUE_OPTIONAL],
+                [self::XML_PATH_SUFFIX_OPTIONS => $optionValuesWithBlank],
+                $expectedValuesWithBlank,
+            ],
+            'suffix_required_with_blank_option' => [
+                $optionSuffixName,
+                [self::XML_PATH_SUFFIX_SHOW => Nooptreq::VALUE_OPTIONAL],
+                [self::XML_PATH_SUFFIX_OPTIONS => $optionValuesWithBlank],
+                $expectedValuesWithBlank,
+            ],
+        ];
+    }
+
+    /**
+     * @inheritdoc
+     */
+    protected function tearDown(): void
+    {
+        $this->objectManager->removeSharedInstance(Address::class);
+    }
+}