fix: accept the ISO-2 country codes when authoring a destination

src/Form/DestinationType.php

@@ -40,14 +40,7 @@ class DestinationType extends AbstractType
             ])
             ->add('country', ChoiceType::class, [
                 'label' => 'Land',
-                'choices' => [
-                    'Österreich' => 'at',
-                    'Schweiz' => 'ch',
-                    'Frankreich' => 'fr',
-                    'Italien' => 'it',
-                    'Deutschland' => 'de',
-                    'Niederlande' => 'nl',
-                ],
+                'choices' => DestinationDto::COUNTRIES,
             ])
             ->addEventListener(FormEvents::PRE_SET_DATA, function (FormEvent $event) {
                 $form = $event->getForm();

src/Model/DestinationDto.php

@@ -7,10 +7,26 @@ use Symfony\Component\Validator\Constraints as Assert;
 
 class DestinationDto
 {
+    /**
+     * The countries a destination can be authored in, as German label => ISO-3166-1 alpha-2.
+     *
+     * Both the form's choice list and the constraint below read this one map. They used to
+     * spell the codes out twice and drifted apart the moment the stored values moved to
+     * ISO-2: the form offered 'at' while the constraint still only accepted 'a'.
+     */
+    public const COUNTRIES = [
+        'Österreich' => 'at',
+        'Schweiz' => 'ch',
+        'Frankreich' => 'fr',
+        'Italien' => 'it',
+        'Deutschland' => 'de',
+        'Niederlande' => 'nl',
+    ];
+
     #[Assert\NotBlank(message: 'Bitte angeben')]
     private ?string $product = null;
 
-    #[Assert\Choice(choices: ['a', 'ch', 'd', 'f', 'i', 'nl'], message: 'Ungültige Auswahl')]
+    #[Assert\Choice(callback: 'countryCodes', message: 'Ungültige Auswahl')]
     private ?string $country = null;
 
     #[Assert\NotNull(message: 'Bitte das Beginndatum angeben')]
@@ -46,6 +62,14 @@ class DestinationDto
         return $instance;
     }
 
+    /**
+     * @return list<string>
+     */
+    public static function countryCodes(): array
+    {
+        return array_values(self::COUNTRIES);
+    }
+
     public function getProduct(): ?string
     {
         return $this->product;

tests/Model/DestinationDtoTest.php

@@ -0,0 +1,86 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Model;
+
+use App\Model\DestinationDto;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Validator\ConstraintViolationListInterface;
+use Symfony\Component\Validator\Validation;
+
+/**
+ * The stored country moved to ISO-3166-1 alpha-2, but the constraint on this DTO kept the
+ * old BusProNet abbreviations while the form was already offering the new codes. Every
+ * country except Schweiz and Niederlande - the two whose code happens to be unchanged -
+ * was rejected as "Ungültige Auswahl" on save, so a destination could not be created or
+ * edited for Österreich, Deutschland, Frankreich or Italien at all.
+ *
+ * The codes are asserted literally rather than read back off the map they come from, so
+ * that changing the map has to be a deliberate act rather than something a test agrees
+ * with by construction.
+ */
+class DestinationDtoTest extends TestCase
+{
+    public function testTheAuthorableCountriesAreTheIsoCodes(): void
+    {
+        $this->assertSame(['at', 'ch', 'fr', 'it', 'de', 'nl'], DestinationDto::countryCodes());
+    }
+
+    /**
+     * @dataProvider isoCountryCodes
+     */
+    public function testAnIsoCountryCodeIsAccepted(string $code): void
+    {
+        $this->assertCount(0, $this->validateCountry($code));
+    }
+
+    /**
+     * The four that the form offered and the constraint refused.
+     *
+     * @dataProvider busProNetCountryAbbreviations
+     */
+    public function testABusProNetAbbreviationIsNoLongerAccepted(string $abbreviation): void
+    {
+        $this->assertCount(1, $this->validateCountry($abbreviation));
+    }
+
+    /**
+     * MyE&P drops a country it cannot map to two letters, so a destination without one is
+     * a normal row rather than an invalid one.
+     */
+    public function testNoCountryIsAccepted(): void
+    {
+        $this->assertCount(0, $this->validateCountry(null));
+    }
+
+    /**
+     * @return iterable<array{string}>
+     */
+    public static function isoCountryCodes(): iterable
+    {
+        foreach (DestinationDto::countryCodes() as $code) {
+            yield $code => [$code];
+        }
+    }
+
+    /**
+     * @return iterable<array{string}>
+     */
+    public static function busProNetCountryAbbreviations(): iterable
+    {
+        yield 'a' => ['a'];
+        yield 'd' => ['d'];
+        yield 'f' => ['f'];
+        yield 'i' => ['i'];
+    }
+
+    private function validateCountry(?string $country): ConstraintViolationListInterface
+    {
+        return Validation::createValidatorBuilder()
+            ->enableAttributeMapping()
+            ->getValidator()
+            ->validateProperty((new DestinationDto())->setCountry($country), 'country')
+        ;
+    }
+}