fix: vcard bday export format with unknown year (#6087)

Author: MarkusDick

app/Services/VCard/ExportVCard.php

@@ -196,14 +196,16 @@ private function exportWorkInformation(Contact $contact, VCard $vcard)
     /**
      * @param  Contact  $contact
      * @param  VCard  $vcard
+     *
+     * @see https://datatracker.ietf.org/doc/html/rfc6350#section-6.2.5
      */
     private function exportBirthday(Contact $contact, VCard $vcard)
     {
         $vcard->remove('BDAY');
 
         if (! is_null($contact->birthdate)) {
             if ($contact->birthdate->is_year_unknown) {
-                $date = $contact->birthdate->date->format('--m-d');
+                $date = $contact->birthdate->date->format('--md');
             } else {
                 $date = $contact->birthdate->date->format('Ymd');
             }

tests/Unit/Services/VCard/ExportVCardTest.php

@@ -311,6 +311,24 @@ public function vcard_add_birthday()
         $this->assertStringContainsString('BDAY:20001005', $vCard->serialize());
     }
 
+    /** @test */
+    public function vcard_add_birthday_with_unknown_year()
+    {
+        $account = factory(Account::class)->create();
+        $contact = factory(Contact::class)->create(['account_id' => $account->id]);
+        $contact->setSpecialDate('birthdate', 0, 10, 5);
+        $vCard = new VCard();
+
+        $exportVCard = app(ExportVCard::class);
+        $this->invokePrivateMethod($exportVCard, 'exportBirthday', [$contact, $vCard]);
+
+        $this->assertCount(
+            self::defaultPropsCount + 1,
+            $vCard->children()
+        );
+        $this->assertStringContainsString('BDAY:--1005', $vCard->serialize());
+    }
+
     /** @test */
     public function vcard_add_contact_fields_empty()
     {