Implemented basic discriminator map for Attachment API access. Now we can properly create part attachments using a POST operation

src/Entity/Attachments/Attachment.php

@@ -43,6 +43,7 @@ use App\Validator\Constraints\Selectable;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Component\Serializer\Annotation\Groups;
 use Symfony\Component\Serializer\Annotation\SerializedName;
+use Symfony\Component\Serializer\Attribute\DiscriminatorMap;
 use Symfony\Component\Validator\Constraints as Assert;
 use function in_array;
 use InvalidArgumentException;
@@ -72,7 +73,7 @@ use LogicException;
     operations: [
         new Get(security: 'is_granted("read", object)'),
         new GetCollection(security: 'is_granted("@attachments.list_attachments")'),
-        //new Post(securityPostDenormalize: 'is_granted("create", object)'),
+        new Post(securityPostDenormalize: 'is_granted("create", object)'),
         new Patch(security: 'is_granted("edit", object)'),
         new Delete(security: 'is_granted("delete", object)'),
     ],
@@ -88,6 +89,7 @@ use LogicException;
 #[ApiFilter(EntityFilter::class, properties: ["attachment_type"])]
 #[ApiFilter(DateFilter::class, strategy: DateFilter::EXCLUDE_NULL)]
 #[ApiFilter(OrderFilter::class, properties: ['name', 'id', 'addedDate', 'lastModified'])]
+#[DiscriminatorMap(typeProperty: '_type', mapping: ['part' => PartAttachment::class])]
 abstract class Attachment extends AbstractNamedDBElement
 {
     /**
@@ -143,6 +145,7 @@ abstract class Attachment extends AbstractNamedDBElement
      * @phpstan-param T|null $element
      */
     #[Groups(['attachment:read:standalone', 'attachment:write:standalone'])]
+    #[ApiProperty(writableLink: false)]
     protected ?AttachmentContainingDBElement $element = null;
 
     #[ORM\Column(type: Types::BOOLEAN)]

src/Entity/Attachments/PartAttachment.php

@@ -23,8 +23,14 @@ declare(strict_types=1);
 namespace App\Entity\Attachments;
 
 use App\Entity\Parts\Part;
+use App\Serializer\OverrideClassDenormalizer;
+use App\Serializer\TypeOverride\TypeOverridableSerializer;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
+use Symfony\Component\PropertyInfo\Type;
+use Symfony\Component\Serializer\Attribute\Context;
+use Symfony\Component\Serializer\Normalizer\AbstractNormalizer;
+use Symfony\Component\Serializer\Normalizer\AbstractObjectNormalizer;
 
 /**
  * A attachment attached to a part element.
@@ -40,5 +46,7 @@ class PartAttachment extends Attachment
      */
     #[ORM\ManyToOne(targetEntity: Part::class, inversedBy: 'attachments')]
     #[ORM\JoinColumn(name: 'element_id', nullable: false, onDelete: 'CASCADE')]
+    // Set the correct type for the element property to use
+    #[Context(denormalizationContext: [OverrideClassDenormalizer::CONTEXT_KEY => Part::class])]
     protected ?AttachmentContainingDBElement $element = null;
 }

src/Serializer/OverrideClassDenormalizer.php

@@ -0,0 +1,61 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2024 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+
+namespace App\Serializer;
+
+use Symfony\Component\Serializer\Normalizer\DenormalizerAwareInterface;
+use Symfony\Component\Serializer\Normalizer\DenormalizerAwareTrait;
+use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;
+
+/**
+ * The idea of this denormalizer is to allow to override the type of the object created using a certain context key.
+ * This is required to resolve the issue of the serializer/API platform not correctly being able to determine the type
+ * of the "element" properties of the Attachment and Parameter subclasses.
+ */
+class OverrideClassDenormalizer implements DenormalizerInterface, DenormalizerAwareInterface
+{
+    use DenormalizerAwareTrait;
+
+    public const CONTEXT_KEY = '__override_type__';
+
+    public function denormalize(mixed $data, string $type, ?string $format = null, array $context = [])
+    {
+        //Deserialize the data with the overridden type
+        $overrideType = $context[self::CONTEXT_KEY];
+        unset($context[self::CONTEXT_KEY]);
+
+        return $this->denormalizer->denormalize($data, $overrideType, $format, $context);
+    }
+
+    public function supportsDenormalization(mixed $data, string $type, ?string $format = null, array $context = []): bool
+    {
+        return isset($context[self::CONTEXT_KEY]);
+    }
+
+    public function getSupportedTypes(?string $format): array
+    {
+        return [
+            '*' => false,
+        ];
+    }
+}