Support OpenAPI Polymorphism in ObjectModelDescriber

This is the default "symfony support" class, so seems like the right
place.

ModelDescriber/ObjectModelDescriber.php

@@ -22,11 +22,13 @@ use Nelmio\ApiDocBundle\PropertyDescriber\PropertyDescriberInterface;
 use OpenApi\Annotations as OA;
 use Symfony\Component\PropertyInfo\PropertyInfoExtractorInterface;
 use Symfony\Component\PropertyInfo\Type;
+use Symfony\Component\Serializer\Annotation\DiscriminatorMap;
 use Symfony\Component\Serializer\NameConverter\NameConverterInterface;
 
 class ObjectModelDescriber implements ModelDescriberInterface, ModelRegistryAwareInterface
 {
     use ModelRegistryAwareTrait;
+    use ApplyOpenApiDiscriminatorTrait;
 
     /** @var PropertyInfoExtractorInterface */
     private $propertyInfo;
@@ -71,6 +73,17 @@ class ObjectModelDescriber implements ModelDescriberInterface, ModelRegistryAwar
         $annotationsReader = new AnnotationsReader($this->doctrineReader, $this->modelRegistry, $this->mediaTypes);
         $annotationsReader->updateDefinition($reflClass, $schema);
 
+        $discriminatorMap = $this->doctrineReader->getClassAnnotation($reflClass, DiscriminatorMap::class);
+        if ($discriminatorMap && $schema->discriminator === OA\UNDEFINED) {
+            $this->applyOpenApiDiscriminator(
+                $model,
+                $schema,
+                $this->modelRegistry,
+                $discriminatorMap->getTypeProperty(),
+                $discriminatorMap->getMapping()
+            );
+        }
+
         $propertyInfoProperties = $this->propertyInfo->getProperties($class, $context);
 
         if (null === $propertyInfoProperties) {

Tests/Functional/Controller/ApiController.php

@@ -18,6 +18,7 @@ use Nelmio\ApiDocBundle\Annotation\Security;
 use Nelmio\ApiDocBundle\Tests\Functional\Entity\Article;
 use Nelmio\ApiDocBundle\Tests\Functional\Entity\CompoundEntity;
 use Nelmio\ApiDocBundle\Tests\Functional\Entity\SymfonyConstraints;
+use Nelmio\ApiDocBundle\Tests\Functional\Entity\SymfonyDiscriminator;
 use Nelmio\ApiDocBundle\Tests\Functional\Entity\User;
 use Nelmio\ApiDocBundle\Tests\Functional\Form\DummyType;
 use Nelmio\ApiDocBundle\Tests\Functional\Form\UserType;
@@ -221,4 +222,13 @@ class ApiController
     public function compoundEntityAction()
     {
     }
+
+    /**
+     * @Route("/discriminator-mapping", methods={"GET", "POST"})
+     *
+     * @OA\Response(response=200, description="Worked well!", @Model(type=SymfonyDiscriminator::class))
+     */
+    public function discriminatorMappingAction()
+    {
+    }
 }

Tests/Functional/Entity/SymfonyDiscriminator.php

@@ -0,0 +1,28 @@
+<?php
+
+/*
+ * This file is part of the NelmioApiDocBundle package.
+ *
+ * (c) Nelmio
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Nelmio\ApiDocBundle\Tests\Functional\Entity;
+
+use Symfony\Component\Serializer\Annotation\DiscriminatorMap;
+
+/**
+ * @DiscriminatorMap(typeProperty="type", mapping={
+ *      "one": SymfonyDiscriminatorOne::class,
+ *      "two": SymfonyDiscriminatorTwo::class,
+ * })
+ */
+abstract class SymfonyDiscriminator
+{
+    /**
+     * @var string
+     */
+    public $type;
+}

Tests/Functional/Entity/SymfonyDiscriminatorOne.php

@@ -0,0 +1,20 @@
+<?php
+
+/*
+ * This file is part of the NelmioApiDocBundle package.
+ *
+ * (c) Nelmio
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Nelmio\ApiDocBundle\Tests\Functional\Entity;
+
+class SymfonyDiscriminatorOne extends SymfonyDiscriminator
+{
+    /**
+     * @var string
+     */
+    public $one;
+}

Tests/Functional/Entity/SymfonyDiscriminatorTwo.php

@@ -0,0 +1,20 @@
+<?php
+
+/*
+ * This file is part of the NelmioApiDocBundle package.
+ *
+ * (c) Nelmio
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Nelmio\ApiDocBundle\Tests\Functional\Entity;
+
+class SymfonyDiscriminatorTwo extends SymfonyDiscriminator
+{
+    /**
+     * @var string
+     */
+    public $two;
+}

Tests/Functional/FunctionalTest.php

@@ -498,4 +498,24 @@ class FunctionalTest extends WebTestCase
         $this->assertNotHasProperty('protectedField', $model);
         $this->assertNotHasProperty('protected', $model);
     }
+
+    public function testModelsWithDiscriminatorMapAreLoadedWithOpenApiPolymorphism()
+    {
+        $model = $this->getModel('SymfonyDiscriminator');
+
+        $this->assertInstanceOf(OA\Discriminator::class, $model->discriminator);
+        $this->assertSame('type', $model->discriminator->propertyName);
+        $this->assertCount(2, $model->discriminator->mapping);
+        $this->assertArrayHasKey('one', $model->discriminator->mapping);
+        $this->assertArrayHasKey('two', $model->discriminator->mapping);
+        $this->assertNotSame(OA\UNDEFINED, $model->oneOf);
+        $this->assertCount(2, $model->oneOf);
+    }
+
+    public function testDiscriminatorMapLoadsChildrenModels()
+    {
+        // get model does its own assertions
+        $this->getModel('SymfonyDiscriminatorOne');
+        $this->getModel('SymfonyDiscriminatorTwo');
+    }
 }