ObjectHydrator: defer initialization of potentially empty collections

If ObjectHydrator faces an empty row to an uninitialized collection,
it initializes it, to prevent it from querying again (DDC-1526).
However, if that row is the first but not the only in the collection,
the next rows will be ignored, as the collection will be considered
"existing", and "existing" collections are only replaced if REFRESH hint
is present. To prevent it, we defer initialization to the end of the
hydration.

Fixes GH-9807

lib/Doctrine/ORM/Internal/Hydration/ObjectHydrator.php

@@ -44,6 +44,9 @@ class ObjectHydrator extends AbstractHydrator
     /** @var mixed[] */
     private $initializedCollections = [];
 
+    /** @var array<string, PersistentCollection> */
+    private $uninitializedCollections = [];
+
     /** @var mixed[] */
     private $existingCollections = [];
 
@@ -148,6 +151,12 @@ protected function hydrateAllData()
             $coll->takeSnapshot();
         }
 
+        foreach ($this->uninitializedCollections as $coll) {
+            if (! $coll->isInitialized()) {
+                $coll->setInitialized(true);
+            }
+        }
+
         return $result;
     }
 
@@ -411,8 +420,8 @@ protected function hydrateRowData(array $row, array &$result)
                         }
                     } elseif (! $reflFieldValue) {
                         $this->initRelatedCollection($parentObject, $parentClass, $relationField, $parentAlias);
-                    } elseif ($reflFieldValue instanceof PersistentCollection && $reflFieldValue->isInitialized() === false) {
-                        $reflFieldValue->setInitialized(true);
+                    } elseif ($reflFieldValue instanceof PersistentCollection && $reflFieldValue->isInitialized() === false && ! isset($this->uninitializedCollections[$oid . $relationField])) {
+                        $this->uninitializedCollections[$oid . $relationField] = $reflFieldValue;
                     }
                 } else {
                     // PATH B: Single-valued association

tests/Doctrine/Tests/ORM/Functional/Ticket/GH9807Test.php

@@ -0,0 +1,129 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\Tests\ORM\Functional\Ticket;
+
+use Doctrine\Common\Collections\Collection;
+use Doctrine\ORM\Internal\Hydration\ObjectHydrator;
+use Doctrine\ORM\Mapping as ORM;
+use Doctrine\ORM\Mapping\Column;
+use Doctrine\ORM\Mapping\Entity;
+use Doctrine\ORM\Mapping\GeneratedValue;
+use Doctrine\ORM\Mapping\Id;
+use Doctrine\ORM\Query\ResultSetMapping;
+use Doctrine\Tests\Mocks\ArrayResultFactory;
+use Doctrine\Tests\OrmFunctionalTestCase;
+
+final class GH9807Test extends OrmFunctionalTestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->createSchemaForModels(GH9807Main::class, GH9807Join::class);
+    }
+
+    public function testHydrateJoinedCollectionWithFirstNullishRow(): void
+    {
+        $rsm = new ResultSetMapping();
+        $rsm->addEntityResult(GH9807Main::class, 'm');
+        $rsm->addJoinedEntityResult(GH9807Join::class, 'j', 'm', 'joins');
+
+        $rsm->addFieldResult('m', 'id_0', 'id');
+        $rsm->addFieldResult('j', 'id_1', 'id');
+        $rsm->addFieldResult('j', 'value_2', 'value');
+
+        $hydrator = new ObjectHydrator($this->_em);
+
+        $uow = $this->_em->getUnitOfWork();
+
+        $uow->createEntity(
+            GH9807Main::class,
+            ['id' => 1]
+        );
+
+        $resultSet = [
+            [
+                'id_0' => 1,
+                'id_1' => null,
+                'value_2' => null,
+            ],
+            [
+                'id_0' => 1,
+                'id_1' => 1,
+                'value_2' => '2',
+            ],
+            [
+                'id_0' => 1,
+                'id_1' => 2,
+                'value_2' => '2',
+            ],
+        ];
+
+        $stmt = ArrayResultFactory::createFromArray($resultSet);
+
+        /** @var GH9807Main[] $result */
+        $result = $hydrator->hydrateAll($stmt, $rsm);
+
+        self::assertInstanceOf(GH9807Main::class, $result[0]);
+        self::assertCount(2, $result[0]->getJoins());
+    }
+}
+
+/**
+ * @Entity
+ */
+class GH9807Main
+{
+    /**
+     * @var int
+     * @Column(type="integer")
+     * @Id
+     * @GeneratedValue
+     */
+    private $id;
+
+    /**
+     * @ORM\ManyToMany(targetEntity="GH9807Join", inversedBy="starts")
+     *
+     * @var Collection<int, GH9807Join>
+     */
+    private $joins;
+
+    /**
+     * @return Collection<int, GH9807Join>
+     */
+    public function getJoins(): Collection
+    {
+        return $this->joins;
+    }
+}
+
+/**
+ * @Entity
+ */
+class GH9807Join
+{
+    /**
+     * @var int
+     * @Column(type="integer")
+     * @Id
+     * @GeneratedValue
+     */
+    private $id;
+
+    /**
+     * @ORM\ManyToMany(targetEntity="GH9807Main", mappedBy="bases")
+     *
+     * @var Collection<int, GH9807Main>
+     */
+    private $mains;
+
+    /**
+     * @ORM\Column(type="string", nullable=false)
+     *
+     * @var string
+     */
+    private $value;
+}