From 9aa8d556b16112c8df7b99b5f4cb084efdbb3fa0 Mon Sep 17 00:00:00 2001
From: Matthias Pigulla <mp@webfactory.de>
Date: Thu, 9 Oct 2025 14:37:09 +0200
Subject: [PATCH 1/2] Experiment: Use comparator functions from a global
 registry for changeset detection

---
 src/ComparatorRegistry.php                    | 46 ++++++++++++
 src/UnitOfWork.php                            |  5 ++
 tests/Tests/ORM/ComparatorRegistryTest.php    | 52 +++++++++++++
 ...aratorRegistryBasedChangeDetectionTest.php | 75 +++++++++++++++++++
 4 files changed, 178 insertions(+)
 create mode 100644 src/ComparatorRegistry.php
 create mode 100644 tests/Tests/ORM/ComparatorRegistryTest.php
 create mode 100644 tests/Tests/ORM/Functional/ComparatorRegistryBasedChangeDetectionTest.php

diff --git a/src/ComparatorRegistry.php b/src/ComparatorRegistry.php
new file mode 100644
index 0000000000..4a26274171
--- /dev/null
+++ b/src/ComparatorRegistry.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace Doctrine\ORM;
+
+class ComparatorRegistry
+{
+    /** @param array<class-string, callable> */
+    private static array $callbacks = [];
+
+    /**
+     * @template T of object
+     * @param class-string<T> $class
+     * @param callable(T, object): ?int
+     */
+    public static function register(string $class, callable $callback): void
+    {
+        self::$callbacks[$class] = $callback;
+    }
+
+    public static function reset(): void
+    {
+        self::$callbacks = [];
+    }
+
+    public static function compare(object $a, object $b): ?int
+    {
+        foreach (self::$callbacks as $class => $callback) {
+            if (is_a($a, $class, false)) {
+                $result = $callback($a, $b);
+
+                if ($result !== null) {
+                    return $result;
+                }
+            }
+            if (is_a($b, $class, false)) {
+                $result = $callback($b, $a);
+
+                if ($result !== null) {
+                    return -$result;
+                }
+            }
+        }
+
+        return null;
+    }
+}
diff --git a/src/UnitOfWork.php b/src/UnitOfWork.php
index 4c55b72877..10acf6d12d 100644
--- a/src/UnitOfWork.php
+++ b/src/UnitOfWork.php
@@ -683,6 +683,11 @@ public function computeChangeSet(ClassMetadata $class, object $entity): void
                     continue;
                 }
 
+                // skip if Comparator from registry tells us that objects represent equal values
+                if (is_object($orgValue) && is_object($actualValue) && ComparatorRegistry::compare($orgValue, $actualValue) === 0) {
+                    continue;
+                }
+
                 // if regular field
                 if (! isset($class->associationMappings[$propName])) {
                     $changeSet[$propName] = [$orgValue, $actualValue];
diff --git a/tests/Tests/ORM/ComparatorRegistryTest.php b/tests/Tests/ORM/ComparatorRegistryTest.php
new file mode 100644
index 0000000000..efa7900866
--- /dev/null
+++ b/tests/Tests/ORM/ComparatorRegistryTest.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace Doctrine\Tests\ORM;
+
+use Doctrine\ORM\ComparatorRegistry;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+class ComparatorRegistryTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        ComparatorRegistry::reset();
+    }
+
+    protected function tearDown(): void
+    {
+        ComparatorRegistry::reset();
+    }
+
+    #[Test]
+    public function compareDateTimeTypes(): void
+    {
+        ComparatorRegistry::register(\DateTimeInterface::class, function (\DateTimeInterface $a, object $b): ?int {
+            if ($b instanceof \DateTimeInterface) {
+                return $a <=> $b;
+            }
+        });
+
+        $nowMutable = new \DateTime();
+        $nowImmutable = \DateTimeImmutable::createFromMutable($nowMutable);
+        $yesterdayMutable = new \DateTime('yesterday');
+        $yesterdayImmutable = \DateTimeImmutable::createFromMutable($yesterdayMutable);
+
+        self::assertSame(null, ComparatorRegistry::compare($nowMutable, new \stdClass()));
+
+        self::assertSame(0, ComparatorRegistry::compare($nowMutable, $nowMutable));
+        self::assertSame(0, ComparatorRegistry::compare($nowMutable, $nowImmutable));
+        self::assertSame(0, ComparatorRegistry::compare($nowImmutable, $nowMutable));
+        self::assertSame(0, ComparatorRegistry::compare($nowImmutable, $nowImmutable));
+
+        self::assertSame(1, ComparatorRegistry::compare($nowMutable, $yesterdayMutable));
+        self::assertSame(1, ComparatorRegistry::compare($nowImmutable, $yesterdayMutable));
+        self::assertSame(1, ComparatorRegistry::compare($nowMutable, $yesterdayImmutable));
+        self::assertSame(1, ComparatorRegistry::compare($nowImmutable, $yesterdayImmutable));
+
+        self::assertSame(-1, ComparatorRegistry::compare($yesterdayMutable, $nowMutable));
+        self::assertSame(-1, ComparatorRegistry::compare($yesterdayMutable, $nowImmutable));
+        self::assertSame(-1, ComparatorRegistry::compare($yesterdayImmutable, $nowMutable));
+        self::assertSame(-1, ComparatorRegistry::compare($yesterdayImmutable, $nowImmutable));
+    }
+}
diff --git a/tests/Tests/ORM/Functional/ComparatorRegistryBasedChangeDetectionTest.php b/tests/Tests/ORM/Functional/ComparatorRegistryBasedChangeDetectionTest.php
new file mode 100644
index 0000000000..a5ce4a963f
--- /dev/null
+++ b/tests/Tests/ORM/Functional/ComparatorRegistryBasedChangeDetectionTest.php
@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\Tests\ORM\Functional;
+
+use Doctrine\ORM\ComparatorRegistry;
+use Doctrine\Tests\Models\TypedProperties\UserTyped;
+use Doctrine\Tests\OrmFunctionalTestCase;
+
+class ComparatorRegistryBasedChangeDetectionTest extends OrmFunctionalTestCase
+{
+    public function setUp(): void
+    {
+        ComparatorRegistry::reset();
+        parent::setUp();
+
+        $this->setUpEntitySchema([UserTyped::class]);
+    }
+
+    protected function tearDown(): void
+    {
+        ComparatorRegistry::reset();
+    }
+
+    public function testChangingDateTimeInstanceWithoutComparator(): void
+    {
+        $user = new UserTyped();
+        $user->dateTime = new \DateTime();
+        $this->initializeChangesetState($user);
+
+        $user->dateTime = clone $user->dateTime;
+        $this->recomputeChangeset($user);
+
+        self::assertTrue($this->_em->getUnitOfWork()->isScheduledForUpdate($user));
+    }
+
+    public function testChangingDateTimeInstanceWithComparator(): void
+    {
+        ComparatorRegistry::register(\DateTimeInterface::class, function (\DateTimeInterface $a, object $b) {
+            if ($b instanceof \DateTimeInterface) {
+                return $a <=> $b;
+            }
+        });
+
+        $user = new UserTyped();
+        $user->dateTime = new \DateTime();
+        $this->initializeChangesetState($user);
+
+        $user->dateTime = clone $user->dateTime;
+        $this->recomputeChangeset($user);
+
+        self::assertFalse($this->_em->getUnitOfWork()->isScheduledForUpdate($user));
+    }
+
+    private function initializeChangesetState(object $entity): void
+    {
+        // Initialize UoW state
+        $this->_em->persist($entity);
+        $cm = $this->_em->getClassMetadata(get_class($entity));
+        $this->_em->getUnitOfWork()->computeChangeSet($cm, $entity);
+
+        // Run change set computation with no changes
+        $this->_em->getUnitOfWork()->computeChangeSet($cm, $entity);
+
+        // sanity check
+        self::assertFalse($this->_em->getUnitOfWork()->isScheduledForUpdate($entity));
+    }
+
+    private function recomputeChangeset(object $entity): void
+    {
+        $cm = $this->_em->getClassMetadata(get_class($entity));
+        $this->_em->getUnitOfWork()->computeChangeSet($cm, $entity);
+    }
+}

From ea8748480ea6cd56f65649b20d5a1193c43664bf Mon Sep 17 00:00:00 2001
From: Matthias Pigulla <mp@webfactory.de>
Date: Thu, 9 Oct 2025 15:20:04 +0200
Subject: [PATCH 2/2] Add a test where a mutable object is mutated

---
 ...paratorRegistryBasedChangeDetectionTest.php | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tests/Tests/ORM/Functional/ComparatorRegistryBasedChangeDetectionTest.php b/tests/Tests/ORM/Functional/ComparatorRegistryBasedChangeDetectionTest.php
index a5ce4a963f..2ef71138f1 100644
--- a/tests/Tests/ORM/Functional/ComparatorRegistryBasedChangeDetectionTest.php
+++ b/tests/Tests/ORM/Functional/ComparatorRegistryBasedChangeDetectionTest.php
@@ -53,6 +53,24 @@ public function testChangingDateTimeInstanceWithComparator(): void
         self::assertFalse($this->_em->getUnitOfWork()->isScheduledForUpdate($user));
     }
 
+    public function testChangingMutableObject(): void
+    {
+        ComparatorRegistry::register(\DateTimeInterface::class, function (\DateTimeInterface $a, object $b) {
+            if ($b instanceof \DateTimeInterface) {
+                return $a <=> $b;
+            }
+        });
+
+        $user = new UserTyped();
+        $user->dateTime = new \DateTime();
+        $this->initializeChangesetState($user);
+
+        $user->dateTime->add(new \DateInterval('P7D'));
+        $this->recomputeChangeset($user);
+
+        self::assertTrue($this->_em->getUnitOfWork()->isScheduledForUpdate($user));
+    }
+
     private function initializeChangesetState(object $entity): void
     {
         // Initialize UoW state