From f55efc324827d0a794090668b953d223a8a0784a Mon Sep 17 00:00:00 2001
From: Andreas Allacher <andreas@allacher.com>
Date: Sun, 24 Oct 2021 11:03:53 +0200
Subject: [PATCH] UniqueEntityValidator: Retrieve at max two entities for
 unique entity check.

Fixes: #43254
---
 src/Symfony/Bridge/Doctrine/CHANGELOG.md            |  1 +
 .../Validator/Constraints/UniqueEntityValidator.php | 13 ++++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/Symfony/Bridge/Doctrine/CHANGELOG.md b/src/Symfony/Bridge/Doctrine/CHANGELOG.md
index 37b39cf8d980e..d2e0a7761eeef 100644
--- a/src/Symfony/Bridge/Doctrine/CHANGELOG.md
+++ b/src/Symfony/Bridge/Doctrine/CHANGELOG.md
@@ -6,6 +6,7 @@ CHANGELOG
 
  * Add `DoctrineOpenTransactionLoggerMiddleware` to log when a transaction has been left open
  * Deprecate `PdoCacheAdapterDoctrineSchemaSubscriber` and add `DoctrineDbalCacheAdapterSchemaSubscriber` instead
+ * `UniqueEntity` constraint retrieves a maximum of two entities if the default repository method is used.
 
 5.3
 ---
diff --git a/src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php b/src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php
index 4996848143b73..c1caadd9df3dd 100644
--- a/src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php
+++ b/src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php
@@ -134,7 +134,18 @@ public function validate($entity, Constraint $constraint)
             $repository = $em->getRepository(\get_class($entity));
         }
 
-        $result = $repository->{$constraint->repositoryMethod}($criteria);
+        $arguments = [$criteria];
+
+        /* If the default repository method is used, it is always enough to retrieve at most two entities because:
+         * - No entity returned, the current entity is definitely unique.
+         * - More than one entity returned, the current entity cannot be unique.
+         * - One entity returned the uniqueness depends on the current entity.
+         */
+        if ('findBy' === $constraint->repositoryMethod) {
+            $arguments = [$criteria, null, 2];
+        }
+
+        $result = $repository->{$constraint->repositoryMethod}(...$arguments);
 
         if ($result instanceof \IteratorAggregate) {
             $result = $result->getIterator();