Ensure nested transactions are not wrongly rolled back

src/Connection.php

@@ -9,6 +9,7 @@
 use Doctrine\DBAL\Cache\QueryCacheProfile;
 use Doctrine\DBAL\Driver\API\ExceptionConverter;
 use Doctrine\DBAL\Driver\Connection as DriverConnection;
+use Doctrine\DBAL\Driver\Exception as TheDriverException;
 use Doctrine\DBAL\Driver\ServerInfoAwareConnection;
 use Doctrine\DBAL\Driver\Statement as DriverStatement;
 use Doctrine\DBAL\Event\TransactionBeginEventArgs;
@@ -1279,12 +1280,29 @@ public function transactional(Closure $func)
     {
         $this->beginTransaction();
 
+        $successful = false;
+
         try {
             $res = $func($this);
 
+            $successful = true;
+        } finally {
+            if (! $successful) {
+                $this->rollBack();
+            }
+        }
+
+        $shouldRollback = true;
+        try {
             $this->commit();
+
+            $shouldRollback = false;
+        } catch (TheDriverException $t) {
+            $shouldRollback = false;
+
+            throw $t;
         } finally {
-            if ($this->isTransactionActive()) {
+            if ($shouldRollback) {
                 $this->rollBack();
             }
         }

tests/Functional/TransactionTest.php

@@ -2,26 +2,23 @@
 
 namespace Doctrine\DBAL\Tests\Functional;
 
+use Doctrine\DBAL\Connection;
 use Doctrine\DBAL\Driver\Exception as DriverException;
 use Doctrine\DBAL\Platforms\AbstractMySQLPlatform;
+use Doctrine\DBAL\Platforms\OraclePlatform;
 use Doctrine\DBAL\Tests\FunctionalTestCase;
 use PDOException;
 
 use function sleep;
 
 class TransactionTest extends FunctionalTestCase
 {
-    protected function setUp(): void
+    public function testCommitFalse(): void
     {
-        if ($this->connection->getDatabasePlatform() instanceof AbstractMySQLPlatform) {
-            return;
+        if (! $this->connection->getDatabasePlatform() instanceof AbstractMySQLPlatform) {
+            $this->markTestSkipped('Restricted to MySQL.');
         }
 
-        $this->markTestSkipped('Restricted to MySQL.');
-    }
-
-    public function testCommitFalse(): void
-    {
         $this->connection->executeStatement('SET SESSION wait_timeout=1');
 
         self::assertTrue($this->connection->beginTransaction());
@@ -40,4 +37,19 @@ public function testCommitFalse(): void
             $this->connection->close();
         }
     }
+
+    public function testNestedTransactionWalkthrough(): void
+    {
+        $query = $this->connection->getDatabasePlatform() instanceof OraclePlatform
+            ? 'SELECT 1 FROM DUAL'
+            : 'SELECT 1';
+
+        $result = $this->connection->transactional(
+            static fn (Connection $connection) => $connection->transactional(
+                static fn (Connection $connection) => $connection->fetchOne($query),
+            ),
+        );
+
+        self::assertSame('1', (string) $result);
+    }
 }