Connection::setNestTransactionsWithSavepoints() should not break lazy connection (#6362)

|      Q       |   A
|------------- | -----------
| Type         | bug
| Fixed issues | N/A

#### Summary

When calling `Connection::setNestTransactionsWithSavepoints()`, the
platform is fetched to check if savepoints are actually supported. This
is a problem because it might cause the connection to be opened.

I've removed the check which will postpone the exception to the first
time we attempt to create a savepoint.

Author: derrabus

src/Connection.php

@@ -1317,10 +1317,6 @@ public function setNestTransactionsWithSavepoints($nestTransactionsWithSavepoint
             throw ConnectionException::mayNotAlterNestedTransactionWithSavepointsInTransaction();
         }
 
-        if (! $this->getDatabasePlatform()->supportsSavepoints()) {
-            throw ConnectionException::savepointsNotSupported();
-        }
-
         $this->nestTransactionsWithSavepoints = (bool) $nestTransactionsWithSavepoints;
     }
 

tests/ConnectionTest.php

@@ -2,12 +2,14 @@
 
 namespace Doctrine\DBAL\Tests;
 
+use BadMethodCallException;
 use Doctrine\Common\EventManager;
 use Doctrine\DBAL\Cache\QueryCacheProfile;
 use Doctrine\DBAL\Configuration;
 use Doctrine\DBAL\Connection;
 use Doctrine\DBAL\ConnectionException;
 use Doctrine\DBAL\Driver;
+use Doctrine\DBAL\Driver\API\ExceptionConverter;
 use Doctrine\DBAL\Driver\Connection as DriverConnection;
 use Doctrine\DBAL\Driver\ServerInfoAwareConnection;
 use Doctrine\DBAL\DriverManager;
@@ -81,6 +83,46 @@ public function testNoTransactionActiveByDefault(): void
         self::assertFalse($this->connection->isTransactionActive());
     }
 
+    public function testSetNestTransactionsWithSavepointsDoesNotConnect(): void
+    {
+        $this->expectNotToPerformAssertions();
+
+        $connection = new Connection(
+            [],
+            new class implements VersionAwarePlatformDriver {
+                /** {@inheritDoc} */
+                public function connect(array $params): DriverConnection
+                {
+                    throw new BadMethodCallException('The connection must not be opened');
+                }
+
+                public function getDatabasePlatform(): AbstractPlatform
+                {
+                    throw new BadMethodCallException('The connection must not be opened');
+                }
+
+                public function getSchemaManager(Connection $conn, AbstractPlatform $platform): AbstractSchemaManager
+                {
+                    throw new BadMethodCallException('The connection must not be opened');
+                }
+
+                public function getExceptionConverter(): ExceptionConverter
+                {
+                    throw new BadMethodCallException('The connection must not be opened');
+                }
+
+                /** {@inheritDoc} */
+                public function createDatabasePlatformForVersion($version): AbstractPlatform
+                {
+                    throw new BadMethodCallException('The connection must not be opened');
+                }
+            },
+            new Configuration(),
+        );
+
+        $connection->setNestTransactionsWithSavepoints(true);
+    }
+
     public function testCommitWithNoActiveTransactionThrowsException(): void
     {
         $this->expectException(ConnectionException::class);

tests/Functional/ConnectionTest.php

@@ -195,18 +195,6 @@ public function testTransactionIsInactiveAfterConnectionClose(): void
         self::assertFalse($this->connection->isTransactionActive());
     }
 
-    public function testSetNestedTransactionsThroughSavepointsNotSupportedThrowsException(): void
-    {
-        if ($this->connection->getDatabasePlatform()->supportsSavepoints()) {
-            self::markTestSkipped('This test requires the platform not to support savepoints.');
-        }
-
-        $this->expectException(ConnectionException::class);
-        $this->expectExceptionMessage('Savepoints are not supported by this driver.');
-
-        $this->connection->setNestTransactionsWithSavepoints(true);
-    }
-
     public function testCreateSavepointsNotSupportedThrowsException(): void
     {
         if ($this->connection->getDatabasePlatform()->supportsSavepoints()) {