Merge pull request #4094 from morozov/psalm-lvl5

Bump Psalm level to 5

lib/Doctrine/DBAL/Connection.php

@@ -12,7 +12,6 @@ use Doctrine\DBAL\Driver\Connection as DriverConnection;
 use Doctrine\DBAL\Driver\PingableConnection;
 use Doctrine\DBAL\Driver\ResultStatement;
 use Doctrine\DBAL\Driver\ServerInfoAwareConnection;
-use Doctrine\DBAL\Driver\Statement as DriverStatement;
 use Doctrine\DBAL\Exception\InvalidArgumentException;
 use Doctrine\DBAL\Platforms\AbstractPlatform;
 use Doctrine\DBAL\Query\Expression\ExpressionBuilder;
@@ -851,7 +850,7 @@ class Connection implements DriverConnection
      *
      * @param string $statement The SQL statement to prepare.
      *
-     * @return DriverStatement The prepared statement.
+     * @return Statement The prepared statement.
      *
      * @throws DBALException
      */
@@ -1456,6 +1455,8 @@ class Connection implements DriverConnection
     {
         $this->connect();
 
+        assert($this->_conn !== null);
+
         return $this->_conn;
     }
 

lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php

@@ -12,6 +12,7 @@ use Doctrine\DBAL\Platforms\MySQL80Platform;
 use Doctrine\DBAL\Platforms\MySqlPlatform;
 use Doctrine\DBAL\Schema\MySqlSchemaManager;
 use Doctrine\DBAL\VersionAwarePlatformDriver;
+use function assert;
 use function preg_match;
 use function stripos;
 use function version_compare;
@@ -197,7 +198,15 @@ abstract class AbstractMySQLDriver implements Driver, ExceptionConverterDriver,
     {
         $params = $conn->getParams();
 
-        return $params['dbname'] ?? $conn->query('SELECT DATABASE()')->fetchColumn();
+        if (isset($params['dbname'])) {
+            return $params['dbname'];
+        }
+
+        $database = $conn->query('SELECT DATABASE()')->fetchColumn();
+
+        assert($database !== false);
+
+        return $database;
     }
 
     /**

lib/Doctrine/DBAL/Driver/AbstractPostgreSQLDriver.php

@@ -13,6 +13,7 @@ use Doctrine\DBAL\Platforms\PostgreSQL94Platform;
 use Doctrine\DBAL\Platforms\PostgreSqlPlatform;
 use Doctrine\DBAL\Schema\PostgreSqlSchemaManager;
 use Doctrine\DBAL\VersionAwarePlatformDriver;
+use function assert;
 use function preg_match;
 use function strpos;
 use function version_compare;
@@ -119,7 +120,15 @@ abstract class AbstractPostgreSQLDriver implements Driver, ExceptionConverterDri
     {
         $params = $conn->getParams();
 
-        return $params['dbname'] ?? $conn->query('SELECT CURRENT_DATABASE()')->fetchColumn();
+        if (isset($params['dbname'])) {
+            return $params['dbname'];
+        }
+
+        $database = $conn->query('SELECT CURRENT_DATABASE()')->fetchColumn();
+
+        assert($database !== false);
+
+        return $database;
     }
 
     /**

lib/Doctrine/DBAL/Driver/AbstractSQLAnywhereDriver.php

@@ -12,6 +12,7 @@ use Doctrine\DBAL\Platforms\SQLAnywhere16Platform;
 use Doctrine\DBAL\Platforms\SQLAnywherePlatform;
 use Doctrine\DBAL\Schema\SQLAnywhereSchemaManager;
 use Doctrine\DBAL\VersionAwarePlatformDriver;
+use function assert;
 use function preg_match;
 use function version_compare;
 
@@ -119,7 +120,15 @@ abstract class AbstractSQLAnywhereDriver implements Driver, ExceptionConverterDr
     {
         $params = $conn->getParams();
 
-        return $params['dbname'] ?? $conn->query('SELECT DB_NAME()')->fetchColumn();
+        if (isset($params['dbname'])) {
+            return $params['dbname'];
+        }
+
+        $database = $conn->query('SELECT DB_NAME()')->fetchColumn();
+
+        assert($database !== false);
+
+        return $database;
     }
 
     /**

lib/Doctrine/DBAL/Driver/AbstractSQLServerDriver.php

@@ -11,6 +11,7 @@ use Doctrine\DBAL\Platforms\SQLServer2012Platform;
 use Doctrine\DBAL\Platforms\SQLServerPlatform;
 use Doctrine\DBAL\Schema\SQLServerSchemaManager;
 use Doctrine\DBAL\VersionAwarePlatformDriver;
+use function assert;
 use function preg_match;
 use function version_compare;
 
@@ -60,7 +61,15 @@ abstract class AbstractSQLServerDriver implements Driver, VersionAwarePlatformDr
     {
         $params = $conn->getParams();
 
-        return $params['dbname'] ?? $conn->query('SELECT DB_NAME()')->fetchColumn();
+        if (isset($params['dbname'])) {
+            return $params['dbname'];
+        }
+
+        $database = $conn->query('SELECT DB_NAME()')->fetchColumn();
+
+        assert($database !== false);
+
+        return $database;
     }
 
     /**

lib/Doctrine/DBAL/Driver/IBMDB2/DB2Statement.php

@@ -13,6 +13,7 @@ use ReflectionObject;
 use ReflectionProperty;
 use stdClass;
 use function array_change_key_case;
+use function assert;
 use function db2_bind_param;
 use function db2_execute;
 use function db2_fetch_array;
@@ -30,6 +31,7 @@ use function func_get_args;
 use function func_num_args;
 use function fwrite;
 use function gettype;
+use function is_int;
 use function is_object;
 use function is_resource;
 use function is_string;
@@ -91,6 +93,8 @@ class DB2Statement implements IteratorAggregate, Statement
      */
     public function bindValue($param, $value, $type = ParameterType::STRING)
     {
+        assert(is_int($param));
+
         return $this->bindParam($param, $value, $type);
     }
 
@@ -99,6 +103,8 @@ class DB2Statement implements IteratorAggregate, Statement
      */
     public function bindParam($column, &$variable, $type = ParameterType::STRING, $length = null)
     {
+        assert(is_int($column));
+
         switch ($type) {
             case ParameterType::INTEGER:
                 $this->bind($column, $variable, DB2_PARAM_IN, DB2_LONG);

lib/Doctrine/DBAL/Driver/OCI8/OCI8Connection.php

@@ -222,11 +222,12 @@ class OCI8Connection implements Connection, ServerInfoAwareConnection
     public function errorCode()
     {
         $error = oci_error($this->dbh);
+
         if ($error !== false) {
-            $error = $error['code'];
+            return $error['code'];
         }
 
-        return $error;
+        return null;
     }
 
     /**

lib/Doctrine/DBAL/Driver/PDOConnection.php

@@ -38,7 +38,10 @@ class PDOConnection extends PDO implements Connection, ServerInfoAwareConnection
     public function exec($statement)
     {
         try {
-            return parent::exec($statement);
+            $result = parent::exec($statement);
+            assert($result !== false);
+
+            return $result;
         } catch (\PDOException $exception) {
             throw new PDOException($exception);
         }

lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereStatement.php

@@ -12,6 +12,7 @@ use ReflectionClass;
 use ReflectionObject;
 use stdClass;
 use function array_key_exists;
+use function assert;
 use function func_get_args;
 use function func_num_args;
 use function gettype;
@@ -91,6 +92,8 @@ class SQLAnywhereStatement implements IteratorAggregate, Statement
      */
     public function bindParam($column, &$variable, $type = ParameterType::STRING, $length = null)
     {
+        assert(is_int($column));
+
         switch ($type) {
             case ParameterType::INTEGER:
             case ParameterType::BOOLEAN:
@@ -125,6 +128,8 @@ class SQLAnywhereStatement implements IteratorAggregate, Statement
      */
     public function bindValue($param, $value, $type = ParameterType::STRING)
     {
+        assert(is_int($param));
+
         return $this->bindParam($param, $value, $type);
     }
 

lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php

@@ -190,7 +190,7 @@ class SQLSrvConnection implements Connection, ServerInfoAwareConnection
             return $errors[0]['code'];
         }
 
-        return false;
+        return null;
     }
 
     /**

lib/Doctrine/DBAL/Driver/Statement.php

@@ -19,12 +19,12 @@ interface Statement extends ResultStatement
      * As mentioned above, the named parameters are not natively supported by the mysqli driver, use executeQuery(),
      * fetchAll(), fetchArray(), fetchColumn(), fetchAssoc() methods to have the named parameter emulated by doctrine.
      *
-     * @param mixed $param Parameter identifier. For a prepared statement using named placeholders,
-     *                     this will be a parameter name of the form :name. For a prepared statement
-     *                     using question mark placeholders, this will be the 1-indexed position of the parameter.
-     * @param mixed $value The value to bind to the parameter.
-     * @param int   $type  Explicit data type for the parameter using the {@link \Doctrine\DBAL\ParameterType}
-     *                     constants.
+     * @param int|string $param Parameter identifier. For a prepared statement using named placeholders,
+     *                          this will be a parameter name of the form :name. For a prepared statement
+     *                          using question mark placeholders, this will be the 1-indexed position of the parameter.
+     * @param mixed      $value The value to bind to the parameter.
+     * @param int        $type  Explicit data type for the parameter using the {@link \Doctrine\DBAL\ParameterType}
+     *                          constants.
      *
      * @return bool TRUE on success or FALSE on failure.
      */
@@ -44,15 +44,15 @@ interface Statement extends ResultStatement
      * of stored procedures that return data as output parameters, and some also as input/output
      * parameters that both send in data and are updated to receive it.
      *
-     * @param mixed    $column   Parameter identifier. For a prepared statement using named placeholders,
-     *                           this will be a parameter name of the form :name. For a prepared statement using
-     *                           question mark placeholders, this will be the 1-indexed position of the parameter.
-     * @param mixed    $variable Name of the PHP variable to bind to the SQL statement parameter.
-     * @param int      $type     Explicit data type for the parameter using the {@link \Doctrine\DBAL\ParameterType}
-     *                           constants. To return an INOUT parameter from a stored procedure, use the bitwise
-     *                           OR operator to set the PDO::PARAM_INPUT_OUTPUT bits for the data_type parameter.
-     * @param int|null $length   You must specify maxlength when using an OUT bind
-     *                           so that PHP allocates enough memory to hold the returned value.
+     * @param int|string $column   Parameter identifier. For a prepared statement using named placeholders,
+     *                             this will be a parameter name of the form :name. For a prepared statement using
+     *                             question mark placeholders, this will be the 1-indexed position of the parameter.
+     * @param mixed      $variable Name of the PHP variable to bind to the SQL statement parameter.
+     * @param int        $type     Explicit data type for the parameter using the {@link \Doctrine\DBAL\ParameterType}
+     *                             constants. To return an INOUT parameter from a stored procedure, use the bitwise
+     *                             OR operator to set the PDO::PARAM_INPUT_OUTPUT bits for the data_type parameter.
+     * @param int|null   $length   You must specify maxlength when using an OUT bind
+     *                             so that PHP allocates enough memory to hold the returned value.
      *
      * @return bool TRUE on success or FALSE on failure.
      */

lib/Doctrine/DBAL/Query/QueryBuilder.php

@@ -395,7 +395,7 @@ class QueryBuilder
      * Gets the maximum number of results the query object was set to retrieve (the "limit").
      * Returns NULL if all results will be returned.
      *
-     * @return int The maximum number of results.
+     * @return int|null The maximum number of results.
      */
     public function getMaxResults()
     {

phpstan.neon.dist

@@ -95,3 +95,8 @@ parameters:
             message: '~Method Doctrine\\DBAL\\Driver\\PDOSqlsrv\\Connection\:\:lastInsertId\(\) should return string but returns string\|false\|null\.~'
             paths:
                 - %currentWorkingDirectory%/lib/Doctrine/DBAL/Driver/PDOSqlsrv/Connection.php
+
+        -
+            message: '~Method Doctrine\\DBAL\\Portability\\Connection::prepare\(\) should return Doctrine\\DBAL\\Statement but returns Doctrine\\DBAL\\Portability\\Statement\.~'
+            paths:
+                - %currentWorkingDirectory%/lib/Doctrine/DBAL/Portability/Connection.php

psalm.xml

 <?xml version="1.0"?>
 <psalm
     totallyTyped="false"
-    errorLevel="6"
+    errorLevel="5"
     resolveFromConfigFile="true"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="https://getpsalm.org/schema/config"
@@ -32,6 +32,15 @@
                 <file name="lib/Doctrine/DBAL/Driver/OCI8/OCI8Statement.php"/>
             </errorLevel>
         </ConflictingReferenceConstraint>
+        <FalsableReturnStatement>
+            <errorLevel type="suppress">
+                <!--
+                    Fixing these issues requires an API change
+                -->
+                <file name="lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereConnection.php"/>
+                <file name="lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php"/>
+            </errorLevel>
+        </FalsableReturnStatement>
         <MethodSignatureMismatch>
             <errorLevel type="suppress">
                 <!--
@@ -41,6 +50,14 @@
                 <file name="lib/Doctrine/DBAL/Driver/PDOConnection.php"/>
             </errorLevel>
         </MethodSignatureMismatch>
+        <NullableReturnStatement>
+            <errorLevel type="suppress">
+                <!--
+                    Fixing this issue requires an API change
+                -->
+                <file name="lib/Doctrine/DBAL/Driver/AbstractSQLiteDriver.php"/>
+            </errorLevel>
+        </NullableReturnStatement>
         <TooFewArguments>
             <errorLevel type="suppress">
                 <!--

tests/Doctrine/Tests/DBAL/Driver/DrizzlePDOMySql/DriverTest.php

@@ -39,7 +39,7 @@ class DriverTest extends PDOMySQLDriverTest
     }
 
     /**
-     * @return mixed[][]
+     * {@inheritDoc}
      */
     protected function getDatabasePlatformsForVersions() : array
     {

tests/Doctrine/Tests/DBAL/Driver/StatementIteratorTest.php

@@ -5,12 +5,14 @@ namespace Doctrine\Tests\DBAL\Driver;
 use Doctrine\DBAL\Driver\IBMDB2\DB2Statement;
 use Doctrine\DBAL\Driver\Mysqli\MysqliStatement;
 use Doctrine\DBAL\Driver\OCI8\OCI8Statement;
+use Doctrine\DBAL\Driver\ResultStatement;
 use Doctrine\DBAL\Driver\SQLAnywhere\SQLAnywhereStatement;
 use Doctrine\DBAL\Driver\SQLSrv\SQLSrvStatement;
 use Doctrine\DBAL\Driver\Statement;
 use Doctrine\DBAL\Driver\StatementIterator;
 use Doctrine\DBAL\Portability\Statement as PortabilityStatement;
 use Doctrine\Tests\DbalTestCase;
+use IteratorIterator;
 use PHPUnit\Framework\MockObject\MockObject;
 use Traversable;
 use function extension_loaded;
@@ -18,16 +20,19 @@ use function extension_loaded;
 class StatementIteratorTest extends DbalTestCase
 {
     /**
+     * @param class-string<ResultStatement> $class
+     *
      * @dataProvider statementProvider()
      */
     public function testGettingIteratorDoesNotCallFetch(string $class) : void
     {
         $stmt = $this->createPartialMock($class, ['fetch', 'fetchAll', 'fetchColumn']);
+
         $stmt->expects($this->never())->method('fetch');
         $stmt->expects($this->never())->method('fetchAll');
         $stmt->expects($this->never())->method('fetchColumn');
 
-        $stmt->getIterator();
+        new IteratorIterator($stmt);
     }
 
     public function testIteratorIterationCallsFetchOncePerStep() : void

tests/Doctrine/Tests/DBAL/Functional/Driver/PDOSqlsrv/DriverTest.php

@@ -3,7 +3,7 @@
 namespace Doctrine\Tests\DBAL\Functional\Driver\PDOSqlsrv;
 
 use Doctrine\DBAL\Driver as DriverInterface;
-use Doctrine\DBAL\Driver\Connection;
+use Doctrine\DBAL\Driver\PDOConnection;
 use Doctrine\DBAL\Driver\PDOSqlsrv\Driver;
 use Doctrine\Tests\DBAL\Functional\Driver\AbstractDriverTest;
 use Doctrine\Tests\TestUtil;
@@ -40,7 +40,7 @@ class DriverTest extends AbstractDriverTest
     /**
      * @param int[]|string[] $driverOptions
      */
-    protected function getConnection(array $driverOptions) : Connection
+    private function getConnection(array $driverOptions) : PDOConnection
     {
         $params = TestUtil::getConnectionParams();
 

tests/Doctrine/Tests/DBAL/Functional/Ticket/DBAL630Test.php

@@ -3,6 +3,7 @@
 namespace Doctrine\Tests\DBAL\Functional\Ticket;
 
 use Doctrine\DBAL\DBALException;
+use Doctrine\DBAL\Driver\PDOConnection;
 use Doctrine\DBAL\ParameterType;
 use Doctrine\Tests\DbalFunctionalTestCase;
 use PDO;
@@ -38,7 +39,7 @@ class DBAL630Test extends DbalFunctionalTestCase
     protected function tearDown() : void
     {
         if ($this->running) {
-            $this->connection->getWrappedConnection()->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
+            $this->getWrappedConnection()->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
         }
 
         parent::tearDown();
@@ -72,7 +73,7 @@ class DBAL630Test extends DbalFunctionalTestCase
 
     public function testBooleanConversionBoolParamEmulatedPrepares() : void
     {
-        $this->connection->getWrappedConnection()->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
+        $this->getWrappedConnection()->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
 
         $platform = $this->connection->getDatabasePlatform();
 
@@ -96,7 +97,7 @@ class DBAL630Test extends DbalFunctionalTestCase
         ?bool $statementValue,
         ?bool $databaseConvertedValue
     ) : void {
-        $this->connection->getWrappedConnection()->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
+        $this->getWrappedConnection()->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
 
         $platform = $this->connection->getDatabasePlatform();
 
@@ -120,7 +121,7 @@ class DBAL630Test extends DbalFunctionalTestCase
         ?bool $statementValue,
         bool $databaseConvertedValue
     ) : void {
-        $this->connection->getWrappedConnection()->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
+        $this->getWrappedConnection()->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
 
         $platform = $this->connection->getDatabasePlatform();
 
@@ -170,4 +171,12 @@ class DBAL630Test extends DbalFunctionalTestCase
             [null, null],
         ];
     }
+
+    private function getWrappedConnection() : PDOConnection
+    {
+        $connection = $this->connection->getWrappedConnection();
+        self::assertInstanceOf(PDOConnection::class, $connection);
+
+        return $connection;
+    }
 }

tests/Doctrine/Tests/DBAL/Platforms/AbstractMySQLPlatformTestCase.php

@@ -152,7 +152,7 @@ abstract class AbstractMySQLPlatformTestCase extends AbstractPlatformTestCase
         return 'CREATE UNIQUE INDEX index_name ON test (test, test2)';
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }

tests/Doctrine/Tests/DBAL/Platforms/AbstractPlatformTestCase.php

@@ -250,7 +250,7 @@ abstract class AbstractPlatformTestCase extends DbalTestCase
         self::assertEquals($sql, $this->getGenerateForeignKeySql());
     }
 
-    abstract public function getGenerateForeignKeySql() : string;
+    abstract protected function getGenerateForeignKeySql() : string;
 
     public function testGeneratesConstraintCreationSql() : void
     {

tests/Doctrine/Tests/DBAL/Platforms/AbstractPostgreSqlPlatformTestCase.php

@@ -65,7 +65,7 @@ abstract class AbstractPostgreSqlPlatformTestCase extends AbstractPlatformTestCa
         return 'CREATE INDEX my_idx ON mytable (user_name, last_login)';
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id) NOT DEFERRABLE INITIALLY IMMEDIATE';
     }

tests/Doctrine/Tests/DBAL/Platforms/AbstractSQLServerPlatformTestCase.php

@@ -181,7 +181,7 @@ abstract class AbstractSQLServerPlatformTestCase extends AbstractPlatformTestCas
         return 'CREATE UNIQUE INDEX index_name ON test (test, test2) WHERE test IS NOT NULL AND test2 IS NOT NULL';
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }

tests/Doctrine/Tests/DBAL/Platforms/DB2PlatformTest.php

@@ -42,7 +42,7 @@ class DB2PlatformTest extends AbstractPlatformTestCase
         ];
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }

tests/Doctrine/Tests/DBAL/Platforms/OraclePlatformTest.php

@@ -93,7 +93,7 @@ class OraclePlatformTest extends AbstractPlatformTestCase
     }
 
     /**
-     * @return mixed[]
+     * {@inheritDoc}
      */
     public function getGenerateTableWithMultiColumnUniqueIndexSql() : array
     {
@@ -234,7 +234,7 @@ class OraclePlatformTest extends AbstractPlatformTestCase
         return 'CREATE UNIQUE INDEX index_name ON test (test, test2)';
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }
@@ -408,7 +408,7 @@ class OraclePlatformTest extends AbstractPlatformTestCase
     }
 
     /**
-     * @return mixed[]
+     * {@inheritDoc}
      */
     protected function getQuotedColumnInPrimaryKeySQL() : array
     {
@@ -416,7 +416,7 @@ class OraclePlatformTest extends AbstractPlatformTestCase
     }
 
     /**
-     * @return mixed[]
+     * {@inheritDoc}
      */
     protected function getQuotedColumnInIndexSQL() : array
     {
@@ -427,7 +427,7 @@ class OraclePlatformTest extends AbstractPlatformTestCase
     }
 
     /**
-     * @return mixed[]
+     * {@inheritDoc}
      */
     protected function getQuotedNameInIndexSQL() : array
     {
@@ -438,7 +438,7 @@ class OraclePlatformTest extends AbstractPlatformTestCase
     }
 
     /**
-     * @return mixed[]
+     * {@inheritDoc}
      */
     protected function getQuotedColumnInForeignKeySQL() : array
     {

tests/Doctrine/Tests/DBAL/Platforms/SQLAnywherePlatformTest.php

@@ -43,7 +43,7 @@ class SQLAnywherePlatformTest extends AbstractPlatformTestCase
         ];
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }

tests/Doctrine/Tests/DBAL/Platforms/SqlitePlatformTest.php

@@ -286,9 +286,9 @@ class SqlitePlatformTest extends AbstractPlatformTestCase
         parent::testGeneratesConstraintCreationSql();
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
-        return null;
+        return '';
     }
 
     public function testModifyLimitQuery() : void