Expressions like SELECT DATABASE() will always return one row

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;
     }
 
     /**