Schema manager errors on custom MySQL index

[dbu]

Bug Report

Q	A
Version	3.9.4

Summary

With a custom calculated index, the schema tool fails with an exception:

Argument #1 ($column) must be of type string, null given, called in /www/vendor/doctrine/dbal/src/Schema/Index.php on line 72

The index i created is CREATE INDEX json_author ON auction_json_indexed ( (JSON_VALUE(item, '$.author' RETURNING CHAR(255))) )

Current behavior

Exception trace:
  at /www/vendor/doctrine/dbal/src/Schema/Index.php:81
 Doctrine\DBAL\Schema\Index->_addColumn() at /www/vendor/doctrine/dbal/src/Schema/Index.php:72
 Doctrine\DBAL\Schema\Index->__construct() at /www/vendor/doctrine/dbal/src/Schema/AbstractSchemaManager.php:1500
 Doctrine\DBAL\Schema\AbstractSchemaManager->_getPortableTableIndexesList() at /www/vendor/doctrine/dbal/src/Schema/MySQLSchemaManager.php:153
 Doctrine\DBAL\Schema\MySQLSchemaManager->_getPortableTableIndexesList() at /www/vendor/doctrine/dbal/src/Schema/AbstractSchemaManager.php:424
 Doctrine\DBAL\Schema\AbstractSchemaManager->doListTables() at /www/vendor/doctrine/dbal/src/Schema/MySQLSchemaManager.php:66
 Doctrine\DBAL\Schema\MySQLSchemaManager->listTables() at /www/vendor/doctrine/dbal/src/Schema/AbstractSchemaManager.php:1651
 Doctrine\DBAL\Schema\AbstractSchemaManager->createSchema() at /www/vendor/doctrine/dbal/src/Schema/AbstractSchemaManager.php:1663
 Doctrine\DBAL\Schema\AbstractSchemaManager->introspectSchema() at /www/vendor/doctrine/migrations/src/Generator/DiffGenerator.php:117
 Doctrine\Migrations\Generator\DiffGenerator->createFromSchema() at /www/vendor/doctrine/migrations/src/Generator/DiffGenerator.php:63
 Doctrine\Migrations\Generator\DiffGenerator->generate() at /www/vendor/doctrine/migrations/src/Tools/Console/Command/DiffCommand.php:135
 Doctrine\Migrations\Tools\Console\Command\DiffCommand->execute() at /www/vendor/symfony/console/Command/Command.php:279
 Symfony\Component\Console\Command\Command->run() at /www/vendor/symfony/console/Application.php:1047
 Symfony\Component\Console\Application->doRunCommand() at /www/vendor/symfony/framework-bundle/Console/Application.php:123
 Symfony\Bundle\FrameworkBundle\Console\Application->doRunCommand() at /www/vendor/symfony/console/Application.php:316
 Symfony\Component\Console\Application->doRun() at /www/vendor/symfony/framework-bundle/Console/Application.php:77
 Symfony\Bundle\FrameworkBundle\Console\Application->doRun() at /www/vendor/symfony/console/Application.php:167
 Symfony\Component\Console\Application->run() at /www/vendor/symfony/runtime/Runner/Symfony/ConsoleApplicationRunner.php:49
 Symfony\Component\Runtime\Runner\Symfony\ConsoleApplicationRunner->run() at /www/vendor/autoload_runtime.php:29

Expected behavior

I would expect the schema tool to ignore an index without column, as it was not defined by doctrine.

How to reproduce

Create the index from the description, then run the doctrine:migrations:diff command.

Workaround

I added a check in AbstractSchemaManager::_getPortableTableIndexesList right before creating the new $index instance: if (! $defaultPrevented && ! in_array(null, $data['columns'], true)) {. I am not sure if that is a reasonable fix or has other side effects. That change would hide the index from doctrine.

Of note: With postgres, I get no error and the index is not seen in the schema tool.