<?php declare(strict_types=1);

namespace DoctrineMigrations;

use Doctrine\DBAL\Schema\Schema;
use Doctrine\Migrations\AbstractMigration;

/**
 * Auto-generated Migration: Please modify to your needs!
 */
final class Version20181205175053 extends AbstractMigration
{
    public function up(Schema $schema) : void
    {
        // this up() migration is auto-generated, please modify it to your needs
        $this->abortIf($this->connection->getDatabasePlatform()->getName() !== 'mysql', 'Migration can only be executed safely on \'mysql\'.');

        $this->addSql('ALTER TABLE additional_field CHANGE name name VARCHAR(255) NOT NULL, CHANGE applies_to applies_to VARCHAR(255) NOT NULL, CHANGE display_name display_name VARCHAR(255) NOT NULL, CHANGE type type VARCHAR(255) NOT NULL, CHANGE type_info type_info VARCHAR(255) DEFAULT NULL');
    }

    public function down(Schema $schema) : void
    {
        // this down() migration is auto-generated, please modify it to your needs
        $this->abortIf($this->connection->getDatabasePlatform()->getName() !== 'mysql', 'Migration can only be executed safely on \'mysql\'.');

        $this->addSql('ALTER TABLE additional_field CHANGE name name TINYTEXT NOT NULL COLLATE utf8mb4_unicode_ci, CHANGE applies_to applies_to TINYTEXT NOT NULL COLLATE utf8mb4_unicode_ci, CHANGE display_name display_name TINYTEXT NOT NULL COLLATE utf8mb4_unicode_ci, CHANGE type type TINYTEXT NOT NULL COLLATE utf8mb4_unicode_ci, CHANGE type_info type_info LONGTEXT NOT NULL COLLATE utf8mb4_unicode_ci');
    }
}

Add migration which changes the datatypes on the additional fields table and also makes the type info field nullable
Add migration which changes the datatypes on the additional fields table and also makes the type info field nullable
