TYPO3 Migration: From gridelementsteam/gridelements to b13/container

So you need to know what the layouts (before tt_content.tx_gridelements_backend_layout and after tt_content.CType) are called. In addition, you should also know how to migrate the columns (before tt_content.tx_gridelements_columns and after tt_content.colPos). You pack this into your ContentMigration with the help of two new PropertyHelper classes. The whole thing can then look like this in ContentMigrator.php, for example:

<?php
declare(strict_types=1);
namespace In2code\MigrationExtend\Migration\Migrator;

use In2code\Migration\Migration\Migrator\AbstractMigrator;
use In2code\Migration\Migration\Migrator\MigratorInterface;
use In2code\Migration\Migration\PropertyHelpers\GridelementsToContainerChildrenPropertyHelper;
use In2code\Migration\Migration\PropertyHelpers\GridelementsToContainerParentPropertyHelper;

/**
 * Class ContentMigrator
 */
class ContentMigrator extends AbstractMigrator implements MigratorInterface
{
    /**
     * @var string
     */
    protected $tableName = 'tt_content';

    /**
     * @var array
     */
    protected $propertyHelpers = [
        '_dummy' => [
            [
                'className' => GridelementsToContainerParentPropertyHelper::class,
                'configuration' => [
                    'types' => [
                        // tt_content.tx_gridelements_backend_layout => tt_content.CType
                        1 => 'container-50-50',
                        3 => 'container-33-33-33',
                        4 => 'container-70-30',
                        5 => 'container-30-70',
                        10 => 'container-accordion',
                        11 => 'container-tab',
                        12 => 'container-container',
                    ],
                ],
            ],
            [
                'className' => GridelementsToContainerChildrenPropertyHelper::class,
                'configuration' => [
                    'columns' => [
                        // old value in tt_content.tx_gridelements_backend_layout
                        1 => [
                            // tt_content.tx_gridelements_columns => tt_content.colPos
                            12 => 12,
                            22 => 22,
                        ],
                        3 => [
                            1 => 12,
                            2 => 22,
                            3 => 32,
                        ],
                        4 => [
                            1 => 12,
                            2 => 22,
                        ],
                        5 => [
                            1 => 12,
                            2 => 22,
                        ],
                        10 => [
                            0 => 12,
                        ],
                        11 => [
                            0 => 12,
                        ],
                        12 => [
                            0 => 12,
                        ],
                    ],
                ],
            ],
        ],
    ];
}

The Migration.php configuration file would then look like this:

<?php
return [
    // Default values if not given from CLI
    'configuration' => [
        'key' => '',
        'dryrun' => true,
        'limitToRecord' => null,
        'limitToPage' => 0,
        'recursive' => true
    ],

    // Define your migrations
    'migrations' => [
        [
            'className' => \In2code\MigrationExtend\Migration\Migrator\ContentMigrator::class,
            'keys' => [
                'content',
            ]
        ],
    ]
];

And then you can start the migration as usual via the CLI:

./vendor/bin/typo3cms migration:migrate --configuration EXT:migration_extend/Configuration/Migration.php --key content --dryrun 0

Happy migrating

P.S.: If error messages like "Unused elements detected on this page" appears, you can use the CLI comand container:fixContainerParentForConnectedModeCommand