Migrate custom blocks from D6 to D7

Migrate and migrate_d2d projects make it super easy to transfer content from one Drupal installation to another regardless of versions. Recently, the possibility was added to handle custom blocks migrations. With a minimal setup we’re going to see how we can import these from a D6 to a D7 installation (all the while conserving the region they were originally setup in).

Requirements

Of course you will need to download and enable:

• migrate
• migrate_d2d

If you have drush installed, just copy and paste this in your terminal:

drush dl migrate migrate_d2d && drush en migrate migrate_d2d -y

Step 1 : Database definition

On your D7 installation, update the settings.php so that Drupal can interact with the D6 database (here I named it legacy).

$databases = array (
  'default' => 
  array (
    'default' => 
    array (
      'database' => 'd7_database',
      'username' => 'login',
      'password' => 'password',
      'host' => 'localhost',
      'driver' => 'mysql',
      'prefix' => '',
    ),
  ),
  'legacy' => 
  array (
    'default' => 
    array (
      'database' => 'd6_database',
      'username' => 'login',
      'password' => 'password',
      'host' => 'localhost',
      'driver' => 'mysql',
      'prefix' => '',
    ),
  ),
);

Step 2 : Module creation

Now create a custom module, let’s name it migration_from_d6 for example. Here is the content of migration_from_d6.info:

name = Migrate from Drupal 6
description = Migrate content from Drupal 6 to Drupal 7
core = 7.x
package = Migration
version = "7.x-1.0"
core = "7.x"
project = "migration_from_d6"

dependencies[] = migrate
dependencies[] = migrate_d2d

files[] = migration_from_d6.migrate.inc
files[] = blocks.inc

Create the migration_from_d6.module but leave it empty. The migrations settings are going to be defined in migration_from_d6.migrate.inc, create the file and paste the following inside:

<?php

/**
 * @file
 * Declares our migrations.
 */

/**
 * Implements hook_migrate_api().
 */
function migration_from_d6_migrate_api() {
  // Define api settings and common arguments.
  $api = array(
    'api' => 2,
    'groups' => array(
      'd6' => array(
        'title' => t('D6 Migrations'),
      ),
      'migrations' => array(),
    )
  );

  $common_arguments = array(
    'source_connection' => 'legacy',
    'source_version' => 6,
    'group_name' => 'd6',
  );

  // Register the blocks migration.
  $api['migrations']['BlockMigration'] = $common_arguments + array(
    'title' => t('Blocks Migration'),
    'description' => t('Migration of blocks from Drupal 6'),
    'class_name' => 'BlockMigration',
    'machine_name' => 'Block',
    'source_type' => 'block',
    'destination_type' => 'block',
  );

  return $api;
}

Now that we have registered our migration, we need to define the BlockMigration class used to import our custom blocks. Create a blocks.inc file and copy/paste this:

class BlockMigration extends DrupalCustomBlock6Migration {
  public function __construct(array $arguments) {
    parent::__construct($arguments);
  }

 /**
   * Implementation of MigrateDestination::complete().
   */
  public function complete($block, stdClass $row) {
    // Rebuild block table.
    block_flush_caches();

    // Retrieve the source region.
    $region = Database::getConnection('default', 'legacy')->query('SELECT region FROM {blocks} WHERE bid = :bid', array('bid' => $row->bid))->fetchField();

    // If a region is set, update created block.
    if(!empty($region)) {
      db_update('block')
        ->fields(array(
          'region' => $region,
          'status' => 1,
        ))
        ->condition('delta', $block->bid)
        ->execute();
    }
  }
}

Here we extend the existing DrupalCustomBlock6Migration class (provided by migrate_d2d) and we tell migrate that each time a block is imported into our D7 installation (complete method), we check if the block had a region and update the newly created block if that’s the case.

Step 3 : Migration

Okay we are now ready to import our custom blocks! First enable your custom migration module.

Then, go to admin/content/migrate/configure and click on “Register statically defined classes”, this will force migrate to register the BlockMigration class we just created. Click on your D6 Migrations, you should see the task BlockMigration and the number of blocks left to migrate.

Check the row for BlockMigration, select “Import” and launch the migration.

Everything should go smoothly and you should soon see your custom blocks imported in their respective regions.