MigrateDestinationEntity::prepare() ignores results from $migration->prepare($entity, $source_row);

Adding an & should not make any difference - objects are effectively passed by reference in PHP (you would only need an & if you were trying to change $node itself, e.g. $node = new stdClass - not if you're changing the contents of the node e.g. $node->title).

How are you confirming that your changes are made in $migration->prepare() but are not present after the call to $this->prepare() in MigrateDestinationNode::import()?

What does your migration prepare() handler look like? Are you by any chance assigning directly to $node itself, instead of just modifying fields within $node? That's the only scenario I can imagine where making the parameter a reference would make it work for you.

To test, I added this to BeerNodeMigration in migration_example's beer.inc:

  public function prepare($node, $row) {
    $node->foobar = "hello there";
  }

When I do drush_print_r($node) after the call to prepare() in node.inc, the foobar field is there.

That should work - have you tried a drush_print_r($node) after the call to prepare() in node.inc to confirm it's not changing?

No further information provided.

In migrating some quiz nodes from Drupal 6 to Drupal 7, I experienced this very thing. Quiz needs some fields set on the node before node_save(), or it will freak out about some columns being null.

After lots of debugging, and reading this issue, it seems that changing the $entity object is not permitted. I can change its values, but not its members.

So, adding a & to $entity in MigrateDestinationEntity::prepare() and in my local Migration class seems to fix it right up. I can now add fields to the node object before it is saved.

Here's how my migration is set up:

class MayaQuizMultichoiceMigration extends DrupalNode6Migration {

  // snipped all the construct stuff

/**
   * Makes changes the node object just before it is saved.
   *
   * Called from MigrationEntity::prepare().
   *
   * @see MultiChoiceQuestion::saveNodeProperties()
   */
  function prepare(&$entity, $source_row) {
    $properties = $this->getMultichoiceProperties($source_row->nid, $source_row->vid);
    $entity = (object) array_merge((array) $entity, (array) $properties);
  }

  function getMultichoiceProperties($nid, $vid) {
    $query = DataBase::getConnection('default', $this->sourceConnection)
      ->select('quiz_multichoice_properties', 'p')
      ->fields('p', array('choice_multi', 'choice_random', 'choice_boolean'))
      ->condition('p.nid', $nid)
      ->condition('p.vid', $vid);
    return $query->execute()->fetchObject();
  }

}

Drupal6NodeMigration comes from drupal_to_drupal_data_migration, and implements MigrateDestinationNode.

I've attached a patch, hopefully it is useful to someone.

The problem is that you are changing the $entity variable itself, not its contents:

  function prepare(&$entity, $source_row) {
    $properties = $this->getMultichoiceProperties($source_row->nid, $source_row->vid);
    $entity = (object) array_merge((array) $entity, (array) $properties);
  }

This is the proper way to update the object:

  function prepare($entity, $source_row) {
    $properties = $this->getMultichoiceProperties($source_row->nid, $source_row->vid);
    foreach ($properties as $key => $value) {
      $entity->$key = $value;
    }
  }

Wicked, thanks for that tip.