How to declare class that extends Drupal d2d Migrate class

Question

I am trying to follow the guidance from https://www.drupal.org/node/1819738 "Extending migrate_d2d classes". I am using the Migrate d2d UI. It brings back the nodes I want to migrate, but there are a couple of fields I need to add. Essentially I want to extend the DrupalNode6Migration class to add these fields to the source query used by the UI.

I created this class (which appears to be exactly like the example given in the d2d document above):

<?php
class CadeMigrateFields extends DrupalNode6Migration {

  public function __construct(array $arguments) {
    parent::__construct($arguments);
  }

  protected function query() {
    // Get the default query 
    $query = parent::query();

    // Get OG stuff as per: https://www.drupal.org/node/2033293#comment-9371471

    $query->leftJoin('og_ancestry','oga','n.nid = oga.nid');
    $query->addExpression('GROUP_CONCAT(DISTINCT og.group_nid)', 'og_group_ref');       

    $query->addField('oga', 'group_nid', 'gid');
    $query->addField('oga', 'is_public', 'is_public');

    return $query;
  }
}
?>

This is supposed to include the additinal fields I want in the parent query. I added the path to this file to my module.info file:

; Migrate from 6.x to 7.x
files[] = cade_fields.migrate.inc

My question is: How do I declare it in the Migrate api so that Migrate sees it and executes it correctly?

If I don't add it anywhere in the api, Migrate doesn't see it. It is ignored and doesn't work.

If I code it as a migration,

   $migrations = array();

   $migrations['CadeFields'] = array(
        'class_name' => 'CadeMigrateFields',
   );

  $api = array(
    'api' => 2,
    'migrations' => $migrations,
   );


  return $api;

I get errors saying that several arguments (source type, description, destination type, etct) are missing. And it still doesn't work. This missing information should be provided by the arguments passed to the parent query (created by DrupalNode6Migration) by the UI, whose query I am simply trying to extend, not override.

So, how do I declare this type of class so that:

1. Migrate (d2d) sees it?
2. Migrate passes the arguments from the parent class (created by UI) it is extending to it?
3. It extends the parent class query to include the desired fields?

Thanks so much for any assistance!

Answer 1

Change your code like and try

 $migrations['CadeFields'] = array(
  'class_name' => 'CadeMigrateFields',
  'description' => t('Give your description abt this migration'),
  'source_type' => 'GIVE THE DRUPAL 6 NODE TYPE YOU ARE MIGRATING',
  'destination_type' => 'GIVE THE DRUPAL 7 NODE TYPE',
 );

Answer 2

I answered my own question here: https://www.drupal.org/node/2471863#comment-9840131

What I wanted:

I run migrate d2d ui and save settings. I go to dashboard, click on group, get a list migration tasks. I click on a listed node task, then click on "Source" for that node migration. I see a query.

I need two fields added to this query. So, I figure I can use "Extending migrate_d2d classes" code to "extend" this query so that the next time I run this migration, go to the dashboard, locate the same node task and look at it's source, the two fields I need will be included in the query and available to map.

To me, and I suspect to others, that is what "Extending migrate d2d classes" means.

The way it works:

You have to create a new migration class. Just follow existing documentation on how this is done. If you want to use, for example, the node query from the DrupalNode6Migration class, then you create the class with

<?php
 class MyNewClass extends DrupalNode6Migration class 
?>

Then, you insert into your MyNewClass:

<?php
  protected function query() {
    // Get the default query 
    $query = parent::query();
    ...
   }
?>

Now, you can "extend" this query to be used in your new Migration class, which now should also appear in the Migration dashboard -- but in a different migration group from that created by the migrate_d2d ui.

It would be nice if there was a way to pass the arguments dynamically generated in the migrate_d2d ui and pop them into our "extending" class. Then we'd really be "extending" as opposed to re-creating.

But, that's a question for another day.