Remapping taxonomy terms breaks term reference import on dependant migrations

Hi mikeryan. Thanks for the reply.

I'll try to describe what I'm doing.

The source is a MySQL DB from a bespoke CMS. I have a migration class to import 'themes' into a taxonomy in Drupal. However, this needs re-mapping on import.

So, for example, lets say that the source data is:

1, Theme 1
2, Theme 2
3, Theme 3
...
10, Theme 10

But lets say we re-map the data but we don't want to bring across Theme 3 and Theme 7 so we omit them from the crosswalk csv file that handles the remapping. In the mapping table for this migration, it still inserts a row for all ten source rows - including 3 and 7. Except 3 and 7 have a null destination ID but the rest have the ID of the Drupal taxonomy term that they have been mapped to.

I then import the users and one of the mappings is which themes (term reference field) they have opted to receive emails about:

this->addFieldMapping('field_theme', 'themes')
  ->sourceMigration('Themes');
$this->addFieldMapping('field_theme:source_type')
  ->defaultValue('tid');

Because of the way the source DB is setup, I can't get all the related term data as part of the source query. Instead, I'm getting all the additional data for all users in one query at the start of the migration and adding it to an array keyed by user ID. This data then gets added to each row in 'prepareRow'. So '$row->theme = array(1, 3, 6...)' - basically an array of the themes for that user.

From what I've seen, using the example above where 3 and 7 are not imported over but are mapped:

• If '$row->theme = array(1, 2, 4, 5)', all the term references are setup correctly
• However, if any of the source IDs are those that have not been import - '$row->theme = array(1, 2, 3, 4)' - then none of the term references are created - not even 1, 2 or 4.

So it's not that the data during the user import contains NULL values, it's that it contains valid IDs in the source DB, but these are mapped to NULL values in the dependant migration mapping table.

I hope this makes a bit more sense.

Thanks