How to attach media item created during migration to media field in node

Question

I am migrating content from Drupal 7 to Drupal 8. There is an audio field that I am currently moving to media via a custom process during migration.

When I get the id of the new media created I can't seem to get it to attach to my new media reference field in the also newly created node.

Can anyone tell me what is wrong with the import below?

field_audio_fileinfo:
-
  plugin: sub_process
  source: field_audio_fileinfo
  process:
    target_id:
      -
        plugin: migration_lookup
        method: process
        source: fid
        migration: upgrade_d7_file
      -
        plugin: my_custom_process
        destination: field_media_audio

In my custom process I can save the media and get it's ID via:

$media_id = $audio_media->id();
$arr[] = array(
  'target_id' => $media_id,
  'display' => NULL,
  'description' => NULL
);
return $arr;

But it doesn't seem to populate the destination field.

This is also the case if I just return the ID directly from the process.

Answer 1

When I have done a similar type of migration at that time I did the following steps:

• First I created media type Audio in Drupal 8 and it's fields.

• Then I exported all audio file details and FID from D7 and created csv file.

• Written migration script to import audio into media.

Example:

source:
  plugin: csv
  path: 'csv file path'
  header_row_count: 1
  keys:
    - fid
  type: audio
  constants:
    bundle: audio
process:
  mid: fid
  bundle: constants/bundle
  langcode:
    plugin: default_value
    source: language
    default_value: und
  name: filename
  uid: uid
  created: upload_date
  changed: upload_date
  field_media_audio_file/target_id: fid
destination:
  plugin: 'entity:media'
  migration_dependencies: {  }
migration_dependencies: null

• The same csv I used to import data into file entity and written migration script.

Example:

source:
  plugin: csv
  path: 'csv file path'
  header_row_count: 1
  keys:
    - fid
process:
  uid: uid
  fid: fid
  filename: filename
  created: upload_date
  changed: upload_date
  filemime: mime
  uri: uri
destination:
  plugin: 'entity:file'
  source_path_property: filepath
  destination_path_property: uri
migration_dependencies: {  }

• After that, I attached the FID to my node field.

process:
  field_audio/target_id: fid

I am keeping media id, FID of Drupal 8 same as FID of Drupal 7. So we can attach the same FID to the node directly.

Answer 2

There was a fault with my migration yaml.

The destination field in Drupal 8 was field_media_audio but as you can see in the question I had it trying to save to field_audio_fileinfo which was the Drupal 7 source. Silly me.

Once I realised and corrected the destination it all worked and now media is created and referenced in the one pass of my migration script.

  field_media_audio:
-
  plugin: sub_process
  source: field_audio_fileinfo
  destination: field_media_audio
  process:
    target_id:
      -
        plugin: migration_lookup
        method: process
        source: fid
        migration: upgrade_d7_file
      -
        plugin: my_custom_process