In this post I will show a custom process plugin that I created to migrate taxonomy terms. The plugin handles the creation of new terms and prevents duplicates.

Below is a portion of the migration template. In the example, I am migrating new terms into keywords vocabulary via field_keywords field.

  field_keywords:    -      plugin: existing_term      # Destination (Drupal) vocabulary name      vocabulary: keywords      # Source query should return term name      source: term_name    -      plugin: skip_on_empty      method: row

This is the source code for the process plugin.