Migrate Drupal 7 wysiwyg files to media

Media in Drupal 7 added fields to files but still handled things in a primitive way compared to what Media does today. Drupal 8 has Media in core with a dedicated Media entity.

File Entity and Media Entity were contrib modules that did something similar before Media was added to core.

Here is what Media WYSIWYG puts into the text field in D7:

Screenshot of Media WYSIWYG token in D7

This token references the image by file id and has some extra info to import. The problem is that this isn't recognized by Drupal 8's media embed filter.

Drupal 8 embed tokens

File image (using image button w/ file uploads).

Screenshot of Drupal 8 image embed token

Media image (using new Media Library button).

Screenshot of Media Library embed token

Entity Embed (using Entity Embed module). You may see this if a site was built before Media Library was available. You can configure your embed button for other content and use the new one for images.

Screenshot of Drupal 8 Entity Embed token

You may see data-entity-uuid instead of data-entity-id. This is what I got from the Media Migration module.

Convert embedded view mode

Media elements will be created with data-view-mode="default".

Use dom_str_replace process plugin to change it.

body/0/value:
  -
    plugin: get
    source: body/0/value
  -
    plugin: media_wysiwyg_filter
    media_migrations:
      - upgrade_d7_file_entity_image_public
    file_migrations:
      - upgrade_d7_file
  -
    plugin: img_tag_to_embed
    migrations:
      - upgrade_d7_file_entity_image_public
  -
    plugin: dom
    method: import
  -
    plugin: dom_str_replace  # Here's where the magic is.
    mode: attribute
    attribute_options:
      name: data-view-mode
    xpath: //drupal-media
    search: default
    replace: blog_image
  -
    plugin: dom
    method: export