Book Schema Author Field: Replace “logo” with “image” for Person Compatibility

I ran into this same problem, but for the Article author field, where Google also expects Person.image instead of logo.

As a workaround (and a relatively clean extension of the existing API), I added an image sub-property to the organization property type via hook_schema_metatag_property_type_plugins_alter(). Since the schema_article_author tag uses property_type = "organization" and can represent either Person or Organization, this makes a new image field appear in the Author complex widget, which I can then map via Metatag tokens.

Here’s the snippet:

/**
 * Implements hook_schema_metatag_property_type_plugins_alter().
 */
function MYMODULE_schema_metatag_property_type_plugins_alter(array &$definitions): void {
  if (empty($definitions['organization'])) {
    return;
  }

  if (empty($definitions['organization']['sub_properties']['image'])) {
    $definitions['organization']['sub_properties']['image'] = [
      // Use the simple URL property type so the JSON-LD will output:
      //   "image": "https://example.com/author.jpg"
      // instead of an ImageObject.
      'id' => 'url',
      'label' => t('image'),
      'description' => t('The image URL of the person or organization (used for Article/Book author).'),
      'tree_parent' => [],
      'tree_depth' => 0,
    ];
  }
}

After clearing caches, the Author widget exposes an image field which I can set to a token for the author picture URL. The resulting JSON-LD for the author becomes:

"author": {
  "@type": "Person",
  "name": "…",
  "image": "https://…/author.jpg",
  "sameAs": [ "…" ]
}