Fair enough, @hube2!
We were able to bypass this issue by manually exposing the field:
function our_expose_attribution() {
// Field name to register.
$field = 'attribution';
register_rest_field(
'attachment',
$field,
array(
'get_callback' => function ( $object ) use ( $field ) {
// Get field as single value from post meta.
return get_post_meta( $object['id'], $field, true );
},
'update_callback' => function ( $value, $object ) use ( $field ) {
// Update the field/meta value.
update_post_meta( $object->ID, $field, $value );
},
'schema' => array(
'type' => 'string',
'arg_options' => array(
'sanitize_callback' => function ( $value ) {
// Make the value safe for storage.
return sanitize_text_field( $value );
},
'validate_callback' => function ( $value ) {
// Validate
return is_string( $value );
},
),
),
)
);
}
add_action( 'rest_api_init', 'our_expose_attribution' );
