For the moment, I’ve created this workaround here thanks to this post here. It’s basically the same, just a little more general.
Assuming a custom post type with the your_custom_post_type slug, and three custom taxonomies with these names here:
first_custom_taxonomy_namesecond_custom_taxonomy_namethird_custom_taxonomy_name
The code below enables to query via their slug value if you query not via their $taxonomy_name in the REST API, but via {$taxonomy_name}_slug.
More precisely:
- Using the taxonomy name in the REST endpoint, you’d have to use the ID:
http://example.org/wp-json/wp/v2/your_custom_post_type?first_custom_taxonomy_name=12
- Using the taxonomy name +
_slugsuffix, you can query in f(slug):
http://example.org/wp-json/wp/v2/your_custom_post_type?first_custom_taxonomy_name_slug=slug-value
/**
* Querying via taxonomy slug is by default not possible in WP, we have to create a
* filter to do so
*
* @param array $args array of arguments to be used in WP_Query
* @param WP_REST_Request $request The REST API Request
*
* @return array $args array of arguments to be used in WP_Query, updated by this function
*/
add_filter(
"rest_your_custom_post_type_query",
function (
array $args,
WP_REST_Request $request
): array {
// Get parameters of the query
$params = $request->get_params();
// Enable this feature for all of the custom taxonomies
$custom_taxonomies = [
'first_custom_taxonomy_name',
'second_custom_taxonomy_name',
'third_custom_taxonomy_name'
];
foreach ( $custom_taxonomies as $custom_taxonomy ) {
if ( isset( $params["{$custom_taxonomy}_slug"] ) ) {
$args['tax_query'][] = [
'taxonomy' => $custom_taxonomy,
'field' => 'slug',
'terms' => explode(
",",
$params["{$custom_taxonomy}_slug"]
)
];
}
}
return $args;
},
10,
2
);
You can easily extend this with additional taxonomies, just by adding the respective taxonomy name into $custom_taxonomies.