WPML Causes HTTP 500 Error On Save When Post Type Is Public

When saving a recipe with the post type set to public, and the WPML plugin enabled, the REST API returns a HTTP status code of 500.

Error log (with paths shortened)

Stack trace:
#0 /web/app/plugins/wpml-multilingual-cms/sitepress.class.php(1493): Rareloop\Lumberjack\Bootstrappers\RegisterExceptionHandler->handleError(2, 'Undefined array...', '/shared/httpd/t...', 1493)
#1 /web/wp/wp-includes/class-wp-hook.php(324): SitePress->set_element_language_details_action(Array)
#2 /web/wp/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array)
#3 /web/wp/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#4 /web/app/plugins/wp-recipe-maker/includes/public/class-wprm-compatibility.php(534): do_action('wpml_set_elemen...', Array)
#5 /web/app/plugins/wp-recipe-maker/includes/public/class-wprm-recipe-saver.php(235): WPRM_Compatibility::set_language_for(17510, 'en')
#6 /web/app/plugins/wp-recipe-maker/includes/public/api/class-wprm-api-recipe.php(98): WPRM_Recipe_Saver::update_recipe(17510, Array, true)
#7 /web/wp/wp-includes/class-wp-hook.php(324): WPRM_Api_Recipe::api_insert_update_recipe(Object(WP_Post), Object(WP_REST_Request), true)
#8 /web/wp/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array)
#9 /web/wp/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#10 /web/wp/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php(708): do_action('rest_insert_wpr...', Object(WP_Post), Object(WP_REST_Request), true)
#11 /web/wp/wp-includes/rest-api/class-wp-rest-server.php(1230): WP_REST_Posts_Controller->create_item(Object(WP_REST_Request))
#12 /web/wp/wp-includes/rest-api/class-wp-rest-server.php(1063): WP_REST_Server->respond_to_request(Object(WP_REST_Request), '/wp/v2/wprm_rec...', Array, NULL)
#13 /web/wp/wp-includes/rest-api/class-wp-rest-server.php(439): WP_REST_Server->dispatch(Object(WP_REST_Request))
#14 /web/wp/wp-includes/rest-api.php(428): WP_REST_Server->serve_request('/wp/v2/wprm_rec...')
#15 /web/wp/wp-includes/class-wp-hook.php(324): rest_api_loaded(Object(WP))
#16 /web/wp/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array)
#17 /web/wp/wp-includes/plugin.php(565): WP_Hook->do_action(Array)
#18 /web/wp/wp-includes/class-wp.php(418): do_action_ref_array('parse_request', Array)
#19 /web/wp/wp-includes/class-wp.php(813): WP->parse_request('')
#20 /web/wp/wp-includes/functions.php(1336): WP->main('')
#21 /web/wp/wp-blog-header.php(16): wp()
#22 /web/index.php(6): require('/shared/httpd/t...')
#23 {main}

It looks like on line 534 of class-wprm-compatibility.php you’re calling the wpml_set_element_language_details action and failing to set the trid(translation group id) in the second argument array — which is required.

https://wpml.org/wpml-hook/wpml_set_element_language_details/

if ( $multilingual ) {
	// WPML.
	if ( 'wpml' === $multilingual['plugin'] ) {
		do_action( 'wpml_set_element_language_details', array(
			'element_id' => $recipe_id,
			'element_type' => 'post_' . WPRM_POST_TYPE,
			'language_code' => $language ? $language : null,
		) );
	}
}

Should probably look something like

if ( $multilingual ) {
	// WPML.
	if ( 'wpml' === $multilingual['plugin'] ) {
		$post_type = 'post_' . WPRM_POST_TYPE;
		$translation_group_id = apply_filters( 'wpml_element_trid', NULL, $recipe_id, $post_type );

		do_action( 'wpml_set_element_language_details', array(
			'element_id' => $recipe_id,
			'trid' => $translation_group_id ?: false,
			'element_type' => $post_type,
			'language_code' => $language ? $language : null,
		) );
	}
}

This seems to fix the issue. Though there might be some side effects I’m not aware of.

Also a bit of a tangent, but the short form the short form ternary operator has been available since PHP 5.3. So it’s probably safe to write $language ? $language : null as $language ?: null.

Any help you could offer would be greatly appreciated.

Thanks,

Andrew