Compatibility for the Custom Post Type order plugin and WPGraphQL

wp-graphql-post-type-order.php

<?php
/**
 * Plugin Name: WPGraphQL Post Type Order Fix
 * Description: Fixes a bug with WPGraphQL pagination when the "Post Type Order" plugin is also active and in use
 */

add_action( 'pre_get_posts', function () {

	// access the custom post type order class
	global $CPTO;

	// if WPGraphQL isn't active or CPTUI isn't active, carry on and bail early
	if ( ! function_exists( 'is_graphql_request' ) || ! is_graphql_request() || ! $CPTO ) {
		return;
	}

	// Remove the Post Type Order plugin's "posts_orderby" filter for WPGraphQL requests
	// This filter hooks in too late and modifies the SQL directly so WPGraphQL
	// can't properly map the orderby args to generate the SQL for proper pagination
	remove_filter( 'posts_orderby', [ $CPTO, 'posts_orderby' ], 99 );

	// Add a filter
	add_filter( 'graphql_post_object_connection_query_args', function ( $args, $source, $input_args, $context, $info ) {

		$orderby = [];

		// If the connection has explicit orderby arguments set,
		// use them
		if ( ! empty( $input_args['where']['orderby'] ) ) {
			return $args;
		}

		// Else use any orderby args set on the WP_Query
		if ( isset( $args['orderby'] ) ) {
			$orderby = [];

			if ( is_string( $args['orderby'] ) ) {
				$orderby[] = $args['orderby'];
			} else {
				$orderby = $args['orderby'];
			}
		}

		$orderby['menu_order'] = ! empty( $input_args['last'] ) ? 'DESC' : 'ASC';
		$args['orderby']       = $orderby;

		return $args;
	}, 10, 5 );

});