WP GraphQL Meta Field Ordering

class-wpgraphqlorderbymetafield.php

<?php
/**
 * Plugin Name: WP GraphQL Meta Field Ordering
 * Description: Adds functionality to order by a meta field as specified by the user.
 * See: https://gist.github.com/jasonbahl/da87dbccb58f1323a324a9b3e8952d6c
 * and also:
 * https://github.com/wp-graphql/wp-graphql/issues/287
 * https://github.com/wp-graphql/wp-graphql/pull/721
 * https://github.com/wp-graphql/wp-graphql-meta-query/blob/develop/wp-graphql-meta-query.php
 */

namespace GQL;

defined( 'ABSPATH' ) || die( 'Direct script access disallowed.' );

/**
 * WPGraphQLOrderByMetaField class
 */
class WPGraphQLOrderByMetaField {
	/**
	 * Constructor
	 */
	public function __construct() {
		$class = get_called_class();

		add_action(
			'graphql_register_types',
			array( $class, 'register_types' )
		);

		add_filter(
			'graphql_PostObjectsConnectionOrderbyEnum_values',
			array(
				$class,
				'gql_add_orderby_enum_values',
			)
		);
		add_filter(
			'graphql_TermObjectsConnectionOrderbyEnum_values',
			array(
				$class,
				'gql_add_orderby_enum_values',
			)
		);

		add_filter(
			'graphql_PostObjectsConnectionOrderbyInput_fields',
			array(
				$class,
				'gql_add_orderby_input_fields',
			)
		);
		add_filter(
			'graphql_TermObjectsConnectionOrderbyInput_fields',
			array(
				$class,
				'gql_add_orderby_input_fields',
			)
		);

		add_filter(
			'graphql_post_object_connection_query_args',
			array( $class, 'gql_object_connection_query_args' ),
			10,
			5
		);
		add_filter(
			'graphql_term_object_connection_query_args',
			array( $class, 'gql_object_connection_query_args' ),
			10,
			5
		);
	}

	/**
	 * Register custom GraphQL types.
	 */
	public static function register_types() {
		register_graphql_enum_type(
			'MetaKeyTypeEnum',
			array(
				'description' => __( 'Cast type for META_KEY ordering. Maps to WP_Query meta_type.', 'wp-graphql' ),
				'values'      => array(
					'CHAR'     => array( 'value' => 'CHAR' ),
					'NUMERIC'  => array( 'value' => 'NUMERIC' ),
					'DECIMAL'  => array( 'value' => 'DECIMAL' ),
					'SIGNED'   => array( 'value' => 'SIGNED' ),
					'UNSIGNED' => array( 'value' => 'UNSIGNED' ),
					'DATE'     => array( 'value' => 'DATE' ),
					'DATETIME' => array( 'value' => 'DATETIME' ),
					'TIME'     => array( 'value' => 'TIME' ),
					'BINARY'   => array( 'value' => 'BINARY' ),
				),
			)
		);
	}

	/**
	 * Add meta key to orderby field values
	 *
	 * @param array $values  Existing values
	 * @return array         Returns update values
	 */
	public static function gql_add_orderby_enum_values( $values ) {
		$values['META_KEY'] = array(
			'value'       => 'META_KEY',
			'description' => __( 'META_KEY option to orderby field.', 'wp-graphql' ),
		);

		return $values;
	}

	/**
	 * Add meta key field to orderby fields
	 *
	 * @param array $fields  Existing fields
	 * @return array         Returns updated fields
	 */
	public static function gql_add_orderby_input_fields( $fields ) {
		$fields['metaKeyField'] = array(
			'type'        => 'String',
			'description' => __( 'META_KEY value for orderby field.', 'wp-graphql' ),
		);

		$fields['metaKeyType'] = array(
			'type'        => 'MetaKeyTypeEnum',
			'description' => __( 'Cast type for META_KEY ordering. Defaults to CHAR (string comparison).', 'wp-graphql' ),
		);

		return $fields;
	}

	/**
	 * Update WP_Query args for orderby by META_KEY
	 *
	 * @param array                  $query_args  Query arguments
	 * @param mixed                  $source      Source passed down from the resolve tree
	 * @param array                  $args        The inputArgs on the field
	 * @param \WPGraphQL\AppContext  $context     The AppContext passed down the GraphQL tree
	 * @param \WPGraphQL\ResolveInfo $info        The ResolveInfo passed down the GraphQL tree
	 * @return array                              Returns updated query arguments
	 */
	public static function gql_object_connection_query_args(
		$query_args,
		$source,
		$args,
		$context,
		$info
	) {
		if ( isset( $args['where']['orderby'] ) && is_array( $args['where']['orderby'] ) ) {
			foreach ( $args['where']['orderby'] as $orderby ) {
				if (
					! isset( $orderby['field'] ) ||
					'META_KEY' !== $orderby['field'] ||
					! isset( $orderby['metaKeyField'] )
				) {
					continue;
				}

				// phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_key
				$query_args['meta_key'] = $orderby['metaKeyField'];

				// Extract the order direction from WPGraphQL's processed orderby
				// array (e.g. ['META_KEY' => 'DESC']) before we overwrite it below.
				// See: https://developer.wordpress.org/reference/classes/wp_query/#order-orderby-parameters
				$query_args['order'] = isset( $query_args['orderby']['META_KEY'] )
					? $query_args['orderby']['META_KEY']
					: 'DESC';

				// Use meta_value_num for numeric types, meta_value for everything else.
				$meta_type     = ! empty( $orderby['metaKeyType'] ) ? strtoupper( $orderby['metaKeyType'] ) : '';
				$numeric_types = array( 'NUMERIC', 'DECIMAL', 'SIGNED', 'UNSIGNED' );

				$query_args['orderby'] = in_array( $meta_type, $numeric_types, true )
					? 'meta_value_num'
					: 'meta_value';

				if ( $meta_type ) {
					// phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_type
					$query_args['meta_type'] = $meta_type;
				}
			}
		}

		return $query_args;
	}
}