Add field to output URLs for Sitemap

The following code is an example of how you can create a field called allUrls that will output site URLs that could be used to generate a sitemap.

The resolver uses mostly hard-coded data, but shows what a potential solution could look like.

add_action( 'graphql_register_types', function() {

	register_graphql_field( 'RootQuery', 'allUrls', [
		'type' => [ 'list_of' => 'String' ],
		'description' => __( 'A list of all urls. Helpful for rendering sitemaps', 'your-textdomain' ),
		'resolve' => function() {

			// Start collecting all URLS
			$meta_urls = array( get_home_url() );

                        // Hardcoded array. You would need to fetch the URLs for all Posts
			$all_posts = [ 'site.com/post', 'site.com/post-2' ];

                        // Hardcoded array. You would need to fetch the URLs for all Terms
			$all_terms = [ 'site.com/tag', 'site.com/category' ];

			return array_merge($meta_urls, $all_posts, $all_terms);

		}
	]  );

});

You can then query this field using:

{
  allUrls
}