primary-cat-connection-with-seo-framework.php

add_action( 'init', function() {

	register_graphql_connection([
		'fromType' => 'Post',
		'toType' => 'Category',
		'fromFieldName' => 'primaryCat',
		'oneToOne' => true,
		'resolve' => function( \WPGraphQL\Model\Post $post, $args, $context, $info ) {

			$primary_term = null;

			if ( function_exists( 'the_seo_framework' ) ) {
				$primary_term = the_seo_framework()->get_primary_term( $post->ID, 'category' );
			}

			// If there's no primary term from the SEO Framework, get the first category assigned
			if ( empty( $primary_term ) ) {
				$terms = get_the_terms( $post->ID, 'category' );
				if ( ! empty( $terms ) ) {
					$primary_term = $terms[0]->term_id;
				}
			}

			// If there's no primary term, return null for the connection
			if ( empty( $primary_term ) ) {
				return null;
			}

			$resolver = new \WPGraphQL\Data\Connection\TermObjectConnectionResolver( $post, $args, $context, $info, 'category' );
			$resolver->set_query_arg( 'include', absint( $primary_term ) );
			return $resolver->one_to_one()->get_connection();

		}
	]);

} );