#13: author_rewrite_rules bonus functions

author_rewrite_rules_bonus.php

<?php
/**
 * Add 'redirect' query var
 *
 * @see WP::parse_request()
 *
 * @param array $query_vars The query vars array.
 *
 * @return array The filtered query vars array.
 */
function wpdocs_add_redirect_var( $query_vars ) {
	$query_vars[] = 'redirect';
	return $query_vars;
}
add_filter( 'query_vars', 'wpdocs_add_redirect_var' );

/**
 * Redirect old 'author' links
 *
 * @see WP::parse_request()
 *
 * @param object $request The request object.
 *
 * @return object The request object.
 */
function wpdocs_redirect_old_author_links( $request ) {
	if ( isset( $request->public_query_vars['redirect'] )
		&& $request->public_query_vars['redirect']
		&& isset( $request->public_query_vars['author_name'] ) ) {
			wp_redirect( get_author_posts_url( 0, $request->public_query_vars['author_name'] ) );
			exit;
	}

	return $request;
}
add_action( 'parse_request', 'wpdocs_redirect_old_author_links' );

http://fotd.werdswords.com/author_rewrite_rules/