<?php
function recently_viewed_products_shortcode() {
    $viewed_products = ! empty( $_COOKIE['woocommerce_recently_viewed'] ) ? (array) explode( '|', wp_unslash( $_COOKIE['woocommerce_recently_viewed'] ) ) : array(); // @codingStandardsIgnoreLine
    $viewed_products = array_reverse( array_filter( array_map( 'absint', $viewed_products ) ) );
    if ( empty( $viewed_products ) ) return;
    $product_ids = implode( ',', $viewed_products );
    return do_shortcode( "[products ids='$product_ids']" );
}

function callback_woocommerce_init() {
    add_shortcode( 'recently_viewed_products', 'recently_viewed_products_shortcode' );
}

add_action( 'woocommerce_init', 'callback_woocommerce_init' );