Add Downloadable Products to Woocommerce Completed Order & Invoice Emails as Attachments

woocommerce_emails_attach_downloadables.php

<?php
// Add Downloadable Products to Woocommerce Completed Order & Invoice Emails as Attachments
function woocommerce_emails_attach_downloadables($attachments, $status, $order) {

    if ( ! is_object( $order ) || ! isset( $status ) ) {
        return $attachments;
    }

    if ( empty( $order ) ) {
        return $attachments;
    }

    if ( ! $order->has_downloadable_item() ) {
        return $attachments;
    }

    $allowed_statuses = array( 'customer_invoice', 'customer_completed_order' );

    if ( isset( $status ) && in_array( $status, $allowed_statuses ) ) {
        foreach ( $order->get_items() as $item_id => $item ) {
            foreach ( $order->get_item_downloads( $item ) as $download ) {
                $attachments[] = str_replace( content_url(), WP_CONTENT_DIR, $download['file'] );
            }
        }
    }

    return $attachments;
}
add_filter( 'woocommerce_email_attachments', 'woocommerce_emails_attach_downloadables', 10, 3);