WooCommerce product attributes as selectable options without variations

attributes-as-options.php

<?php


/**
 * List available attributes on product page in a drop-down selection
 */
add_action('woocommerce_before_add_to_cart_button', 'list_attributes_on_product_page');
function list_attributes_on_product_page() {
    global $product;
    $attributes = $product->get_attributes();

    if ( ! $attributes ) {
        return;
    }

    if ($product->is_type( 'variable' )) {
        return;
    }

    echo '<div style="padding-bottom:15px;">';

    foreach ( $attributes as $attribute ) {
        $taxonomy = get_taxonomy($attribute['name']);
        $options = wc_get_product_terms( $product->id, $attribute['name'], array( 'fields' => 'all' ) );
        $label = str_replace('Product ', '', $taxonomy->label);
        ?>
        <div style="padding-bottom:8px;">
            <label for="attribute[<?php echo $attribute['id']; ?>]"><?php echo $label; ?></label>
            <br />
            <select required name="attribute[<?php echo $attribute['id']; ?>]" id="attribute[<?php echo $attribute['id']; ?>]">
                <option value disabled selected>Choose an option</option>
                <?php foreach ( $options as $pa ): ?>
                    <option value="<?php echo $pa->name; ?>"><?php echo $pa->name; ?></option>
                <?php endforeach; ?>
            </select>
        </div>
        <?php
    }

    echo '</div>';
}

/**
 * Add selected attributes to cart items
 */
add_filter('woocommerce_add_cart_item_data', 'add_attributes_to_cart_item', 10, 3 );
function add_attributes_to_cart_item( $cart_item_data, $product_id, $variation_id ) {
    $attributes = $_POST['attribute'];
 
    if (empty( $attributes ) ) {
        return $cart_item_data;
    }
 
    $cart_item_data['attributes'] = serialize($attributes);
 
    return $cart_item_data;
}

/**
 * Display attributes in cart
 */
add_filter( 'woocommerce_get_item_data', 'display_attributes_in_cart', 10, 2 );
function display_attributes_in_cart( $item_data, $cart_item ) {
    if ( empty( $cart_item['attributes'] ) ) {
        return $item_data;
    }

    foreach (unserialize($cart_item['attributes']) as $attributeID => $value) {
        $attribute = wc_get_attribute($attributeID);
        $item_data[] = array(
            'key'     => $attribute->name,
            'value'   => $value,
            'display' => '',
        );
    }

    return $item_data;
}

/**
 * Add attribute data to order items
 */
add_action( 'woocommerce_checkout_create_order_line_item', 'add_attributes_to_order_items', 10, 4 );
function add_attributes_to_order_items( $item, $cart_item_key, $values, $order ) {
    if ( empty( $values['attributes'] ) ) {
        return;
    }

    foreach (unserialize($values['attributes']) as $attributeID => $value) {
        $attribute = wc_get_attribute($attributeID);
        $item->add_meta_data( $attribute->name, $value );
    }
}
 

Something I've noticed is that when customers view an order from their account and click the 'Order again' button, these attributes are not added to the item. I'm trying to work around this now through the woocommerce_order_again_cart_item_data hook.