I’m trying to set the shipping costs to 0 or change the shipping class to free shipping for specific products.

I’ve built a snippet which will be called correctly if the product is in cart via WC()->cart->get_cart().

The problem which I can’t figure out is how to set shipping to zero or change to free shipping.

This is working, but here my payment provider has a problem, because negative values for are not allowed:

$cart->add_fee( 'Versandkostenfrei', -$cart->get_shipping_total(), true, '' );`

The ‘unitPrice’ field cannot be negative, unless the ‘type’ is one of
the following: ‘discount’, ‘store_credit’, and ‘gift_card’.

But even if this is “fixed”, the shiping costs will be shown in checkout with a separate negative position to set the shipping to zero.
This is also not nice customer view.

So I tried with:

function set_shipping_costs_to_zero( $rates ) {
        foreach ( $rates as $rate_id => $rate ) {
            $rates[ $rate_id ]->cost = 0;
            if ( isset( $rates[ $rate_id ]->taxes ) && is_array( $rates[ $rate_id ]->taxes ) ) {
                foreach ( $rates[ $rate_id ]->taxes as $key => $value ) {
                    $rates[ $rate_id ]->taxes[ $key ] = 0;
                }
            }
        }
        return $rates;
}

Which doesn’t set the price to 0.

Or even with this simple unset:

unset( $rates[$rate_id] );

Used the function in the following hooks without success:

• woocommerce_before_calculate_totals,
• woocommerce_package_rates,
• woocommerce_cart_calculate_fees.

Any ideas?