Mandatory coupon before checkout in WooCommerce (optional: for specific products)

Question

I want to force the customer to add a coupon code before they can go to checkout. I would like it to work with every coupon code and every product in my WooCommerce store.

I am using this code and it is almost solving the problem, but it only works on a single coupon code (freev1)

How is it possible to make it work on every coupon code generated?

add_action( 'woocommerce_check_cart_items', 'mandatory_coupon_code' );
function mandatory_coupon_code() {
    // HERE set your coupon code
    $mandatory_coupon = 'freev1';

    $applied_coupons = WC()->cart->get_applied_coupons();

    // If coupon is found we exit
    if( in_array( $mandatory_coupon, $applied_coupons ) ) return;

    // Not found: display an error notice
    wc_add_notice( __( 'Add coupon before checkout.', 'woocommerce' ), 'error' );
}

Answer 1

Just check if $applied_coupons is empty, when empty add notice. Remove $mandatory_coupon & if ( in_array...

So you get:

function action_woocommerce_check_cart_items() {
    // Isset
    if ( WC()->cart ) {
        // Get applied coupons
        $applied_coupons = WC()->cart->get_applied_coupons();

        // When empty
        if ( empty ( $applied_coupons ) ) {
            // Not found: display an error notice
            wc_add_notice( __( 'Add coupon before checkout.', 'woocommerce' ), 'error' );   
        }
    }
}
add_action( 'woocommerce_check_cart_items', 'action_woocommerce_check_cart_items', 10 );

---

Update:

To apply this for specific products in cart, use:

function action_woocommerce_check_cart_items() {
    // The targeted product ids
    $targeted_ids = array( 30, 815 );

    // Flag
    $found = false;
    
    // Isset
    if ( WC()->cart ) {
        // Get applied coupons
        $applied_coupons = WC()->cart->get_applied_coupons();

        // When empty
        if ( empty ( $applied_coupons ) ) {
            // Loop through cart items
            foreach ( WC()->cart->get_cart() as $cart_item ) {
                if ( array_intersect( $targeted_ids, array( $cart_item['product_id'], $cart_item['variation_id'] ) ) ) {
                    $found = true;
                    break;
                }
            }
        }
    }
    
    // True
    if ( $found ) {
        // Not found: display an error notice
        wc_add_notice( __( 'Add coupon before checkout.', 'woocommerce' ), 'error' );
    }
}
add_action( 'woocommerce_check_cart_items', 'action_woocommerce_check_cart_items', 10 );

---

Additional question:

"Will it be possible to use almost same code, but instead make it work from the checkout page and force the use of a coupon before placing a order?"

You could replace woocommerce_check_cart_items with the woocommerce_checkout_process hook for the checkout page