WooCommerce buy one get one 50% off, excluding a product variation

I am using WooCommerce discount: buy one get one 50% off with a notice answer code, if customer purchases a specific product, customer get 50% discount off on the 2nd item.

Now If the targeted product id is a variable product with for example 3 variations “A”, “B” and “C”, how can I exclude for example the variation “A” from discount calculation? Where should put that condition?

Answer

The following will handle variation exclusion from the original answer code:

add_action('woocommerce_cart_calculate_fees', 'add_custom_discount_2nd_at_50', 10, 1 );
function add_custom_discount_2nd_at_50( $cart ){
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    // YOUR SETTINGS:
    $variable_product_id = 40; // <== HERE your targeted variable product ID
    $excl_variations_ids = array( 41, 42); // <== HERE your variations to be excluded

    // Initializing variables
    $discount = $qty_notice = 0;
    $items_prices = array();

    // Loop through cart items
    foreach ( $cart->get_cart() as $key => $cart_item ) {
        if( $variable_product_id == $cart_item['product_id'] && in_array( $cart_item['variation_id'], $excl_variations_ids ) ) {
            $quantity = (int) $cart_item['quantity'];
            $qty_notice += $quantity;
            for( $i = 0; $i < $quantity; $i++ ) {
                $items_prices[] = floatval( $cart_item['data']->get_price());
            }
        }
    }

    $count_items = count($items_prices); // Count items

    rsort($items_prices); // Sorting prices descending order

    if( $count_items > 1 ) {
        foreach( $items_prices as $key => $price ) {
            if( $key % 2 == 1 )
                $discount -= number_format( $price / 2, 2 );
        }
    }

    // Applying the discount
    if( $discount != 0 ){
        $cart->add_fee('Buy one get one 50% off' ,$discount  ); // true

        // Displaying a custom notice (optional)
        wc_clear_notices(); // clear other notices on checkout page.
        if( ! is_checkout() ){
            wc_add_notice( __("You get 50% of discount on the 2nd item"), 'notice');
        }
    }
    //  Display a custom notice on cart page when quantity is equal to 1.
    elseif( $qty_notice == 1 ){
        wc_clear_notices(); // clear other notices on checkout page.
        if( ! is_checkout() ){
            wc_add_notice( __( "Add one more to get 50% off on 2nd item" ), 'notice');
        }
    }
}

Code goes in functions.php file of your active child theme (or active theme). Tested and works.