Quickly, I thought about that :
(but it’s not my best! Maybe I’ll come rewrite a more thoughtful code sometimes but for now, this code’ll work)
add_action( 'woocommerce_before_cart', 'webroom_check_if_product_category_is_in_cart' );
function webroom_check_if_product_category_is_in_cart() {
$cat1_in_cart = false;
$cat2_in_cart = false;
foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
if ( has_term( 'cat1', 'product_cat', $cart_item['product_id'] ) ) {
$cat1_in_cart = true;
} elseif(has_term( 'cat2', 'product_cat', $cart_item['product_id'] )){
$cat2_in_cart = true;
}
}
if ($cat1_in_cart === true && $cat2_in_cart === true) {
$notice="Notification";
wc_print_notice($notice, 'notice');
}
}