woocommerce_add_cart_item_data return internal server error

Hey,

i want to add a custom price with woocommerce_add_cart_item_data, when i then use a mutation like:

mutation MyMutation {
addToCart(input: {productId: 24, extraData: "100"}) {
cartItem {
product {
node {
id
}
}
extraData {
id
}
}
}
}

i get a internal server error with: “Cannot use a scalar value as an array”

my plugin code looks like:

function add_width_data_field_to_product($cart_item_data, $product_id, $variation_id) {

$writeToFile = fopen("cartdata.txt", "w");

fwrite($writeToFile, "test");

fclose($writeToFile);

$product = wc_get_product($product_id);

$price = $product->get_price();

$cart_item_data["calculatedPrice"] = $price * 2;

return $cart_item_data;

}

add_filter('woocommerce_add_cart_item_data', 'add_width_data_field_to_product', 10, 3);

It would be really nice if someone has a hint, what I make wrong here.

kindly,

felix