Magento 2 Graphql Exception handling

Question

I would like to customise the error messages displayed in my GraphQL queries for a coupon code in m2.

You should implement the \GraphQL\Error\ClientAware interface to handle errors in your module that are directly related to a GraphQL field having an anticipated exception. - Magento Documentation

{
    class ApplyCouponToCart implements ResolverInterface

/**
 * @var CouponManagementInterface
 */
private $couponManagement;

/**
 * @param GetCartForUser $getCartForUser
 * @param CouponManagementInterface $couponManagement
 */
public function __construct(
    GetCartForUser $getCartForUser,
    CouponManagementInterface $couponManagement
) {
    $this->getCartForUser = $getCartForUser;
    $this->couponManagement = $couponManagement;
}

/**
 * @inheritdoc
 */
public function resolve(Field $field, $context, ResolveInfo $info, array $value = null, array $args = null)
{
    if (empty($args['input']['cart_id'])) {
        throw new GraphQlInputException(__('Required parameter "cart_id" is missing'));
    }
    $maskedCartId = $args['input']['cart_id'];

    if (empty($args['input']['coupon_code'])) {
        throw new GraphQlInputException(__('Required parameter "coupon_code" is missing'));
    }
    $couponCode = $args['input']['coupon_code'];

    $currentUserId = $context->getUserId();
    $storeId = (int)$context->getExtensionAttributes()->getStore()->getId();
    $cart = $this->getCartForUser->execute($maskedCartId, $currentUserId, $storeId);
    $cartId = $cart->getId();

    /* Check current cart does not have coupon code applied */
    $appliedCouponCode = $this->couponManagement->get($cartId);
    if (!empty($appliedCouponCode)) {
        throw new GraphQlInputException(
            __('A coupon is already applied to the cart. Please remove it to apply another')
        );
    }

I need an example of how I can catch this exceptions below, and customize just the text errors like

    throw new GraphQlInputException(
        __('I want to customise this text ')

Answer 1

if the text that dosn't have any variable you can add translation in your i18n file this is best and simple way to change Message

in you app/i18n/en_US.csv file

"A coupon is already applied to the cart. Please remove it to apply another","I want to customise this text",module,Magento_QuoteGraphQl