How to fetch a product by ID in Shopify Checkout Validation app

Technical Q&A
1

Hello.

I have followed the below tutorial and everything is working as expected

https://shopify.dev/docs/apps/checkout/validation/cart-checkout

I have updated the extensions/cart-checkout-validation/input.graphql as per the below to suite my applications specific needs.

query Input {
  cart {
    buyerIdentity {
      customer {
        numberOfOrders
      }
    }
    lines {
        merchandise {
               ...on ProductVariant {
                 id
               }
        }
        quantity
    }
  }
}

This is working and fetching the specific data associated to the users cart that I need.

However, I addition to the above, I would also like to fetch a product and its variant (that may be unrelated to the current users cart) via ID (although in the future I will want to fetch it by tag)

How do I go about doing this?

Is this something I add to my extensions/cart-checkout-validation/input.graphql query*?*

I would like the product exposed in my extensions/cart-checkout-validation/src/index.js

// @ts-check
// Use JSDoc annotations for type safety
/**
 * @typedef {import("../generated/api").InputQuery} InputQuery
 * @typedef {import("../generated/api").FunctionResult} FunctionResult
 */
// The @shopify/shopify_function package will use the default export as your function entrypoint
export default
/**
 * @param {InputQuery} input
 * @returns {FunctionResult}
 */

(input) => {

    // The error
    const error = {
        localizedMessage:
            "This is a test",
        target: "cart"
    };

    const errors = [];
    errors.push(error);

   // TODO: here I want to access a single product with it variant by ID
  //  Maybe something like input.my_product - if this is not the right approach,
  //  How can I go about achieving this?

    return {errors};
};

Please, any help, guidance or advice would be greatly appreciated.