Code used for Shopify's product discount Function: https://www.youtube.com/watch?v=4ie7HX2HjSk

sample_code.txt

// input.graphql file for a Shopify product discount Function

query Input {
  cart {
    attribute(key: "addedPrePurchase") {
      value
    }
    lines {
      quantity
      merchandise {
        ... on ProductVariant {
          id
        }
      }
    }
  }
}



// default export from src/index.js of a Shopify product discount Function

 export default /**
 * @param {InputQuery} input
 * @returns {FunctionResult}
 */
(input) => {
  const attribute = input?.cart?.attribute;
  const variantId = attribute?.value?.toString() || "";
  const lines = input.cart.lines;

  const isInCart = lines.find((line) => line.merchandise?.id === variantId);

  if (isInCart) {
    return {
      discountApplicationStrategy: DiscountApplicationStrategy.First,
      discounts: [
        {
          value: {
            percentage: {
              value: 25,
            },
          },
          targets: [
            {
              productVariant: {
                id: variantId,
              },
            },
          ],
          message: "25% off",
        },
      ],
    };
  }

  return EMPTY_DISCOUNT;
};



// Gadget code effect used to create a new Discount in Shopify
// NOTE: if placed on the Shopify Shop install action, you can use `connections.shopify.current` to get the current connection

module.exports = async ({ api, scope, logger, params, connections }) => {
  const shopify = await connections.shopify.forShopId("<YOUR SHOP ID>");

  if (shopify) {
    // create the discount object to be created in Shopify
    const discount = {
      functionId: process.env.FUNCTION_ID,
      title: "pre-purchase discount",
      startsAt: new Date(),
    };
    logger.debug({ discount }, "discount to create");

    // query to create a new discount on the current store
    const query = `
      mutation discountAutomaticAppCreate($automaticAppDiscount: DiscountAutomaticAppInput!) {
        discountAutomaticAppCreate(automaticAppDiscount: $automaticAppDiscount) {
          automaticAppDiscount {
            title
          }
          userErrors {
            field
            message
          }
        }
      }
    `;

    const discountResponse = await shopify.graphql(query, {
      automaticAppDiscount: discount,
    });

    logger.info({ discountResponse }, "discount creation response")
  }
};