Product discount function

Shopify Apps
1

Hi, I’m a new user and I’m developing a Shopify app to give discounts in my store. Everything was working before, but now the function stopped returning the expected result and I’m getting this error:

Function export "cart-lines-discounts-generate-run" failed to execute with error: InvalidOutputError

Here’s my code:

import {
  CartInput,
  CartLinesDiscountsGenerateRunResult,
  ProductDiscountSelectionStrategy,
} from "../generated/api";

export async function cartLinesDiscountsGenerateRun(
  input: CartInput
): Promise<CartLinesDiscountsGenerateRunResult> {
  console.log("input: ", JSON.stringify(input), null, 2);

  return {
    operations: [
      {
        productDiscountsAdd: {
          selectionStrategy: ProductDiscountSelectionStrategy.All,
          candidates: [
            {
              message: `PRIME DISCOUNT`,
              targets: [
                {
                  cartLine: {
                    id: "gid://shopify/CartLine/0",
                  },
                },
              ],
              value: {
                percentage: {
                  value: 10,
                },
              },
            },
          ],
        },
      },
    ],
  };
}


api_version = "2025-07"

[[extensions]]
name = "t:name"
handle = "discount-function"
type = "function"
uid = "..."
description = "t:description"

  [[extensions.targeting]]
  target = "cart.lines.discounts.generate.run"
  input_query = "src/cart_lines_discounts_generate_run.graphql"
  export = "cart-lines-discounts-generate-run"

  [extensions.build]
  command = ""
  path = "dist/function.wasm"

[access_scopes]
scopes = “write_discounts,read_customers”

2

I resolved removing async/await

export function cartLinesDiscountsGenerateRun(input: CartInput): CartLinesDiscountsGenerateRunResult {
…
}