Shopify App troubleshoot

checkout.jsx

import { useEffect, useState } from "react";
import {
  useCartLineTarget,
  Text,
  reactExtension,
  useApplyCartLinesChange,
} from "@shopify/ui-extensions-react/checkout";

// Entry point
export default reactExtension("purchase.checkout.cart-line-item.render-after", () => <App />);

function App() {
  const triggerWord = "Rezeptgebühr";
  const cartLineTarget = useCartLineTarget();
  const applyCartLinesChange = useApplyCartLinesChange();

  const title = cartLineTarget?.merchandise?.product?.title ?? "";
  const prodTitle = cartLineTarget?.merchandise?.title ?? "";
  const quantity = cartLineTarget?.quantity ?? 0;

  const [titleHasTrigger, setTitleHasTrigger] = useState(false);
  const [wasAdjusted, setWasAdjusted] = useState(false);

  function adjustQuantity(qty) {
    if (qty < 5) return 5;
    return Math.floor(qty / 5) * 5;
  }

  useEffect(() => {
    async function handleQuantityAdjustment() {
      const hasTrigger = title.toLowerCase().includes(triggerWord.toLowerCase());
      setTitleHasTrigger(hasTrigger);
  
      if (!hasTrigger && quantity % 5 !== 0) {
        const newQuantity = adjustQuantity(quantity);
  
        try {
          await applyCartLinesChange({
            type: "updateCartLine",
            updates: [
              {
                id: String(cartLineTarget.id), // Ensure ID is a string
                quantity: newQuantity,
              },
            ],
          });
          setWasAdjusted(true);
        } catch (error) {
          
        }
      }
    }
  
    handleQuantityAdjustment();
  }, [title, quantity, triggerWord]);

  return (
    <Text>
      {`Adjust applied: ${wasAdjusted ? "Yes" : "No"} | `}
      {`CartLineTarget: ${JSON.stringify(cartLineTarget)} | `}
    </Text>
  );
}

preview-link

https://can-doc.de/checkouts/cn/Z2NwLWV1cm9wZS13ZXN0MzowMUpRQzc1VFo2S1hZRjRLMkY1R0hOMVdZTQ?adminUrl=admin.shopify.com&cart_link_id=6xKh1p5o&editedAt=2025-04-07T11%3A17%3A53Z&isPublished=false&profileName=PX+auto+discount+in+checkout+v2&profile_preview_token=eyJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJtZWRpY2FsZ3JlZW5zLm15c2hvcGlmeS5jb20iLCJhdWQiOiJtZWRpY2FsZ3JlZW5zLm15c2hvcGlmeS5jb20iLCJuYmYiOjE3NDQwMjUyNjgsImNoZWNrb3V0X3Byb2ZpbGVfaWQiOjYwNzg0NjQzMjUsImNoZWNrb3V0X3Byb2ZpbGVfcHVibGlzaGVkIjpmYWxzZSwiY2hlY2tvdXRfcHJvZmlsZV90eXBfb3NwX2FjdGl2ZSI6dHJ1ZSwiZXhwIjoxNzQ0MDI4ODY4fQ.f4ju3mEBhhVQVPw0-bKUxJz4AiHhJRC1gQKNO0P2h4E

shopify.extension.toml

# Learn more about configuring your checkout UI extension:
# https://shopify.dev/api/checkout-extensions/checkout/configuration

# The version of APIs your extension will receive. Learn more:
# https://shopify.dev/docs/api/usage/versioning
api_version = "2025-01"

[[extensions]]
name = "Quantity auto-adjustment"
handle = "quantity-auto-adjustment"
type = "ui_extension"


# Controls where in Shopify your extension will be injected,
# and the file that contains your extension’s source code. Learn more:
# https://shopify.dev/docs/api/checkout-ui-extensions/unstable/extension-targets-overview

[[extensions.targeting]]
module = "./src/Checkout.jsx"
target = "purchase.checkout.cart-line-item.render-after"

  # Loads metafields on checkout resources, including the cart,
  # products, customers, and more. Learn more:
  # https://shopify.dev/docs/api/checkout-ui-extensions/unstable/configuration#metafields

  # [[extensions.targeting.metafields]]
  # namespace = "custom"
  # key = "standard_selling_unit"

# [[extensions.metafields]]
# namespace = "custom"
# key = "standard_selling_unit"

[extensions.capabilities]
# Gives your extension access to directly query Shopify’s storefront API.
# https://shopify.dev/docs/api/checkout-ui-extensions/unstable/configuration#api-access
api_access = true

# Gives your extension access to make external network calls, using the
# JavaScript `fetch()` API. Learn more:
# https://shopify.dev/docs/api/checkout-ui-extensions/unstable/configuration#network-access
# network_access = true

# Defines settings that will be collected from merchants installing
# your extension. Learn more:
# https://shopify.dev/docs/api/checkout-ui-extensions/unstable/configuration#settings-definition

# [extensions.settings]
# [[extensions.settings.fields]]
# key = "excluded_products_title_trigger"
# type = "single_line_text_field"
# name = "Excluded products trigger word"