How can I fix a cart transform function error in a custom bundle app?

Technical Q&A
1

I’m currently trying to build a custom bundle app - but I’m encountering issues with the extension’s output. Unfortunately, the only docs they have for custom bundles are in Rust language - which I need to be more comfortable in for a production app. I appreciate any help/input, below I’ve attached the input/output/error of the extension runs and the source code of both the run.js and the run.graphql

Input

{
  "cart": {
    "lines": [
      {
        "id": "gid://shopify/CartLine/17d66918-72fc-4f23-9b67-8105c4e85e4b",
        "quantity": 1,
        "merchandise": {
          "__typename": "ProductVariant",
          "id": "gid://shopify/ProductVariant/43739736604825",
          "component_reference": {
            "value": "[\"gid://shopify/ProductVariant/43702370304153\",\"gid://shopify/ProductVariant/43738015236249\",\"gid://shopify/ProductVariant/43738015334553\",\"gid://shopify/ProductVariant/43738015465625\"]"
          }
        }
      }
    ]
  }
}

Output:

{
  "operations": [
    {
      "merge": {
        "parentVariantId": "gid://shopify/ProductVariant/43739736604825",
        "cartLines": [
          {
            "cart_line_id": "gid://shopify/CartLine/17d66918-72fc-4f23-9b67-8105c4e85e4b",
            "quantity": 1,
            "merchandise_id": [
              "gid://shopify/ProductVariant/gid://shopify/ProductVariant/43702370304153",
              "gid://shopify/ProductVariant/gid://shopify/ProductVariant/43738015236249",
              "gid://shopify/ProductVariant/gid://shopify/ProductVariant/43738015334553",
              "gid://shopify/ProductVariant/gid://shopify/ProductVariant/43738015465625"
            ]
          }
        ],
        "title": "Mix Merge"
      }
    }
  ]
}

Error:

[
  {
    "path": [
      "operations",
      0,
      "merge",
      "cartLines",
      0,
      "cartLineId"
    ],
    "explanation": "Expected value to not be null"
  },
  {
    "path": [
      "operations",
      0,
      "merge",
      "cartLines",
      0,
      "cart_line_id"
    ],
    "explanation": "Field is not defined on CartLineInput"
  },
  {
    "path": [
      "operations",
      0,
      "merge",
      "cartLines",
      0,
      "merchandise_id"
    ],
    "explanation": "Field is not defined on CartLineInput"
  }
]

Source Run.js

// -check

/**
 * @typedef {import("../generated/api").RunInput} RunInput
 * @typedef {import("../generated/api").FunctionRunResult} FunctionRunResult
 */

/**
 * @type {FunctionRunResult}
 */
const NO_CHANGES = {
  operations: [],
};

/**
 *  {RunInput} input
 * @returns {FunctionRunResult}
 */
function run(input) {
  const cartOperations = getExpandCartOperations(input.cart);

  return {
    operations: cartOperations,
  };
}

function getExpandCartOperations(cart) {
  const result = [];

  for (const line of cart.lines) {
    const variant = line.merchandise;

    if (!variant || variant.__typename !== "ProductVariant") {
      continue;
    }

    const componentReferences = getComponentReferences(variant);

    if (componentReferences.length === 0) {
      continue;
    }

    const expandedCartItems = componentReferences.map((reference) => ({
      merchandise_id: `gid://shopify/ProductVariant/${reference}`,
      quantity: 1,
    }));

    const expandOperation = {
      merge: {
        parentVariantId: `gid://shopify/ProductVariant/${variant.id}`,
        cartLines: componentReferences.map((reference) => ({
          cartLineId: line.id, // use the line id here
          merchandise: {
            id: `gid://shopify/ProductVariant/${reference}`,
          },
          quantity: 1,
        })),
        title: "Mix Merge",
      },
    };
    
    result.push(expandOperation);
  }

  return result;
}

function getComponentReferences(variant) {
  if (variant.component_reference) {
    return JSON.parse(variant.component_reference.value);
  }

  return [];
}

Source run.graphql

query Input {
  cart {
    lines {
      id
      quantity
      merchandise {
        __typename
        ... on ProductVariant {
          id
          component_reference: metafield(
            namespace: "custom"
            key: "component_reference"
          ) {
            value
          }
        }
      }
    }
  }
}
2

Sample output should be like the one below.

{
“operations”: [
{
“merge”: {
“cartLines”: [
{
“cartLineId”: “gid://shopify/CartLine/2”,
“quantity”: 1
},
{
“cartLineId”: “gid://shopify/CartLine/3”,
“quantity”: 1
},
{
“cartLineId”: “gid://shopify/CartLine/4”,
“quantity”: 1
}
],
“parentVariantId”: “gid://shopify/ProductVariant/123”,
“price”: {
“percentageDecrease”: {
“value”: 10.5
}
},
“title”: “Meal Kit”,
“image”: {
“url”: “https://cdn.shopify.com/[…]/custom-image.png”
}
}
}
]
}