fix: Update tax lines on cart when region changes (#9367)

**What**
- Removes broken cart retrieval step `retrieveWithCartLinks` in favor of `useRemoteQueryStep` in `updateTaxLinesWorkflows`

**Why**
- Filters variables in the step were passed with an incorrect shape
  - I removed the step, since it's only used once and the behavior is identical to the generic remote query step

**Note**
- Because the filters were passed incorrectly, the, now-removed, step has always returned the first cart in the database. As a result all tax calculations so far have been based on whatever the shape of that cart has. It basically ignores all input to this workflow

integration-tests/modules/__tests__/cart/store/carts.spec.ts

@@ -1001,6 +1001,137 @@ medusaIntegrationTestRunner({
           )
         })
 
+        it("should update tax lines on cart items when region changes", async () => {
+          await setupTaxStructure(taxModule)
+
+          const region = await regionModule.createRegions({
+            name: "us",
+            currency_code: "usd",
+            countries: ["us"],
+          })
+
+          const otherRegion = await regionModule.createRegions({
+            name: "dk",
+            currency_code: "dkk",
+            countries: ["dk"],
+          })
+
+          const salesChannel = await scModule.createSalesChannels({
+            name: "Webshop",
+          })
+
+          const [productWithDefaultTax] = await productModule.createProducts([
+            {
+              title: "Test product default tax",
+              variants: [
+                { title: "Test variant default tax", manage_inventory: false },
+              ],
+            },
+          ])
+
+          const [priceSetDefaultTax] = await pricingModule.createPriceSets([
+            {
+              prices: [{ amount: 2000, currency_code: "usd" }],
+            },
+          ])
+
+          await remoteLink.create([
+            {
+              Product: {
+                variant_id: productWithDefaultTax.variants[0].id,
+              },
+              Pricing: { price_set_id: priceSetDefaultTax.id },
+            },
+          ])
+
+          await api.post(
+            "/admin/price-preferences",
+            {
+              attribute: "currency_code",
+              value: "usd",
+              is_tax_inclusive: true,
+            },
+            adminHeaders
+          )
+
+          let response = await api.post(
+            `/store/carts`,
+            {
+              sales_channel_id: salesChannel.id,
+              shipping_address: {
+                country_code: "us",
+              },
+              region_id: region.id,
+              items: [
+                {
+                  variant_id: productWithDefaultTax.variants[0].id,
+                  quantity: 1,
+                },
+              ],
+            },
+            storeHeaders
+          )
+
+          expect(response.data.cart).toEqual(
+            expect.objectContaining({
+              id: response.data.cart.id,
+              currency_code: "usd",
+              region_id: region.id,
+              items: expect.arrayContaining([
+                expect.objectContaining({
+                  unit_price: 2000,
+                  quantity: 1,
+                  title: "Test variant default tax",
+                  tax_lines: [
+                    // Uses the california default rate
+                    expect.objectContaining({
+                      description: "US Default Rate",
+                      code: "US_DEF",
+                      rate: 2,
+                      provider_id: "system",
+                    }),
+                  ],
+                }),
+              ]),
+            })
+          )
+
+          response = await api.post(
+            `/store/carts/${response.data.cart.id}`,
+            {
+              region_id: otherRegion.id,
+              shipping_address: {
+                country_code: "dk",
+              },
+            },
+            storeHeaders
+          )
+
+          expect(response.data.cart).toEqual(
+            expect.objectContaining({
+              id: response.data.cart.id,
+              currency_code: "dkk",
+              region_id: otherRegion.id,
+              items: expect.arrayContaining([
+                expect.objectContaining({
+                  unit_price: 2000,
+                  quantity: 1,
+                  title: "Test variant default tax",
+                  tax_lines: [
+                    // Uses the danish default rate
+                    expect.objectContaining({
+                      description: "Denmark Default Rate",
+                      code: "DK_DEF",
+                      rate: 25,
+                      provider_id: "system",
+                    }),
+                  ],
+                }),
+              ]),
+            })
+          )
+        })
+
         it("should remove invalid shipping methods", async () => {
           await setupTaxStructure(taxModule)
 
@@ -1714,6 +1845,7 @@ medusaIntegrationTestRunner({
             name: "US",
             currency_code: "usd",
             automatic_taxes: false,
+            countries: ["us"],
           })
 
           const cart = await cartModule.createCarts({

packages/core/core-flows/src/cart/steps/index.ts

@@ -16,12 +16,11 @@ export * from "./get-variant-price-sets"
 export * from "./get-variants"
 export * from "./prepare-adjustments-from-promotion-actions"
 export * from "./refresh-cart-shipping-methods"
-export * from "./reserve-inventory"
 export * from "./remove-line-item-adjustments"
 export * from "./remove-shipping-method-adjustments"
 export * from "./remove-shipping-method-from-cart"
+export * from "./reserve-inventory"
 export * from "./retrieve-cart"
-export * from "./retrieve-cart-with-links"
 export * from "./set-tax-lines-for-items"
 export * from "./update-cart-promotions"
 export * from "./update-carts"
@@ -29,3 +28,4 @@ export * from "./update-line-items"
 export * from "./validate-cart-payments"
 export * from "./validate-cart-shipping-options"
 export * from "./validate-variant-prices"
+

packages/core/core-flows/src/cart/steps/retrieve-cart-with-links.ts

@@ -1,41 +0,0 @@
-import { CartWorkflowDTO } from "@medusajs/framework/types"
-import { ContainerRegistrationKeys, isObject } from "@medusajs/framework/utils"
-import { createStep, StepResponse } from "@medusajs/framework/workflows-sdk"
-
-export interface RetrieveCartWithLinksStepInput {
-  cart_or_cart_id: string | CartWorkflowDTO
-  fields: string[]
-}
-
-export const retrieveCartWithLinksStepId = "retrieve-cart-with-links"
-/**
- * This step retrieves a cart's details with its linked records.
- */
-export const retrieveCartWithLinksStep = createStep(
-  retrieveCartWithLinksStepId,
-  async (data: RetrieveCartWithLinksStepInput, { container }) => {
-    const { cart_or_cart_id: cartOrCartId, fields } = data
-
-    if (isObject(cartOrCartId)) {
-      return new StepResponse(cartOrCartId)
-    }
-
-    const id = cartOrCartId
-    const remoteQuery = container.resolve(
-      ContainerRegistrationKeys.REMOTE_QUERY
-    )
-    const query = {
-      entryPoint: "cart",
-      fields,
-      variables: {
-        cart: {
-          id,
-        },
-      },
-    }
-
-    const [cart] = await remoteQuery(query)
-
-    return new StepResponse(cart)
-  }
-)

packages/core/core-flows/src/cart/workflows/add-shipping-method-to-cart.ts

@@ -112,7 +112,7 @@ export const addShippingMethodToWorkflow = createWorkflow(
 
     updateTaxLinesWorkflow.runAsStep({
       input: {
-        cart_or_cart_id: input.cart_id,
+        cart_id: input.cart_id,
         shipping_methods: shippingMethodsToAdd,
       },
     })

packages/core/core-flows/src/cart/workflows/add-to-cart.ts

@@ -124,7 +124,7 @@ export const addToCartWorkflow = createWorkflow(
       refreshCartShippingMethodsStep({ cart }),
       updateTaxLinesWorkflow.runAsStep({
         input: {
-          cart_or_cart_id: input.cart.id,
+          cart_id: input.cart.id,
           items,
         },
       })

packages/core/core-flows/src/cart/workflows/create-carts.ts

@@ -155,7 +155,7 @@ export const createCartWorkflow = createWorkflow(
 
     updateTaxLinesWorkflow.runAsStep({
       input: {
-        cart_or_cart_id: cart.id,
+        cart_id: cart.id,
       },
     })
 

packages/core/core-flows/src/cart/workflows/update-cart.ts

@@ -96,7 +96,7 @@ export const updateCartWorkflow = createWorkflow(
       refreshCartShippingMethodsStep({ cart }),
       updateTaxLinesWorkflow.runAsStep({
         input: {
-          cart_or_cart_id: carts[0].id,
+          cart_id: carts[0].id,
         },
       })
     )

packages/core/core-flows/src/cart/workflows/update-tax-lines.ts

@@ -1,18 +1,14 @@
 import {
   CartLineItemDTO,
   CartShippingMethodDTO,
-  CartWorkflowDTO,
 } from "@medusajs/framework/types"
 import {
   WorkflowData,
   createWorkflow,
   transform,
 } from "@medusajs/framework/workflows-sdk"
-import {
+import { useRemoteQueryStep } from "../../common"
-  getItemTaxLinesStep,
+import { getItemTaxLinesStep, setTaxLinesForItemsStep } from "../steps"
-  retrieveCartWithLinksStep,
-  setTaxLinesForItemsStep,
-} from "../steps"
 
 const cartFields = [
   "id",
@@ -61,7 +57,7 @@ const cartFields = [
 ]
 
 export type UpdateTaxLinesWorkflowInput = {
-  cart_or_cart_id: string | CartWorkflowDTO
+  cart_id: string
   items?: CartLineItemDTO[]
   shipping_methods?: CartShippingMethodDTO[]
   force_tax_calculation?: boolean
@@ -74,17 +70,20 @@ export const updateTaxLinesWorkflowId = "update-tax-lines"
 export const updateTaxLinesWorkflow = createWorkflow(
   updateTaxLinesWorkflowId,
   (input: WorkflowData<UpdateTaxLinesWorkflowInput>): WorkflowData<void> => {
-    const cart = retrieveCartWithLinksStep({
+    const cart = useRemoteQueryStep({
-      cart_or_cart_id: input.cart_or_cart_id,
+      entry_point: "cart",
       fields: cartFields,
+      variables: {
+        id: input.cart_id,
+      },
+      list: false,
     })
 
     const taxLineItems = getItemTaxLinesStep(
       transform({ input, cart }, (data) => ({
         cart: data.cart,
         items: data.input.items || data.cart.items,
-        shipping_methods:
+        shipping_methods: data.input.shipping_methods || data.cart.shipping_methods,
-          data.input.shipping_methods || data.cart.shipping_methods,
         force_tax_calculation: data.input.force_tax_calculation,
       }))
     )

packages/medusa/src/api/store/carts/[id]/taxes/route.ts

@@ -1,17 +1,15 @@
 import { updateTaxLinesWorkflow } from "@medusajs/core-flows"
+import { HttpTypes } from "@medusajs/framework/types"
 import { MedusaRequest, MedusaResponse } from "../../../../../types/routing"
 import { refetchCart } from "../../helpers"
-import { HttpTypes } from "@medusajs/framework/types"
 
 export const POST = async (
   req: MedusaRequest,
   res: MedusaResponse<HttpTypes.StoreCartResponse>
 ) => {
-  const workflow = updateTaxLinesWorkflow(req.scope)
+  await updateTaxLinesWorkflow(req.scope).run({
-
-  await workflow.run({
     input: {
-      cart_or_cart_id: req.params.id,
+      cart_id: req.params.id,
       force_tax_calculation: true,
     },
   })