feat(medusa): Improve addShippingMethod on store cart route (#3222)

.changeset/brown-drinks-flow.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/medusa": patch
+---
+
+chore(medusa): Improve addShippingMethod on store cart route to use new totals calculation algo

packages/medusa/src/api/routes/store/carts/add-shipping-method.ts

@@ -80,6 +80,7 @@ export default async (req, res) => {
     )
 
     const updated = await txCartService.retrieve(id, {
+      select: ["id"],
       relations: ["payment_sessions"],
     })
 

packages/medusa/src/services/cart.ts

@@ -2072,16 +2072,12 @@ class CartService extends TransactionBaseService {
   ): Promise<Cart> {
     return await this.atomicPhase_(
       async (transactionManager: EntityManager) => {
-        const cart = await this.retrieve(cartId, {
-          select: ["subtotal", "total"],
+        const cart = await this.retrieveWithTotals(cartId, {
           relations: [
             "shipping_methods",
-            "discounts",
-            "discounts.rule",
             "shipping_methods.shipping_option",
             "items",
             "items.variant",
-            "payment_sessions",
             "items.variant.product",
           ],
         })