fix(medusa): Update line item adjustments upon cart discount removal (#2751)

**What**

When a discount is deleted from a cart, the line item adjustments must be refreshed. Now, the cart service `removeDiscount` includes updating the adjustments.

**Tests**

**Add a new integration test which:**
- create a cart with a discount 
- add a line item
- validate the adjustments
- remove the discount
- check that the adjustments are not present anymore

**Update unit tests**
The actual tests cases now check that the adjustments repository is called when needed

FIXES CORE-890

packages/medusa/src/services/__tests__/cart.js

@@ -2281,6 +2281,10 @@ describe("CartService", () => {
       await cartService.update(IdMap.getId("with-d"), {
         discounts: [],
       })
+
+      expect(LineItemAdjustmentServiceMock.delete).toHaveBeenCalledTimes(1)
+      expect(LineItemAdjustmentServiceMock.createAdjustments).toHaveBeenCalledTimes(1)
+
       expect(eventBusService.emit).toHaveBeenCalledTimes(1)
       expect(eventBusService.emit).toHaveBeenCalledWith(
         "cart.updated",
@@ -2329,6 +2333,7 @@ describe("CartService", () => {
               },
             },
           ],
+          items: [],
           region_id: IdMap.getId("good"),
         })
       },
@@ -2339,6 +2344,7 @@ describe("CartService", () => {
       totalsService,
       cartRepository,
       eventBusService,
+      lineItemAdjustmentService: LineItemAdjustmentServiceMock,
       taxProviderService: taxProviderServiceMock,
       newTotalsService: newTotalsServiceMock,
       featureFlagRouter: new FlagRouter({}),
@@ -2351,6 +2357,9 @@ describe("CartService", () => {
     it("successfully removes discount", async () => {
       await cartService.removeDiscount(IdMap.getId("fr-cart"), "1234")
 
+      expect(LineItemAdjustmentServiceMock.delete).toHaveBeenCalledTimes(1)
+      expect(LineItemAdjustmentServiceMock.createAdjustments).toHaveBeenCalledTimes(1)
+
       expect(eventBusService.emit).toHaveBeenCalledTimes(1)
       expect(eventBusService.emit).toHaveBeenCalledWith(
         "cart.updated",
@@ -2361,6 +2370,7 @@ describe("CartService", () => {
       expect(cartRepository.save).toHaveBeenCalledWith({
         id: IdMap.getId("cart"),
         region_id: IdMap.getId("good"),
+        items: [],
         discounts: [
           {
             code: "FS1234",

packages/medusa/src/services/cart.ts

@@ -1053,7 +1053,7 @@ class CartService extends TransactionBaseService {
           }
         }
 
-        if (isDefined(data.discounts)) {
+        if (isDefined(data.discounts) && data.discounts.length) {
           const previousDiscounts = [...cart.discounts]
           cart.discounts.length = 0
 
@@ -1081,6 +1081,9 @@ class CartService extends TransactionBaseService {
           if (hasFreeShipping) {
             await this.adjustFreeShipping_(cart, true)
           }
+        } else if (isDefined(data.discounts) && !data.discounts.length) {
+          cart.discounts.length = 0
+          await this.refreshAdjustments_(cart)
         }
 
         if ("gift_cards" in data) {
@@ -1411,6 +1414,8 @@ class CartService extends TransactionBaseService {
       async (transactionManager: EntityManager) => {
         const cart = await this.retrieve(cartId, {
           relations: [
+            "items",
+            "region",
             "discounts",
             "discounts.rule",
             "payment_sessions",
@@ -1435,7 +1440,9 @@ class CartService extends TransactionBaseService {
         )
         const updatedCart = await cartRepo.save(cart)
 
-        if (updatedCart.payment_sessions?.length) {
+        await this.refreshAdjustments_(updatedCart)
+
+        if (cart.payment_sessions?.length) {
           await this.setPaymentSessions(cartId)
         }