chore: add a validation in the service layer to conform to 1 region rule

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

@@ -9,7 +9,6 @@ const featureFlagRouter = new FlagRouter({})
 describe("DiscountService", () => {
   describe("create", () => {
     const discountRepository = MockRepository({})
-
     const discountRuleRepository = MockRepository({})
 
     const regionService = {
@@ -54,6 +53,24 @@ describe("DiscountService", () => {
       }
     })
 
+    it("fails to create a discount without regions", async () => {
+      expect.assertions(3)
+      try {
+        await discountService.create({
+          code: "test",
+          rule: {
+            type: "fixed",
+            allocation: "total",
+            value: 20,
+          },
+        })
+      } catch (err) {
+        expect(err.type).toEqual("invalid_data")
+        expect(err.message).toEqual("Discount must have atleast 1 region")
+        expect(discountRepository.create).toHaveBeenCalledTimes(0)
+      }
+    })
+
     it("successfully creates discount", async () => {
       await discountService.create({
         code: "test",

packages/medusa/src/services/discount.ts

@@ -212,6 +212,13 @@ class DiscountService extends TransactionBaseService {
         )) as Region[]
       }
 
+      if (isEmpty(discount.regions)) {
+        throw new MedusaError(
+          MedusaError.Types.INVALID_DATA,
+          "Discount must have atleast 1 region"
+        )
+      }
+
       const discountRule = ruleRepo.create(validatedRule)
       const createdDiscountRule = await ruleRepo.save(discountRule)