fix(core-flows): variants update unsets prices (#11349)

* fix: update variant flow for prices

* fix: import add test

* fix: test name

integration-tests/http/__tests__/product/admin/product.spec.ts

@@ -3182,6 +3182,103 @@ medusaIntegrationTestRunner({
           )
         })
 
+        it("should preserve variant prices when batch updating variants", async () => {
+          const productWithMultipleVariants = getProductFixture({
+            title: "Test batch variants",
+            handle: "test-batch-variants",
+            shipping_profile_id: shippingProfile.id,
+            variants: [
+              {
+                title: "Variant 1",
+                prices: [
+                  {
+                    currency_code: "usd",
+                    amount: 100,
+                  },
+                ],
+              },
+              {
+                title: "Variant 2",
+                prices: [
+                  {
+                    currency_code: "usd",
+                    amount: 200,
+                  },
+                ],
+              },
+            ],
+          })
+
+          const createdProduct = (
+            await api.post(
+              "/admin/products",
+              productWithMultipleVariants,
+              adminHeaders
+            )
+          ).data.product
+
+          const variant1Id = createdProduct.variants.find(
+            (v) => v.title === "Variant 1"
+          ).id
+
+          const variant2Id = createdProduct.variants.find(
+            (v) => v.title === "Variant 2"
+          ).id
+
+          const updatePayload1 = {
+            id: variant1Id,
+            title: "Test batch update variant",
+          }
+
+          const updatePayload2 = {
+            id: variant2Id,
+            prices: [{ currency_code: "usd", amount: 300 }],
+          }
+
+          const response = await api.post(
+            `/admin/products/${createdProduct.id}/variants/batch`,
+            {
+              update: [updatePayload1, updatePayload2],
+            },
+            adminHeaders
+          )
+
+          const dbData = (
+            await api.get(
+              `/admin/products/${createdProduct.id}?fields=*variants.prices`,
+              adminHeaders
+            )
+          ).data.product.variants
+
+          expect(response.status).toEqual(200)
+          expect(dbData).toHaveLength(2)
+          expect(dbData).toEqual(
+            expect.arrayContaining([
+              expect.objectContaining({
+                id: variant1Id,
+                title: "Test batch update variant",
+                prices: expect.arrayContaining([
+                  // updated title but price remains the same
+                  expect.objectContaining({
+                    currency_code: "usd",
+                    amount: 100,
+                  }),
+                ]),
+              }),
+              expect.objectContaining({
+                id: variant2Id,
+                prices: expect.arrayContaining([
+                  expect.objectContaining({
+                    // updated price
+                    currency_code: "usd",
+                    amount: 300,
+                  }),
+                ]),
+              }),
+            ])
+          )
+        })
+
         it("successfully adds and removes products to a collection", async () => {
           const response = await api.post(
             `/admin/collections/${baseCollection.id}/products`,