fix(core-flows): fixes case where inventory attempts delete when input is empty (#9156)

what:

- when an empty array is passed to the workflow, it attempts to delete all inventory locations. This PR adds a conditional to prevent it from happening.

RESOLVES CC-477

Fixes https://github.com/medusajs/medusa/issues/9154

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

@@ -175,6 +175,38 @@ medusaIntegrationTestRunner({
             message: `Cannot remove Inventory Levels for ${stockLocation1.id} because there are stocked or reserved items at the locations`,
           })
         })
+
+        it("should successfully add an inventory location", async () => {
+          await api.post(
+            `/admin/inventory-items/${inventoryItem1.id}/location-levels/${stockLocation1.id}`,
+            { stocked_quantity: 10 },
+            adminHeaders
+          )
+
+          await api.post(
+            `/admin/inventory-items/${inventoryItem1.id}/location-levels/batch`,
+            { create: [{ location_id: stockLocation2.id }] },
+            adminHeaders
+          )
+
+          const {
+            data: { inventory_levels: inventoryLevels },
+          } = await api.get(
+            `/admin/inventory-items/${inventoryItem1.id}/location-levels`,
+            adminHeaders
+          )
+
+          expect(inventoryLevels).toEqual(
+            expect.arrayContaining([
+              expect.objectContaining({
+                location_id: stockLocation1.id,
+              }),
+              expect.objectContaining({
+                location_id: stockLocation2.id,
+              }),
+            ])
+          )
+        })
       })
 
       describe("DELETE /admin/inventory-items/:id/location-levels/:id", () => {

packages/core/core-flows/src/inventory/workflows/bulk-create-delete-levels.ts

@@ -1,6 +1,7 @@
 import { InventoryLevelDTO, InventoryTypes } from "@medusajs/types"
 import {
   createWorkflow,
+  when,
   WorkflowData,
   WorkflowResponse,
 } from "@medusajs/workflows-sdk"
@@ -22,12 +23,22 @@ export const bulkCreateDeleteLevelsWorkflow = createWorkflow(
   (
     input: WorkflowData<BulkCreateDeleteLevelsWorkflowInput>
   ): WorkflowResponse<InventoryLevelDTO[]> => {
-    deleteInventoryLevelsWorkflow.runAsStep({
-      input: {
-        $or: input.deletes,
-      },
+    when({ input }, ({ input }) => {
+      return !!input.deletes?.length
+    }).then(() => {
+      deleteInventoryLevelsWorkflow.runAsStep({
+        input: {
+          $or: input.deletes,
+        },
+      })
     })
 
-    return new WorkflowResponse(createInventoryLevelsStep(input.creates))
+    const created = when({ input }, ({ input }) => {
+      return !!input.creates?.length
+    }).then(() => {
+      return createInventoryLevelsStep(input.creates)
+    })
+
+    return new WorkflowResponse(created || [])
   }
 )