Bug fix for purchase order pricing (#4373)

* Account for pack size when calculating purchase_price for received line items

* Clearer display of "unit pricing" when part has units

* Add data migration to fix historical pricing bugs

* Remove debug statement

InvenTree/order/models.py

@@ -501,6 +501,11 @@ class PurchaseOrder(Order):
             # Take the 'pack_size' of the SupplierPart into account
             pack_quantity = Decimal(quantity) * Decimal(line.part.pack_size)
 
+            if line.purchase_price:
+                unit_purchase_price = line.purchase_price / line.part.pack_size
+            else:
+                unit_purchase_price = None
+
             # Determine if we should individually serialize the items, or not
             if type(serials) is list and len(serials) > 0:
                 serialize = True
@@ -519,7 +524,7 @@ class PurchaseOrder(Order):
                     status=status,
                     batch=batch_code,
                     serial=sn,
-                    purchase_price=line.purchase_price,
+                    purchase_price=unit_purchase_price,
                     barcode_hash=barcode_hash
                 )
 

InvenTree/order/tests.py

@@ -8,12 +8,14 @@ from django.contrib.auth import get_user_model
 from django.contrib.auth.models import Group
 from django.test import TestCase
 
+from djmoney.money import Money
+
 import common.models
 import order.tasks
 from company.models import Company, SupplierPart
 from InvenTree.status_codes import PurchaseOrderStatus
 from part.models import Part
-from stock.models import StockLocation
+from stock.models import StockItem, StockLocation
 from users.models import Owner
 
 from .models import PurchaseOrder, PurchaseOrderLineItem
@@ -255,7 +257,8 @@ class OrderTest(TestCase):
         line_1 = PurchaseOrderLineItem.objects.create(
             order=po,
             part=sp_1,
-            quantity=3
+            quantity=3,
+            purchase_price=Money(1000, 'USD'),  # "Unit price" should be $100USD
         )
 
         # 13 x 0.1 = 1.3
@@ -263,6 +266,7 @@ class OrderTest(TestCase):
             order=po,
             part=sp_2,
             quantity=13,
+            purchase_price=Money(10, 'USD'),  # "Unit price" should be $100USD
         )
 
         po.place_order()
@@ -299,6 +303,23 @@ class OrderTest(TestCase):
             round(in_stock + Decimal(10.5), 1)
         )
 
+        # Check that the unit purchase price value has been updated correctly
+        si = StockItem.objects.filter(supplier_part=sp_1)
+        self.assertEqual(si.count(), 1)
+
+        # Ensure that received quantity and unit purchase price data are correct
+        si = si.first()
+        self.assertEqual(si.quantity, 10)
+        self.assertEqual(si.purchase_price, Money(100, 'USD'))
+
+        si = StockItem.objects.filter(supplier_part=sp_2)
+        self.assertEqual(si.count(), 1)
+
+        # Ensure that received quantity and unit purchase price data are correct
+        si = si.first()
+        self.assertEqual(si.quantity, 0.5)
+        self.assertEqual(si.purchase_price, Money(100, 'USD'))
+
     def test_overdue_notification(self):
         """Test overdue purchase order notification