Fix stock item splitting bug (#6335)

* Fix stock item splitting bug

- StockItem tree was not being rebuilt correctly
- Add unit tests

* Account for zero tree_id value

InvenTree/part/migrations/0112_auto_20230525_1606.py

@@ -57,7 +57,6 @@ class AddFieldOrSkip(migrations.AddField):
 
         try:
             super().database_forwards(app_label, schema_editor, from_state, to_state)
-            print(f'Added field {self.name} to model {self.model_name}')
         except Exception as exc:
             pass
 

InvenTree/stock/models.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import logging
 import os
 from datetime import datetime, timedelta
 from decimal import Decimal, InvalidOperation
@@ -49,6 +50,8 @@ from part import models as PartModels
 from plugin.events import trigger_event
 from users.models import Owner
 
+logger = logging.getLogger('inventree')
+
 
 class StockLocationType(MetadataMixin, models.Model):
     """A type of stock location like Warehouse, room, shelf, drawer.
@@ -1706,9 +1709,12 @@ class StockItem(
         # Nullify the PK so a new record is created
         new_stock = StockItem.objects.get(pk=self.pk)
         new_stock.pk = None
-        new_stock.parent = self
         new_stock.quantity = quantity
 
+        # Update the new stock item to ensure the tree structure is observed
+        new_stock.parent = self
+        new_stock.level = self.level + 1
+
         # Move to the new location if specified, otherwise use current location
         if location:
             new_stock.location = location
@@ -1748,6 +1754,19 @@ class StockItem(
             stockitem=new_stock,
         )
 
+        # Rebuild the tree for this parent item
+        try:
+            StockItem.objects.partial_rebuild(tree_id=self.tree_id)
+        except Exception:
+            logger.warning('Rebuilding entire StockItem tree')
+            StockItem.objects.rebuild()
+
+        # Attempt to reload the new item from the database
+        try:
+            new_stock.refresh_from_db()
+        except Exception:
+            pass
+
         # Return a copy of the "new" stock item
         return new_stock
 

InvenTree/stock/tests.py

@@ -502,9 +502,18 @@ class StockTest(StockTestBase):
         ait = it.allocateToCustomer(
             customer, quantity=an, order=order, user=None, notes='Allocated some stock'
         )
+
+        self.assertEqual(ait.quantity, an)
+        self.assertTrue(ait.parent, it)
+
+        # There should be only quantity 10x remaining
+        it.refresh_from_db()
+        self.assertEqual(it.quantity, 10)
+
         ait.return_from_customer(it.location, None, notes='Stock removed from customer')
 
         # When returned stock is returned to its original (parent) location, check that the parent has correct quantity
+        it.refresh_from_db()
         self.assertEqual(it.quantity, n)
 
         ait = it.allocateToCustomer(
@@ -987,6 +996,63 @@ class VariantTest(StockTestBase):
         item.save()
 
 
+class StockTreeTest(StockTestBase):
+    """Unit test for StockItem tree structure."""
+
+    def test_stock_split(self):
+        """Test that stock splitting works correctly."""
+        StockItem.objects.rebuild()
+
+        part = Part.objects.create(name='My part', description='My part description')
+        location = StockLocation.objects.create(name='Test Location')
+
+        # Create an initial stock item
+        item = StockItem.objects.create(part=part, quantity=1000, location=location)
+
+        # Test that the initial MPTT values are correct
+        self.assertEqual(item.level, 0)
+        self.assertEqual(item.lft, 1)
+        self.assertEqual(item.rght, 2)
+
+        children = []
+
+        self.assertEqual(item.get_descendants(include_self=False).count(), 0)
+        self.assertEqual(item.get_descendants(include_self=True).count(), 1)
+
+        # Create child items by splitting stock
+        for idx in range(10):
+            child = item.splitStock(50, None, None)
+            children.append(child)
+
+            # Check that the child item has been correctly created
+            self.assertEqual(child.parent.pk, item.pk)
+            self.assertEqual(child.tree_id, item.tree_id)
+            self.assertEqual(child.level, 1)
+
+            item.refresh_from_db()
+            self.assertEqual(item.get_children().count(), idx + 1)
+            self.assertEqual(item.get_descendants(include_self=True).count(), idx + 2)
+
+        item.refresh_from_db()
+        n = item.get_descendants(include_self=True).count()
+
+        for child in children:
+            # Create multiple sub-childs
+            for _idx in range(3):
+                sub_child = child.splitStock(10, None, None)
+                self.assertEqual(sub_child.parent.pk, child.pk)
+                self.assertEqual(sub_child.tree_id, child.tree_id)
+                self.assertEqual(sub_child.level, 2)
+
+                self.assertEqual(sub_child.get_ancestors(include_self=True).count(), 3)
+
+            child.refresh_from_db()
+            self.assertEqual(child.get_descendants(include_self=True).count(), 4)
+
+        item.refresh_from_db()
+        self.assertEqual(item.get_descendants(include_self=True).count(), n + 30)
+
+
 class TestResultTest(StockTestBase):
     """Tests for the StockItemTestResult model."""
 
@@ -1050,6 +1116,9 @@ class TestResultTest(StockTestBase):
     def test_duplicate_item_tests(self):
         """Test duplicate item behaviour."""
         # Create an example stock item by copying one from the database (because we are lazy)
+
+        StockItem.objects.rebuild()
+
         item = StockItem.objects.get(pk=522)
 
         item.pk = None