[bug] Quantity fixes (#12375)

- Ensure valid quantity values on stock operations
- Regression testing

src/backend/InvenTree/stock/models.py

@@ -1376,9 +1376,16 @@ class StockItem(
             user: User that performed the action
             notes: Notes field
         """
-        if quantity is None:
+        if quantity is None or self.serialized:
             quantity = self.quantity
 
+        # Cannot allocate more than the available quantity
+        # (also ensures the recorded history matches the actual allocation)
+        quantity = min(quantity, self.quantity)
+
+        if quantity <= 0:
+            raise ValidationError({'quantity': _('Quantity must be greater than zero')})
+
         if quantity >= self.quantity:
             item = self
         else:
@@ -1708,6 +1715,18 @@ class StockItem(
             notes: Any notes associated with the operation
             build: The BuildOrder to associate with the operation (optional)
         """
+        try:
+            quantity = Decimal(quantity)
+        except (InvalidOperation, TypeError):
+            raise ValidationError({'quantity': _('Invalid quantity value')})
+
+        if quantity <= 0:
+            raise ValidationError({'quantity': _('Quantity must be greater than zero')})
+
+        # Cannot install more than the available quantity
+        # (also ensures the recorded history matches the actual installation)
+        quantity = min(quantity, other_item.quantity)
+
         # If the quantity is less than the stock item, split the stock!
         stock_item = other_item.splitStock(quantity, None, user)
 
@@ -3065,6 +3084,10 @@ class StockItem(
         except InvalidOperation:
             return False
 
+        # Cannot remove more than the available quantity
+        # (also ensures the recorded history matches the actual removal)
+        quantity = min(quantity, self.quantity)
+
         if quantity <= 0:
             return False
 

src/backend/InvenTree/stock/tests.py

@@ -351,6 +351,92 @@ class StockTest(StockTestBase):
         stock.splitStock(stock.quantity, None, self.user)
         self.assertEqual(StockItem.objects.filter(part=3).count(), n + 1)
 
+    def test_over_adjustment_quantities(self):
+        """Stock adjustments are clamped to the available stock quantity.
+
+        Regression test: take_stock / allocateToCustomer / installStockItem
+        previously recorded the *requested* quantity in the stock history,
+        even when less stock was actually removed / allocated / installed.
+        """
+        part = Part.objects.create(
+            name='Clamp part',
+            description='A part for quantity clamping tests',
+            salable=True,
+            component=True,
+        )
+
+        # --- take_stock: remove more than available ---
+        item = StockItem.objects.create(part=part, quantity=10, delete_on_deplete=False)
+
+        self.assertTrue(item.take_stock(25, self.user, notes='over-remove'))
+
+        item.refresh_from_db()
+        self.assertEqual(item.quantity, 0)
+
+        # History records the quantity which was *actually* removed
+        entry = item.tracking_info.latest('pk')
+        self.assertEqual(entry.deltas['removed'], 10.0)
+        self.assertEqual(entry.deltas['quantity'], 0.0)
+
+        # Removing stock from an empty item fails, and adds no history
+        n = item.tracking_info.count()
+        self.assertFalse(item.take_stock(5, self.user))
+        self.assertEqual(item.tracking_info.count(), n)
+
+        # --- allocateToCustomer: allocate more than available ---
+        customer = Company.objects.create(name='Clamp customer', is_customer=True)
+
+        item = StockItem.objects.create(part=part, quantity=10)
+
+        allocated = item.allocateToCustomer(customer, quantity=25, user=self.user)
+
+        # The whole item is allocated (no split occurs)
+        self.assertEqual(allocated.pk, item.pk)
+        self.assertEqual(allocated.customer, customer)
+
+        # History records the quantity which was *actually* allocated
+        entry = allocated.tracking_info.latest('pk')
+        self.assertEqual(entry.deltas['quantity'], 10.0)
+
+        # A zero quantity is rejected outright
+        item = StockItem.objects.create(part=part, quantity=10)
+
+        with self.assertRaises(ValidationError):
+            item.allocateToCustomer(customer, quantity=0, user=self.user)
+
+        # --- installStockItem: install more than available ---
+        assembly = Part.objects.create(
+            name='Clamp assembly',
+            description='An assembly for quantity clamping tests',
+            assembly=True,
+        )
+
+        parent_item = StockItem.objects.create(part=assembly, quantity=1)
+        component = StockItem.objects.create(part=part, quantity=10)
+
+        parent_item.installStockItem(component, 25, self.user, 'over-install')
+
+        component.refresh_from_db()
+        self.assertEqual(component.belongs_to, parent_item)
+        self.assertEqual(component.quantity, 10)
+
+        # Both history entries record the quantity which was *actually* installed
+        entry = component.tracking_info.filter(
+            tracking_type=StockHistoryCode.INSTALLED_INTO_ASSEMBLY
+        ).latest('pk')
+        self.assertEqual(entry.deltas['quantity'], 10.0)
+
+        entry = parent_item.tracking_info.filter(
+            tracking_type=StockHistoryCode.INSTALLED_CHILD_ITEM
+        ).latest('pk')
+        self.assertEqual(entry.deltas['quantity'], 10.0)
+
+        # A zero quantity is rejected outright
+        other = StockItem.objects.create(part=part, quantity=5)
+
+        with self.assertRaises(ValidationError):
+            parent_item.installStockItem(other, 0, self.user, 'bad install')
+
     def test_uninstall_into_structural_location(self):
         """Test that an item cannot be uninstalled into a structural location."""
         parent = StockItem.objects.get(pk=1)