OrderChangeManager: Respect addons on cancellation check (Z#23193427) (#5132)

* OrderChangeManager: Respect addons on cancellation check (Z#23193427)

* Update src/tests/base/test_orders.py

Co-authored-by: luelista <weller@rami.io>

---------

Co-authored-by: luelista <weller@rami.io>

src/pretix/base/services/orders.py

@@ -2768,7 +2768,11 @@ class OrderChangeManager:
 
     def _check_complete_cancel(self):
         current = self.order.positions.count()
-        cancels = len([o for o in self._operations if isinstance(o, (self.CancelOperation, self.SplitOperation))])
+        cancels = sum([
+            1 + o.position.addons.count() for o in self._operations if isinstance(o, self.CancelOperation)
+        ]) + len([
+            o for o in self._operations if isinstance(o, self.SplitOperation)
+        ])
         adds = len([o for o in self._operations if isinstance(o, self.AddOperation)])
         if current > 0 and current - cancels + adds < 1:
             raise OrderError(self.error_messages['complete_cancel'])

src/tests/base/test_orders.py

@@ -1759,11 +1759,19 @@ class OrderChangeManagerTests(TestCase):
 
     @classscope(attr='o')
     def test_cancel_all_in_order(self):
+        self.shirt.category = self.event.categories.create(name='Add-ons', is_addon=True)
+        self.ticket.addons.create(addon_category=self.shirt.category)
+        self.ocm.add_position(self.shirt, None, Decimal('13.00'), addon_to=self.op1)
+        self.ocm.commit()
+        self.order.refresh_from_db()
+        self.ocm = OrderChangeManager(self.order, None)
+
+        assert self.order.positions.count() == 3
         self.ocm.cancel(self.op1)
         self.ocm.cancel(self.op2)
         with self.assertRaises(OrderError):
             self.ocm.commit()
-        assert self.order.positions.count() == 2
+        assert self.order.positions.count() == 3
 
     @classscope(attr='o')
     def test_empty(self):