Do not remove unavailable addons when changing order (Z#23150855) (#4086)

src/pretix/base/services/orders.py

@@ -2013,6 +2013,20 @@ class OrderChangeManager:
                     for a in current_addons[cp][k][:current_num - input_num]:
                         if a.canceled:
                             continue
+                        is_unavailable = (
+                            # If an item is no longer available due to time, it should usually also be no longer
+                            # user-removable, because e.g. the stock has already been ordered.
+                            # We always pass has_voucher=True because if a product now requires a voucher, it usually does
+                            # not mean it should be unremovable for others.
+                            # This also prevents accidental removal through the UI because a hidden product will no longer
+                            # be part of the input.
+                            (a.variation and a.variation.unavailability_reason(has_voucher=True, subevent=a.subevent))
+                            or (a.variation and self.order.sales_channel not in a.variation.sales_channels)
+                            or a.item.unavailability_reason(has_voucher=True, subevent=a.subevent)
+                            or self.order.sales_channel not in item.sales_channels
+                        )
+                        if is_unavailable:
+                            continue
                         if a.checkins.filter(list__consider_tickets_used=True).exists():
                             raise OrderError(
                                 error_messages['addon_already_checked_in'] % {

src/tests/presale/test_order_change.py

@@ -993,6 +993,47 @@ class OrderChangeAddonsTest(BaseOrdersTest):
             self.order.refresh_from_db()
             assert self.order.total == Decimal('23.00')
 
+    def test_do_not_remove_unavailable_on_adding(self):
+        self.iao.max_count = 2
+        self.iao.save()
+        self.workshop1.available_until = now() - datetime.timedelta(days=1)
+        self.workshop1.save()
+        with scopes_disabled():
+            OrderPosition.objects.create(
+                order=self.order,
+                item=self.workshop1,
+                variation=None,
+                price=Decimal("12"),
+                addon_to=self.ticket_pos,
+                attendee_name_parts={'full_name': "Peter"}
+            )
+            self.order.total += Decimal("12")
+            self.order.save()
+
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 200
+        assert 'Workshop 1' not in response.content.decode()
+
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret),
+            {
+                f'cp_{self.ticket_pos.pk}_variation_{self.workshop2.pk}_{self.workshop2a.pk}': '1'
+            },
+            follow=True
+        )
+        doc = BeautifulSoup(response.content.decode(), "lxml")
+        form_data = extract_form_fields(doc.select('.main-box form')[0])
+        form_data['confirm'] = 'true'
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), form_data, follow=True
+        )
+        assert 'alert-success' in response.content.decode()
+
+        with scopes_disabled():
+            assert self.ticket_pos.addons.count() == 2
+
     def test_remove_addon_checked_in(self):
         with scopes_disabled():
             self.event.settings.change_allow_user_if_checked_in = True
@@ -1578,7 +1619,6 @@ class OrderChangeAddonsTest(BaseOrdersTest):
             },
             follow=True
         )
-        print(response.content.decode())
         assert 'alert-danger' not in response.content.decode()
 
         response = self.client.post(