Add-on selection: Fix incorrect pre-selection across multiple base positions

src/pretix/presale/checkoutflow.py

@@ -513,7 +513,11 @@ class AddOnsStep(CartMixin, AsyncAction, TemplateFlowStep):
                     )
                     item_cache[ckey] = items
                 else:
-                    items = item_cache[ckey]
+                    # We can use the cache to prevent a database fetch, but we need separate Python objects
+                    # or our things below like setting `i.initial` will do the wrong thing.
+                    items = [copy.copy(i) for i in item_cache[ckey]]
+                    for i in items:
+                        i.available_variations = [copy.copy(v) for v in i.available_variations]
 
                 for i in items:
                     i.allow_waitinglist = False

src/pretix/presale/templates/pretixpresale/event/order_change_confirm.html

@@ -82,12 +82,12 @@
                             <tr>
                                 <td>
                                     {% if op.variation %}
-                                        {% blocktrans trimmed with positionid=op.position.positionid item=op.item.name variation=op.variation.value %}
+                                        {% blocktrans trimmed with item=op.item.name variation=op.variation.value %}
-                                            Add position #{{ positionid }} ({{ item }} – {{ variation }})
+                                            Add position ({{ item }} – {{ variation }})
                                         {% endblocktrans %}
                                     {% else %}
-                                        {% blocktrans trimmed with positionid=op.position.positionid item=op.item.name %}
+                                        {% blocktrans trimmed with item=op.item.name %}
-                                            Add position #{{ positionid }} ({{ item }})
+                                            Add position ({{ item }})
                                         {% endblocktrans %}
                                     {% endif %}
                                     {% if op.addon_to %}

src/pretix/presale/views/order.py

@@ -32,7 +32,7 @@
 # Unless required by applicable law or agreed to in writing, software distributed under the Apache License 2.0 is
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations under the License.
-
+import copy
 import inspect
 import json
 import mimetypes
@@ -1242,7 +1242,11 @@ class OrderChange(EventViewMixin, OrderDetailMixin, TemplateView):
                         )
                         item_cache[ckey] = items
                     else:
-                        items = item_cache[ckey]
+                        # We can use the cache to prevent a database fetch, but we need separate Python objects
+                        # or our things below like setting `i.initial` will do the wrong thing.
+                        items = [copy.copy(i) for i in item_cache[ckey]]
+                        for i in items:
+                            i.available_variations = [copy.copy(v) for v in i.available_variations]
 
                     for i in items:
                         i.allow_waitinglist = False