oops

- one product in the cart is expired and sold out, and therefore can't be renewed
- another product is expired but still available, so it can be renewed

src/pretix/base/migrations/0280_cartposition_max_extend.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.20 on 2025-05-14 14:58
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0279_discount_event_date_from_discount_event_date_until'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='cartposition',
+            name='max_extend',
+            field=models.DateTimeField(null=True),
+        ),
+    ]

src/pretix/base/models/orders.py

@@ -3098,7 +3098,10 @@ class CartPosition(AbstractPosition):
         verbose_name=_("Expiration date"),
         db_index=True
     )
-
+    max_extend = models.DateTimeField(
+        verbose_name=_("Limit for extending expiration date"),
+        null=True
+    )
     tax_rate = models.DecimalField(
         max_digits=7, decimal_places=2, default=Decimal('0.00'),
         verbose_name=_('Tax rate')

src/pretix/base/services/cart.py

@@ -45,6 +45,7 @@ from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.db import DatabaseError, transaction
 from django.db.models import Count, Exists, IntegerField, OuterRef, Q, Value
+from django.db.models.aggregates import Min
 from django.dispatch import receiver
 from django.utils.timezone import make_aware, now
 from django.utils.translation import (
@@ -275,7 +276,10 @@ class CartManager:
     }
 
     def __init__(self, event: Event, cart_id: str, sales_channel: SalesChannel,
-                 invoice_address: InvoiceAddress=None, widget_data=None, expiry=None):
+                 invoice_address: InvoiceAddress=None, widget_data=None, reservation_time: timedelta=None):
+        """
+        Creates a new CartManager for an event.
+        """
         self.event = event
         self.cart_id = cart_id
         self.real_now_dt = now()
@@ -286,11 +290,17 @@ class CartManager:
         self._subevents_cache = {}
         self._variations_cache = {}
         self._seated_cache = {}
-        self._expiry = None
-        self._explicit_expiry = expiry
         self.invoice_address = invoice_address
         self._widget_data = widget_data or {}
         self._sales_channel = sales_channel
+        self.num_extended_positions = 0
+
+        if reservation_time:
+            self._reservation_time = reservation_time
+        else:
+            self._reservation_time = timedelta(minutes=self.event.settings.get('reservation_time', as_type=int))
+        self._expiry = self.real_now_dt + self._reservation_time
+        self._max_expiry_extend = self.real_now_dt + (self._reservation_time * 11)
 
     @property
     def positions(self):
@@ -305,14 +315,6 @@ class CartManager:
             self._seated_cache[item, subevent] = item.seat_category_mappings.filter(subevent=subevent).exists()
         return self._seated_cache[item, subevent]
 
-    def _calculate_expiry(self):
-        if self._explicit_expiry:
-            self._expiry = self._explicit_expiry
-        else:
-            self._expiry = self.real_now_dt + timedelta(
-                minutes=self.event.settings.get('reservation_time', as_type=int)
-            )
-
     def _check_presale_dates(self):
         if self.event.presale_start and time_machine_now(self.real_now_dt) < self.event.presale_start:
             raise CartError(error_messages['not_started'])
@@ -329,9 +331,27 @@ class CartManager:
                     raise CartError(error_messages['payment_ended'])
 
     def _extend_expiry_of_valid_existing_positions(self):
+        # real_now_dt is initialized at CartManager instantiation, so it's slightly in the past. Add a small
+        # delta to reduce risk of extending already expired CartPositions.
+        padded_now_dt = self.real_now_dt + timedelta(seconds=5)
+
+        # Make sure we do not extend past the max_extend timestamp, allowing users to extend their valid positions up
+        # to 11 times the reservation time. If we add new positions to the cart while valid positions exist, the new
+        # positions' reservation will also be limited to max_extend of the oldest position.
+        # Only after all positions expire, an ExtendOperation may reset max_extend to another 11x reservation_time.
+        max_extend_existing = self.positions.filter(expires__gt=padded_now_dt).aggregate(m=Min('max_extend'))['m']
+        if max_extend_existing:
+            self._expiry = min(self._expiry, max_extend_existing)
+            self._max_expiry_extend = max_extend_existing
+
         # Extend this user's cart session to ensure all items in the cart expire at the same time
         # We can extend the reservation of items which are not yet expired without risk
-        self.positions.filter(expires__gt=self.real_now_dt).update(expires=self._expiry)
+        if self._expiry > padded_now_dt:
+            self.num_extended_positions += self.positions.filter(
+                expires__gt=padded_now_dt, expires__lt=self._expiry,
+            ).update(
+                expires=self._expiry,
+            )
 
     def _delete_out_of_timeframe(self):
         err = None
@@ -1246,6 +1266,7 @@ class CartManager:
                             item=op.item,
                             variation=op.variation,
                             expires=self._expiry,
+                            max_extend=self._max_expiry_extend,
                             cart_id=self.cart_id,
                             voucher=op.voucher,
                             addon_to=op.addon_to if op.addon_to else None,
@@ -1294,7 +1315,9 @@ class CartManager:
                                         event=self.event,
                                         item=b.item,
                                         variation=b.variation,
-                                        expires=self._expiry, cart_id=self.cart_id,
+                                        expires=self._expiry,
+                                        max_extend=self._max_expiry_extend,
+                                        cart_id=self.cart_id,
                                         voucher=None,
                                         addon_to=cp,
                                         subevent=b.subevent,
@@ -1321,12 +1344,14 @@ class CartManager:
                         op.position.delete()
                     elif available_count == 1:
                         op.position.expires = self._expiry
+                        op.position.max_extend = self._max_expiry_extend
                         op.position.listed_price = op.listed_price
                         op.position.price_after_voucher = op.price_after_voucher
                         # op.position.price will be updated by recompute_final_prices_and_taxes()
                         if op.position.pk not in deleted_positions:
                             try:
-                                op.position.save(force_update=True, update_fields=['expires', 'listed_price', 'price_after_voucher'])
+                                op.position.save(force_update=True, update_fields=['expires', 'max_extend', 'listed_price', 'price_after_voucher'])
+                                self.num_extended_positions += 1
                             except DatabaseError:
                                 # Best effort... The position might have been deleted in the meantime!
                                 pass
@@ -1416,14 +1441,11 @@ class CartManager:
     def commit(self):
         self._check_presale_dates()
         self._check_max_cart_size()
-        self._calculate_expiry()
 
         err = self._delete_out_of_timeframe()
         err = self.extend_expired_positions() or err
         err = err or self._check_min_per_voucher()
 
-        self.real_now_dt = now()
-
         self._extend_expiry_of_valid_existing_positions()
         err = self._perform_operations() or err
         self.recompute_final_prices_and_taxes()
@@ -1632,6 +1654,31 @@ def clear_cart(self, event: Event, cart_id: str=None, locale='en', sales_channel
             raise CartError(error_messages['busy'])
 
 
+@app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(CartError,))
+def extend_cart_reservation(self, event: Event, cart_id: str=None, locale='en', sales_channel='web', override_now_dt: datetime=None) -> None:
+    """
+    Resets the expiry time of a cart to the configured reservation time of this event.
+    Limited to 11x the reservation time.
+
+    :param event: The event ID in question
+    :param cart_id: The cart ID of the cart to modify
+    """
+    with language(locale), time_machine_now_assigned(override_now_dt):
+        try:
+            sales_channel = event.organizer.sales_channels.get(identifier=sales_channel)
+        except SalesChannel.DoesNotExist:
+            raise CartError("Invalid sales channel.")
+        try:
+            try:
+                cm = CartManager(event=event, cart_id=cart_id, sales_channel=sales_channel)
+                cm.commit()
+                return cm.num_extended_positions
+            except LockTimeoutException:
+                self.retry()
+        except (MaxRetriesExceededError, LockTimeoutException):
+            raise CartError(error_messages['busy'])
+
+
 @app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(CartError,))
 def set_cart_addons(self, event: Event, addons: List[dict], add_to_cart_items: List[dict], cart_id: str=None, locale='en',
                     invoice_address: int=None, sales_channel='web', override_now_dt: datetime=None) -> None:

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

@@ -492,15 +492,21 @@
 <div class="row">
     <div class="col-md-12">
     {% if not cart.is_ordered %}
-        <p class="text-muted" id="cart-deadline" data-expires="{{ cart.first_expiry|date:"Y-m-d H:i:sO" }}">
-            {% if cart.minutes_left > 0 or cart.seconds_left > 0 %}
-                {% blocktrans trimmed with minutes=cart.minutes_left %}
-                    The items in your cart are reserved for you for {{ minutes }} minutes.
-                {% endblocktrans %}
-            {% else %}
-                {% trans "The items in your cart are no longer reserved for you. You can still complete your order as long as they’re available." %}
-            {% endif %}
-        </p>
+        <form class="text-muted"
+                method="post" data-asynctask action="{% eventurl request.event "presale:event.cart.extend" cart_namespace=cart_namespace %}">
+            {% csrf_token %}
+            <span id="cart-deadline" data-expires="{{ cart.first_expiry|date:"Y-m-d H:i:sO" }}">
+                {% if cart.minutes_left > 0 or cart.seconds_left > 0 %}
+                    {% blocktrans trimmed with minutes=cart.minutes_left %}
+                        The items in your cart are reserved for you for {{ minutes }} minutes.
+                    {% endblocktrans %}
+                {% else %}
+                    {% trans "The items in your cart are no longer reserved for you. You can still complete your order as long as they’re available." %}
+                {% endif %}
+            </span>
+            <button class="btn btn-link" type="submit" id="cart-extend-button">
+                <i class="fa fa-refresh" aria-hidden="true"></i> {% trans "Extend" %}</button>
+        </form>
     {% else %}
         <p class="sr-only" id="cart-description">{% trans "Overview of your ordered products." %}</p>
     {% endif %}

src/pretix/presale/urls.py

@@ -56,6 +56,7 @@ frame_wrapped_urls = [
     re_path(r'^cart/remove$', pretix.presale.views.cart.CartRemove.as_view(), name='event.cart.remove'),
     re_path(r'^cart/voucher$', pretix.presale.views.cart.CartApplyVoucher.as_view(), name='event.cart.voucher'),
     re_path(r'^cart/clear$', pretix.presale.views.cart.CartClear.as_view(), name='event.cart.clear'),
+    re_path(r'^cart/extend$', pretix.presale.views.cart.CartExtendReservation.as_view(), name='event.cart.extend'),
     re_path(r'^cart/answer/(?P<answer>[^/]+)/$',
             pretix.presale.views.cart.AnswerDownload.as_view(),
             name='event.cart.download.answer'),

src/pretix/presale/views/cart.py

@@ -62,7 +62,7 @@ from pretix.base.models import (
 )
 from pretix.base.services.cart import (
     CartError, add_items_to_cart, apply_voucher, clear_cart, error_messages,
-    remove_cart_position,
+    extend_cart_reservation, remove_cart_position,
 )
 from pretix.base.timemachine import time_machine_now
 from pretix.base.views.tasks import AsyncAction
@@ -537,6 +537,20 @@ class CartClear(EventViewMixin, CartActionMixin, AsyncAction, View):
                        request.sales_channel.identifier, time_machine_now(default=None))
 
 
+@method_decorator(allow_frame_if_namespaced, 'dispatch')
+class CartExtendReservation(EventViewMixin, CartActionMixin, AsyncAction, View):
+    task = extend_cart_reservation
+    known_errortypes = ['CartError']
+
+    def get_success_message(self, value):
+        if value > 0:
+            return _('Your cart timeout was extended.')
+
+    def post(self, request, *args, **kwargs):
+        return self.do(self.request.event.id, get_or_create_cart_id(self.request), translation.get_language(),
+                       request.sales_channel.identifier, time_machine_now(default=None))
+
+
 @method_decorator(allow_cors_if_namespaced, 'dispatch')
 @method_decorator(allow_frame_if_namespaced, 'dispatch')
 @method_decorator(iframe_entry_view_wrapper, 'dispatch')

src/pretix/static/pretixpresale/js/ui/cart.js

@@ -55,6 +55,7 @@ var cart = {
                 pad(diff_minutes.toString(), 2) + ':' + pad(diff_seconds.toString(), 2)
             );
         }
+        $("#cart-extend-button").toggle(diff_minutes < 3);
     },
 
     init: function () {