Time machine mode [Z#23129725] (#3961)

Allows organizers to test their shop as if it were a different date and time.

Implemented using a time_machine_now() function which is used instead of regular now(), which can overlay the real date time with a value from a ContextVar, assigned from a session value in EventMiddleware.

For more information, see doc/development/implementation/timemachine.rst

---------

Co-authored-by: Richard Schreiber <schreiber@rami.io>
Co-authored-by: Raphael Michel <michel@rami.io>

src/pretix/base/forms/questions.py

@@ -57,7 +57,7 @@ from django.forms.widgets import FILE_INPUT_CONTRADICTION
 from django.utils.formats import date_format
 from django.utils.html import escape
 from django.utils.safestring import mark_safe
-from django.utils.timezone import get_current_timezone, now
+from django.utils.timezone import get_current_timezone
 from django.utils.translation import gettext_lazy as _, pgettext_lazy
 from django_countries import countries
 from django_countries.fields import Country, CountryField
@@ -86,6 +86,7 @@ from pretix.base.settings import (
     PERSON_NAME_SCHEMES, PERSON_NAME_TITLE_GROUPS,
 )
 from pretix.base.templatetags.rich_text import rich_text
+from pretix.base.timemachine import time_machine_now
 from pretix.control.forms import (
     ExtFileField, ExtValidationMixin, SizeValidationMixin, SplitDateTimeField,
 )
@@ -606,13 +607,13 @@ class BaseQuestionsForm(forms.Form):
 
         if cartpos and item.validity_mode == Item.VALIDITY_MODE_DYNAMIC and item.validity_dynamic_start_choice:
             if item.validity_dynamic_start_choice_day_limit:
-                max_date = now().astimezone(event.timezone) + timedelta(days=item.validity_dynamic_start_choice_day_limit)
+                max_date = time_machine_now().astimezone(event.timezone) + timedelta(days=item.validity_dynamic_start_choice_day_limit)
             else:
                 max_date = None
-            min_date = now()
+            min_date = time_machine_now()
             initial = None
             if (item.require_membership or (pos.variation and pos.variation.require_membership)) and pos.used_membership:
-                if pos.used_membership.date_start >= now():
+                if pos.used_membership.date_start >= time_machine_now():
                     initial = min_date = pos.used_membership.date_start
                 max_date = min(max_date, pos.used_membership.date_end) if max_date else pos.used_membership.date_end
             if item.validity_dynamic_duration_months or item.validity_dynamic_duration_days:

src/pretix/base/models/event.py

@@ -68,6 +68,7 @@ from i18nfield.fields import I18nCharField, I18nTextField
 from pretix.base.models.base import LoggedModel
 from pretix.base.models.fields import MultiStringField
 from pretix.base.reldate import RelativeDateWrapper
+from pretix.base.timemachine import time_machine_now
 from pretix.base.validators import EventSlugBanlistValidator
 from pretix.helpers.database import GroupConcat
 from pretix.helpers.daterange import daterange
@@ -235,7 +236,7 @@ class EventMixin:
         if not self.settings.waiting_list_enabled:
             return False
         if self.settings.waiting_list_auto_disable:
-            return self.settings.waiting_list_auto_disable.datetime(self) > now()
+            return self.settings.waiting_list_auto_disable.datetime(self) > time_machine_now()
         return True
 
     @property
@@ -244,11 +245,11 @@ class EventMixin:
         Is true, when ``presale_end`` is set and in the past.
         """
         if self.effective_presale_end:
-            return now() > self.effective_presale_end
+            return time_machine_now() > self.effective_presale_end
         elif self.date_to:
-            return now() > self.date_to
+            return time_machine_now() > self.date_to
         else:
-            return now().astimezone(self.timezone).date() > self.date_from.astimezone(self.timezone).date()
+            return time_machine_now().astimezone(self.timezone).date() > self.date_from.astimezone(self.timezone).date()
 
     @property
     def effective_presale_start(self):
@@ -268,7 +269,7 @@ class EventMixin:
         Is true, when ``presale_end`` is not set or in the future and ``presale_start`` is not
         set or in the past.
         """
-        if self.effective_presale_start and now() < self.effective_presale_start:
+        if self.effective_presale_start and time_machine_now() < self.effective_presale_start:
             return False
         return not self.presale_has_ended
 
@@ -316,11 +317,11 @@ class EventMixin:
         q_variation = (
             Q(active=True)
             & Q(sales_channels__contains=channel)
-            & Q(Q(available_from__isnull=True) | Q(available_from__lte=now()))
-            & Q(Q(available_until__isnull=True) | Q(available_until__gte=now()))
+            & Q(Q(available_from__isnull=True) | Q(available_from__lte=time_machine_now()))
+            & Q(Q(available_until__isnull=True) | Q(available_until__gte=time_machine_now()))
             & Q(item__active=True)
-            & Q(Q(item__available_from__isnull=True) | Q(item__available_from__lte=now()))
-            & Q(Q(item__available_until__isnull=True) | Q(item__available_until__gte=now()))
+            & Q(Q(item__available_from__isnull=True) | Q(item__available_from__lte=time_machine_now()))
+            & Q(Q(item__available_until__isnull=True) | Q(item__available_until__gte=time_machine_now()))
             & Q(Q(item__category__isnull=True) | Q(item__category__is_addon=False))
             & Q(item__sales_channels__contains=channel)
             & Q(item__require_bundling=False)
@@ -695,7 +696,7 @@ class Event(EventMixin, LoggedModel):
     @property
     def presale_has_ended(self):
         if self.has_subevents:
-            return self.presale_end and now() > self.presale_end
+            return self.presale_end and time_machine_now() > self.presale_end
         else:
             return super().presale_has_ended
 
@@ -1188,8 +1189,8 @@ class Event(EventMixin, LoggedModel):
             )
         ).filter(
             Q(active=True) & Q(is_public=True) & (
-                Q(Q(date_to__isnull=True) & Q(date_from__gte=now() - timedelta(hours=24)))
-                | Q(date_to__gte=now() - timedelta(hours=24))
+                Q(Q(date_to__isnull=True) & Q(date_from__gte=time_machine_now() - timedelta(hours=24)))
+                | Q(date_to__gte=time_machine_now() - timedelta(hours=24))
             )
         )  # order_by doesn't make sense with I18nField
         if ordering in ("date_ascending", "date_descending"):
@@ -1509,7 +1510,7 @@ class SubEvent(EventMixin, LoggedModel):
             disabled_items=Coalesce(
                 Subquery(
                     SubEventItem.objects.filter(
-                        Q(disabled=True) | Q(available_from__gt=now()) | Q(available_until__lt=now()),
+                        Q(disabled=True) | Q(available_from__gt=time_machine_now()) | Q(available_until__lt=time_machine_now()),
                         subevent=OuterRef('pk'),
                     ).order_by().values('subevent').annotate(items=GroupConcat('item_id', delimiter=',')).values('items'),
                     output_field=models.TextField(),
@@ -1520,7 +1521,7 @@ class SubEvent(EventMixin, LoggedModel):
             disabled_vars=Coalesce(
                 Subquery(
                     SubEventItemVariation.objects.filter(
-                        Q(disabled=True) | Q(available_from__gt=now()) | Q(available_until__lt=now()),
+                        Q(disabled=True) | Q(available_from__gt=time_machine_now()) | Q(available_until__lt=time_machine_now()),
                         subevent=OuterRef('pk'),
                     ).order_by().values('subevent').annotate(items=GroupConcat('variation_id', delimiter=',')).values('items'),
                     output_field=models.TextField(),

src/pretix/base/models/items.py

@@ -55,7 +55,7 @@ from django.db.models import Q
 from django.utils import formats
 from django.utils.crypto import get_random_string
 from django.utils.functional import cached_property
-from django.utils.timezone import is_naive, make_aware, now
+from django.utils.timezone import is_naive, make_aware
 from django.utils.translation import gettext_lazy as _, pgettext_lazy
 from django_countries.fields import Country
 from django_scopes import ScopedManager
@@ -65,6 +65,7 @@ from pretix.base.models import fields
 from pretix.base.models.base import LoggedModel
 from pretix.base.models.fields import MultiStringField
 from pretix.base.models.tax import TaxedPrice
+from pretix.base.timemachine import time_machine_now
 
 from ...helpers.images import ImageSizeValidator
 from ..media import MEDIA_TYPES
@@ -192,7 +193,7 @@ class SubEventItem(models.Model):
             self.subevent.event.cache.clear()
 
     def is_available(self, now_dt: datetime=None) -> bool:
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         if self.disabled:
             return False
         if self.available_from and self.available_from > now_dt:
@@ -248,7 +249,7 @@ class SubEventItemVariation(models.Model):
             self.subevent.event.cache.clear()
 
     def is_available(self, now_dt: datetime=None) -> bool:
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         if self.disabled:
             return False
         if self.available_from and self.available_from > now_dt:
@@ -263,8 +264,8 @@ def filter_available(qs, channel='web', voucher=None, allow_addons=False):
         # IMPORTANT: If this is updated, also update the ItemVariation query
         # in models/event.py: EventMixin.annotated()
         Q(active=True)
-        & Q(Q(available_from__isnull=True) | Q(available_from__lte=now()) | Q(available_from_mode='info'))
-        & Q(Q(available_until__isnull=True) | Q(available_until__gte=now()) | Q(available_until_mode='info'))
+        & Q(Q(available_from__isnull=True) | Q(available_from__lte=time_machine_now()) | Q(available_from_mode='info'))
+        & Q(Q(available_until__isnull=True) | Q(available_until__gte=time_machine_now()) | Q(available_until_mode='info'))
         & Q(sales_channels__contains=channel) & Q(require_bundling=False)
     )
     if not allow_addons:
@@ -782,7 +783,7 @@ class Item(LoggedModel):
         return t
 
     def is_available_by_time(self, now_dt: datetime=None) -> bool:
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         if self.available_from and self.available_from > now_dt:
             return False
         if self.available_until and self.available_until < now_dt:
@@ -794,13 +795,13 @@ class Item(LoggedModel):
         Returns whether this item is available according to its ``active`` flag
         and its ``available_from`` and ``available_until`` fields
         """
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         if not self.active or not self.is_available_by_time(now_dt):
             return False
         return True
 
     def unavailability_reason(self, now_dt: datetime=None, has_voucher=False, subevent=None) -> Optional[str]:
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         subevent_item = subevent and subevent.item_overrides.get(self.pk)
         if not self.active:
             return 'active'
@@ -957,11 +958,11 @@ class Item(LoggedModel):
             return self.validity_fixed_from, self.validity_fixed_until
         elif self.validity_mode == Item.VALIDITY_MODE_DYNAMIC:
             tz = override_tz or self.event.timezone
-            requested_start = requested_start or now()
+            requested_start = requested_start or time_machine_now()
             if enforce_start_limit and not self.validity_dynamic_start_choice:
-                requested_start = now()
+                requested_start = time_machine_now()
             if enforce_start_limit and self.validity_dynamic_start_choice_day_limit is not None:
-                requested_start = min(requested_start, now() + timedelta(days=self.validity_dynamic_start_choice_day_limit))
+                requested_start = min(requested_start, time_machine_now() + timedelta(days=self.validity_dynamic_start_choice_day_limit))
 
             valid_until = requested_start.astimezone(tz)
 
@@ -1290,7 +1291,7 @@ class ItemVariation(models.Model):
         return ItemVariation.objects.filter(item=self.item).count() == 1
 
     def is_available_by_time(self, now_dt: datetime=None) -> bool:
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         if self.available_from and self.available_from > now_dt:
             return False
         if self.available_until and self.available_until < now_dt:
@@ -1302,13 +1303,13 @@ class ItemVariation(models.Model):
         Returns whether this item is available according to its ``active`` flag
         and its ``available_from`` and ``available_until`` fields
         """
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         if not self.active or not self.is_available_by_time(now_dt):
             return False
         return True
 
     def unavailability_reason(self, now_dt: datetime=None, has_voucher=False, subevent=None) -> Optional[str]:
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         subevent_var = subevent and subevent.var_overrides.get(self.pk)
         if not self.active:
             return 'active'

src/pretix/base/models/memberships.py

@@ -23,7 +23,6 @@ from django.db import models
 from django.db.models import Count, OuterRef, Subquery, Value
 from django.db.models.functions import Coalesce
 from django.utils.formats import date_format
-from django.utils.timezone import now
 from django.utils.translation import gettext_lazy as _
 from django_scopes import ScopedManager, scopes_disabled
 from i18nfield.fields import I18nCharField
@@ -31,6 +30,7 @@ from i18nfield.fields import I18nCharField
 from pretix.base.models import Customer
 from pretix.base.models.base import LoggedModel
 from pretix.base.models.organizer import Organizer
+from pretix.base.timemachine import time_machine_now
 from pretix.helpers.names import build_name
 
 
@@ -165,13 +165,13 @@ class Membership(models.Model):
 
     def is_valid(self, ev=None, ticket_valid_from=None, valid_from_not_chosen=False):
         if valid_from_not_chosen:
-            return not self.canceled and self.date_end >= now()
+            return not self.canceled and self.date_end >= time_machine_now()
         elif ticket_valid_from:
             dt = ticket_valid_from
         elif ev:
             dt = ev.date_from
         else:
-            dt = now()
+            dt = time_machine_now()
 
         return not self.canceled and dt >= self.date_start and dt <= self.date_end
 

src/pretix/base/models/orders.py

@@ -80,6 +80,7 @@ from pretix.base.models import Customer, User
 from pretix.base.reldate import RelativeDateWrapper
 from pretix.base.settings import PERSON_NAME_SCHEMES
 from pretix.base.signals import allow_ticket_download, order_gracefully_delete
+from pretix.base.timemachine import time_machine_now
 
 from ...helpers import OF_SELF
 from ...helpers.countries import CachedCountries, FastCountryField
@@ -681,7 +682,7 @@ class Order(LockModel, LoggedModel):
         for op in positions:
             if op.issued_gift_cards.all():
                 return False
-        if self.user_change_deadline and now() > self.user_change_deadline:
+        if self.user_change_deadline and time_machine_now() > self.user_change_deadline:
             return False
 
         return (
@@ -713,7 +714,7 @@ class Order(LockModel, LoggedModel):
                     return False
             if op.granted_memberships.with_usages().filter(usages__gt=0):
                 return False
-        if self.user_cancel_deadline and now() > self.user_cancel_deadline:
+        if self.user_cancel_deadline and time_machine_now() > self.user_cancel_deadline:
             return False
 
         if self.status == Order.STATUS_PAID:
@@ -854,7 +855,7 @@ class Order(LockModel, LoggedModel):
             return False
 
         modify_deadline = self.modify_deadline
-        if modify_deadline is not None and now() > modify_deadline:
+        if modify_deadline is not None and time_machine_now() > modify_deadline:
             return False
 
         positions = list(
@@ -906,7 +907,7 @@ class Order(LockModel, LoggedModel):
         return self.event.settings.ticket_download and (
             self.event.settings.ticket_download_date is None
             or self.ticket_download_date is None
-            or now() > self.ticket_download_date
+            or time_machine_now() > self.ticket_download_date
         ) and (
             self.status == Order.STATUS_PAID
             or (
@@ -978,7 +979,7 @@ class Order(LockModel, LoggedModel):
                 return error_messages['require_approval']
             term_last = self.payment_term_last
             if term_last and not ignore_date:
-                if now() > term_last:
+                if time_machine_now() > term_last:
                     return error_messages['late_lastdate']
 
         if self.status == self.STATUS_PENDING:
@@ -1001,7 +1002,7 @@ class Order(LockModel, LoggedModel):
             'voucher_budget': _('The voucher "{voucher}" no longer has sufficient budget.'),
             'voucher_usages': _('The voucher "{voucher}" has been used in the meantime.'),
         }
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         positions = list(self.positions.all().select_related('item', 'variation', 'seat', 'voucher'))
         quota_cache = {}
         v_budget = {}
@@ -2575,9 +2576,9 @@ class OrderPosition(AbstractPosition):
             if cartpos.item.validity_mode:
                 valid_from, valid_until = cartpos.item.compute_validity(
                     requested_start=(
-                        max(cartpos.requested_valid_from, now())
+                        max(cartpos.requested_valid_from, time_machine_now())
                         if cartpos.requested_valid_from and cartpos.item.validity_dynamic_start_choice
-                        else now()
+                        else time_machine_now()
                     ),
                     enforce_start_limit=True,
                     override_tz=order.event.timezone,
@@ -3103,9 +3104,9 @@ class CartPosition(AbstractPosition):
     def predicted_validity(self):
         return self.item.compute_validity(
             requested_start=(
-                max(self.requested_valid_from, now())
+                max(self.requested_valid_from, time_machine_now())
                 if self.requested_valid_from and self.item.validity_dynamic_start_choice
-                else now()
+                else time_machine_now()
             ),
             override_tz=self.event.timezone,
         )

src/pretix/base/payment.py

@@ -67,6 +67,7 @@ from pretix.base.settings import SettingsSandbox
 from pretix.base.signals import register_payment_providers
 from pretix.base.templatetags.money import money_filter
 from pretix.base.templatetags.rich_text import rich_text
+from pretix.base.timemachine import time_machine_now
 from pretix.helpers import OF_SELF
 from pretix.helpers.countries import CachedCountries
 from pretix.helpers.format import format_map
@@ -1441,7 +1442,7 @@ class GiftCardPayment(BasePaymentProvider):
             if not gc.testmode and self.event.testmode:
                 messages.error(request, _("Only test gift cards can be used in test mode."))
                 return
-            if gc.expires and gc.expires < now():
+            if gc.expires and gc.expires < time_machine_now():
                 messages.error(request, _("This gift card is no longer valid."))
                 return
             if gc.value <= Decimal("0.00"):
@@ -1491,7 +1492,7 @@ class GiftCardPayment(BasePaymentProvider):
             if not gc.testmode and payment.order.testmode:
                 messages.error(request, _("Only test gift cards can be used in test mode."))
                 return
-            if gc.expires and gc.expires < now():
+            if gc.expires and gc.expires < time_machine_now():
                 messages.error(request, _("This gift card is no longer valid."))
                 return
             if gc.value <= Decimal("0.00"):
@@ -1539,7 +1540,7 @@ class GiftCardPayment(BasePaymentProvider):
                     raise PaymentException(_("This gift card can only be used in test mode."))
                 if not gc.testmode and payment.order.testmode:
                     raise PaymentException(_("Only test gift cards can be used in test mode."))
-                if gc.expires and gc.expires < now():
+                if gc.expires and gc.expires < time_machine_now():
                     raise PaymentException(_("This gift card is no longer valid."))
 
                 trans = gc.transactions.create(

src/pretix/base/services/cart.py

@@ -74,6 +74,7 @@ from pretix.base.services.tasks import ProfiledEventTask
 from pretix.base.settings import PERSON_NAME_SCHEMES, LazyI18nStringList
 from pretix.base.signals import validate_cart_addons
 from pretix.base.templatetags.rich_text import rich_text
+from pretix.base.timemachine import time_machine_now, time_machine_now_assigned
 from pretix.celery_app import app
 from pretix.presale.signals import (
     checkout_confirm_messages, fee_calculation_for_cart,
@@ -278,7 +279,7 @@ class CartManager:
                  sales_channel='web'):
         self.event = event
         self.cart_id = cart_id
-        self.now_dt = now()
+        self.real_now_dt = now()
         self._operations = []
         self._quota_diff = Counter()
         self._voucher_use_diff = Counter()
@@ -305,10 +306,10 @@ class CartManager:
         return self._seated_cache[item, subevent]
 
     def _calculate_expiry(self):
-        self._expiry = self.now_dt + timedelta(minutes=self.event.settings.get('reservation_time', as_type=int))
+        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 self.now_dt < self.event.presale_start:
+        if self.event.presale_start and time_machine_now(self.real_now_dt) < self.event.presale_start:
             raise CartError(error_messages['not_started'])
         if self.event.presale_has_ended:
             raise CartError(error_messages['ended'])
@@ -319,13 +320,13 @@ class CartManager:
                     tlv.datetime(self.event).date(),
                     time(hour=23, minute=59, second=59)
                 ), self.event.timezone)
-                if term_last < self.now_dt:
+                if term_last < time_machine_now(self.real_now_dt):
                     raise CartError(error_messages['payment_ended'])
 
     def _extend_expiry_of_valid_existing_positions(self):
         # 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.now_dt).update(expires=self._expiry)
+        self.positions.filter(expires__gt=self.real_now_dt).update(expires=self._expiry)
 
     def _delete_out_of_timeframe(self):
         err = None
@@ -333,12 +334,12 @@ class CartManager:
             if not cp.pk:
                 continue
 
-            if cp.subevent and cp.subevent.presale_start and self.now_dt < cp.subevent.presale_start:
+            if cp.subevent and cp.subevent.presale_start and time_machine_now(self.real_now_dt) < cp.subevent.presale_start:
                 err = error_messages['some_subevent_not_started']
                 cp.addons.all().delete()
                 cp.delete()
 
-            if cp.subevent and cp.subevent.presale_end and self.now_dt > cp.subevent.presale_end:
+            if cp.subevent and cp.subevent.presale_end and time_machine_now(self.real_now_dt) > cp.subevent.presale_end:
                 err = error_messages['some_subevent_ended']
                 cp.addons.all().delete()
                 cp.delete()
@@ -350,7 +351,7 @@ class CartManager:
                         tlv.datetime(cp.subevent).date(),
                         time(hour=23, minute=59, second=59)
                     ), self.event.timezone)
-                    if term_last < self.now_dt:
+                    if term_last < time_machine_now(self.real_now_dt):
                         err = error_messages['some_subevent_ended']
                         cp.addons.all().delete()
                         cp.delete()
@@ -449,7 +450,7 @@ class CartManager:
             if op.subevent and not op.subevent.active:
                 raise CartError(error_messages['inactive_subevent'])
 
-            if op.subevent and op.subevent.presale_start and self.now_dt < op.subevent.presale_start:
+            if op.subevent and op.subevent.presale_start and time_machine_now(self.real_now_dt) < op.subevent.presale_start:
                 raise CartError(error_messages['not_started'])
 
             if op.subevent and op.subevent.presale_has_ended:
@@ -472,7 +473,7 @@ class CartManager:
                         tlv.datetime(op.subevent).date(),
                         time(hour=23, minute=59, second=59)
                     ), self.event.timezone)
-                    if term_last < self.now_dt:
+                    if term_last < time_machine_now(self.real_now_dt):
                         raise CartError(error_messages['payment_ended'])
 
         if isinstance(op, self.AddOperation):
@@ -509,7 +510,7 @@ class CartManager:
         )
         if not self.event.settings.seating_choice:
             requires_seat = Value(0, output_field=IntegerField())
-        expired = self.positions.filter(expires__lte=self.now_dt).select_related(
+        expired = self.positions.filter(expires__lte=self.real_now_dt).select_related(
             'item', 'variation', 'voucher', 'addon_to', 'addon_to__item'
         ).annotate(
             requires_seat=requires_seat
@@ -690,7 +691,7 @@ class CartManager:
                         # than either of the possible default assumptions.
                         predicted_redeemed_after = (
                             voucher.redeemed +
-                            CartPosition.objects.filter(voucher=voucher, expires__gte=self.now_dt).count() +
+                            CartPosition.objects.filter(voucher=voucher, expires__gte=self.real_now_dt).count() +
                             self._voucher_use_diff[voucher] +
                             voucher_use_diff[voucher]
                         )
@@ -982,7 +983,7 @@ class CartManager:
                 current_num = len(current_addons[cp].get(k, []))
                 if input_num < current_num:
                     for a in current_addons[cp][k][:current_num - input_num]:
-                        if a.expires > self.now_dt:
+                        if a.expires > self.real_now_dt:
                             quotas = list(a.quotas)
 
                             for quota in quotas:
@@ -996,7 +997,7 @@ class CartManager:
 
     def _get_voucher_availability(self):
         vouchers_ok, self._voucher_depend_on_cart = _get_voucher_availability(
-            self.event, self._voucher_use_diff, self.now_dt,
+            self.event, self._voucher_use_diff, self.real_now_dt,
             exclude_position_ids=[
                 op.position.id for op in self._operations if isinstance(op, self.ExtendOperation)
             ]
@@ -1101,7 +1102,7 @@ class CartManager:
                 shared_lock_objects=[self.event]
             )
         vouchers_ok = self._get_voucher_availability()
-        quotas_ok = _get_quota_availability(self._quota_diff, self.now_dt)
+        quotas_ok = _get_quota_availability(self._quota_diff, self.real_now_dt)
         err = None
         new_cart_positions = []
         deleted_positions = set()
@@ -1118,7 +1119,7 @@ class CartManager:
 
         for iop, op in enumerate(self._operations):
             if isinstance(op, self.RemoveOperation):
-                if op.position.expires > self.now_dt:
+                if op.position.expires > self.real_now_dt:
                     for q in op.position.quotas:
                         quotas_ok[q] += 1
                 addons = op.position.addons.all()
@@ -1395,7 +1396,7 @@ class CartManager:
         err = self.extend_expired_positions() or err
         err = err or self._check_min_per_voucher()
 
-        self.now_dt = now()
+        self.real_now_dt = now()
 
         self._extend_expiry_of_valid_existing_positions()
         err = self._perform_operations() or err
@@ -1487,7 +1488,7 @@ def get_fees(event, request, total, invoice_address, payments, positions):
 
 @app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(CartError,))
 def add_items_to_cart(self, event: int, items: List[dict], cart_id: str=None, locale='en',
-                      invoice_address: int=None, widget_data=None, sales_channel='web') -> None:
+                      invoice_address: int=None, widget_data=None, sales_channel='web', override_now_dt: datetime=None) -> None:
     """
     Adds a list of items to a user's cart.
     :param event: The event ID in question
@@ -1495,7 +1496,7 @@ def add_items_to_cart(self, event: int, items: List[dict], cart_id: str=None, lo
     :param cart_id: Session ID of a guest
     :raises CartError: On any error that occurred
     """
-    with language(locale):
+    with language(locale), time_machine_now_assigned(override_now_dt):
         ia = False
         if invoice_address:
             try:
@@ -1517,14 +1518,14 @@ def add_items_to_cart(self, event: int, items: List[dict], cart_id: str=None, lo
 
 
 @app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(CartError,))
-def apply_voucher(self, event: Event, voucher: str, cart_id: str=None, locale='en', sales_channel='web') -> None:
+def apply_voucher(self, event: Event, voucher: str, cart_id: str=None, locale='en', sales_channel='web', override_now_dt: datetime=None) -> None:
     """
     Removes a list of items from a user's cart.
     :param event: The event ID in question
     :param voucher: A voucher code
     :param session: Session ID of a guest
     """
-    with language(locale):
+    with language(locale), time_machine_now_assigned(override_now_dt):
         try:
             try:
                 cm = CartManager(event=event, cart_id=cart_id, sales_channel=sales_channel)
@@ -1537,14 +1538,14 @@ def apply_voucher(self, event: Event, voucher: str, cart_id: str=None, locale='e
 
 
 @app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(CartError,))
-def remove_cart_position(self, event: Event, position: int, cart_id: str=None, locale='en', sales_channel='web') -> None:
+def remove_cart_position(self, event: Event, position: int, cart_id: str=None, locale='en', sales_channel='web', override_now_dt: datetime=None) -> None:
     """
     Removes a list of items from a user's cart.
     :param event: The event ID in question
     :param position: A cart position ID
     :param session: Session ID of a guest
     """
-    with language(locale):
+    with language(locale), time_machine_now_assigned(override_now_dt):
         try:
             try:
                 cm = CartManager(event=event, cart_id=cart_id, sales_channel=sales_channel)
@@ -1557,13 +1558,13 @@ def remove_cart_position(self, event: Event, position: int, cart_id: str=None, l
 
 
 @app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(CartError,))
-def clear_cart(self, event: Event, cart_id: str=None, locale='en', sales_channel='web') -> None:
+def clear_cart(self, event: Event, cart_id: str=None, locale='en', sales_channel='web', override_now_dt: datetime=None) -> None:
     """
     Removes a list of items from a user's cart.
     :param event: The event ID in question
     :param session: Session ID of a guest
     """
-    with language(locale):
+    with language(locale), time_machine_now_assigned(override_now_dt):
         try:
             try:
                 cm = CartManager(event=event, cart_id=cart_id, sales_channel=sales_channel)
@@ -1577,14 +1578,14 @@ def clear_cart(self, event: Event, cart_id: str=None, locale='en', sales_channel
 
 @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], cart_id: str=None, locale='en',
-                    invoice_address: int=None, sales_channel='web') -> None:
+                    invoice_address: int=None, sales_channel='web', override_now_dt: datetime=None) -> None:
     """
     Removes a list of items from a user's cart.
     :param event: The event ID in question
     :param addons: A list of dicts with the keys addon_to, item, variation
     :param session: Session ID of a guest
     """
-    with language(locale):
+    with language(locale), time_machine_now_assigned(override_now_dt):
         ia = False
         if invoice_address:
             try:

src/pretix/base/services/memberships.py

@@ -25,13 +25,13 @@ from typing import List, Optional
 from dateutil.relativedelta import relativedelta
 from django.core.exceptions import ValidationError
 from django.utils.formats import date_format
-from django.utils.timezone import now
 from django.utils.translation import gettext_lazy as _
 
 from pretix.base.models import (
     AbstractPosition, CartPosition, Customer, Event, Item, Membership, Order,
     OrderPosition, SubEvent,
 )
+from pretix.base.timemachine import time_machine_now
 from pretix.helpers import OF_SELF
 
 
@@ -48,7 +48,7 @@ def membership_validity(item: Item, subevent: Optional[SubEvent], event: Event):
 
     else:
         # Always start at start of day
-        date_start = now().astimezone(tz).replace(hour=0, minute=0, second=0, microsecond=0)
+        date_start = time_machine_now().astimezone(tz).replace(hour=0, minute=0, second=0, microsecond=0)
         date_end = date_start
 
         if item.grant_membership_duration_months:

src/pretix/base/services/orders.py

@@ -102,6 +102,7 @@ from pretix.base.signals import (
     order_fee_calculation, order_paid, order_placed, order_reactivated,
     order_split, order_valid_if_pending, periodic_task, validate_order,
 )
+from pretix.base.timemachine import time_machine_now, time_machine_now_assigned
 from pretix.celery_app import app
 from pretix.helpers import OF_SELF
 from pretix.helpers.models import modelcopy
@@ -648,10 +649,11 @@ def _check_date(event: Event, now_dt: datetime):
                 raise OrderError(error_messages['ended'])
 
 
-def _check_positions(event: Event, now_dt: datetime, positions: List[CartPosition], address: InvoiceAddress=None,
+def _check_positions(event: Event, now_dt: datetime, time_machine_now_dt: datetime, positions: List[CartPosition],
+                     address: InvoiceAddress = None,
                      sales_channel='web', customer=None):
     err = None
-    _check_date(event, now_dt)
+    _check_date(event, time_machine_now_dt)
 
     products_seen = Counter()
     q_avail = Counter()
@@ -729,7 +731,7 @@ def _check_positions(event: Event, now_dt: datetime, positions: List[CartPositio
                 delete(cp)
                 continue
 
-        if cp.subevent and cp.subevent.presale_start and now_dt < cp.subevent.presale_start:
+        if cp.subevent and cp.subevent.presale_start and time_machine_now_dt < cp.subevent.presale_start:
             err = err or error_messages['some_subevent_not_started']
             delete(cp)
             break
@@ -741,7 +743,7 @@ def _check_positions(event: Event, now_dt: datetime, positions: List[CartPositio
                     tlv.datetime(cp.subevent).date(),
                     time(hour=23, minute=59, second=59)
                 ), event.timezone)
-                if term_last < now_dt:
+                if term_last < time_machine_now_dt:
                     err = err or error_messages['some_subevent_ended']
                     delete(cp)
                     break
@@ -787,19 +789,19 @@ def _check_positions(event: Event, now_dt: datetime, positions: List[CartPositio
             delete(cp)
             continue
 
-        if cp.subevent and cp.item.pk in cp.subevent.item_overrides and not cp.subevent.item_overrides[cp.item.pk].is_available(now_dt):
+        if cp.subevent and cp.item.pk in cp.subevent.item_overrides and not cp.subevent.item_overrides[cp.item.pk].is_available(time_machine_now_dt):
             err = err or error_messages['unavailable']
             delete(cp)
             continue
 
         if cp.subevent and cp.variation and cp.variation.pk in cp.subevent.var_overrides and \
-                not cp.subevent.var_overrides[cp.variation.pk].is_available(now_dt):
+                not cp.subevent.var_overrides[cp.variation.pk].is_available(time_machine_now_dt):
             err = err or error_messages['unavailable']
             delete(cp)
             continue
 
         if cp.voucher:
-            if cp.voucher.valid_until and cp.voucher.valid_until < now_dt:
+            if cp.voucher.valid_until and cp.voucher.valid_until < time_machine_now_dt:
                 err = err or error_messages['voucher_expired']
                 delete(cp)
                 continue
@@ -1163,7 +1165,8 @@ def _perform_order(event: Event, payment_requests: List[dict], position_ids: Lis
     warnings = []
     any_payment_failed = False
 
-    now_dt = now()
+    real_now_dt = now()
+    time_machine_now_dt = time_machine_now(real_now_dt)
     err_out = None
     with transaction.atomic(durable=True):
         positions = list(
@@ -1175,14 +1178,15 @@ def _perform_order(event: Event, payment_requests: List[dict], position_ids: Lis
         if len(position_ids) != len(positions):
             raise OrderError(error_messages['internal'])
         try:
-            _check_positions(event, now_dt, positions, address=addr, sales_channel=sales_channel, customer=customer)
+            _check_positions(event, real_now_dt, time_machine_now_dt, positions,
+                             address=addr, sales_channel=sales_channel, customer=customer)
         except OrderError as e:
             err_out = e  # Don't raise directly to make sure transaction is committed, as it might have deleted things
         else:
             if 'sleep-after-quota-check' in debugflags_var.get():
                 sleep(2)
 
-            order, payment_objs = _create_order(event, email, positions, now_dt, payment_requests,
+            order, payment_objs = _create_order(event, email, positions, real_now_dt, payment_requests,
                                                 locale=locale, address=addr, meta_info=meta_info, sales_channel=sales_channel,
                                                 shown_total=shown_total, customer=customer, valid_if_pending=valid_if_pending)
 
@@ -2849,8 +2853,8 @@ class OrderChangeManager:
 @app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(OrderError,))
 def perform_order(self, event: Event, payments: List[dict], positions: List[str],
                   email: str=None, locale: str=None, address: int=None, meta_info: dict=None,
-                  sales_channel: str='web', shown_total=None, customer=None):
-    with language(locale):
+                  sales_channel: str='web', shown_total=None, customer=None, override_now_dt: datetime=None):
+    with language(locale), time_machine_now_assigned(override_now_dt):
         try:
             try:
                 return _perform_order(event, payments, positions, email, locale, address, meta_info,

src/pretix/base/services/pricing.py

@@ -25,7 +25,6 @@ from typing import List, Optional, Tuple
 
 from django import forms
 from django.db.models import Q
-from django.utils.timezone import now
 
 from pretix.base.decimal import round_decimal
 from pretix.base.models import (
@@ -33,6 +32,7 @@ from pretix.base.models import (
 )
 from pretix.base.models.event import Event, SubEvent
 from pretix.base.models.tax import TAXED_ZERO, TaxedPrice, TaxRule
+from pretix.base.timemachine import time_machine_now
 
 
 def get_price(item: Item, variation: ItemVariation = None,
@@ -167,8 +167,8 @@ def apply_discounts(event: Event, sales_channel: str,
     new_prices = {}
 
     discount_qs = event.discounts.filter(
-        Q(available_from__isnull=True) | Q(available_from__lte=now()),
-        Q(available_until__isnull=True) | Q(available_until__gte=now()),
+        Q(available_from__isnull=True) | Q(available_from__lte=time_machine_now()),
+        Q(available_until__isnull=True) | Q(available_until__gte=time_machine_now()),
         sales_channels__contains=sales_channel,
         active=True,
     ).prefetch_related('condition_limit_products', 'benefit_limit_products').order_by('position', 'pk')

src/pretix/base/timemachine.py

@@ -0,0 +1,85 @@
+#
+# This file is part of pretix (Community Edition).
+#
+# Copyright (C) 2014-2020 Raphael Michel and contributors
+# Copyright (C) 2020-2021 rami.io GmbH and contributors
+#
+# This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General
+# Public License as published by the Free Software Foundation in version 3 of the License.
+#
+# ADDITIONAL TERMS APPLY: Pursuant to Section 7 of the GNU Affero General Public License, additional terms are
+# applicable granting you additional permissions and placing additional restrictions on your usage of this software.
+# Please refer to the pretix LICENSE file to obtain the full terms applicable to this work. If you did not receive
+# this file, see <https://pretix.eu/about/en/license>.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
+# <https://www.gnu.org/licenses/>.
+#
+import contextvars
+from contextlib import contextmanager
+
+from dateutil.parser import parse
+from django.utils.timezone import now
+
+timemachine_now_var = contextvars.ContextVar('timemachine_now', default=None)
+
+
+@contextmanager
+def time_machine_now_assigned_from_request(request):
+    if hasattr(request, 'event') and f'timemachine_now_dt:{request.event.pk}' in request.session and \
+            request.event.testmode and has_time_machine_permission(request, request.event):
+        request.now_dt = parse(request.session[f'timemachine_now_dt:{request.event.pk}'])
+        request.now_dt_is_fake = True
+    else:
+        request.now_dt = now()
+        request.now_dt_is_fake = False
+
+    try:
+        timemachine_now_var.set(request.now_dt if request.now_dt_is_fake else None)
+
+        yield
+    finally:
+        timemachine_now_var.set(None)
+
+
+def time_machine_now(default=False):
+    """
+    Return the datetime to use as current datetime for checking order restrictions in event
+    index and checkout flow.
+
+    :param default:   Value to return if time machine mode is disabled. By default the current datetime is used.
+    """
+    if default is False:
+        default = now()
+    return timemachine_now_var.get() or default
+
+
+@contextmanager
+def time_machine_now_assigned(now_dt):
+    """
+    Use this context manager to assign current datetime for time machine mode. Useful e.g. for background tasks.
+
+    :param now_dt: The datetime value to assign. May be `None` to disable time machine.
+    """
+    try:
+        timemachine_now_var.set(now_dt)
+        yield
+    finally:
+        timemachine_now_var.set(None)
+
+
+def has_time_machine_permission(request, event):
+    permission = 'can_change_event_settings'
+
+    return (
+        request.user.is_authenticated and
+        request.user.has_event_permission(request.organizer, request.event, permission, request=request)
+    ) or (
+        getattr(request, 'event_access_user', None) and
+        request.event_access_user.is_authenticated and
+        request.event_access_user.has_event_permission(request.organizer, request.event, permission, request=request)
+    )

src/pretix/control/context.py

@@ -46,11 +46,11 @@ from pretix.base.settings import GlobalSettingsObject
 from pretix.control.navigation import (
     get_event_navigation, get_global_navigation, get_organizer_navigation,
 )
-
-from ..helpers.i18n import (
+from pretix.helpers.i18n import (
     get_javascript_format, get_javascript_output_format, get_moment_locale,
 )
-from ..multidomain.urlreverse import get_event_domain
+from pretix.multidomain.urlreverse import get_event_domain
+
 from .signals import html_head, nav_topbar
 
 SessionStore = import_module(settings.SESSION_ENGINE).SessionStore
@@ -106,7 +106,7 @@ def _default_context(request):
         else:
             ctx['complain_testmode_orders'] = False
 
-        if not request.event.live and ctx['has_domain']:
+        if (request.event.testmode or not request.event.live) and ctx['has_domain']:
             child_sess = request.session.get('child_session_{}'.format(request.event.pk))
             s = SessionStore()
             if not child_sess or not s.exists(child_sess):
@@ -114,10 +114,8 @@ def _default_context(request):
                 s.create()
                 ctx['new_session'] = s.session_key
                 request.session['child_session_{}'.format(request.event.pk)] = s.session_key
-                request.session['event_access'] = True
             else:
                 ctx['new_session'] = child_sess
-                request.session['event_access'] = True
 
         if request.GET.get('subevent', ''):
             # Do not use .get() for lazy evaluation

src/pretix/control/templates/pretixcontrol/event/live.html

@@ -46,7 +46,7 @@
                             {% endfor %}
                         </ul>
                     </div>
-                    <div class="test-right">
+                    <div class="text-right">
                         <button type="submit" class="btn btn-primary btn-lg btn-save" disabled>
                             {% trans "Go live" %}
                         </button>
@@ -82,10 +82,10 @@
                     <p>
                         {% trans "Your shop is currently in test mode. All orders are not persistent and can be deleted at any point." %}
                     </p>
-                    <div class="form-inline">
-                        <label class="checkbox">
+                    <div class="checkbox">
+                        <label>
                             <input type="checkbox" name="delete" value="yes" />
-                            {% trans "Permanently delete all orders created in test mode" %}
+                            <b>{% trans "Permanently delete all orders created in test mode" %}</b>
                         </label>
                     </div>
                     <div class="text-right">

src/pretix/control/templates/pretixcontrol/event/transfer_session.html

@@ -0,0 +1,9 @@
+{% load eventurl %}
+{% load static %}
+<form action="{% eventurl request.event "presale:event.auth" %}{% if request.GET.next %}?next={{ request.GET.next }}{% endif %}" method="post">
+    <input type="hidden" value="{{ new_session }}" name="session">
+    <button type="submit">
+        Continue
+    </button>
+</form>
+<script src="{% static "pretixcontrol/js/send_form.js" %}"></script>

src/pretix/control/urls.py

@@ -247,6 +247,7 @@ urlpatterns = [
         re_path(r'^widgets.json$', dashboards.event_index_widgets_lazy, name='event.index.widgets'),
         re_path(r'^logs/embed$', dashboards.event_index_log_lazy, name='event.index.logs'),
         re_path(r'^live/$', event.EventLive.as_view(), name='event.live'),
+        re_path(r'^transfer_session/$', event.EventTransferSession.as_view(), name='event.transfer_session'),
         re_path(r'^logs/$', event.EventLog.as_view(), name='event.log'),
         re_path(r'^delete/$', event.EventDelete.as_view(), name='event.delete'),
         re_path(r'^comment/$', event.EventComment.as_view(),

src/pretix/control/views/event.py

@@ -1017,6 +1017,11 @@ class EventLive(EventPermissionRequiredMixin, TemplateView):
         })
 
 
+class EventTransferSession(EventPermissionRequiredMixin, TemplateView):
+    permission = 'can_change_event_settings'
+    template_name = 'pretixcontrol/event/transfer_session.html'
+
+
 class EventDelete(RecentAuthenticationRequiredMixin, EventPermissionRequiredMixin, FormView):
     permission = 'can_change_event_settings'
     template_name = 'pretixcontrol/event/delete.html'

src/pretix/multidomain/templatetags/eventurl.py

@@ -27,7 +27,7 @@ from django.urls import NoReverseMatch
 from django.utils.encoding import smart_str
 from django.utils.html import conditional_escape
 
-from pretix.multidomain.urlreverse import build_absolute_uri
+from pretix.multidomain.urlreverse import build_absolute_uri, mainreverse
 
 register = template.Library()
 
@@ -45,11 +45,13 @@ class EventURLNode(URLNode):
             for k, v in self.kwargs.items()
         }
         view_name = self.view_name.resolve(context)
-        event = self.event.resolve(context)
+        event = self.event.resolve(context) if self.event is not False else False
         url = ''
         try:
             if self.absolute:
                 url = build_absolute_uri(event, view_name, kwargs=kwargs)
+            elif self.event is False:
+                url = mainreverse(view_name, kwargs)
             else:
                 url = eventreverse(event, view_name, kwargs=kwargs)
         except NoReverseMatch:
@@ -65,21 +67,34 @@ class EventURLNode(URLNode):
             return url
 
 
-@register.tag
-def eventurl(parser, token, absolute=False):
+def multidomainurl(parser, token, has_event, absolute):
     """
-    Similar to {% url %} in the same way that eventreverse() is similar to reverse().
+    Similar to {% url %}, but multidomain-aware. Used by eventurl, abseventurl and absmainurl.
 
-    Takes an event or organizer object, an url name and optional keyword arguments
+    If has_event=True, takes an event or organizer object as first template tag parameter.
+    Always takes an url name and optional keyword arguments after that.
+
+    Returns an absolute URL in the following cases:
+    - absolute=True
+    - has_event=True and the event has a custom domain
+    Returns a relative URL otherwise.
     """
     bits = token.split_contents()
-    if len(bits) < 3:
-        raise TemplateSyntaxError("'%s' takes at least two arguments, an event and the name of a url()." % bits[0])
-    viewname = parser.compile_filter(bits[2])
-    event = parser.compile_filter(bits[1])
+    tagname = bits[0]
+    if has_event:
+        if len(bits) < 3:
+            raise TemplateSyntaxError("'%s' takes at least two arguments, an event and the name of a url()." % tagname)
+        viewname = parser.compile_filter(bits[2])
+        event = parser.compile_filter(bits[1])
+        bits = bits[3:]
+    else:
+        if len(bits) < 2:
+            raise TemplateSyntaxError("'%s' takes at least one arguments, the name of a url()." % tagname)
+        viewname = parser.compile_filter(bits[1])
+        event = False
+        bits = bits[2:]
     kwargs = {}
     asvar = None
-    bits = bits[3:]
     if len(bits) >= 2 and bits[-2] == 'as':
         asvar = bits[-1]
         bits = bits[:-2]
@@ -88,16 +103,26 @@ def eventurl(parser, token, absolute=False):
         for bit in bits:
             match = kwarg_re.match(bit)
             if not match:
-                raise TemplateSyntaxError("Malformed arguments to eventurl tag")
+                raise TemplateSyntaxError("Malformed arguments to %s tag" % tagname)
             name, value = match.groups()
             if name:
                 kwargs[name] = parser.compile_filter(value)
             else:
-                raise TemplateSyntaxError('Event urls only have keyword arguments.')
+                raise TemplateSyntaxError('Multidomain urls only have keyword arguments.')
 
     return EventURLNode(event, viewname, kwargs, asvar, absolute)
 
 
+@register.tag
+def eventurl(parser, token):
+    """
+    Similar to {% url %} in the same way that eventreverse() is similar to reverse().
+
+    Takes an event or organizer object, an url name and optional keyword arguments
+    """
+    return multidomainurl(parser, token, has_event=True, absolute=False)
+
+
 @register.tag
 def abseventurl(parser, token):
     """
@@ -105,4 +130,12 @@ def abseventurl(parser, token):
 
     Returns an absolute URL.
     """
-    return eventurl(parser, token, absolute=True)
+    return multidomainurl(parser, token, has_event=True, absolute=True)
+
+
+@register.tag
+def absmainurl(parser, token):
+    """
+    Like {% url %}, but always returns an absolute URL on the main domain.
+    """
+    return multidomainurl(parser, token, has_event=False, absolute=True)

src/pretix/multidomain/urlreverse.py

@@ -180,7 +180,7 @@ def build_absolute_uri(obj, urlname, kwargs=None):
     """
     Works similar to ``eventreverse`` but always returns an absolute URL.
 
-    :param obj: An ``Event`` or ``Organizer`` object
+    :param obj: An ``Event`` or ``Organizer`` object, or ``False`` to generate main domain URLs
     :param name: The name of the URL route
     :type name: str
     :param kwargs: A dictionary of additional keyword arguments that should be used. You do not
@@ -188,7 +188,10 @@ def build_absolute_uri(obj, urlname, kwargs=None):
         needed.
     :returns: An absolute URL (including scheme and host) as a string
     """
-    reversedurl = eventreverse(obj, urlname, kwargs)
+    if obj is False:
+        reversedurl = mainreverse(urlname, kwargs)
+    else:
+        reversedurl = eventreverse(obj, urlname, kwargs)
     if '://' in reversedurl:
         return reversedurl
     return urljoin(settings.SITE_URL, reversedurl)

src/pretix/presale/checkoutflow.py

@@ -73,6 +73,7 @@ from pretix.base.signals import validate_cart_addons
 from pretix.base.templatetags.money import money_filter
 from pretix.base.templatetags.phone_format import phone_format
 from pretix.base.templatetags.rich_text import rich_text_snippet
+from pretix.base.timemachine import time_machine_now
 from pretix.base.views.tasks import AsyncAction
 from pretix.celery_app import app
 from pretix.helpers.http import redirect_to_url
@@ -706,7 +707,7 @@ class AddOnsStep(CartMixin, AsyncAction, TemplateFlowStep):
 
         return self.do(self.request.event.id, data, get_or_create_cart_id(self.request),
                        invoice_address=self.invoice_address.pk, locale=get_language(),
-                       sales_channel=request.sales_channel.identifier)
+                       sales_channel=request.sales_channel.identifier, override_now_dt=time_machine_now(default=None))
 
 
 class QuestionsStep(QuestionsViewMixin, CartMixin, TemplateFlowStep):
@@ -1548,6 +1549,7 @@ class ConfirmStep(CartMixin, AsyncAction, TemplateFlowStep):
             sales_channel=request.sales_channel.identifier,
             shown_total=self.cart_session.get('shown_total'),
             customer=self.cart_session.get('customer'),
+            override_now_dt=time_machine_now(default=None),
         )
 
     def get_success_message(self, value):

src/pretix/presale/middleware.py

@@ -37,6 +37,7 @@ from django.urls import resolve
 from django_scopes import scope
 
 from pretix.base.channels import WebshopSalesChannel
+from pretix.base.timemachine import time_machine_now_assigned_from_request
 from pretix.presale.signals import process_response
 
 from .utils import _detect_event
@@ -68,7 +69,8 @@ class EventMiddleware:
             if redirect:
                 return redirect
 
-        with scope(organizer=getattr(request, 'organizer', None)):
+        with scope(organizer=getattr(request, 'organizer', None)), \
+             time_machine_now_assigned_from_request(request):
             response = self.get_response(request)
 
             if hasattr(request, '_namespace') and request._namespace == 'presale' and hasattr(request, 'event'):

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

@@ -111,9 +111,40 @@
     {% if request.event.testmode %}
         {% if request.sales_channel.testmode_supported %}
             <div class="alert alert-warning">
-                <p><strong><span class="sr-only">{% trans "Warning" context "alert-messages" %}:</span>
-                    {% trans "This ticket shop is currently in test mode. Please do not perform any real purchases as your order might be deleted without notice." %}
+                <p><strong>
+                    <span class="sr-only">{% trans "Warning" context "alert-messages" %}:</span>
+                    {% trans "This ticket shop is currently in test mode." %}
                 </strong></p>
+                <p>
+                    {% trans "Please do not perform any real purchases as your order might be deleted without notice." %}
+                </p>
+                {% if request.now_dt_is_fake %}
+                    <p>
+                        {% blocktrans trimmed with datetime=request.now_dt|date:"SHORT_DATETIME_FORMAT" %}
+                        You are currently using the time machine. The ticket shop is rendered as if it were {{ datetime }}.
+                        {% endblocktrans %}
+                        <a href="{% eventurl event "presale:event.timemachine" %}"><span class="fa fa-clock-o" aria-hidden="true"></span>{% trans "Change" %}</a>
+                    </p>
+                {% elif request.user.is_authenticated or request.event_access_user.is_authenticated %}
+                    <p>
+                        {% eventurl event "presale:event.timemachine" as time_machine_link %}
+                        {% blocktrans trimmed with time_machine_link=time_machine_link %}
+                            To view your shop at different points in time, you can enable
+                            <a href="{{ time_machine_link }}"><span class="fa fa-clock-o" aria-hidden="true"></span>time machine</a>.
+                        {% endblocktrans %}
+                    </p>
+                {% elif request.event_domain or request.organizer_domain %}
+                    <p>
+                        {% absmainurl "control:event.transfer_session" event=event.slug organizer=event.organizer.slug as transfer_session_link %}
+                        {% eventurl event "presale:event.timemachine" as time_machine_link %}
+                        {% with time_machine_link_encoded=time_machine_link|urlencode %}
+                            {% blocktrans trimmed with time_machine_link=transfer_session_link|add:"?next="|add:time_machine_link_encoded %}
+                                To view your shop at different points in time, you can enable
+                                <a href="{{ time_machine_link }}"><span class="fa fa-clock-o" aria-hidden="true"></span>time machine</a>.
+                            {% endblocktrans %}
+                        {% endwith %}
+                    </p>
+                {% endif %}
             </div>
         {% else %}
             <div class="alert alert-danger">
@@ -122,6 +153,8 @@
                 </strong></p>
             </div>
         {% endif %}
+
+
     {% endif %}
     {% if messages %}
         {% for message in messages %}
@@ -152,9 +185,13 @@
     {% if request.event.testmode %}
         {% if request.sales_channel.testmode_supported %}
             <div class="alert alert-testmode alert-warning">
-                <p><strong><span class="sr-only">{% trans "Warning" context "alert-messages" %}:</span>
-                    {% trans "This ticket shop is currently in test mode. Please do not perform any real purchases as your order might be deleted without notice." %}
+                <p><strong>
+                    <span class="sr-only">{% trans "Warning" context "alert-messages" %}:</span>
+                    {% trans "This ticket shop is currently in test mode." %}
                 </strong></p>
+                <p>
+                    {% trans "Please do not perform any real purchases as your order might be deleted without notice." %}
+                </p>
             </div>
         {% else %}
             <div class="alert alert-testmode alert-danger">

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

@@ -0,0 +1,47 @@
+{% extends "pretixpresale/event/base.html" %}
+{% load i18n %}
+{% load l10n %}
+{% load money %}
+{% load eventurl %}
+{% load eventsignal %}
+{% load thumb %}
+{% load rich_text %}
+{% load bootstrap3 %}
+{% block title %}{% trans "Time machine" %}{% endblock %}
+
+{% block content %}
+    <div class="panel {% if request.session.timemachine_now_dt %}panel-success{% else %}panel-default{% endif %}">
+        <div class="panel-heading">
+            {% trans "Time machine" %}
+        </div>
+        <div class="panel-body">
+            <form action="" method="post" class="">
+                {% csrf_token %}
+                {% bootstrap_form_errors timemachine_form "all" %}
+
+                <p>{% trans "Test your shop as if it were a different date and time." %}</p>
+
+                <div class="row">
+                    <div class="col-md-6">
+                        {% bootstrap_field timemachine_form.now_dt layout="inline" show_label=False  %}
+                    </div>
+                    <div class="col-md-6 text-right">
+                        <button type="submit" class="btn btn-primary btn-lg btn-save">
+                            {% if request.session.timemachine_now_dt %}{% trans "Change" %}{% else %}{% trans "Enable time machine" %}{% endif %}
+                        </button>
+                        {% if request.session.timemachine_now_dt %}
+                        <button form="disable_form" type="submit" class="btn btn-default btn-lg btn-save">
+                            {% trans "Disable" %}
+                        </button>
+                        {% endif %}
+                    </div>
+                </div>
+            </form>
+            <form action="" method="post" class="" id="disable_form">
+                {% csrf_token %}
+                <input type="hidden" name="timemachine_disable" value="true">
+            </form>
+            <div class="clear"></div>
+        </div>
+    </div>
+{% endblock %}

src/pretix/presale/urls.py

@@ -176,6 +176,8 @@ event_patterns = [
     re_path(r'^(?P<subevent>\d+)/widget/product_list$', pretix.presale.views.widget.WidgetAPIProductList.as_view(),
             name='event.widget.productlist'),
 
+    re_path(r'timemachine/$', pretix.presale.views.event.EventTimeMachine.as_view(), name='event.timemachine'),
+
     # Account management is done on org level, but we at least need a logout
     re_path(r'^account/logout$', pretix.presale.views.customer.LogoutView.as_view(), name='organizer.customer.logout'),
 ]

src/pretix/presale/utils.py

@@ -38,6 +38,9 @@ from importlib import import_module
 from urllib.parse import urljoin
 
 from django.conf import settings
+from django.contrib.auth import (
+    BACKEND_SESSION_KEY, SESSION_KEY, get_user_model, load_backend,
+)
 from django.db.models import Q
 from django.http import Http404, HttpResponseForbidden
 from django.middleware.csrf import rotate_token
@@ -52,6 +55,7 @@ from django_scopes import scope
 
 from pretix.base.middleware import LocaleMiddleware
 from pretix.base.models import Customer, Event, Organizer
+from pretix.base.timemachine import time_machine_now_assigned_from_request
 from pretix.helpers.http import redirect_to_url
 from pretix.multidomain.urlreverse import (
     get_event_domain, get_organizer_domain,
@@ -218,6 +222,17 @@ def customer_logout(request):
     request._cached_customer = None
 
 
+def _get_user_from_session_data(sessiondata):
+    if SESSION_KEY not in sessiondata:
+        return None
+    user_id = get_user_model()._meta.pk.to_python(sessiondata[SESSION_KEY])
+    backend_path = sessiondata[BACKEND_SESSION_KEY]
+    if backend_path in settings.AUTHENTICATION_BACKENDS:
+        backend = load_backend(backend_path)
+        user = backend.get_user(user_id)
+        return user
+
+
 @scope(organizer=None)
 def _detect_event(request, require_live=True, require_plugin=None):
 
@@ -303,14 +318,13 @@ def _detect_event(request, require_live=True, require_plugin=None):
             # Restrict locales to the ones available for this event
             LocaleMiddleware(NotImplementedError).process_request(request)
 
-            if require_live and not request.event.live:
+            if require_live and (request.event.testmode or not request.event.live):
                 can_access = (
                     url.url_name == 'event.auth'
                     or (
                         request.user.is_authenticated
                         and request.user.has_event_permission(request.organizer, request.event, request=request)
                     )
-
                 )
                 if not can_access and 'pretix_event_access_{}'.format(request.event.pk) in request.session:
                     sparent = SessionStore(request.session.get('pretix_event_access_{}'.format(request.event.pk)))
@@ -319,9 +333,12 @@ def _detect_event(request, require_live=True, require_plugin=None):
                     except:
                         pass
                     else:
-                        can_access = 'event_access' in parentdata
+                        user = _get_user_from_session_data(parentdata)
+                        if user and user.is_authenticated and user.has_event_permission(request.organizer, request.event, request=request):
+                            can_access = True
+                            request.event_access_user = user
 
-                if not can_access:
+                if not can_access and not request.event.live:
                     # Directly construct view instead of just calling `raise` since this case is so common that we
                     # don't want it to show in our log files.
                     template = loader.get_template("pretixpresale/event/offline.html")
@@ -393,7 +410,8 @@ def _event_view(function=None, require_live=True, require_plugin=None):
             if ret:
                 return ret
             else:
-                with scope(organizer=getattr(request, 'organizer', None)):
+                with scope(organizer=getattr(request, 'organizer', None)), \
+                     time_machine_now_assigned_from_request(request):
                     response = func(request=request, *args, **kwargs)
                     if getattr(request, 'event', None):
                         for receiver, r in process_response.send(request.event, request=request, response=response):

src/pretix/presale/views/cart.py

@@ -63,6 +63,7 @@ from pretix.base.services.cart import (
     CartError, add_items_to_cart, apply_voucher, clear_cart, error_messages,
     remove_cart_position,
 )
+from pretix.base.timemachine import time_machine_now
 from pretix.base.views.tasks import AsyncAction
 from pretix.helpers.http import redirect_to_url
 from pretix.multidomain.urlreverse import eventreverse
@@ -429,7 +430,8 @@ class CartApplyVoucher(EventViewMixin, CartActionMixin, AsyncAction, View):
     def post(self, request, *args, **kwargs):
         if 'voucher' in request.POST:
             return self.do(self.request.event.id, request.POST.get('voucher'), get_or_create_cart_id(self.request),
-                           translation.get_language(), request.sales_channel.identifier)
+                           translation.get_language(), request.sales_channel.identifier,
+                           time_machine_now(default=None))
         else:
             if 'ajax' in self.request.GET or 'ajax' in self.request.POST:
                 return JsonResponse({
@@ -455,7 +457,8 @@ class CartRemove(EventViewMixin, CartActionMixin, AsyncAction, View):
         if 'id' in request.POST:
             try:
                 return self.do(self.request.event.id, int(request.POST.get('id')), get_or_create_cart_id(self.request),
-                               translation.get_language(), request.sales_channel.identifier)
+                               translation.get_language(), request.sales_channel.identifier,
+                               time_machine_now(default=None))
             except ValueError:
                 return redirect_to_url(self.get_error_url())
         else:
@@ -478,7 +481,7 @@ class CartClear(EventViewMixin, CartActionMixin, AsyncAction, View):
 
     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)
+                       request.sales_channel.identifier, time_machine_now(default=None))
 
 
 @method_decorator(allow_cors_if_namespaced, 'dispatch')
@@ -534,7 +537,8 @@ class CartAdd(EventViewMixin, CartActionMixin, AsyncAction, View):
         items = self._items_from_post_data()
         if items:
             return self.do(self.request.event.id, items, cart_id, translation.get_language(),
-                           self.invoice_address.pk, widget_data, self.request.sales_channel.identifier)
+                           self.invoice_address.pk, widget_data, self.request.sales_channel.identifier,
+                           time_machine_now(default=None))
         else:
             if 'ajax' in self.request.GET or 'ajax' in self.request.POST:
                 return JsonResponse({

src/pretix/presale/views/event.py

@@ -42,24 +42,29 @@ from importlib import import_module
 from urllib.parse import urlencode
 
 import isoweek
+from dateutil import parser
+from django import forms
 from django.conf import settings
+from django.contrib import messages
 from django.core.exceptions import PermissionDenied
 from django.db.models import (
     Count, Exists, IntegerField, OuterRef, Prefetch, Q, Value,
 )
 from django.db.models.lookups import Exact
 from django.http import Http404, HttpResponse
-from django.shortcuts import get_object_or_404, render
+from django.shortcuts import get_object_or_404, redirect, render
 from django.utils.decorators import method_decorator
 from django.utils.formats import get_format
 from django.utils.functional import SimpleLazyObject
-from django.utils.timezone import now
+from django.utils.http import url_has_allowed_host_and_scheme
+from django.utils.timezone import get_current_timezone, now
 from django.utils.translation import gettext_lazy as _, pgettext_lazy
 from django.views import View
 from django.views.decorators.csrf import csrf_exempt
 from django.views.generic import TemplateView
 
 from pretix.base.channels import get_all_sales_channels
+from pretix.base.forms.widgets import SplitDateTimePickerWidget
 from pretix.base.models import (
     ItemVariation, Quota, SeatCategoryMapping, Voucher,
 )
@@ -69,7 +74,12 @@ from pretix.base.models.items import (
 )
 from pretix.base.services.placeholders import PlaceholderContext
 from pretix.base.services.quotas import QuotaAvailability
+from pretix.base.timemachine import has_time_machine_permission
 from pretix.helpers.compat import date_fromisocalendar
+from pretix.helpers.formats.en.formats import (
+    SHORT_MONTH_DAY_FORMAT, WEEK_FORMAT,
+)
+from pretix.helpers.http import redirect_to_url
 from pretix.multidomain.urlreverse import eventreverse
 from pretix.presale.ical import get_public_ical
 from pretix.presale.signals import item_description
@@ -78,8 +88,6 @@ from pretix.presale.views.organizer import (
     filter_qs_by_attr, has_before_after, weeks_for_template,
 )
 
-from ...helpers.formats.en.formats import SHORT_MONTH_DAY_FORMAT, WEEK_FORMAT
-from ...helpers.http import redirect_to_url
 from . import (
     CartMixin, EventViewMixin, allow_frame_if_namespaced, get_cart,
     iframe_entry_view_wrapper,
@@ -913,8 +921,58 @@ class EventAuth(View):
         except:
             raise PermissionDenied(_('Please go back and try again.'))
         else:
-            if 'event_access' not in parentdata:
+            if 'child_session_{}'.format(request.event.pk) not in parentdata:
                 raise PermissionDenied(_('Please go back and try again.'))
 
         request.session['pretix_event_access_{}'.format(request.event.pk)] = parent
-        return redirect_to_url(eventreverse(request.event, 'presale:event.index'))
+
+        if "next" in self.request.GET and url_has_allowed_host_and_scheme(
+                url=self.request.GET.get("next"), allowed_hosts=request.host, require_https=True):
+            return redirect_to_url(self.request.GET.get('next'))
+        else:
+            return redirect_to_url(eventreverse(request.event, 'presale:event.index'))
+
+
+class TimemachineForm(forms.Form):
+    now_dt = forms.SplitDateTimeField(
+        label=_('Fake date time'),
+        widget=SplitDateTimePickerWidget(),
+        initial=lambda: now().astimezone(get_current_timezone()),
+    )
+
+
+class EventTimeMachine(EventViewMixin, TemplateView):
+    template_name = 'pretixpresale/event/timemachine.html'
+
+    def setup(self, request, *args, **kwargs):
+        super().setup(request, *args, **kwargs)
+        if not has_time_machine_permission(request, request.event):
+            raise PermissionDenied(_('You are not allowed to access time machine mode.'))
+        if not request.event.testmode:
+            raise PermissionDenied(_('This feature is only available in test mode.'))
+        self.timemachine_form = TimemachineForm(
+            data=request.method == 'POST' and request.POST or None,
+            initial=(
+                {'now_dt': parser.parse(request.session.get(f'timemachine_now_dt:{request.event.pk}', None))}
+                if request.session.get(f'timemachine_now_dt:{request.event.pk}', None) else {}
+            )
+        )
+
+    def get_context_data(self, **kwargs):
+        ctx = super().get_context_data(**kwargs)
+        ctx['timemachine_form'] = self.timemachine_form
+        return ctx
+
+    def post(self, request, *args, **kwargs):
+        if request.POST.get("timemachine_disable"):
+            del request.session[f'timemachine_now_dt:{request.event.pk}']
+            messages.success(self.request, _('Time machine disabled!'))
+            return redirect(self.get_success_url())
+        elif self.timemachine_form.is_valid():
+            request.session[f'timemachine_now_dt:{request.event.pk}'] = str(self.timemachine_form.cleaned_data['now_dt'])
+            return redirect(eventreverse(request.event, "presale:event.index"))
+        else:
+            return self.get(request)
+
+    def get_success_url(self) -> str:
+        return eventreverse(self.request.event, 'presale:event.timemachine')

src/pretix/static/pretixcontrol/js/send_form.js

@@ -0,0 +1 @@
+document.forms[0].submit();

src/pretix/static/pretixpresale/scss/_event.scss

@@ -194,7 +194,7 @@ div.front-page {
     padding: 5px;
     text-align: center;
 
-    a {
+    a, .btn-link {
         text-decoration: underline;
         color: white;
     }

src/pretix/static/pretixpresale/scss/main.scss

@@ -39,6 +39,7 @@ $body-bg: #f5f5f5 !default;
 h1 a, .btn {
     text-decoration: none;
 }
+a .fa:first-child { margin-right: 0.5ch }
 /*
 a, .btn-link {
     text-decoration: underline;