Allow attendees to modify their data (Z#23152886) (#4138)

* Allow attendees to modify their data

* Allow attendees to change ticket information

* Update src/pretix/control/templates/pretixcontrol/event/settings.html

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

* Update src/pretix/presale/views/order.py

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

* Update src/pretix/base/services/placeholders.py

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

* Tests fix

* Fix test

---------

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

src/pretix/base/models/orders.py

@@ -850,6 +850,9 @@ class Order(LockModel, LoggedModel):
         if self.status not in (Order.STATUS_PENDING, Order.STATUS_PAID, Order.STATUS_EXPIRED):
             return False
 
+        if self.event.settings.allow_modifications not in ("order", "attendee"):
+            return False
+
         modify_deadline = self.modify_deadline
         if modify_deadline is not None and now() > modify_deadline:
             return False
@@ -2513,6 +2516,43 @@ class OrderPosition(AbstractPosition):
                 reasons[b] = b
         return reasons
 
+    @property
+    def can_modify_answers(self) -> bool:
+        """
+        ``True`` if the user can change the question answers / attendee names that are
+        related to the position. This checks order status and modification deadlines. It also
+        returns ``False`` if there are no questions that can be answered.
+        """
+        from .checkin import Checkin
+
+        if self.order.status not in (Order.STATUS_PENDING, Order.STATUS_PAID, Order.STATUS_EXPIRED):
+            return False
+
+        if self.event.settings.allow_modifications != "attendee":
+            return False
+
+        modify_deadline = self.order.modify_deadline
+        if modify_deadline is not None and now() > modify_deadline:
+            return False
+
+        positions = list(
+            self.order.positions.all().annotate(
+                has_checkin=Exists(Checkin.objects.filter(position_id=OuterRef('pk'), list__consider_tickets_used=True))
+            ).select_related('item').prefetch_related('item__questions')
+        )
+        if not self.event.settings.allow_modifications_after_checkin:
+            for cp in positions:
+                if cp.has_checkin:
+                    return False
+
+        ask_names = self.event.settings.get('attendee_names_asked', as_type=bool)
+        for cp in positions:
+            if cp.pk == self.pk or cp.addon_to_id == self.pk:
+                if (cp.item.ask_attendee_data and ask_names) or cp.item.questions.all():
+                    return True
+
+        return False  # nothing there to modify
+
     @classmethod
     def transform_cart_positions(cls, cp: List, order) -> list:
         from . import Voucher

src/pretix/base/services/placeholders.py

@@ -337,6 +337,40 @@ def base_placeholders(sender, **kwargs):
                 }
             ),
         ),
+        SimpleFunctionalTextPlaceholder(
+            'url_info_change', ['position', 'event'], lambda position, event: build_absolute_uri(
+                event,
+                'presale:event.order.position.modify', kwargs={
+                    'order': position.order.code,
+                    'secret': position.web_secret,
+                    'position': position.positionid
+                }
+            ), lambda event: build_absolute_uri(
+                event,
+                'presale:event.order.position.modify', kwargs={
+                    'order': 'F8VVL',
+                    'secret': '6zzjnumtsx136ddy',
+                    'position': '123',
+                }
+            ),
+        ),
+        SimpleFunctionalTextPlaceholder(
+            'url_products_change', ['position', 'event'], lambda position, event: build_absolute_uri(
+                event,
+                'presale:event.order.position.change', kwargs={
+                    'order': position.order.code,
+                    'secret': position.web_secret,
+                    'position': position.positionid
+                }
+            ), lambda event: build_absolute_uri(
+                event,
+                'presale:event.order.position.change', kwargs={
+                    'order': 'F8VVL',
+                    'secret': '6zzjnumtsx136ddy',
+                    'position': '123'
+                }
+            ),
+        ),
         SimpleFunctionalTextPlaceholder(
             'order_modification_deadline_date_and_time', ['order', 'event'],
             lambda order, event:

src/pretix/base/settings.py

@@ -1653,6 +1653,28 @@ DEFAULTS = {
                         "calendar.")
         )
     },
+    'allow_modifications': {
+        'default': 'order',
+        'type': str,
+        'form_class': forms.ChoiceField,
+        'serializer_class': serializers.ChoiceField,
+        'serializer_kwargs': dict(
+            choices=(
+                ('no', _('No modifications after order was submitted')),
+                ('order', _('Only the person who ordered can make changes')),
+                ('attendee', _('Both the attendee and the person who ordered can make changes')),
+            )
+        ),
+        'form_kwargs': dict(
+            label=_("Allow customers to modify their information"),
+            widget=forms.RadioSelect,
+            choices=(
+                ('no', _('No modifications after order was submitted')),
+                ('order', _('Only the person who ordered can make changes')),
+                ('attendee', _('Both the attendee and the person who ordered can make changes')),
+            )
+        ),
+    },
     'allow_modifications_after_checkin': {
         'default': 'False',
         'type': bool,
@@ -1660,6 +1682,8 @@ DEFAULTS = {
         'serializer_class': serializers.BooleanField,
         'form_kwargs': dict(
             label=_("Allow customers to modify their information after they checked in."),
+            help_text=_("By default, no more modifications are possible for an order as soon as one of the tickets "
+                        "in the order has been checked in.")
         )
     },
     'last_order_modification_date': {