first steps

src/pretix/base/models/orders.py

@@ -12,7 +12,7 @@ import pytz
 from django.conf import settings
 from django.db import models, transaction
 from django.db.models import (
-    Case, Exists, F, Max, OuterRef, Q, Subquery, Sum, Value, When,
+    Case, Exists, F, Max, OuterRef, Prefetch, Q, Subquery, Sum, Value, When,
 )
 from django.db.models.functions import Coalesce
 from django.db.models.signals import post_delete
@@ -404,14 +404,13 @@ class Order(LockModel, LoggedModel):
             else:
                 return until.datetime(self.event)
 
-    @cached_property
-    def user_cancel_fee(self):
+    def user_partial_cancel_fee(self, total: Decimal):
         fee = Decimal('0.00')
         if self.event.settings.cancel_allow_user_paid_keep:
             fee += self.event.settings.cancel_allow_user_paid_keep
         if self.event.settings.cancel_allow_user_paid_keep_percentage:
-            fee += self.event.settings.cancel_allow_user_paid_keep_percentage / Decimal('100.0') * self.total
-        if self.event.settings.cancel_allow_user_paid_keep_fees:
+            fee += self.event.settings.cancel_allow_user_paid_keep_percentage / Decimal('100.0') * total
+        if self.event.settings.cancel_allow_user_paid_keep_fees and self.total == total:
             fee += self.fees.filter(
                 fee_type__in=(OrderFee.FEE_TYPE_PAYMENT, OrderFee.FEE_TYPE_SHIPPING, OrderFee.FEE_TYPE_SERVICE)
             ).aggregate(
@@ -419,6 +418,62 @@ class Order(LockModel, LoggedModel):
             )['s'] or 0
         return round_decimal(fee, self.event.currency)
 
+    @cached_property
+    def user_cancel_fee(self):
+        return self.user_partial_cancel_fee(self.total)
+
+    @property
+    def user_cancel_partial_positions(self) -> list:
+        """
+        Returns a list of positions in this order that can be cancelled individually.
+        """
+        from .checkin import Checkin
+
+        if self.user_cancel_deadline and now() > self.user_cancel_deadline:
+            return []
+
+        if self.status == Order.STATUS_PENDING:
+            if not self.event.settings.cancel_allow_user or not self.event.settings.cancel_allow_user_per_position:
+                return []
+        elif self.status == Order.STATUS_PAID:
+            if not self.event.settings.cancel_allow_user_paid or not self.event.settings.cancel_allow_user_paid_per_position:
+                return []
+            if self.total == Decimal('0.00'):
+                if not self.event.settings.cancel_allow_user or not self.event.settings.cancel_allow_user_per_position:
+                    return []
+        else:
+            return []
+
+        pos = list(
+            self.positions.annotate(
+                has_checkin=Exists(Checkin.objects.filter(position_id=OuterRef('pk')))
+            ).filter(
+                has_checkin=False,
+                item__allow_cancel=True
+            ).select_related('item', 'addon_to').prefetch_related(
+                'item__addons',
+                Prefetch(
+                    'addon_to__addons',
+                    to_attr='siblings'
+                )
+            ).distinct()
+        )
+        allowed = []
+        for p in pos:
+            if p.addon_to_id:
+                addonconf = [a for a in p.item.addons.all() if a.category_id == p.item.category_id]
+                if len(addonconf) > 0:
+                    addonconf = addonconf[0]
+                    if addonconf.min_count > 0 and len(p.siblings) <= addonconf.min_count:
+                        continue
+
+            allowed.append(p)
+
+        if len(allowed) == self.positions.count():
+            return []
+
+        return pos
+
     @property
     def user_cancel_allowed(self) -> bool:
         """

src/pretix/control/forms/event.py

@@ -450,6 +450,10 @@ class CancelSettingsForm(SettingsForm):
         label=_("Do not allow cancellations after"),
         required=False
     )
+    cancel_allow_user_per_position = forms.BooleanField(
+        label=_("Customers can cancel individual products in their order"),
+        required=False
+    )
     cancel_allow_user_paid = forms.BooleanField(
         label=_("Customers can cancel their paid orders"),
         help_text=_("Paid money will be automatically paid back if the payment method allows it. "
@@ -472,6 +476,10 @@ class CancelSettingsForm(SettingsForm):
         label=_("Do not allow cancellations after"),
         required=False
     )
+    cancel_allow_user_paid_per_position = forms.BooleanField(
+        label=_("Customers can cancel individual products in their order"),
+        required=False
+    )
 
 
 class PaymentSettingsForm(SettingsForm):

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

@@ -10,6 +10,7 @@
             <legend>{% trans "Cancellation of unpaid or free orders" %}</legend>
             {% bootstrap_field form.cancel_allow_user layout="control" %}
             {% bootstrap_field form.cancel_allow_user_until layout="control" %}
+            {% bootstrap_field form.cancel_allow_user_per_position layout="control" %}
         </fieldset>
         <fieldset>
             <legend>{% trans "Cancellation of paid orders" %}</legend>
@@ -18,6 +19,7 @@
             {% bootstrap_field form.cancel_allow_user_paid_keep_percentage layout="control" %}
             {% bootstrap_field form.cancel_allow_user_paid_keep_fees layout="control" %}
             {% bootstrap_field form.cancel_allow_user_paid_until layout="control" %}
+            {% bootstrap_field form.cancel_allow_user_paid_per_position layout="control" %}
             {% if not gets_notification %}
                 <div class="alert alert-warning">
                     {% blocktrans trimmed %}

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

@@ -292,6 +292,25 @@
                             {% trans "Cancel order" %}
                         </a>
                     {% endif %}
+                {% elif order.user_cancel_partial_positions %}
+                    {% if order.status == "p" and order.total != 0 %}
+                        <p>
+                            {% blocktrans trimmed %}
+                                You can cancel parts of this order and receive a refund to your original payment method.
+                            {% endblocktrans %}
+                        </p>
+                    {% else %}
+                        <p>
+                            {% blocktrans trimmed %}
+                                You can cancel parts of this order.
+                            {% endblocktrans %}
+                        </p>
+                    {% endif %}
+                    <a href="{% eventurl event 'presale:event.order.cancel' secret=order.secret order=order.code %}"
+                       class="btn btn-danger">
+                        <span class="fa fa-remove"></span>
+                        {% trans "Start cancellation" %}
+                    </a>
                 {% else %}
                     <p>
                         {% blocktrans trimmed %}

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

@@ -9,13 +9,28 @@
             Cancel order: {{ code }}
         {% endblocktrans %}
     </h2>
-    <p>
-        {% blocktrans trimmed %}
-            Do you really want to cancel this order? You cannot revert this action.
-        {% endblocktrans %}
-        {% trans "This will invalidate all of your tickets." %}
-    </p>
-    {% if can_auto_refund %}
+    {% if selected_positions %}
+        <p>
+            {% trans "The following positions of your order will be canceled:" %}
+        </p>
+        <ul>
+            {% for pos in selected_positions %}
+                <li>
+                    #{{ pos.positionid }} –
+                    {{ pos.item }} {% if pos.variation %}– {{ pos.variation }}{% endif %}
+                    {% if pos.attendee_name %}({{ pos.attendee_name }}){% endif %}
+                </li>
+            {% endfor %}
+        </ul>
+    {% else %}
+        <p>
+            {% blocktrans trimmed %}
+                Do you really want to cancel this order? You cannot revert this action.
+            {% endblocktrans %}
+            {% trans "This will invalidate all of your tickets." %}
+        </p>
+    {% endif %}
+    {% if can_auto_refund and refund_amount != 0 %}
         <p>
             <strong>
                 {% blocktrans trimmed with amount=refund_amount|money:request.event.currency %}
@@ -24,7 +39,7 @@
                 {% endblocktrans %}
             </strong>
         </p>
-    {% else %}
+    {% elif refund_amount != 0 %}
         <div class="alert alert-warning">
             {% blocktrans trimmed with amount=refund_amount|money:request.event.currency %}
                 With to the payment method you used, the refund amount of {{ amount }} <strong>can not be sent back to you automatically</strong>. Instead, the

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

@@ -0,0 +1,70 @@
+{% extends "pretixpresale/event/base.html" %}
+{% load i18n %}
+{% load money %}
+{% load eventurl %}
+{% block title %}{% trans "Cancel order" %}{% endblock %}
+{% block content %}
+    <h2>
+        {% blocktrans trimmed with code=order.code %}
+            Cancel order: {{ code }}
+        {% endblocktrans %}
+    </h2>
+
+    <form method="post"
+          {% if order.status == "p" and order.total != 0 %}
+              action=""
+          {% else %}
+              action="{% eventurl request.event "presale:event.order.cancel.do" secret=order.secret order=order.code %}" data-asynctask
+          {% endif %}
+    >
+        {% csrf_token %}
+
+        <p>
+            {% blocktrans trimmed %}
+                Please choose which parts of your order you want to cancel:
+            {% endblocktrans %}
+        </p>
+
+        {% for pos in cancellable_positions %}
+            <div class="checkbox">
+                <label for="id_pos_{{ pos.pk }}">
+                    <input type="checkbox" name="position" value="{{ pos.pk }}"
+                           class="scrolling-multiple-choice" checked="checked" id="id_pos_{{ pos.pk }}">
+                    #{{ pos.positionid }} –
+                    {{ pos.item }} {% if pos.variation %}– {{ pos.variation }}{% endif %}
+                    {% if pos.attendee_name %}({{ pos.attendee_name }}){% endif %}
+                </label>
+            </div>
+        {% endfor %}
+
+        {% if order.status == "p" and order.total != 0 %}
+            <p>
+                {% blocktrans trimmed %}
+                    Before your purchase is cancelled, you will be shown the refund amount and asked to confirm the cancellation.
+                {% endblocktrans %}
+            </p>
+        {% endif %}
+
+        <div class="row checkout-button-row">
+            <div class="col-md-4">
+                <a class="btn btn-block btn-default btn-lg"
+                   href="{% eventurl request.event "presale:event.order" secret=order.secret order=order.code %}">
+                    {% trans "No, take me back" %}
+                </a>
+            </div>
+            <div class="col-md-4 col-md-offset-4">
+                {% if order.status == "p" and order.total != 0 %}
+                    <button class="btn btn-block btn-primary btn-lg" type="submit">
+                        {% trans "Calculate refund amount" %}
+                    </button>
+                {% else %}
+                    <button class="btn btn-block btn-danger btn-lg" type="submit">
+                        {% trans "Yes, cancel order" %}
+                    </button>
+                {% endif %}
+            </div>
+            <div class="clearfix"></div>
+        </div>
+    </form>
+
+{% endblock %}

src/pretix/presale/views/order.py

@@ -558,28 +558,49 @@ class OrderModify(EventViewMixin, OrderDetailMixin, OrderQuestionsViewMixin, Tem
 
 @method_decorator(xframe_options_exempt, 'dispatch')
 class OrderCancel(EventViewMixin, OrderDetailMixin, TemplateView):
-    template_name = "pretixpresale/event/order_cancel.html"
+
+    def get_template_names(self):
+        if self.cancellable_positions and not self.selected_positions:
+            return ["pretixpresale/event/order_cancel_choose.html"]
+        else:
+            return ["pretixpresale/event/order_cancel.html"]
+
+    @cached_property
+    def selected_positions(self):
+        if self.request.method == "POST":
+            return [
+                p for p in self.order.user_cancel_partial_positions
+                if str(p.pk) in self.request.POST.getlist("position")
+            ]
+        return []
+
+    @cached_property
+    def cancellable_positions(self):
+        return self.order.user_cancel_partial_positions
 
     def dispatch(self, request, *args, **kwargs):
         self.request = request
         self.kwargs = kwargs
         if not self.order:
             raise Http404(_('Unknown order code or not authorized to access this order.'))
-        if not self.order.user_cancel_allowed:
+        if not self.order.user_cancel_allowed and not self.cancellable_positions:
             messages.error(request, _('You cannot cancel this order.'))
             return redirect(self.get_order_url())
         return super().dispatch(request, *args, **kwargs)
 
-    def get(self, request, *args, **kwargs):
+    def post(self, request, *args, **kwargs):
         return super().get(request, *args, **kwargs)
 
     def get_context_data(self, **kwargs):
         ctx = super().get_context_data(**kwargs)
         ctx['order'] = self.order
-        refund_amount = self.order.total - self.order.user_cancel_fee
+        total = sum(p.price for p in self.selected_positions) if self.selected_positions else self.order.total - self.order.pending_sum
+        refund_amount = total - self.order.user_partial_cancel_fee(total)
         proposals = self.order.propose_auto_refunds(refund_amount)
         ctx['refund_amount'] = refund_amount
         ctx['can_auto_refund'] = sum(proposals.values()) == refund_amount
+        ctx['cancellable_positions'] = self.cancellable_positions
+        ctx['selected_positions'] = self.selected_positions
         return ctx