Self-service cancellation: Do not allow to adjust fee on free orders

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

@@ -21,7 +21,7 @@
             action="{% eventurl request.event "presale:event.order.cancel.do" secret=order.secret order=order.code %}"
             data-asynctask
             class="">
-        {% if request.event.settings.cancel_allow_user_paid_require_approval %}
+        {% if request.event.settings.cancel_allow_user_paid_require_approval and order.status == "p" and order.total != 0 %}
             <p>
                 {% blocktrans trimmed %}
                     You can request the cancellation of your order on this page. The event organizer will then decide
@@ -37,7 +37,7 @@
             </p>
         {% endif %}
 
-        {% if request.event.settings.cancel_allow_user_paid_adjust_fees %}
+        {% if request.event.settings.cancel_allow_user_paid_adjust_fees and order.status == "p" and order.total != 0 %}
             <p>
                 {% if cancel_fee %}
                     {% blocktrans trimmed with fee=order.user_cancel_fee|money:request.event.currency %}

src/pretix/presale/views/order.py

@@ -878,7 +878,9 @@ class OrderCancelDo(EventViewMixin, OrderDetailMixin, AsyncAction, View):
             require_approval = self.request.event.settings.cancel_allow_user_paid_require_approval
             fee = self.order.user_cancel_fee
             auto_refund = True
-        if 'cancel_fee' in request.POST and self.request.event.settings.cancel_allow_user_paid_adjust_fees:
+        if self.order.total == Decimal('0.00'):
+            fee = Decimal('0.00')
+        elif 'cancel_fee' in request.POST and self.request.event.settings.cancel_allow_user_paid_adjust_fees:
             fee = fee or Decimal('0.00')
             fee_in = re.sub('[^0-9.,]', '', request.POST.get('cancel_fee'))
             try:

src/tests/presale/test_orders.py

@@ -511,6 +511,34 @@ class OrdersTest(BaseOrdersTest):
             assert not self.order.refunds.exists()
             assert not self.order.cancellation_requests.exists()
 
+    def test_orders_cancel_free_ignore_fixed_fee(self):
+        self.order.status = Order.STATUS_PAID
+        self.order.total = Decimal('0.00')
+        self.order.save()
+        with scopes_disabled():
+            self.order.payments.create(provider='testdummy_partialrefund', amount=self.order.total, state=OrderPayment.PAYMENT_STATE_CONFIRMED)
+        self.event.settings.cancel_allow_user_paid = True
+        self.event.settings.cancel_allow_user_paid_keep = Decimal('3.00')
+        self.event.settings.cancel_allow_user_paid_require_approval = True
+        self.event.settings.cancel_allow_user_paid_adjust_fees = True
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/cancel' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 200
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/cancel/do' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
+                'cancel_fee': '3.00'
+            }, follow=True)
+        self.assertRedirects(response,
+                             '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
+                                                      self.order.secret),
+                             target_status_code=200)
+        self.order.refresh_from_db()
+        assert self.order.status == Order.STATUS_CANCELED
+        with scopes_disabled():
+            assert not self.order.refunds.exists()
+            assert not self.order.cancellation_requests.exists()
+
     def test_orders_cancel_paid_fee_autorefund_gift_card_optional(self):
         self.order.status = Order.STATUS_PAID
         self.order.save()