Allow to change fees in existing orders (#1472)

* Allow to change fees in existing orders

* Add tests

* Add special case for payment options

* Fix PK reference in tests

src/pretix/control/forms/orders.py

@@ -400,9 +400,27 @@ class OrderPositionChangeForm(forms.Form):
         self.fields['itemvar'].choices = choices
         change_decimal_field(self.fields['price'], instance.order.event.currency)
 
-    def clean(self):
-        if self.cleaned_data.get('operation') == 'price' and not self.cleaned_data.get('price', '') != '':
-            raise ValidationError(_('You need to enter a price if you want to change the product price.'))
+
+class OrderFeeChangeForm(forms.Form):
+    value = forms.DecimalField(
+        required=False,
+        max_digits=10, decimal_places=2,
+        localize=True,
+        label=_('New price (gross)')
+    )
+    operation_cancel = forms.BooleanField(
+        required=False,
+        label=_('Remove this fee')
+    )
+
+    def __init__(self, *args, **kwargs):
+        instance = kwargs.pop('instance')
+        initial = kwargs.get('initial', {})
+
+        initial['value'] = instance.value
+        kwargs['initial'] = initial
+        super().__init__(*args, **kwargs)
+        change_decimal_field(self.fields['value'], instance.order.event.currency)
 
 
 class OrderContactForm(forms.ModelForm):

src/pretix/control/logdisplay.py

@@ -65,6 +65,15 @@ def _display_order_changed(event: Event, logentry: LogEntry):
             old_price=money_filter(Decimal(data['old_price']), event.currency),
             new_price=money_filter(Decimal(data['new_price']), event.currency),
         )
+    elif logentry.action_type == 'pretix.event.order.changed.feevalue':
+        return text + ' ' + _('A fee was changed from {old_price} to {new_price}.').format(
+            old_price=money_filter(Decimal(data['old_price']), event.currency),
+            new_price=money_filter(Decimal(data['new_price']), event.currency),
+        )
+    elif logentry.action_type == 'pretix.event.order.changed.cancelfee':
+        return text + ' ' + _('A fee of {old_price} was removed.').format(
+            old_price=money_filter(Decimal(data['old_price']), event.currency),
+        )
     elif logentry.action_type == 'pretix.event.order.changed.cancel':
         old_item = str(event.items.get(pk=data['old_item']))
         if data['old_variation']:

src/pretix/control/templates/pretixcontrol/order/change.html

@@ -250,11 +250,67 @@
                 {% endescapescript %}
             </script>
             <p>
-                <button type="button" class="btn btn-default" data-formset-add>
+                <button type="button" class="btn btn-primary" data-formset-add>
                     <i class="fa fa-plus"></i> {% trans "Add product" %}</button>
             </p>
         </div>
 
+        {% for fee in fees %}
+            <div class="panel panel-default items">
+                <div class="panel-heading">
+                    <h3 class="panel-title">
+                        <strong>{{ fee.get_fee_type_display }}</strong>
+                        {% if fee.description %}
+                            – {{ fee.description }}
+                        {% endif %}
+                    </h3>
+                </div>
+                <div class="panel-body">
+                    <div class="form-order-change">
+                        {% bootstrap_form_errors fee.form %}
+                        {% if fee.custom_error %}
+                            <div class="alert alert-danger">
+                                {{ fee.custom_error }}
+                            </div>
+                        {% endif %}
+                        <div class="row">
+                            <div class="col-sm-5 col-sm-offset-3">
+                                <strong>{% trans "Current value" %}</strong>
+                            </div>
+                            <div class="col-sm-4">
+                                <strong>{% trans "Change to" %}</strong>
+                            </div>
+                        </div>
+                        <div class="row">
+                            <div class="col-sm-3">
+                                <strong>{% trans "Price" %}</strong>
+                            </div>
+                            <div class="col-sm-5">
+                                {{ fee.value|money:request.event.currency }}
+                                {% if fee.tax_rate %}
+                                    <br>
+                                    <small>
+                                        ({{ fee.net_value|money:request.event.currency }}
+                                        + {{ fee.tax_rate }}%)
+                                    </small>
+                                {% endif %}
+                            </div>
+                            <div class="col-sm-4 field-container">
+                                {% bootstrap_field fee.form.value addon_after=request.event.currency layout='inline' %}
+                                <small><strong>{% trans "including all taxes" %}</strong></small>
+                            </div>
+                        </div>
+
+                        {% bootstrap_field fee.form.operation_cancel layout='inline' %}
+                        {% if fee.fee_type == "payment" %}
+                            <em class="text-danger">
+                                {% trans "Manually modifying payment fees is discouraged since they might automatically be on subsequent order changes or when choosing a different payment method." %}
+                            </em>
+                        {% endif %}
+                    </div>
+                </div>
+            </div>
+        {% endfor %}
         <div class="panel panel-default items">
             <div class="panel-heading">
                 <h3 class="panel-title">

src/pretix/control/views/orders.py

@@ -71,9 +71,9 @@ from pretix.control.forms.filter import (
 )
 from pretix.control.forms.orders import (
     CancelForm, CommentForm, ConfirmPaymentForm, ExporterForm, ExtendForm,
-    MarkPaidForm, OrderContactForm, OrderLocaleForm, OrderMailForm,
-    OrderPositionAddForm, OrderPositionAddFormset, OrderPositionChangeForm,
-    OrderRefundForm, OtherOperationsForm,
+    MarkPaidForm, OrderContactForm, OrderFeeChangeForm, OrderLocaleForm,
+    OrderMailForm, OrderPositionAddForm, OrderPositionAddFormset,
+    OrderPositionChangeForm, OrderRefundForm, OtherOperationsForm,
 )
 from pretix.control.permissions import EventPermissionRequiredMixin
 from pretix.control.views import PaginationMixin
@@ -1209,6 +1209,19 @@ class OrderChange(OrderView):
             data=self.request.POST if self.request.method == "POST" else None
         )
 
+    @cached_property
+    def fees(self):
+        fees = list(self.order.fees.all())
+        for f in fees:
+            f.form = OrderFeeChangeForm(prefix='of-{}'.format(f.pk), instance=f,
+                                        data=self.request.POST if self.request.method == "POST" else None)
+            try:
+                ia = self.order.invoice_address
+            except InvoiceAddress.DoesNotExist:
+                ia = None
+            f.apply_tax = self.request.event.settings.tax_rate_default and self.request.event.settings.tax_rate_default.tax_applicable(invoice_address=ia)
+        return fees
+
     @cached_property
     def positions(self):
         positions = list(self.order.positions.all())
@@ -1225,6 +1238,7 @@ class OrderChange(OrderView):
     def get_context_data(self, **kwargs):
         ctx = super().get_context_data(**kwargs)
         ctx['positions'] = self.positions
+        ctx['fees'] = self.fees
         ctx['add_formset'] = self.add_formset
         ctx['other_form'] = self.other_form
         return ctx
@@ -1266,6 +1280,24 @@ class OrderChange(OrderView):
                     return False
         return True
 
+    def _process_fees(self, ocm):
+        for f in self.fees:
+            if not f.form.is_valid():
+                return False
+
+            try:
+                if f.form.cleaned_data['operation_cancel']:
+                    ocm.cancel_fee(f)
+                    continue
+
+                if f.form.cleaned_data['value'] != f.value:
+                    ocm.change_fee(f, f.form.cleaned_data['value'])
+
+            except OrderError as e:
+                f.custom_error = str(e)
+                return False
+        return True
+
     def _process_change(self, ocm):
         for p in self.positions:
             if not p.form.is_valid():
@@ -1318,7 +1350,7 @@ class OrderChange(OrderView):
             notify=notify,
             reissue_invoice=self.other_form.cleaned_data['reissue_invoice'] if self.other_form.is_valid() else True
         )
-        form_valid = self._process_add(ocm) and self._process_change(ocm) and self._process_other(ocm)
+        form_valid = self._process_add(ocm) and self._process_fees(ocm) and self._process_change(ocm) and self._process_other(ocm)
 
         if not form_valid:
             messages.error(self.request, _('An error occurred. Please see the details below.'))