Allow not to ask for invoice addresses on free orders

src/pretix/control/forms/event.py

@@ -621,6 +621,10 @@ class InvoiceSettingsForm(SettingsForm):
         widget=forms.CheckboxInput(attrs={'data-checkbox-dependency': '#id_invoice_address_asked'}),
         required=False
     )
+    invoice_address_not_asked_free = forms.BooleanField(
+        label=_('Do not ask for invoice address if an order is free'),
+        required=False
+    )
     invoice_include_free = forms.BooleanField(
         label=_("Show free products on invoices"),
         help_text=_("Note that invoices will never be generated for orders that contain only free "

src/pretix/control/forms/item.py

@@ -43,6 +43,7 @@ class QuestionForm(I18nModelForm):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.fields['items'].queryset = self.instance.event.items.all()
+        self.fields['items'].required = True
         self.fields['dependency_question'].queryset = self.instance.event.questions.filter(
             type__in=(Question.TYPE_BOOLEAN, Question.TYPE_CHOICE, Question.TYPE_CHOICE_MULTIPLE)
         )

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

@@ -24,6 +24,7 @@
             {% bootstrap_field form.invoice_address_company_required layout="control" %}
             {% bootstrap_field form.invoice_address_vatid layout="control" %}
             {% bootstrap_field form.invoice_address_beneficiary layout="control" %}
+            {% bootstrap_field form.invoice_address_not_asked_free layout="control" %}
         </fieldset>
         <fieldset>
             <legend>{% trans "Your invoice details" %}</legend>

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

@@ -18,7 +18,7 @@
     <form method="post" class="form-horizontal" href="" enctype="multipart/form-data">
         {% csrf_token %}
         <div class="panel-group" id="questions_accordion">
-            {% if request.event.settings.invoice_address_asked or order.invoice_address or request.event.settings.invoice_name_required %}
+            {% if invoice_address_asked or order.invoice_address or request.event.settings.invoice_name_required %}
                 <details class="panel panel-default" open>
                     <summary class="panel-heading">
                         <h4 class="panel-title">

src/pretix/control/views/orders.py

@@ -1305,7 +1305,8 @@ class OrderModifyInformation(OrderQuestionsViewMixin, OrderView):
             messages.error(self.request,
                            _("We had difficulties processing your input. Please review the errors below."))
             return self.get(request, *args, **kwargs)
-        self.invoice_form.save()
+        if hasattr(self.invoice_form, 'save'):
+            self.invoice_form.save()
         self.order.log_action('pretix.event.order.modified', {
             'invoice_data': self.invoice_form.cleaned_data,
             'data': [{