Allow to disable self-choice seating

src/pretix/control/forms/orders.py

@@ -399,7 +399,10 @@ class OrderPositionChangeForm(forms.Form):
         self.fields['tax_rule'].queryset = instance.event.tax_rules.all()
         self.fields['tax_rule'].label_from_instance = self.taxrule_label_from_instance
 
-        if not instance.seat:
+        if not instance.seat and not (
+                not instance.event.settings.seating_choice and
+                instance.item.seat_category_mappings.filter(subevent=instance.subevent).exists()
+        ):
             del self.fields['seat']
 
         choices = [

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

@@ -112,7 +112,7 @@
                             </div>
                         {% endif %}
 
-                        {% if position.seat %}
+                        {% if position.form.seat %}
                             <div class="row">
                                 <div class="col-sm-3">
                                     <strong>{% trans "Seat" %}</strong>

src/pretix/control/views/orders.py

@@ -1514,7 +1514,7 @@ class OrderChange(OrderView):
                 elif change_subevent is not None:
                     ocm.change_subevent(p, *change_subevent)
 
-                if p.seat and p.form.cleaned_data['seat'] and p.form.cleaned_data['seat'] != p.seat.seat_guid:
+                if p.form.cleaned_data.get('seat') and (not p.seat or p.form.cleaned_data['seat'] != p.seat.seat_guid):
                     ocm.change_seat(p, p.form.cleaned_data['seat'])
 
                 if p.form.cleaned_data['price'] is not None and p.form.cleaned_data['price'] != p.price:

src/pretix/control/views/organizer.py

@@ -26,8 +26,8 @@ from django.views.generic import (
 from pretix.api.models import WebHook
 from pretix.base.auth import get_auth_backends
 from pretix.base.models import (
-    CachedFile, Device, GiftCard, OrderPayment, Organizer, Team, TeamInvite,
-    User, LogEntry,
+    CachedFile, Device, GiftCard, LogEntry, OrderPayment, Organizer, Team,
+    TeamInvite, User,
 )
 from pretix.base.models.event import Event, EventMetaProperty, EventMetaValue
 from pretix.base.models.giftcards import gen_giftcard_secret