Add note to docs

doc/api/resources/orders.rst

@@ -1943,9 +1943,14 @@ Manipulating individual positions
 
    * ``valid_until``
 
+   * ``secret``
+
    Changing parameters such as ``item`` or ``price`` will **not** automatically trigger creation of a new invoice,
    you need to take care of that yourself.
 
+   Changing ``secret`` does not cause a new PDF ticket to be sent to the customer, nor does it cause the old secret
+   to be added to the revocation list, even if your ticket generator uses one.
+
    **Example request**:
 
    .. sourcecode:: http

src/pretix/api/serializers/orderchange.py

@@ -251,7 +251,7 @@ class OrderPositionChangeSerializer(serializers.ModelSerializer):
     class Meta:
         model = OrderPosition
         fields = (
-            'item', 'variation', 'subevent', 'seat', 'price', 'tax_rule', 'valid_from', 'valid_until'
+            'item', 'variation', 'subevent', 'seat', 'price', 'tax_rule', 'valid_from', 'valid_until', 'secret'
         )
 
     def __init__(self, *args, **kwargs):
@@ -319,6 +319,7 @@ class OrderPositionChangeSerializer(serializers.ModelSerializer):
         tax_rule = validated_data.get('tax_rule', instance.tax_rule)
         valid_from = validated_data.get('valid_from', instance.valid_from)
         valid_until = validated_data.get('valid_until', instance.valid_until)
+        secret = validated_data.get('secret', instance.secret)
 
         change_item = None
         if item != instance.item or variation != instance.variation:
@@ -351,6 +352,9 @@ class OrderPositionChangeSerializer(serializers.ModelSerializer):
             if valid_until != instance.valid_until:
                 ocm.change_valid_until(instance, valid_until)
 
+            if secret != instance.secret:
+                ocm.change_ticket_secret(instance, secret)
+
             if self.context.get('commit', True):
                 ocm.commit()
                 instance.refresh_from_db()

src/pretix/base/services/orders.py

@@ -1564,6 +1564,7 @@ class OrderChangeManager:
     AddFeeOperation = namedtuple('AddFeeOperation', ('fee', 'price_diff'))
     CancelFeeOperation = namedtuple('CancelFeeOperation', ('fee', 'price_diff'))
     RegenerateSecretOperation = namedtuple('RegenerateSecretOperation', ('position',))
+    ChangeSecretOperation = namedtuple('ChangeSecretOperation', ('position', 'new_secret'))
     ChangeValidFromOperation = namedtuple('ChangeValidFromOperation', ('position', 'valid_from'))
     ChangeValidUntilOperation = namedtuple('ChangeValidUntilOperation', ('position', 'valid_until'))
     AddBlockOperation = namedtuple('AddBlockOperation', ('position', 'block_name', 'ignore_from_quota_while_blocked'))
@@ -1671,6 +1672,9 @@ class OrderChangeManager:
     def regenerate_secret(self, position: OrderPosition):
         self._operations.append(self.RegenerateSecretOperation(position))
 
+    def change_ticket_secret(self, position: OrderPosition, new_secret: str):
+        self._operations.append(self.ChangeSecretOperation(position, new_secret))
+
     def change_valid_from(self, position: OrderPosition, new_value: datetime):
         self._operations.append(self.ChangeValidFromOperation(position, new_value))
 
@@ -2441,6 +2445,19 @@ class OrderChangeManager:
                     'position': op.position.pk,
                     'positionid': op.position.positionid,
                 })
+            elif isinstance(op, self.ChangeSecretOperation):
+                if OrderPosition.all.filter(order__event=self.event, secret=op.new_secret).exists():
+                    raise OrderError('You cannot assign a position secret that already exists.')
+                op.position.secret = op.new_secret
+                op.position.save(update_fields=["secret"])
+                if op.position in secret_dirty:
+                    secret_dirty.remove(op.position)
+                tickets.invalidate_cache.apply_async(kwargs={'event': self.event.pk,
+                                                             'order': self.order.pk})
+                self.order.log_action('pretix.event.order.changed.secret', user=self.user, auth=self.auth, data={
+                    'position': op.position.pk,
+                    'positionid': op.position.positionid,
+                })
             elif isinstance(op, self.ChangeValidFromOperation):
                 self.order.log_action('pretix.event.order.changed.valid_from', user=self.user, auth=self.auth, data={
                     'position': op.position.pk,

src/tests/api/test_order_change.py

@@ -1468,6 +1468,31 @@ def test_position_update_change_price_and_tax_rule(token_client, organizer, even
     assert op.tax_rule == tr
 
 
+@pytest.mark.django_db
+def test_position_update_secret(token_client, organizer, event, order, item):
+    with scopes_disabled():
+        order.positions.create(item=item, price=Decimal('23.00'), secret='alreadyused')
+        p = order.positions.first()
+        psw = p.web_secret
+    resp = token_client.patch(
+        '/api/v1/organizers/{}/events/{}/orderpositions/{}/'.format(
+            organizer.slug, event.slug, p.pk,
+        ), format='json', data={'secret': 'nobodyknows'}
+    )
+    assert resp.status_code == 200
+    p.refresh_from_db()
+    with scopes_disabled():
+        assert 'nobodyknows' == p.secret
+        assert psw == p.web_secret
+
+    resp = token_client.patch(
+        '/api/v1/organizers/{}/events/{}/orderpositions/{}/'.format(
+            organizer.slug, event.slug, p.pk,
+        ), format='json', data={'secret': 'alreadyused'}
+    )
+    assert resp.status_code == 400
+
+
 @pytest.mark.django_db
 def test_position_add_simple(token_client, organizer, event, order, quota, item):
     with scopes_disabled():