Add safeguards and tests against duplicate cancellations

src/pretix/base/services/invoices.py

@@ -210,6 +210,8 @@ def build_cancellation(invoice: Invoice):
 
 
 def generate_cancellation(invoice: Invoice, trigger_pdf=True):
+    if invoice.refered.exists():
+        raise ValueError("Invoice should not be canceled twice.")
     cancellation = modelcopy(invoice)
     cancellation.pk = None
     cancellation.invoice_no = None

src/pretix/base/services/orders.py

@@ -156,7 +156,7 @@ def mark_order_expired(order, user=None, auth=None):
 
         order.log_action('pretix.event.order.expired', user=user, auth=auth)
         i = order.invoices.filter(is_cancellation=False).last()
-        if i:
+        if i and not i.refered.exists():
             generate_cancellation(i)
 
     order_expired.send(order.event, order=order)

src/tests/base/test_orders.py

@@ -213,6 +213,28 @@ def test_expiring_paid_invoice(event):
     assert o2.invoices.last().is_cancellation is False
 
 
+@pytest.mark.django_db
+def test_expire_twice(event):
+    o2 = Order.objects.create(
+        code='FO2', event=event, email='dummy@dummy.test',
+        status=Order.STATUS_PENDING, locale='en',
+        datetime=now(), expires=now() - timedelta(days=10),
+        total=12,
+    )
+    generate_invoice(o2)
+    expire_orders(None)
+    o2 = Order.objects.get(id=o2.id)
+    assert o2.status == Order.STATUS_EXPIRED
+    assert o2.invoices.count() == 2
+    # this would usually happen when the deadline is extended, but lets keep the case simple
+    o2.status = Order.STATUS_PENDING
+    o2.save()
+    expire_orders(None)
+    o2 = Order.objects.get(id=o2.id)
+    assert o2.status == Order.STATUS_EXPIRED
+    assert o2.invoices.count() == 2
+
+
 @pytest.mark.django_db
 def test_expiring_auto_disabled(event):
     event.settings.set('payment_term_expire_automatically', False)

src/tests/control/test_orders.py

@@ -591,6 +591,8 @@ def test_order_extend_not_expired(client, env):
     with scopes_disabled():
         q = Quota.objects.create(event=env[0], size=0)
         q.items.add(env[3])
+        o = Order.objects.get(id=env[2].id)
+        generate_invoice(o)
     newdate = (now() + timedelta(days=20)).strftime("%Y-%m-%d %H:%M:%S")
     client.login(email='dummy@dummy.dummy', password='dummy')
     response = client.post('/control/event/dummy/dummy/orders/FOO/extend', {
@@ -600,6 +602,7 @@ def test_order_extend_not_expired(client, env):
     with scopes_disabled():
         o = Order.objects.get(id=env[2].id)
         assert o.expires.strftime("%Y-%m-%d %H:%M:%S") == newdate[:10] + " 23:59:59"
+        assert o.invoices.count() == 1
 
 
 @pytest.mark.django_db
@@ -631,6 +634,7 @@ def test_order_extend_overdue_quota_blocked_by_waiting_list(client, env):
         q = Quota.objects.create(event=env[0], size=1)
         q.items.add(env[3])
         env[0].waitinglistentries.create(item=env[3], email='foo@bar.com')
+        generate_cancellation(generate_invoice(o))
 
     newdate = (now() + timedelta(days=20)).strftime("%Y-%m-%d %H:%M:%S")
     client.login(email='dummy@dummy.dummy', password='dummy')
@@ -642,6 +646,7 @@ def test_order_extend_overdue_quota_blocked_by_waiting_list(client, env):
         o = Order.objects.get(id=env[2].id)
         assert o.expires.strftime("%Y-%m-%d %H:%M:%S") == newdate[:10] + " 23:59:59"
         assert o.status == Order.STATUS_PENDING
+        assert o.invoices.count() == 3
 
 
 @pytest.mark.django_db