Fix incorrect offset payments when changing and splitting orders at the same time

src/pretix/base/services/orders.py

@@ -1430,19 +1430,25 @@ class OrderChangeManager:
                 fee.delete()
             split_order.total += fee.value
 
+        remaining_total = sum([p.price for p in self.order.positions.all()]) + sum([f.value for f in self.order.fees.all()])
+        offset_amount = min(max(0, self.completed_payment_sum - remaining_total), split_order.total)
+        if offset_amount >= split_order.total:
+            split_order.status = Order.STATUS_PAID
+        else:
+            split_order.status = Order.STATUS_PENDING
         split_order.save()
 
-        if split_order.status == Order.STATUS_PAID:
+        if offset_amount > Decimal('0.00'):
             split_order.payments.create(
                 state=OrderPayment.PAYMENT_STATE_CONFIRMED,
-                amount=split_order.total,
+                amount=offset_amount,
                 payment_date=now(),
                 provider='offsetting',
                 info=json.dumps({'orders': [self.order.code]})
             )
             self.order.refunds.create(
                 state=OrderRefund.REFUND_STATE_DONE,
-                amount=split_order.total,
+                amount=offset_amount,
                 execution_date=now(),
                 provider='offsetting',
                 info=json.dumps({'orders': [split_order.code]})

src/tests/base/test_orders.py

@@ -1517,6 +1517,86 @@ class OrderChangeManagerTests(TestCase):
         assert p.amount == Decimal('23.00')
         assert p.state == OrderPayment.PAYMENT_STATE_CONFIRMED
 
+    @classscope(attr='o')
+    def test_split_and_change_higher(self):
+        self.order.status = Order.STATUS_PAID
+        self.order.save()
+        self.order.payments.create(
+            provider='manual',
+            state=OrderPayment.PAYMENT_STATE_CONFIRMED,
+            amount=self.order.total,
+        )
+
+        # Split
+        self.ocm.change_price(self.op2, Decimal('42.00'))
+        self.ocm.split(self.op2)
+        self.ocm.commit()
+        self.order.refresh_from_db()
+        self.op2.refresh_from_db()
+
+        # First order
+        assert self.order.total == Decimal('23.00')
+        assert not self.order.fees.exists()
+        assert self.order.status == Order.STATUS_PAID
+        assert self.order.pending_sum == Decimal('0.00')
+        r = self.order.refunds.last()
+        assert r.provider == 'offsetting'
+        assert r.amount == Decimal('23.00')
+        assert r.state == OrderRefund.REFUND_STATE_DONE
+
+        # New order
+        assert self.op2.order != self.order
+        o2 = self.op2.order
+        assert o2.total == Decimal('42.00')
+        assert o2.status == Order.STATUS_PENDING
+        assert o2.positions.count() == 1
+        assert o2.fees.count() == 0
+        assert o2.pending_sum == Decimal('19.00')
+        p = o2.payments.last()
+        assert p.provider == 'offsetting'
+        assert p.amount == Decimal('23.00')
+        assert p.state == OrderPayment.PAYMENT_STATE_CONFIRMED
+
+    @classscope(attr='o')
+    def test_split_and_change_lower(self):
+        self.order.status = Order.STATUS_PAID
+        self.order.save()
+        self.order.payments.create(
+            provider='manual',
+            state=OrderPayment.PAYMENT_STATE_CONFIRMED,
+            amount=self.order.total,
+        )
+
+        # Split
+        self.ocm.change_price(self.op2, Decimal('10.00'))
+        self.ocm.split(self.op2)
+        self.ocm.commit()
+        self.order.refresh_from_db()
+        self.op2.refresh_from_db()
+
+        # First order
+        assert self.order.total == Decimal('23.00')
+        assert not self.order.fees.exists()
+        assert self.order.status == Order.STATUS_PAID
+        assert self.order.pending_sum == Decimal('-13.00')
+        r = self.order.refunds.last()
+        assert r.provider == 'offsetting'
+        assert r.amount == Decimal('10.00')
+        assert r.state == OrderRefund.REFUND_STATE_DONE
+
+        # New order
+        assert self.op2.order != self.order
+        o2 = self.op2.order
+        assert o2.total == Decimal('10.00')
+        assert o2.status == Order.STATUS_PAID
+        assert o2.positions.count() == 1
+        assert o2.fees.count() == 0
+        assert o2.pending_sum == Decimal('0.00')
+        p = o2.payments.last()
+        assert p.provider == 'offsetting'
+        assert p.amount == Decimal('10.00')
+        assert p.state == OrderPayment.PAYMENT_STATE_CONFIRMED
+
     @classscope(attr='o')
     def test_split_invoice_address(self):
         ia = InvoiceAddress.objects.create(