Create line discount models so we know what discount was applied to what line

src/oscar/apps/order/abstract_models.py

         return self.offer_name or ""
 
 
+class AbstractOrderLineDiscount(models.Model):
+    line = models.ForeignKey(
+        "order.Line",
+        on_delete=models.CASCADE,
+        related_name="discounts",
+        verbose_name=_("Line"),
+    )
+    order_discount = models.ForeignKey(
+        "order.OrderDiscount",
+        on_delete=models.CASCADE,
+        related_name="discount_lines",
+        verbose_name=_("Order discount"),
+    )
+
+    is_incl_tax = models.BooleanField()
+    amount = models.DecimalField(
+        _("Line discount (excl. tax)"), decimal_places=2, max_digits=12, default=0
+    )
+
+    class Meta:
+        abstract = True
+        app_label = "order"
+        ordering = ["pk"]
+        verbose_name = _("Order line discount")
+        verbose_name_plural = _("Order line discounts")
+
+
 class AbstractSurcharge(models.Model):
     order = models.ForeignKey(
         "order.Order",

src/oscar/apps/order/migrations/0015_orderlinediscount.py

+# Generated by Django 4.2.2 on 2023-07-19 13:16
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+from django.utils.module_loading import import_string
+from django.conf import settings
+
+models_AutoField = import_string(settings.DEFAULT_AUTO_FIELD)
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("order", "0014_tax_code"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="OrderLineDiscount",
+            fields=[
+                (
+                    "id",
+                    models_AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("is_incl_tax", models.BooleanField()),
+                (
+                    "amount",
+                    models.DecimalField(
+                        decimal_places=2,
+                        default=0,
+                        max_digits=12,
+                        verbose_name="Line discount (excl. tax)",
+                    ),
+                ),
+                (
+                    "line",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="discounts",
+                        to="order.line",
+                        verbose_name="Line",
+                    ),
+                ),
+                (
+                    "order_discount",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="discount_lines",
+                        to="order.orderdiscount",
+                        verbose_name="Order discount",
+                    ),
+                ),
+            ],
+            options={
+                "verbose_name": "Order line discount",
+                "verbose_name_plural": "Order line discounts",
+                "ordering": ["pk"],
+                "abstract": False,
+            },
+        ),
+    ]

src/oscar/apps/order/models.py

 
     __all__.append("OrderDiscount")
 
+
+if not is_model_registered("order", "OrderLineDiscount"):
+
+    class OrderLineDiscount(AbstractOrderLineDiscount):
+        pass
+
+    __all__.append("OrderDiscount")
+
+
 if not is_model_registered("order", "Surcharge"):
 
     class Surcharge(AbstractSurcharge):

src/oscar/apps/order/utils.py

 Order = get_model("order", "Order")
 Line = get_model("order", "Line")
 OrderDiscount = get_model("order", "OrderDiscount")
+OrderLineDiscount = get_model("order", "OrderLineDiscount")
 CommunicationEvent = get_model("order", "CommunicationEvent")
 CommunicationEventType = get_model("communication", "CommunicationEventType")
 Dispatcher = get_class("communication.utils", "Dispatcher")
                 request,
                 **kwargs
             )
-            for line in basket.all_lines():
-                self.create_line_models(order, line)
-                self.update_stock_records(line)
-
             for voucher in basket.vouchers.select_for_update():
                 if not voucher.is_active():  # basket ignores inactive vouchers
                     basket.vouchers.remove(voucher)
             for voucher in basket.vouchers.all():
                 self.record_voucher_usage(order, voucher, user)
 
+            for line in basket.all_lines():
+                self.create_line_models(order, line)
+                self.update_stock_records(line)
+
         # Send signal for analytics to pick up
         order_placed.send(sender=self, order=order, user=user)
 
         order_line = Line._default_manager.create(**line_data)
         self.create_line_price_models(order, order_line, basket_line)
         self.create_line_attributes(order, order_line, basket_line)
+        self.create_line_discount_models(order, order_line, basket_line)
         self.create_additional_line_models(order, order_line, basket_line)
 
         return order_line
         if line.product.get_product_class().track_stock:
             line.stockrecord.allocate(line.quantity)
 
+    def create_line_discount_models(self, order, order_line, basket_line):
+        for discount in basket_line.discounts:
+            order_discount = order.discounts.filter(offer_id=discount.offer.id).first()
+            if order_discount:
+                order_line.discounts.create(
+                    order_discount=order_discount,
+                    is_incl_tax=discount.incl_tax,
+                    amount=discount.amount,
+                )
+
     def create_additional_line_models(self, order, order_line, basket_line):
         """
         Empty method designed to be overridden.

tests/integration/order/test_creator.py

 from oscar.apps.catalogue.models import Product, ProductClass
 from oscar.apps.checkout import calculators
 from oscar.apps.offer.utils import Applicator
+from oscar.apps.offer import models
 from oscar.apps.order.models import Order
 from oscar.apps.order.utils import OrderCreator
 from oscar.apps.shipping.methods import FixedPrice, Free
 Benefit = get_class("offer.models", "Benefit")
 
 SurchargeApplicator = get_class("checkout.applicator", "SurchargeApplicator")
+UK = get_class("partner.strategy", "UK")
 
 
 def place_order(creator, **kwargs):
         self.assertEqual(D("34.00"), order.total_incl_tax)
 
 
+class TestOrderOfferCreation(TestCase):
+    def setUp(self):
+        self.creator = OrderCreator()
+        self.basket = factories.create_basket(empty=True)
+        self.basket.strategy = UK()
+        self.surcharges = SurchargeApplicator().get_applicable_surcharges(self.basket)
+        product_range = Range.objects.create(
+            name="All products range", includes_all_products=True
+        )
+        condition = models.CountCondition.objects.create(
+            range=product_range, type=models.Condition.COUNT, value=1
+        )
+        benefit = models.PercentageDiscountBenefit.objects.create(
+            range=product_range,
+            type=models.Benefit.PERCENTAGE,
+            value=20,
+        )
+        self.offer = models.ConditionalOffer(
+            name="Test",
+            offer_type=models.ConditionalOffer.SITE,
+            condition=condition,
+            benefit=benefit,
+        )
+        self.offer.save()
+        self.applicator = Applicator()
+
+    def test_multi_lines_discount(self):
+        add_product(self.basket, D(10))
+        add_product(self.basket, D(20))
+
+        self.applicator.apply_offers(self.basket, [self.offer])
+
+        place_order(
+            self.creator,
+            surcharges=self.surcharges,
+            basket=self.basket,
+            order_number="klatsieknoekie666",
+        )
+
+        order = Order.objects.get(number="klatsieknoekie666")
+
+        discount = order.discounts.first()
+        self.assertEqual(discount.amount, D("7.20"))
+        self.assertEqual(discount.discount_lines.count(), 2)
+        self.assertEqual(
+            discount.amount,
+            sum([discount.amount for discount in discount.discount_lines.all()]),
+        )
+
+
 class TestMultiSiteOrderCreation(TestCase):
     def setUp(self):
         self.creator = OrderCreator()