Tests and fixes for a bug where discount quantities did not respect per-line item quantities.

registrasion/controllers/discount.py

@@ -5,7 +5,7 @@ from registrasion.models import commerce
 from registrasion.models import conditions
 
 from django.db.models import Case
-from django.db.models import Q
+from django.db.models import F, Q
 from django.db.models import Sum
 from django.db.models import Value
 from django.db.models import When
@@ -64,9 +64,7 @@ class DiscountController(object):
             discount = clause.discount
             cond = ConditionController.for_condition(discount)
 
-            past_use_count = discount.past_use_count
-
-
+            past_use_count = clause.past_use_count
             if past_use_count >= clause.quantity:
                 # This clause has exceeded its use count
                 pass
@@ -139,7 +137,6 @@ class DiscountController(object):
             discounts = discounttype.objects.filter(id__in=valid_discounts)
             ctrl = ConditionController.for_type(discounttype)
             discounts = ctrl.pre_filter(discounts, user)
-            discounts = cls._annotate_with_past_uses(discounts, user)
             all_subsets.append(discounts)
 
         filtered_discounts = list(itertools.chain(*all_subsets))
@@ -148,11 +145,17 @@ class DiscountController(object):
         # (contains annotations needed in the future)
         from_filter = dict((i.id, i) for i in filtered_discounts)
 
-        # The set of all potential discounts
-        discount_clauses = set(itertools.chain(
+        clause_sets = (
             product_discounts.filter(discount__in=filtered_discounts),
             all_category_discounts.filter(discount__in=filtered_discounts),
-        ))
+        )
+
+        clause_sets = (
+            cls._annotate_with_past_uses(i, user) for i in clause_sets
+        )
+
+        # The set of all potential discount clauses
+        discount_clauses = set(itertools.chain(*clause_sets))
 
         # Replace discounts with the filtered ones
         # These are the correct subclasses (saves query later on), and have
@@ -164,15 +167,26 @@ class DiscountController(object):
 
     @classmethod
     def _annotate_with_past_uses(cls, queryset, user):
-        ''' Annotates the queryset with a usage count for that discount by the
-        given user. '''
+        ''' Annotates the queryset with a usage count for that discount claus
+        by the given user. '''
+
+        if queryset.model == conditions.DiscountForCategory:
+            matches = (
+                Q(category=F('discount__discountitem__product__category'))
+            )
+        elif queryset.model == conditions.DiscountForProduct:
+            matches = (
+                Q(product=F('discount__discountitem__product'))
+            )
+
+        in_carts = (
+            Q(discount__discountitem__cart__user=user) &
+            Q(discount__discountitem__cart__status=commerce.Cart.STATUS_PAID)
+        )
 
         past_use_quantity = When(
-            (
-                Q(discountitem__cart__user=user) &
-                Q(discountitem__cart__status=commerce.Cart.STATUS_PAID)
-            ),
-            then="discountitem__quantity",
+            in_carts & matches,
+            then="discount__discountitem__quantity",
         )
 
         past_use_quantity_or_zero = Case(

registrasion/tests/test_discount.py

@@ -398,6 +398,29 @@ class DiscountTestCase(RegistrationCartTestCase):
         )
         self.assertEqual(2, len(discounts))
 
+    def test_product_discount_applied_on_different_invoices(self):
+        # quantity=1 means "quantity per product"
+        self.add_discount_prod_1_includes_prod_3_and_prod_4(quantity=1)
+        cart = TestingCartController.for_user(self.USER_1)
+        cart.add_to_cart(self.PROD_1, 1)  # Enable the discount
+        discounts = DiscountController.available_discounts(
+            self.USER_1,
+            [],
+            [self.PROD_3, self.PROD_4],
+        )
+        self.assertEqual(2, len(discounts))
+        # adding one of PROD_3 should make it no longer an available discount.
+        cart.add_to_cart(self.PROD_3, 1)
+        cart.next_cart()
+
+        # should still have (and only have) the discount for prod_4
+        discounts = DiscountController.available_discounts(
+            self.USER_1,
+            [],
+            [self.PROD_3, self.PROD_4],
+        )
+        self.assertEqual(1, len(discounts))
+
     def test_discounts_are_released_by_refunds(self):
         self.add_discount_prod_1_includes_prod_2(quantity=2)
         cart = TestingCartController.for_user(self.USER_1)