fix: InvoiceQuerySet.annotate_total()

core/tests/test_user.py

@@ -7,7 +7,7 @@ from django.test import Client, TestCase
 from django.urls import reverse
 from django.utils.timezone import now
 from model_bakery import baker, seq
-from model_bakery.recipe import Recipe
+from model_bakery.recipe import Recipe, foreign_key
 
 from core.baker_recipes import (
     old_subscriber_user,
@@ -16,6 +16,7 @@ from core.baker_recipes import (
 )
 from core.models import User
 from counter.models import Counter, Refilling, Selling
+from eboutic.models import Invoice, InvoiceItem
 
 
 class TestSearchUsers(TestCase):
@@ -148,3 +149,19 @@ class TestFilterInactive(TestCase):
     def test_filter_inactive(self):
         res = User.objects.filter(id__in=[u.id for u in self.users]).filter_inactive()
         assert list(res) == [self.users[0], self.users[5]]
+
+
+@pytest.mark.django_db
+def test_user_invoice_with_multiple_items():
+    """Test that annotate_total() works when invoices contain multiple items."""
+    user: User = subscriber_user.make()
+    item_recipe = Recipe(InvoiceItem, invoice=foreign_key(Recipe(Invoice, user=user)))
+    item_recipe.make(_quantity=3, quantity=1, product_unit_price=5)
+    item_recipe.make(_quantity=1, quantity=1, product_unit_price=5)
+    res = list(
+        Invoice.objects.filter(user=user)
+        .annotate_total()
+        .order_by("-total")
+        .values_list("total", flat=True)
+    )
+    assert res == [15, 5]

eboutic/models.py

@@ -167,10 +167,15 @@ class InvoiceQueryset(models.QuerySet):
         The total amount is the sum of (product_unit_price * quantity)
         for all items related to the invoice.
         """
+        # aggregates within subqueries require a little bit of black magic,
+        # but hopefully, django gives a comprehensive documentation for that :
+        # https://docs.djangoproject.com/en/stable/ref/models/expressions/#using-aggregates-within-a-subquery-expression
         return self.annotate(
             total=Subquery(
                 InvoiceItem.objects.filter(invoice_id=OuterRef("pk"))
-                .annotate(total=Sum(F("product_unit_price") * F("quantity")))
+                .annotate(item_amount=F("product_unit_price") * F("quantity"))
+                .values("item_amount")
+                .annotate(total=Sum("item_amount"))
                 .values("total")
             )
         )