Fix single related model access when predicate contains a primitive

Author: AlexHill

relativity/fields.py

@@ -242,9 +242,11 @@ def get_extra_restriction(self, where_class, alias, related_alias):
     def _resolve_expression_local_references(cls, expr, obj):
         if isinstance(expr, L):
             return expr._relativity_resolve_for_instance(obj)
-        else:
+        elif hasattr(expr, "get_source_expressions"):
             for source_expr in expr.get_source_expressions():
                 cls._resolve_expression_local_references(source_expr, obj)
+        else:
+            return expr
         return expr
 
     def get_forward_related_filter(self, obj):

tests/models.py

@@ -120,6 +120,7 @@ class Product(models.Model):
     colour = models.CharField(max_length=20)
     shape = models.CharField(max_length=20)
     size = models.IntegerField()
+    deleted = models.BooleanField(default=False)
 
     def __str__(self):
         return "Product #%s: a %s %s, size %s" % (
@@ -136,7 +137,7 @@ class CartItem(models.Model):
 
     product = Relationship(
         Product,
-        Q(sku=L("product_code")),
+        Q(deleted=False, sku=L("product_code")),
         related_name="cart_items",
         multiple=False,
         null=False,

tests/tests.py

@@ -90,7 +90,9 @@ def setUpTestData(cls):
                 Product(pk=6, sku="66", size=5, colour="blue", shape="square"),
                 Product(pk=7, sku="77", size=1, colour="yellow", shape="circle"),
                 Product(pk=8, sku="88", size=2, colour="green", shape="triangle"),
-                Product(pk=9, sku="99", size=2, colour="red", shape="square"),
+                Product(
+                    pk=9, sku="99", size=2, colour="red", shape="square", deleted=True
+                ),
             ]
         )
 
@@ -366,7 +368,7 @@ def test_not_nullable(self):
         item = CartItem.objects.create(
             pk=4,
             product_code="nonexistent",
-            description="cart item for anonexistent product",
+            description="cart item for a non-existent product",
         )
         with self.assertRaises(Product.DoesNotExist):
             item.product
@@ -382,3 +384,13 @@ def test_descriptor_not_cached(self):
         item.product.delete()
         with self.assertRaises(Product.DoesNotExist):
             item.product
+
+    def test_primitive_in_predicate(self):
+        product = Product.objects.filter(deleted=True).first()
+        item = CartItem.objects.create(
+            pk=5,
+            product_code=product.sku,
+            description="cart item for a deleted product",
+        )
+        with self.assertRaises(Product.DoesNotExist):
+            item.product