Add get_placeholder to handle automatic check constraint evaluation

netfields/fields.py

@@ -120,6 +120,9 @@ def get_db_prep_lookup(self, lookup_type, value, connection,
         return super(_NetAddressField, self).get_db_prep_lookup(
             lookup_type, value, connection=connection, prepared=prepared)
 
+    def get_placeholder(self, value, compiler, connection):
+        return "%s::{}".format(self.db_type(connection))
+
     def formfield(self, **kwargs):
         defaults = {'form_class': self.form_class()}
         defaults.update(kwargs)

test/models.py

@@ -1,3 +1,4 @@
+from django import VERSION
 from django.contrib.postgres.fields import ArrayField
 from django.db.models import CASCADE, ForeignKey, Model
 
@@ -117,3 +118,20 @@ class AggregateTestChildModel(Model):
     )
     network = CidrAddressField()
     inet = InetAddressField()
+
+
+if VERSION >= (4, 1):
+    from django.db.models import F, Q, CheckConstraint
+
+
+    class ConstraintModel(Model):
+        network = CidrAddressField()
+        inet = InetAddressField()
+
+        class Meta:
+            constraints = (
+                CheckConstraint(
+                    check=Q(network__net_contains=F('inet')),
+                    name='inet_contained',
+                ),
+            )

test/tests/test_sql_fields.py

@@ -772,3 +772,16 @@ def test_aggregate_network(self):
         self.assertEqual(network_qs[0].agg_network, [None])
         AggregateTestChildModel.objects.create(parent=parent, network=network, inet=inet)
         self.assertEqual(network_qs[0].agg_network, [network])
+
+
+class TestConstraints(TestCase):
+
+    @skipIf(VERSION < (4, 1), 'Check constraint validation is supported from django 4.1 onwards')
+    def test_check_constraint(self):
+        from test.models import ConstraintModel
+
+        inet = IPv4Interface('10.10.10.20/32')
+        network = IPv4Network('10.10.10.0/24')
+        model = ConstraintModel(inet=inet, network=network)
+        model.full_clean()
+        model.save()