[5.1.x] Fixed #35638 -- Updated validate_constraints to consider db_default.

Backport of 509763c799 from main.

tests/constraints/models.py

@@ -128,3 +128,10 @@ class JSONFieldModel(models.Model):
 
     class Meta:
         required_db_features = {"supports_json_field"}
+
+
+class ModelWithDatabaseDefault(models.Model):
+    field = models.CharField(max_length=255)
+    field_with_db_default = models.CharField(
+        max_length=255, db_default=models.Value("field_with_db_default")
+    )

tests/constraints/tests.py

@@ -4,7 +4,7 @@ from django.core.exceptions import ValidationError
 from django.db import IntegrityError, connection, models
 from django.db.models import F
 from django.db.models.constraints import BaseConstraint, UniqueConstraint
-from django.db.models.functions import Abs, Lower
+from django.db.models.functions import Abs, Lower, Upper
 from django.db.transaction import atomic
 from django.test import SimpleTestCase, TestCase, skipIfDBFeature, skipUnlessDBFeature
 from django.test.utils import ignore_warnings
@@ -14,6 +14,7 @@ from .models import (
     ChildModel,
     ChildUniqueConstraintProduct,
     JSONFieldModel,
+    ModelWithDatabaseDefault,
     Product,
     UniqueConstraintConditionProduct,
     UniqueConstraintDeferrable,
@@ -396,6 +397,33 @@ class CheckConstraintTests(TestCase):
         with self.assertWarnsRegex(RemovedInDjango60Warning, msg):
             self.assertIs(constraint.check, other_condition)
 
+    def test_database_default(self):
+        models.CheckConstraint(
+            condition=models.Q(field_with_db_default="field_with_db_default"),
+            name="check_field_with_db_default",
+        ).validate(ModelWithDatabaseDefault, ModelWithDatabaseDefault())
+
+        # Ensure that a check also does not silently pass with either
+        # FieldError or DatabaseError when checking with a db_default.
+        with self.assertRaises(ValidationError):
+            models.CheckConstraint(
+                condition=models.Q(
+                    field_with_db_default="field_with_db_default", field="field"
+                ),
+                name="check_field_with_db_default_2",
+            ).validate(
+                ModelWithDatabaseDefault, ModelWithDatabaseDefault(field="not-field")
+            )
+
+        with self.assertRaises(ValidationError):
+            models.CheckConstraint(
+                condition=models.Q(field_with_db_default="field_with_db_default"),
+                name="check_field_with_db_default",
+            ).validate(
+                ModelWithDatabaseDefault,
+                ModelWithDatabaseDefault(field_with_db_default="other value"),
+            )
+
 
 class UniqueConstraintTests(TestCase):
     @classmethod
@@ -1251,3 +1279,30 @@ class UniqueConstraintTests(TestCase):
         msg = "A unique constraint must be named."
         with self.assertRaisesMessage(ValueError, msg):
             models.UniqueConstraint(fields=["field"])
+
+    def test_database_default(self):
+        models.UniqueConstraint(
+            fields=["field_with_db_default"], name="unique_field_with_db_default"
+        ).validate(ModelWithDatabaseDefault, ModelWithDatabaseDefault())
+        models.UniqueConstraint(
+            Upper("field_with_db_default"),
+            name="unique_field_with_db_default_expression",
+        ).validate(ModelWithDatabaseDefault, ModelWithDatabaseDefault())
+
+        ModelWithDatabaseDefault.objects.create()
+
+        msg = (
+            "Model with database default with this Field with db default already "
+            "exists."
+        )
+        with self.assertRaisesMessage(ValidationError, msg):
+            models.UniqueConstraint(
+                fields=["field_with_db_default"], name="unique_field_with_db_default"
+            ).validate(ModelWithDatabaseDefault, ModelWithDatabaseDefault())
+
+        msg = "Constraint “unique_field_with_db_default_expression” is violated."
+        with self.assertRaisesMessage(ValidationError, msg):
+            models.UniqueConstraint(
+                Upper("field_with_db_default"),
+                name="unique_field_with_db_default_expression",
+            ).validate(ModelWithDatabaseDefault, ModelWithDatabaseDefault())

tests/postgres_tests/migrations/0002_create_test_models.py

@@ -434,7 +434,7 @@ class Migration(migrations.Migration):
                         primary_key=True,
                     ),
                 ),
-                ("ints", IntegerRangeField(null=True, blank=True)),
+                ("ints", IntegerRangeField(null=True, blank=True, db_default=(5, 10))),
                 ("bigints", BigIntegerRangeField(null=True, blank=True)),
                 ("decimals", DecimalRangeField(null=True, blank=True)),
                 ("timestamps", DateTimeRangeField(null=True, blank=True)),

tests/postgres_tests/models.py

@@ -130,7 +130,7 @@ class LineSavedSearch(PostgreSQLModel):
 
 
 class RangesModel(PostgreSQLModel):
-    ints = IntegerRangeField(blank=True, null=True)
+    ints = IntegerRangeField(blank=True, null=True, db_default=(5, 10))
     bigints = BigIntegerRangeField(blank=True, null=True)
     decimals = DecimalRangeField(blank=True, null=True)
     timestamps = DateTimeRangeField(blank=True, null=True)

tests/postgres_tests/test_constraints.py

@@ -1238,3 +1238,12 @@ class ExclusionConstraintTests(PostgreSQLTestCase):
             constraint_name,
             self.get_constraints(ModelWithExclusionConstraint._meta.db_table),
         )
+
+    def test_database_default(self):
+        constraint = ExclusionConstraint(
+            name="ints_equal", expressions=[("ints", RangeOperators.EQUAL)]
+        )
+        RangesModel.objects.create()
+        msg = "Constraint “ints_equal” is violated."
+        with self.assertRaisesMessage(ValidationError, msg):
+            constraint.validate(RangesModel, RangesModel())

tests/validation/models.py

@@ -48,7 +48,7 @@ class ModelToValidate(models.Model):
 
 class UniqueFieldsModel(models.Model):
     unique_charfield = models.CharField(max_length=100, unique=True)
-    unique_integerfield = models.IntegerField(unique=True)
+    unique_integerfield = models.IntegerField(unique=True, db_default=42)
     non_unique_field = models.IntegerField()
 
 

tests/validation/test_unique.py

@@ -146,6 +146,20 @@ class PerformUniqueChecksTest(TestCase):
             mtv = ModelToValidate(number=10, name="Some Name")
             mtv.full_clean()
 
+    def test_unique_db_default(self):
+        UniqueFieldsModel.objects.create(unique_charfield="foo", non_unique_field=42)
+        um = UniqueFieldsModel(unique_charfield="bar", non_unique_field=42)
+        with self.assertRaises(ValidationError) as cm:
+            um.full_clean()
+        self.assertEqual(
+            cm.exception.message_dict,
+            {
+                "unique_integerfield": [
+                    "Unique fields model with this Unique integerfield already exists."
+                ]
+            },
+        )
+
     def test_unique_for_date(self):
         Post.objects.create(
             title="Django 1.0 is released",