Support Django 5.0 db_default attribute.

A DB default is not considered backward incompatible, as the default value is kept on DB-level.
See https://docs.djangoproject.com/en/dev/releases/5.0/#database-computed-default-values

tests/fixtures.py

@@ -8,6 +8,9 @@ RENAME_COLUMN = "app_rename_column"
 RENAME_TABLE = "app_rename_table"
 IGNORE_MIGRATION = "app_ignore_migration"
 ADD_NOT_NULL_COLUMN_FOLLOWED_BY_DEFAULT = "app_add_not_null_column_followed_by_default"
+ADD_NOT_NULL_COLUMN_FOLLOWED_BY_DB_DEFAULT = (
+    "app_add_not_null_column_followed_by_db_default"
+)
 ALTER_COLUMN = "app_alter_column"
 ALTER_COLUMN_DROP_NOT_NULL = "app_alter_column_drop_not_null"
 DROP_UNIQUE_TOGETHER = "app_unique_together"

tests/functional/test_migration_linter.py

@@ -2,7 +2,9 @@ from __future__ import annotations
 
 import os
 import unittest
+from unittest import skipIf
 
+import django
 from django.conf import settings
 from django.core.management import call_command
 
@@ -88,6 +90,11 @@ class BaseBackwardCompatibilityDetection:
         app = fixtures.ADD_NOT_NULL_COLUMN_FOLLOWED_BY_DEFAULT
         self._test_linter_finds_no_errors(app)
 
+    @skipIf(django.VERSION[0] < 5, "db_default was implemented in Django 5.0")
+    def test_accept_not_null_column_followed_by_adding_db_default(self):
+        app = fixtures.ADD_NOT_NULL_COLUMN_FOLLOWED_BY_DB_DEFAULT
+        self._test_linter_finds_no_errors(app)
+
     def test_detect_alter_column(self):
         app = fixtures.ALTER_COLUMN
         self._test_linter_finds_no_errors(app)
@@ -128,6 +135,11 @@ class SqliteBackwardCompatibilityDetectionTestCase(
         app = fixtures.MAKE_NOT_NULL_WITH_DJANGO_DEFAULT
         self._test_linter_finds_errors(app)
 
+    @skipIf(django.VERSION[0] < 5, "db_default was implemented in Django 5.0")
+    def test_accept_not_null_column_followed_by_adding_db_default(self):
+        app = fixtures.ADD_NOT_NULL_COLUMN_FOLLOWED_BY_DB_DEFAULT
+        self._test_linter_finds_errors(app)
+
     def test_detect_make_column_not_null_with_lib_default(self):
         # The 'django-add-default-value' doesn't handle sqlite correctly
         app = fixtures.MAKE_NOT_NULL_WITH_LIB_DEFAULT

tests/test_project/app_add_not_null_column_followed_by_db_default/migrations/0001_initial.py

@@ -0,0 +1,30 @@
+# Generated by Django 5.0.1 on 2024-02-04 20:07
+
+from __future__ import annotations
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name="A",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("field", models.IntegerField()),
+            ],
+        ),
+    ]

tests/test_project/app_add_not_null_column_followed_by_db_default/migrations/0002_a_not_null_field_db_default.py

@@ -0,0 +1,21 @@
+# Generated by Django 5.0.1 on 2024-02-04 20:07
+
+from __future__ import annotations
+
+import django.db.models.functions.math
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("app_add_not_null_column_followed_by_db_default", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="a",
+            name="not_null_field_db_default",
+            field=models.IntegerField(db_default=django.db.models.functions.math.Pi()),
+        ),
+    ]

tests/test_project/app_add_not_null_column_followed_by_db_default/models.py

@@ -0,0 +1,12 @@
+from __future__ import annotations
+
+from django.db import models
+from django.db.models.functions import Pi
+
+
+class A(models.Model):
+    field = models.IntegerField()
+    not_null_field_db_default = models.IntegerField(
+        null=False,
+        db_default=Pi(),
+    )

tests/test_project/settings.py

@@ -14,6 +14,8 @@ from __future__ import annotations
 
 import os
 
+import django
+
 # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
@@ -59,6 +61,12 @@ INSTALLED_APPS = [
     "tests.test_project.app_create_index_exclusive",
 ]
 
+if django.VERSION[0] >= 5:
+    # db_default attribute was only added in Django 5.0
+    INSTALLED_APPS.append(
+        "tests.test_project.app_add_not_null_column_followed_by_db_default"
+    )
+
 MIDDLEWARE = [
     "django.middleware.security.SecurityMiddleware",
     "django.contrib.sessions.middleware.SessionMiddleware",

tests/unit/test_sql_analyser.py

@@ -66,6 +66,15 @@ class MySqlAnalyserTestCase(SqlAnalyserTestCase):
         ]
         self.assertBackwardIncompatibleSql(sql)
 
+    def test_add_not_null_without_dropping_default(self):
+        sql = (
+            "ALTER TABLE `app_add_not_null_column_a` ADD COLUMN `new_not_null_field` integer DEFAULT 1 NOT NULL;",
+        )
+        self.assertValidSql(sql)
+
+        sql = "ALTER TABLE `app_add_not_null_column_followed_by_default_a` ADD COLUMN `not_null_field_db_default` integer DEFAULT (PI()) NOT NULL;"
+        self.assertValidSql(sql)
+
     def test_add_not_null_followed_by_default(self):
         sql = [
             "ALTER TABLE `app_add_not_null_column_followed_by_default_a` ADD COLUMN `new_not_null_field` integer DEFAULT 1 NOT NULL;",
@@ -147,6 +156,15 @@ class SqliteAnalyserTestCase(SqlAnalyserTestCase):
         ]
         self.assertBackwardIncompatibleSql(sql)
 
+    def test_add_not_null_without_dropping_default(self):
+        sql = [
+            'CREATE TABLE "new__app_add_not_null_column_followed_by_default_a" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "not_null_field_db_default" integer DEFAULT (PI()) NOT NULL, "field" integer NOT NULL, "not_null_field" integer NOT NULL);',
+            'INSERT INTO "new__app_add_not_null_column_followed_by_default_a" ("id", "field", "not_null_field") SELECT "id", "field", "not_null_field" FROM "app_add_not_null_column_followed_by_default_a";',
+            'DROP TABLE "app_add_not_null_column_followed_by_default_a";',
+            'ALTER TABLE "new__app_add_not_null_column_followed_by_default_a" RENAME TO "app_add_not_null_column_followed_by_default_a";',
+        ]
+        self.assertBackwardIncompatibleSql(sql)
+
     def test_create_table_with_not_null(self):
         sql = 'CREATE TABLE "app_create_table_with_not_null_column_a" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "field" varchar(150) NOT NULL);'
         self.assertValidSql(sql)
@@ -207,6 +225,10 @@ class PostgresqlAnalyserTestCase(SqlAnalyserTestCase):
         sql = 'ALTER TABLE "app_alter_column_a" ALTER COLUMN "field" TYPE varchar(10) USING "field"::varchar(10);'
         self.assertBackwardIncompatibleSql(sql)
 
+    def test_add_not_null_without_dropping_default(self):
+        sql = 'ALTER TABLE "app_add_not_null_column_followed_by_default_a" ADD COLUMN "not_null_field_db_default" integer DEFAULT (PI()) NOT NULL;'
+        self.assertValidSql(sql)
+
     def test_not_null_followed_by_default(self):
         sql = [
             'ALTER TABLE "app_add_not_null_column_followed_by_default_a" ADD COLUMN "not_null_field" integer DEFAULT 1 NOT NULL;',