[3.1.x] Fixed #32012 -- Made test database creation sync apps models when migrations are disabled.

Thanks Jaap Roes for the report.
Backport of 77caeaea88 from master

django/db/backends/base/creation.py

@@ -58,7 +58,14 @@ class BaseDatabaseCreation:
         settings.DATABASES[self.connection.alias]["NAME"] = test_database_name
         self.connection.settings_dict["NAME"] = test_database_name
 
-        if self.connection.settings_dict['TEST']['MIGRATE']:
+        try:
+            if self.connection.settings_dict['TEST']['MIGRATE'] is False:
+                # Disable migrations for all apps.
+                old_migration_modules = settings.MIGRATION_MODULES
+                settings.MIGRATION_MODULES = {
+                    app.label: None
+                    for app in apps.get_app_configs()
+                }
             # We report migrate messages at one level lower than that
             # requested. This ensures we don't get flooded with messages during
             # testing (unless you really ask to be flooded).
@@ -69,6 +76,9 @@ class BaseDatabaseCreation:
                 database=self.connection.alias,
                 run_syncdb=True,
             )
+        finally:
+            if self.connection.settings_dict['TEST']['MIGRATE'] is False:
+                settings.MIGRATION_MODULES = old_migration_modules
 
         # We then serialize the current state of the database into a string
         # and store it on the connection. This slightly horrific process is so people

docs/ref/settings.txt

@@ -787,6 +787,8 @@ on :ref:`controlling the creation order of test databases
 Default: ``True``
 
 When set to ``False``, migrations won't run when creating the test database.
+This is similar to setting ``None`` as a value in :setting:`MIGRATION_MODULES`,
+but for all apps.
 
 .. setting:: TEST_MIRROR
 

docs/releases/3.1.2.txt

@@ -19,3 +19,7 @@ Bugfixes
 
 * Fixed a regression in Django 3.1 where a queryset would crash if it contained
   an aggregation and a ``Q`` object annotation (:ticket:`32007`).
+
+* Fixed a bug in Django 3.1 where a test database was not synced during
+  creation when using the :setting:`MIGRATE <TEST_MIGRATE>` test database
+  setting (:ticket:`32012`).

tests/backends/base/app_unmigrated/migrations/0001_initial.py

@@ -0,0 +1,17 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name='Foo',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('name', models.CharField(max_length=255)),
+            ],
+        ),
+    ]

tests/backends/base/app_unmigrated/models.py

@@ -0,0 +1,8 @@
+from django.db import models
+
+
+class Foo(models.Model):
+    name = models.CharField(max_length=255)
+
+    class Meta:
+        app_label = 'app_unmigrated'

tests/backends/base/test_creation.py

@@ -6,6 +6,7 @@ from django.db.backends.base.creation import (
     TEST_DATABASE_PREFIX, BaseDatabaseCreation,
 )
 from django.test import SimpleTestCase, TransactionTestCase
+from django.test.utils import override_settings
 
 from ..models import (
     CircularA, CircularB, Object, ObjectReference, ObjectSelfReference,
@@ -49,31 +50,57 @@ class TestDbSignatureTests(SimpleTestCase):
         self.assertEqual(signature[3], test_name)
 
 
+@override_settings(INSTALLED_APPS=['backends.base.app_unmigrated'])
 @mock.patch.object(connection, 'ensure_connection')
-@mock.patch('django.core.management.commands.migrate.Command.handle', return_value=None)
+@mock.patch.object(connection, 'prepare_database')
+@mock.patch('django.db.migrations.recorder.MigrationRecorder.has_table', return_value=False)
+@mock.patch('django.db.migrations.executor.MigrationExecutor.migrate')
+@mock.patch('django.core.management.commands.migrate.Command.sync_apps')
 class TestDbCreationTests(SimpleTestCase):
-    def test_migrate_test_setting_false(self, mocked_migrate, mocked_ensure_connection):
+    available_apps = ['backends.base.app_unmigrated']
+
+    def test_migrate_test_setting_false(self, mocked_sync_apps, mocked_migrate, *mocked_objects):
         test_connection = get_connection_copy()
         test_connection.settings_dict['TEST']['MIGRATE'] = False
         creation = test_connection.creation_class(test_connection)
+        if connection.vendor == 'oracle':
+            # Don't close connection on Oracle.
+            creation.connection.close = mock.Mock()
         old_database_name = test_connection.settings_dict['NAME']
         try:
             with mock.patch.object(creation, '_create_test_db'):
                 creation.create_test_db(verbosity=0, autoclobber=True, serialize=False)
-            mocked_migrate.assert_not_called()
+            # Migrations don't run.
+            mocked_migrate.assert_called()
+            args, kwargs = mocked_migrate.call_args
+            self.assertEqual(args, ([],))
+            self.assertEqual(kwargs['plan'], [])
+            # App is synced.
+            mocked_sync_apps.assert_called()
+            mocked_args, _ = mocked_sync_apps.call_args
+            self.assertEqual(mocked_args[1], {'app_unmigrated'})
         finally:
             with mock.patch.object(creation, '_destroy_test_db'):
                 creation.destroy_test_db(old_database_name, verbosity=0)
 
-    def test_migrate_test_setting_true(self, mocked_migrate, mocked_ensure_connection):
+    def test_migrate_test_setting_true(self, mocked_sync_apps, mocked_migrate, *mocked_objects):
         test_connection = get_connection_copy()
         test_connection.settings_dict['TEST']['MIGRATE'] = True
         creation = test_connection.creation_class(test_connection)
+        if connection.vendor == 'oracle':
+            # Don't close connection on Oracle.
+            creation.connection.close = mock.Mock()
         old_database_name = test_connection.settings_dict['NAME']
         try:
             with mock.patch.object(creation, '_create_test_db'):
                 creation.create_test_db(verbosity=0, autoclobber=True, serialize=False)
-            mocked_migrate.assert_called_once()
+            # Migrations run.
+            mocked_migrate.assert_called()
+            args, kwargs = mocked_migrate.call_args
+            self.assertEqual(args, ([('app_unmigrated', '0001_initial')],))
+            self.assertEqual(len(kwargs['plan']), 1)
+            # App is not synced.
+            mocked_sync_apps.assert_not_called()
         finally:
             with mock.patch.object(creation, '_destroy_test_db'):
                 creation.destroy_test_db(old_database_name, verbosity=0)