Fixed #27858 -- Prevented read-only management commands from creating the django_migrations table.

MigrationRecorder now assumes that if the django_migrations table
doesn't exist, then no migrations are applied.

Reverted documentation change from refs #23808.

2 files changed, 14 insertions, 20 deletions

diff --git a/tests/admin_scripts/tests.py b/tests/admin_scripts/tests.py
index 9ef2da83a0..e2d2a3bca1 100644
--- a/tests/admin_scripts/tests.py
+++ b/tests/admin_scripts/tests.py
@@ -22,7 +22,6 @@ from django.core.management import (
     BaseCommand, CommandError, call_command, color,
 )
 from django.db import ConnectionHandler
-from django.db.migrations.exceptions import MigrationSchemaMissing
 from django.db.migrations.recorder import MigrationRecorder
 from django.test import (
     LiveServerTestCase, SimpleTestCase, TestCase, override_settings,
@@ -1339,15 +1338,12 @@ class ManageRunserver(AdminScriptTestCase):
 
     def test_readonly_database(self):
         """
-        Ensure runserver.check_migrations doesn't choke when a database is read-only
-        (with possibly no django_migrations table).
+        runserver.check_migrations() doesn't choke when a database is read-only.
         """
-        with mock.patch.object(
-                MigrationRecorder, 'ensure_schema',
-                side_effect=MigrationSchemaMissing()):
+        with mock.patch.object(MigrationRecorder, 'has_table', return_value=False):
             self.cmd.check_migrations()
-        # Check a warning is emitted
-        self.assertIn("Not checking migrations", self.output.getvalue())
+        # You have # ...
+        self.assertIn('unapplied migration(s)', self.output.getvalue())
 
 
 class ManageRunserverMigrationWarning(TestCase):
diff --git a/tests/migrations/test_commands.py b/tests/migrations/test_commands.py
index 3b022e666c..777081e3c7 100644
--- a/tests/migrations/test_commands.py
+++ b/tests/migrations/test_commands.py
@@ -11,9 +11,7 @@ from django.db import (
     ConnectionHandler, DatabaseError, connection, connections, models,
 )
 from django.db.backends.base.schema import BaseDatabaseSchemaEditor
-from django.db.migrations.exceptions import (
-    InconsistentMigrationHistory, MigrationSchemaMissing,
-)
+from django.db.migrations.exceptions import InconsistentMigrationHistory
 from django.db.migrations.recorder import MigrationRecorder
 from django.test import override_settings
 
@@ -697,35 +695,35 @@ class MakeMigrationsTests(MigrationTestBase):
         The history consistency checks in makemigrations respect
         settings.DATABASE_ROUTERS.
         """
-        def patched_ensure_schema(migration_recorder):
+        def patched_has_table(migration_recorder):
             if migration_recorder.connection is connections['other']:
-                raise MigrationSchemaMissing('Patched')
+                raise Exception('Other connection')
             else:
                 return mock.DEFAULT
 
         self.assertTableNotExists('migrations_unicodemodel')
         apps.register_model('migrations', UnicodeModel)
         with mock.patch.object(
-                MigrationRecorder, 'ensure_schema',
-                autospec=True, side_effect=patched_ensure_schema) as ensure_schema:
+                MigrationRecorder, 'has_table',
+                autospec=True, side_effect=patched_has_table) as has_table:
             with self.temporary_migration_module() as migration_dir:
                 call_command("makemigrations", "migrations", verbosity=0)
                 initial_file = os.path.join(migration_dir, "0001_initial.py")
                 self.assertTrue(os.path.exists(initial_file))
-                self.assertEqual(ensure_schema.call_count, 1)  # 'default' is checked
+                self.assertEqual(has_table.call_count, 1)  # 'default' is checked
 
                 # Router says not to migrate 'other' so consistency shouldn't
                 # be checked.
                 with self.settings(DATABASE_ROUTERS=['migrations.routers.TestRouter']):
                     call_command('makemigrations', 'migrations', verbosity=0)
-                self.assertEqual(ensure_schema.call_count, 2)  # 'default' again
+                self.assertEqual(has_table.call_count, 2)  # 'default' again
 
                 # With a router that doesn't prohibit migrating 'other',
                 # consistency is checked.
                 with self.settings(DATABASE_ROUTERS=['migrations.routers.EmptyRouter']):
-                    with self.assertRaisesMessage(MigrationSchemaMissing, 'Patched'):
+                    with self.assertRaisesMessage(Exception, 'Other connection'):
                         call_command('makemigrations', 'migrations', verbosity=0)
-                self.assertEqual(ensure_schema.call_count, 4)  # 'default' and 'other'
+                self.assertEqual(has_table.call_count, 4)  # 'default' and 'other'
 
                 # With a router that doesn't allow migrating on any database,
                 # no consistency checks are made.
@@ -741,7 +739,7 @@ class MakeMigrationsTests(MigrationTestBase):
                     self.assertIn(connection_alias, ['default', 'other'])
                     # Raises an error if invalid app_name/model_name occurs.
                     apps.get_app_config(app_name).get_model(call_kwargs['model_name'])
-                self.assertEqual(ensure_schema.call_count, 4)
+                self.assertEqual(has_table.call_count, 4)
 
     def test_failing_migration(self):
         # If a migration fails to serialize, it shouldn't generate an empty file. #21280