Refuse to start if DB has an unsafe locale (#12262)

tests/storage/test_unsafe_locale.py

@@ -0,0 +1,46 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from unittest.mock import MagicMock, patch
+
+from synapse.storage.database import make_conn
+from synapse.storage.engines._base import IncorrectDatabaseSetup
+
+from tests.unittest import HomeserverTestCase
+from tests.utils import USE_POSTGRES_FOR_TESTS
+
+
+class UnsafeLocaleTest(HomeserverTestCase):
+    if not USE_POSTGRES_FOR_TESTS:
+        skip = "Requires Postgres"
+
+    @patch("synapse.storage.engines.postgres.PostgresEngine.get_db_locale")
+    def test_unsafe_locale(self, mock_db_locale: MagicMock) -> None:
+        mock_db_locale.return_value = ("B", "B")
+        database = self.hs.get_datastores().databases[0]
+
+        db_conn = make_conn(database._database_config, database.engine, "test_unsafe")
+        with self.assertRaises(IncorrectDatabaseSetup):
+            database.engine.check_database(db_conn)
+        with self.assertRaises(IncorrectDatabaseSetup):
+            database.engine.check_new_database(db_conn)
+        db_conn.close()
+
+    def test_safe_locale(self) -> None:
+        database = self.hs.get_datastores().databases[0]
+
+        db_conn = make_conn(database._database_config, database.engine, "test_unsafe")
+        with db_conn.cursor() as txn:
+            res = database.engine.get_db_locale(txn)
+        self.assertEqual(res, ("C", "C"))
+        db_conn.close()