fix: commit migration session setup

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a053ff-1d6f-7fe2-ac1c-a6eb40a42a0c

tests/test_migration_environment.py

@@ -1,8 +1,14 @@
 from __future__ import annotations
 
+from unittest.mock import Mock, call
+
 import pytest
 
-from hub_core.migrations.roles import migration_role_statement, migration_schema_statement
+from hub_core.migrations.roles import (
+    configure_migration_session,
+    migration_role_statement,
+    migration_schema_statement,
+)
 
 
 def test_migration_role_is_quoted_and_validated() -> None:
@@ -19,3 +25,27 @@ def test_migration_schema_is_explicitly_quoted_and_validated() -> None:
     assert migration_schema_statement(None) is None
     with pytest.raises(ValueError, match="safe PostgreSQL schema"):
         migration_schema_statement('hub_runtime"; DROP SCHEMA public; --')
+
+
+def test_migration_session_commits_setup_before_alembic_transaction() -> None:
+    connection = Mock()
+
+    configure_migration_session(
+        connection,
+        role="hub_runtime_owner",
+        schema="hub_runtime",
+    )
+
+    assert connection.method_calls == [
+        call.exec_driver_sql('SET ROLE "hub_runtime_owner"'),
+        call.exec_driver_sql('SET search_path TO "hub_runtime", public'),
+        call.commit(),
+    ]
+
+
+def test_migration_session_does_not_open_empty_setup_transaction() -> None:
+    connection = Mock()
+
+    configure_migration_session(connection, role=None, schema=None)
+
+    connection.assert_not_called()