test(persistence): alembic 0001 round-trip on SQLite + Postgres

Verifies alembic upgrade 0001 adds users.default_workspace_id (with FK
to workspaces) and that downgrade cleanly removes it. Runs on both
dialects because the migration uses op.batch_alter_table for SQLite
ALTER compatibility.

Tests are intentionally sync — alembic's command layer is sync and
env.py calls asyncio.run(); running under pytest-anyio would deadlock
on the inner event loop.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/tests/test_alembic_default_workspace_id.py

@@ -0,0 +1,148 @@
+"""Alembic revision 0001 round-trips on both Postgres and SQLite.
+
+Verifies the first DeerFlow migration adds `users.default_workspace_id`
+(with FK to `workspaces`) on upgrade and removes it on downgrade. Both
+backends are exercised because the migration relies on
+`op.batch_alter_table` for SQLite ALTER compatibility — we want to know
+if either dialect regresses.
+
+These tests are synchronous: alembic's command layer is sync, and our
+`env.py` calls `asyncio.run(...)` internally. Running under
+pytest-anyio would put us inside an event loop and crash that
+`asyncio.run` call, so we keep the test bodies plain `def`.
+"""
+
+from __future__ import annotations
+
+import tempfile
+from pathlib import Path
+
+import pytest
+from alembic import command
+from alembic.config import Config
+from sqlalchemy import create_engine, inspect, text
+
+_ALEMBIC_INI = Path(__file__).resolve().parents[1] / "packages" / "harness" / "deerflow" / "persistence" / "migrations" / "alembic.ini"
+
+
+def _make_alembic_config(url: str) -> Config:
+    cfg = Config(str(_ALEMBIC_INI))
+    cfg.set_main_option("sqlalchemy.url", url)
+    return cfg
+
+
+def _bootstrap_pre_pr4_schema(sync_url: str) -> None:
+    """Create the minimal pre-PR4 schema the migration needs to ALTER.
+
+    Only `users` (without `default_workspace_id`) and `workspaces` (just `id`)
+    are required so the FK target resolves. The rest of the production
+    schema is irrelevant to this migration.
+    """
+    engine = create_engine(sync_url)
+    with engine.begin() as conn:
+        conn.execute(
+            text(
+                """
+                CREATE TABLE workspaces (
+                    id VARCHAR(36) PRIMARY KEY,
+                    name VARCHAR(64) NOT NULL
+                )
+                """
+            )
+        )
+        conn.execute(
+            text(
+                """
+                CREATE TABLE users (
+                    id VARCHAR(36) PRIMARY KEY,
+                    email VARCHAR(255) NOT NULL
+                )
+                """
+            )
+        )
+    engine.dispose()
+
+
+def _assert_column_present(sync_url: str) -> None:
+    engine = create_engine(sync_url)
+    insp = inspect(engine)
+    cols = {c["name"] for c in insp.get_columns("users")}
+    assert "default_workspace_id" in cols, f"column missing; got {cols}"
+    fks = insp.get_foreign_keys("users")
+    fk_to_ws = [fk for fk in fks if fk.get("referred_table") == "workspaces"]
+    assert fk_to_ws, f"FK to workspaces missing; got {fks}"
+    assert fk_to_ws[0]["constrained_columns"] == ["default_workspace_id"]
+    assert fk_to_ws[0]["referred_columns"] == ["id"]
+    engine.dispose()
+
+
+def _assert_column_absent(sync_url: str) -> None:
+    engine = create_engine(sync_url)
+    insp = inspect(engine)
+    cols = {c["name"] for c in insp.get_columns("users")}
+    assert "default_workspace_id" not in cols, f"column still present; got {cols}"
+    engine.dispose()
+
+
+# ---------- SQLite tests ----------------------------------------------------
+
+
+def test_sqlite_upgrade_adds_default_workspace_id_with_fk() -> None:
+    """SQLite: upgrade 0001 adds column + FK; batch_alter_table works."""
+    with tempfile.TemporaryDirectory() as tmp:
+        db_path = Path(tmp) / "test.db"
+        sync_url = f"sqlite:///{db_path}"
+        async_url = f"sqlite+aiosqlite:///{db_path}"
+
+        _bootstrap_pre_pr4_schema(sync_url)
+
+        cfg = _make_alembic_config(async_url)
+        command.upgrade(cfg, "head")
+
+        _assert_column_present(sync_url)
+
+
+def test_sqlite_downgrade_removes_default_workspace_id() -> None:
+    """SQLite: downgrade 0001 removes the column it added."""
+    with tempfile.TemporaryDirectory() as tmp:
+        db_path = Path(tmp) / "test.db"
+        sync_url = f"sqlite:///{db_path}"
+        async_url = f"sqlite+aiosqlite:///{db_path}"
+
+        _bootstrap_pre_pr4_schema(sync_url)
+
+        cfg = _make_alembic_config(async_url)
+        command.upgrade(cfg, "head")
+        _assert_column_present(sync_url)
+
+        command.downgrade(cfg, "-1")
+        _assert_column_absent(sync_url)
+
+
+# ---------- Postgres tests --------------------------------------------------
+
+
+@pytest.mark.postgres
+def test_postgres_upgrade_adds_default_workspace_id_with_fk(postgres_url: str) -> None:
+    """Postgres: upgrade 0001 adds column + FK pointing at workspaces(id)."""
+    sync_url = postgres_url.replace("+asyncpg", "+psycopg")
+    _bootstrap_pre_pr4_schema(sync_url)
+
+    cfg = _make_alembic_config(postgres_url)
+    command.upgrade(cfg, "head")
+
+    _assert_column_present(sync_url)
+
+
+@pytest.mark.postgres
+def test_postgres_downgrade_removes_default_workspace_id(postgres_url: str) -> None:
+    """Postgres: downgrade 0001 cleanly drops the FK and column."""
+    sync_url = postgres_url.replace("+asyncpg", "+psycopg")
+    _bootstrap_pre_pr4_schema(sync_url)
+
+    cfg = _make_alembic_config(postgres_url)
+    command.upgrade(cfg, "head")
+    _assert_column_present(sync_url)
+
+    command.downgrade(cfg, "-1")
+    _assert_column_absent(sync_url)