refactor: replace exec_dml with CRUD operations in various files and improve session handling

backend/tests/test_db_transaction_safety.py

@@ -0,0 +1,125 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from types import SimpleNamespace
+from typing import Any
+
+import pytest
+from sqlmodel import Field, SQLModel
+
+from app.db import crud
+from app.db import session as db_session
+
+
+class _Thing(SQLModel, table=True):
+    __tablename__ = "_test_thing"
+
+    id: int | None = Field(default=None, primary_key=True)
+    name: str
+
+
+@dataclass
+class _SessionCtx:
+    session: Any
+    entered: int = 0
+    exited: int = 0
+
+    async def __aenter__(self) -> Any:
+        self.entered += 1
+        return self.session
+
+    async def __aexit__(self, _exc_type: Any, _exc: Any, _tb: Any) -> bool:
+        self.exited += 1
+        return False
+
+
+@dataclass
+class _Maker:
+    ctx: _SessionCtx
+
+    def __call__(self) -> _SessionCtx:
+        return self.ctx
+
+
+@pytest.mark.asyncio
+async def test_get_session_rolls_back_on_dependency_error(monkeypatch: pytest.MonkeyPatch) -> None:
+    fake_session = SimpleNamespace(rollbacks=0)
+
+    async def _rollback() -> None:
+        fake_session.rollbacks += 1
+
+    fake_session.rollback = _rollback
+    ctx = _SessionCtx(fake_session)
+    monkeypatch.setattr(db_session, "async_session_maker", _Maker(ctx))
+
+    generator = db_session.get_session()
+    yielded = await anext(generator)
+    assert yielded is fake_session
+
+    with pytest.raises(RuntimeError, match="boom"):
+        await generator.athrow(RuntimeError("boom"))
+
+    assert fake_session.rollbacks == 1
+    assert ctx.entered == 1
+    assert ctx.exited == 1
+
+
+@pytest.mark.asyncio
+async def test_create_rolls_back_when_commit_fails() -> None:
+    @dataclass
+    class _FailCommitSession:
+        rollback_calls: int = 0
+        added: list[Any] = None
+
+        def __post_init__(self) -> None:
+            if self.added is None:
+                self.added = []
+
+        def add(self, value: Any) -> None:
+            self.added.append(value)
+
+        async def flush(self) -> None:
+            return None
+
+        async def commit(self) -> None:
+            raise RuntimeError("commit failed")
+
+        async def rollback(self) -> None:
+            self.rollback_calls += 1
+
+        async def refresh(self, _value: Any) -> None:
+            return None
+
+    session = _FailCommitSession()
+
+    with pytest.raises(RuntimeError, match="commit failed"):
+        await crud.create(session, _Thing, name="demo")
+
+    assert session.rollback_calls == 1
+    assert len(session.added) == 1
+
+
+@pytest.mark.asyncio
+async def test_delete_where_rolls_back_when_commit_fails() -> None:
+    @dataclass
+    class _FailCommitDmlSession:
+        rollback_calls: int = 0
+        exec_calls: int = 0
+
+        async def exec(self, _statement: Any) -> Any:
+            self.exec_calls += 1
+            return SimpleNamespace(rowcount=3)
+
+        async def commit(self) -> None:
+            raise RuntimeError("commit failed")
+
+        async def rollback(self) -> None:
+            self.rollback_calls += 1
+
+    session = _FailCommitDmlSession()
+
+    with pytest.raises(RuntimeError, match="commit failed"):
+        await crud.delete_where(session, _Thing, commit=True)
+
+    assert session.exec_calls == 1
+    assert session.rollback_calls == 1