refactor: replace generic Exception handling with SQLAlchemyError in CRUD and session management

backend/app/db/crud.py

@@ -5,7 +5,7 @@ from typing import Any, TypeVar, cast
 
 from sqlalchemy import delete as sql_delete
 from sqlalchemy import update as sql_update
-from sqlalchemy.exc import IntegrityError
+from sqlalchemy.exc import IntegrityError, SQLAlchemyError
 from sqlmodel import SQLModel, select
 from sqlmodel.ext.asyncio.session import AsyncSession
 from sqlmodel.sql.expression import SelectOfScalar
@@ -24,7 +24,7 @@ class MultipleObjectsReturned(LookupError):
 async def _flush_or_rollback(session: AsyncSession) -> None:
     try:
         await session.flush()
-    except Exception:
+    except SQLAlchemyError:
         await session.rollback()
         raise
 
@@ -32,7 +32,7 @@ async def _flush_or_rollback(session: AsyncSession) -> None:
 async def _commit_or_rollback(session: AsyncSession) -> None:
     try:
         await session.commit()
-    except Exception:
+    except SQLAlchemyError:
         await session.rollback()
         raise
 
@@ -268,7 +268,7 @@ async def get_or_create(
         if existing is not None:
             return existing, False
         raise
-    except Exception:
+    except SQLAlchemyError:
         await session.rollback()
         raise
 

backend/app/db/session.py

@@ -7,6 +7,7 @@ from pathlib import Path
 import anyio
 from alembic import command
 from alembic.config import Config
+from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy.ext.asyncio import AsyncEngine, async_sessionmaker, create_async_engine
 from sqlmodel import SQLModel
 from sqlmodel.ext.asyncio.session import AsyncSession
@@ -69,9 +70,15 @@ async def get_session() -> AsyncGenerator[AsyncSession, None]:
     async with async_session_maker() as session:
         try:
             yield session
-        except Exception:
+        finally:
+            try:
+                in_txn = bool(session.in_transaction())
+            except SQLAlchemyError:
+                logger.exception("Failed to inspect session transaction state.")
+                return
+            if not in_txn:
+                return
             try:
                 await session.rollback()
-            except Exception:
+            except SQLAlchemyError:
                 logger.exception("Failed to rollback session after request error.")
-            raise

backend/tests/test_db_transaction_safety.py

@@ -5,6 +5,7 @@ from types import SimpleNamespace
 from typing import Any
 
 import pytest
+from sqlalchemy.exc import SQLAlchemyError
 from sqlmodel import Field, SQLModel
 
 from app.db import crud
@@ -43,12 +44,17 @@ class _Maker:
 
 @pytest.mark.asyncio
 async def test_get_session_rolls_back_on_dependency_error(monkeypatch: pytest.MonkeyPatch) -> None:
-    fake_session = SimpleNamespace(rollbacks=0)
+    @dataclass
+    class _FakeDependencySession:
+        rollbacks: int = 0
 
-    async def _rollback() -> None:
+        def in_transaction(self) -> bool:
-        fake_session.rollbacks += 1
+            return True
 
-    fake_session.rollback = _rollback
+        async def rollback(self) -> None:
+            self.rollbacks += 1
+
+    fake_session = _FakeDependencySession()
     ctx = _SessionCtx(fake_session)
     monkeypatch.setattr(db_session, "async_session_maker", _Maker(ctx))
 
@@ -66,6 +72,9 @@ async def test_get_session_rolls_back_on_dependency_error(monkeypatch: pytest.Mo
 
 @pytest.mark.asyncio
 async def test_create_rolls_back_when_commit_fails() -> None:
+    class _CommitError(SQLAlchemyError):
+        pass
+
     @dataclass
     class _FailCommitSession:
         rollback_calls: int = 0
@@ -82,7 +91,7 @@ async def test_create_rolls_back_when_commit_fails() -> None:
             return None
 
         async def commit(self) -> None:
-            raise RuntimeError("commit failed")
+            raise _CommitError("commit failed")
 
         async def rollback(self) -> None:
             self.rollback_calls += 1
@@ -92,7 +101,7 @@ async def test_create_rolls_back_when_commit_fails() -> None:
 
     session = _FailCommitSession()
 
-    with pytest.raises(RuntimeError, match="commit failed"):
+    with pytest.raises(SQLAlchemyError, match="commit failed"):
         await crud.create(session, _Thing, name="demo")
 
     assert session.rollback_calls == 1
@@ -101,6 +110,9 @@ async def test_create_rolls_back_when_commit_fails() -> None:
 
 @pytest.mark.asyncio
 async def test_delete_where_rolls_back_when_commit_fails() -> None:
+    class _CommitError(SQLAlchemyError):
+        pass
+
     @dataclass
     class _FailCommitDmlSession:
         rollback_calls: int = 0
@@ -111,14 +123,14 @@ async def test_delete_where_rolls_back_when_commit_fails() -> None:
             return SimpleNamespace(rowcount=3)
 
         async def commit(self) -> None:
-            raise RuntimeError("commit failed")
+            raise _CommitError("commit failed")
 
         async def rollback(self) -> None:
             self.rollback_calls += 1
 
     session = _FailCommitDmlSession()
 
-    with pytest.raises(RuntimeError, match="commit failed"):
+    with pytest.raises(SQLAlchemyError, match="commit failed"):
         await crud.delete_where(session, _Thing, commit=True)
 
     assert session.exec_calls == 1