fixed context manager

src/suou/sqlalchemy_async.py

@@ -31,21 +31,31 @@ class SQLAlchemy:
     """
     base: DeclarativeBase
     engine: Engine
+    _sessions: list[AsyncSession]
     NotFound = NotFoundError
 
     def __init__(self, model_class: DeclarativeBase):
         self.base = model_class
         self.engine = None
+        self._sessions = []
     def bind(self, url: str):
         self.engine = create_async_engine(url)
     async def begin(self) -> AsyncSession:
         if self.engine is None:
             raise RuntimeError('database is not connected')
-        return self.engine.begin()
-    async def __aenter__(self):
-        return self.begin()
+        ## XXX is it accurate?
+        s = self.engine.begin()
+        self._sessions.append(s)
+        return s
+    async def __aenter__(self) -> AsyncSession:
+        return await self.begin()
     async def __aexit__(self, e1, e2, e3):
-        return await self.engine.__aexit__(e1, e2, e3)
+        ## XXX is it accurate?
+        s = self._sessions.pop()
+        if e1:
+            await s.rollback()
+        else:
+            await s.commit()
     async def paginate(self, select: Select, *, 
         page: int | None = None, per_page: int | None = None,
         max_per_page: int | None = None, error_out: bool = True,