unify transactional context managers

Applied consistent behavior to the use case of
calling ``.commit()`` or ``.rollback()`` inside of an existing
``.begin()`` context manager, with the addition of potentially
emitting SQL within the block subsequent to the commit or rollback.
This change continues upon the change first added in
:ticket:`6155` where the use case of calling "rollback" inside of
a ``.begin()`` contextmanager block was proposed:

* calling ``.commit()`` or ``.rollback()`` will now be allowed
without error or warning within all scopes, including
that of legacy and future :class:`_engine.Engine`, ORM
:class:`_orm.Session`, asyncio :class:`.AsyncEngine`.  Previously,
the :class:`_orm.Session` disallowed this.

* The remaining scope of the context manager is then closed;
when the block ends, a check is emitted to see if the transaction
was already ended, and if so the block returns without action.

* It will now raise **an error** if subsequent SQL of any kind
is emitted within the block, **after** ``.commit()`` or
``.rollback()`` is called.   The block should be closed as
the state of the executable object would otherwise be undefined
in this state.

Fixes: #6288
Change-Id: I8b21766ae430f0fa1ac5ef689f4c0fb19fc84336

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/sqlalchemy/ext/asyncio/base.py b/lib/sqlalchemy/ext/asyncio/base.py
index fa8c5006e..d11b059fd 100644
--- a/lib/sqlalchemy/ext/asyncio/base.py
+++ b/lib/sqlalchemy/ext/asyncio/base.py
@@ -5,14 +5,14 @@ from . import exc as async_exc
 
 class StartableContext(abc.ABC):
     @abc.abstractmethod
-    async def start(self) -> "StartableContext":
+    async def start(self, is_ctxmanager=False) -> "StartableContext":
         pass
 
     def __await__(self):
         return self.start().__await__()
 
     async def __aenter__(self):
-        return await self.start()
+        return await self.start(is_ctxmanager=True)
 
     @abc.abstractmethod
     async def __aexit__(self, type_, value, traceback):