contextmanager skips rollback if trans says to skip it

Fixed issue where if an exception occurred when the :class:`_orm.Session`
were to close the connection within the :meth:`_orm.Session.commit` method,
when using a context manager for :meth:`_orm.Session.begin` , it would
attempt a rollback which would not be possible as the :class:`_orm.Session`
was in between where the transaction is committed and the connection is
then to be returned to the pool, raising the exception "this
sessiontransaction is in the committed state". This exception can occur
mostly in an asyncio context where CancelledError can be raised.

Fixes: #7388
Change-Id: I1a85a3a7eae79f3553ddf1e3d245a0d90b0a2f40
(cherry picked from commit a845da8b0fc5bb172e278c399a1de9a2e49d62af)

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index 0c27ea6d9..a5d973a2c 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -2371,6 +2371,13 @@ class Transaction(TransactionalContext):
     def _transaction_is_closed(self):
         return not self._deactivated_from_connection
 
+    def _rollback_can_be_called(self):
+        # for RootTransaction / NestedTransaction, it's safe to call
+        # rollback() even if the transaction is deactive and no warnings
+        # will be emitted.  tested in
+        # test_transaction.py -> test_no_rollback_in_deactive(?:_savepoint)?
+        return True
+
 
 class MarkerTransaction(Transaction):
     """A 'marker' transaction that is used for nested begin() calls.