Merge "Guard against re-entrant autobegin in Core, ORM"

3 files changed, 12 insertions, 5 deletions

diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index 72d66b7c8..31bf885db 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -813,10 +813,11 @@ class Connection(Connectable):
         if self._echo:
             self.engine.logger.info("BEGIN (implicit)")
 
+        self.__in_begin = True
+
         if self._has_events or self.engine._has_events:
             self.dispatch.begin(self)
 
-        self.__in_begin = True
         try:
             self.engine.dialect.do_begin(self.connection)
         except BaseException as e:
diff --git a/lib/sqlalchemy/orm/session.py b/lib/sqlalchemy/orm/session.py
index e8312f393..8a7a64f78 100644
--- a/lib/sqlalchemy/orm/session.py
+++ b/lib/sqlalchemy/orm/session.py
@@ -531,6 +531,10 @@ class SessionTransaction(object):
 
         self._take_snapshot(autobegin=autobegin)
 
+        # make sure transaction is assigned before we call the
+        # dispatch
+        self.session._transaction = self
+
         self.session.dispatch.after_transaction_create(self.session, self)
 
     @property
@@ -1242,7 +1246,8 @@ class Session(_SessionClassMethods):
 
     def _autobegin(self):
         if not self.autocommit and self._transaction is None:
-            self._transaction = SessionTransaction(self, autobegin=True)
+            trans = SessionTransaction(self, autobegin=True)
+            assert self._transaction is trans
             return True
 
         return False
@@ -1299,7 +1304,7 @@ class Session(_SessionClassMethods):
         if self._transaction is not None:
             if subtransactions or _subtrans or nested:
                 trans = self._transaction._begin(nested=nested)
-                self._transaction = trans
+                assert self._transaction is trans
                 if nested:
                     self._nested_transaction = trans
             else:
@@ -1307,7 +1312,8 @@ class Session(_SessionClassMethods):
                     "A transaction is already begun on this Session."
                 )
         else:
-            self._transaction = SessionTransaction(self, nested=nested)
+            trans = SessionTransaction(self, nested=nested)
+            assert self._transaction is trans
         return self._transaction  # needed for __enter__/__exit__ hook
 
     def begin_nested(self):
diff --git a/lib/sqlalchemy/testing/fixtures.py b/lib/sqlalchemy/testing/fixtures.py
index 08cab051e..45ca48444 100644
--- a/lib/sqlalchemy/testing/fixtures.py
+++ b/lib/sqlalchemy/testing/fixtures.py
@@ -93,7 +93,7 @@ class TestBase(object):
         from . import engines
 
         def gen_testing_engine(
-            url=None, options=None, future=False, asyncio=False
+            url=None, options=None, future=None, asyncio=False
         ):
             if options is None:
                 options = {}