- Fixed bug where the session attachment error "object is already

attached to session X" would fail to prevent the object from
also being attached to the new session, in the case that execution
continued after the error raise occurred.
fixes #3301

1 files changed, 7 insertions, 7 deletions

diff --git a/lib/sqlalchemy/orm/session.py b/lib/sqlalchemy/orm/session.py
index f02d8b54e..bc9444040 100644
--- a/lib/sqlalchemy/orm/session.py
+++ b/lib/sqlalchemy/orm/session.py
@@ -1830,7 +1830,7 @@ class Session(_SessionClassMethods):
                 "function to send this object back to the transient state." %
                 state_str(state)
             )
-        self._before_attach(state)
+        self._before_attach(state, check_identity_map=False)
         self._deleted.pop(state, None)
         if discard_existing:
             self.identity_map.replace(state)
@@ -1910,13 +1910,12 @@ class Session(_SessionClassMethods):
         self._attach(state, include_before=True)
         state._load_pending = True
 
-    def _before_attach(self, state):
+    def _before_attach(self, state, check_identity_map=True):
         if state.session_id != self.hash_key and \
                 self.dispatch.before_attach:
             self.dispatch.before_attach(self, state.obj())
 
-    def _attach(self, state, include_before=False):
-        if state.key and \
+        if check_identity_map and state.key and \
             state.key in self.identity_map and \
                 not self.identity_map.contains_state(state):
             raise sa_exc.InvalidRequestError(
@@ -1932,10 +1931,11 @@ class Session(_SessionClassMethods):
                 "(this is '%s')" % (state_str(state),
                                     state.session_id, self.hash_key))
 
+    def _attach(self, state, include_before=False):
+
         if state.session_id != self.hash_key:
-            if include_before and \
-                    self.dispatch.before_attach:
-                self.dispatch.before_attach(self, state.obj())
+            if include_before:
+                self._before_attach(state)
             state.session_id = self.hash_key
             if state.modified and state._strong_obj is None:
                 state._strong_obj = state.obj()