From 4065352c7e9779cfeae34f01073ef6c43aeae488 Mon Sep 17 00:00:00 2001 From: Mike Bayer Date: Tue, 6 Feb 2018 18:13:27 -0500 Subject: Add flag for class-level disallow of events, apply to OptionEngine Fixed bug where events associated with an :class:`Engine` at the class level would be doubled when the :meth:`.Engine.execution_options` method were used. To achieve this, the semi-private class :class:`.OptionEngine` no longer accepts events directly at the class level and will raise an error; the class only propagates class-level events from its parent :class:`.Engine`. Instance-level events continue to work as before. The comments present another way of doing this where we would copy events from the parent engine at option time rather than linking the event listeners, but this would be a behavioral change that adding new events to the parent engine would not take effect for an already-created OptionEngine. Change-Id: Id128516f54103fbad9a2210d6571eceb59c8b0cb Fixes: #4181 --- lib/sqlalchemy/event/attr.py | 35 ++++++++++++++++++++++++++++++----- 1 file changed, 30 insertions(+), 5 deletions(-) (limited to 'lib/sqlalchemy/event') diff --git a/lib/sqlalchemy/event/attr.py b/lib/sqlalchemy/event/attr.py index 1068257cb..efa8fab42 100644 --- a/lib/sqlalchemy/event/attr.py +++ b/lib/sqlalchemy/event/attr.py @@ -30,7 +30,7 @@ as well as support for subclass propagation (e.g. events assigned to """ from __future__ import absolute_import, with_statement - +from .. import exc from .. import util from ..util import threading from . import registry @@ -47,6 +47,20 @@ class RefCollection(util.MemoizedSlots): return weakref.ref(self, registry._collection_gced) +class _empty_collection(object): + def append(self, element): + pass + + def extend(self, other): + pass + + def __iter__(self): + return iter([]) + + def clear(self): + pass + + class _ClsLevelDispatch(RefCollection): """Class-level events on :class:`._Dispatch` classes.""" @@ -91,6 +105,9 @@ class _ClsLevelDispatch(RefCollection): target = event_key.dispatch_target assert isinstance(target, type), \ "Class-level Event targets must be classes." + if not getattr(target, '_sa_propagate_class_events', True): + raise exc.InvalidRequestError( + "Can't assign an event directly to the %s class" % target) stack = [target] while stack: cls = stack.pop(0) @@ -99,7 +116,7 @@ class _ClsLevelDispatch(RefCollection): self.update_subclass(cls) else: if cls not in self._clslevel: - self._clslevel[cls] = collections.deque() + self._assign_cls_collection(cls) self._clslevel[cls].appendleft(event_key._listen_fn) registry._stored_in_collection(event_key, self) @@ -107,7 +124,9 @@ class _ClsLevelDispatch(RefCollection): target = event_key.dispatch_target assert isinstance(target, type), \ "Class-level Event targets must be classes." - + if not getattr(target, '_sa_propagate_class_events', True): + raise exc.InvalidRequestError( + "Can't assign an event directly to the %s class" % target) stack = [target] while stack: cls = stack.pop(0) @@ -116,13 +135,19 @@ class _ClsLevelDispatch(RefCollection): self.update_subclass(cls) else: if cls not in self._clslevel: - self._clslevel[cls] = collections.deque() + self._assign_cls_collection(cls) self._clslevel[cls].append(event_key._listen_fn) registry._stored_in_collection(event_key, self) + def _assign_cls_collection(self, target): + if getattr(target, '_sa_propagate_class_events', True): + self._clslevel[target] = collections.deque() + else: + self._clslevel[target] = _empty_collection() + def update_subclass(self, target): if target not in self._clslevel: - self._clslevel[target] = collections.deque() + self._assign_cls_collection(target) clslevel = self._clslevel[target] for cls in target.__mro__[1:]: if cls in self._clslevel: -- cgit v1.2.1