Fixed #20943 -- Weakly reference senders when caching their associated receivers (63378163) · Commits · Dom Sekotill / django

django/db/models/signals.py

+1 −1

Original line number	Diff line number	Diff line
		@@ -14,7 +14,7 @@ post_delete = Signal(providing_args=["instance", "using"], use_caching=True)

		pre_migrate = Signal(providing_args=["app", "create_models", "verbosity", "interactive", "db"])
		pre_syncdb = pre_migrate
		post_migrate = Signal(providing_args=["class", "app", "created_models", "verbosity", "interactive", "db"], use_caching=True)
		post_migrate = Signal(providing_args=["class", "app", "created_models", "verbosity", "interactive", "db"])
		post_syncdb = post_migrate

		m2m_changed = Signal(providing_args=["action", "instance", "reverse", "model", "pk_set", "using"], use_caching=True)

django/dispatch/dispatcher.py

+8 −4

Original line number	Diff line number	Diff line
		@@ -4,8 +4,10 @@ import threading
		from django.dispatch import saferef
		from django.utils.six.moves import xrange


		WEAKREF_TYPES = (weakref.ReferenceType, saferef.BoundMethodWeakref)


		def _make_id(target):
		if hasattr(target, '__func__'):
		return (id(target.__self__), id(target.__func__))
		@@ -15,6 +17,7 @@ NONE_ID = _make_id(None)
		# A marker for caching
		NO_RECEIVERS = object()


		class Signal(object):
		"""
		Base class for all signals
		@@ -42,7 +45,7 @@ class Signal(object):
		# distinct sender we cache the receivers that sender has in
		# 'sender_receivers_cache'. The cache is cleaned when .connect() or
		# .disconnect() is called and populated on send().
		self.sender_receivers_cache = {}
		self.sender_receivers_cache = weakref.WeakKeyDictionary() if use_caching else {}

		def connect(self, receiver, sender=None, weak=True, dispatch_uid=None):
		"""
		@@ -116,7 +119,7 @@ class Signal(object):
		break
		else:
		self.receivers.append((lookup_key, receiver))
		self.sender_receivers_cache = {}
		self.sender_receivers_cache.clear()

		def disconnect(self, receiver=None, sender=None, weak=True, dispatch_uid=None):
		"""
		@@ -151,7 +154,7 @@ class Signal(object):
		if r_key == lookup_key:
		del self.receivers[index]
		break
		self.sender_receivers_cache = {}
		self.sender_receivers_cache.clear()

		def has_listeners(self, sender=None):
		return bool(self._live_receivers(sender))
		@@ -276,7 +279,8 @@ class Signal(object):
		for idx, (r_key, _) in enumerate(reversed(self.receivers)):
		if r_key == key:
		del self.receivers[last_idx - idx]
		self.sender_receivers_cache = {}
		self.sender_receivers_cache.clear()


		def receiver(signal, **kwargs):
		"""

tests/dispatch/tests/test_dispatcher.py

+21 −0

Original line number	Diff line number	Diff line
		@@ -2,6 +2,7 @@ import gc
		import sys
		import time
		import unittest
		import weakref

		from django.dispatch import Signal, receiver

		@@ -35,6 +36,8 @@ class Callable(object):
		a_signal = Signal(providing_args=["val"])
		b_signal = Signal(providing_args=["val"])
		c_signal = Signal(providing_args=["val"])
		d_signal = Signal(providing_args=["val"], use_caching=True)


		class DispatcherTests(unittest.TestCase):
		"""Test suite for dispatcher (barely started)"""
		@@ -72,6 +75,24 @@ class DispatcherTests(unittest.TestCase):
		self.assertEqual(result, expected)
		self._testIsClean(a_signal)

		def testCachedGarbagedCollected(self):
		"""
		Make sure signal caching sender receivers don't prevent garbage
		collection of senders.
		"""
		class sender:
		pass
		wref = weakref.ref(sender)
		d_signal.connect(receiver_1_arg)
		d_signal.send(sender, val='garbage')
		del sender
		garbage_collect()
		try:
		self.assertIsNone(wref())
		finally:
		# Disconnect after reference check since it flushes the tested cache.
		d_signal.disconnect(receiver_1_arg)

		def testMultipleRegistration(self):
		a = Callable()
		a_signal.connect(a)