Fixed removal of signal receivers in Python 3.4 (52cad43b) · Commits · Dom Sekotill / django

django/dispatch/dispatcher.py

+36 −27

Original line number	Diff line number	Diff line
		import weakref
		import sys
		import threading
		import weakref

		from django.dispatch import saferef
		from django.utils.six.moves import xrange


		WEAKREF_TYPES = (weakref.ReferenceType, saferef.BoundMethodWeakref)
		if sys.version_info < (3,4):
		from .weakref_backports import WeakMethod
		else:
		from weakref import WeakMethod


		def _make_id(target):
		@@ -57,9 +59,7 @@ class Signal(object):
		A function or an instance method which is to receive signals.
		Receivers must be hashable objects.

		If weak is True, then receiver must be weak-referencable (more
		precisely saferef.safeRef() must be able to create a reference
		to the receiver).
		If weak is True, then receiver must be weak-referencable.

		Receivers must be able to accept keyword arguments.

		@@ -105,20 +105,33 @@ class Signal(object):
		assert argspec[2] is not None, \
		"Signal receivers must accept keyword arguments (**kwargs)."

		receiver_id = _make_id(receiver)
		if dispatch_uid:
		lookup_key = (dispatch_uid, _make_id(sender))
		else:
		lookup_key = (_make_id(receiver), _make_id(sender))
		lookup_key = (receiver_id, _make_id(sender))

		if weak:
		receiver = saferef.safeRef(receiver, onDelete=self._remove_receiver)
		ref = weakref.ref
		original_receiver = receiver
		# Check for bound methods
		if hasattr(receiver, '__self__') and hasattr(receiver, '__func__'):
		ref = WeakMethod
		original_receiver = original_receiver.__self__
		if sys.version_info >= (3, 4):
		receiver = ref(receiver)
		weakref.finalize(original_receiver, self._remove_receiver, receiver_id=receiver_id)
		else:
		receiver = ref(receiver, self._remove_receiver)
		# Use the id of the weakref, since that's what passed to the weakref callback!
		receiver_id = _make_id(receiver)

		with self.lock:
		for r_key, _ in self.receivers:
		for r_key, _, _ in self.receivers:
		if r_key == lookup_key:
		break
		else:
		self.receivers.append((lookup_key, receiver))
		self.receivers.append((lookup_key, receiver, receiver_id))
		self.sender_receivers_cache.clear()

		def disconnect(self, receiver=None, sender=None, weak=True, dispatch_uid=None):
		@@ -150,7 +163,7 @@ class Signal(object):

		with self.lock:
		for index in xrange(len(self.receivers)):
		(r_key, _) = self.receivers[index]
		(r_key, _, _) = self.receivers[index]
		if r_key == lookup_key:
		del self.receivers[index]
		break
		@@ -242,7 +255,7 @@ class Signal(object):
		with self.lock:
		senderkey = _make_id(sender)
		receivers = []
		for (receiverkey, r_senderkey), receiver in self.receivers:
		for (receiverkey, r_senderkey), receiver, _ in self.receivers:
		if r_senderkey == NONE_ID or r_senderkey == senderkey:
		receivers.append(receiver)
		if self.use_caching:
		@@ -253,7 +266,7 @@ class Signal(object):
		self.sender_receivers_cache[sender] = receivers
		non_weak_receivers = []
		for receiver in receivers:
		if isinstance(receiver, WEAKREF_TYPES):
		if isinstance(receiver, weakref.ReferenceType):
		# Dereference the weak reference.
		receiver = receiver()
		if receiver is not None:
		@@ -262,23 +275,19 @@ class Signal(object):
		non_weak_receivers.append(receiver)
		return non_weak_receivers

		def _remove_receiver(self, receiver):
		def _remove_receiver(self, receiver=None, receiver_id=None, _make_id=_make_id):
		"""
		Remove dead receivers from connections.
		"""

		`receiver_id` is used by python 3.4 and up. `receiver` is used in older
		versions and is the weakref to the receiver (if the connection was defined
		as `weak`). We also need to pass on `_make_id` since the original reference
		will be None during module shutdown.
		"""
		with self.lock:
		to_remove = []
		for key, connected_receiver in self.receivers:
		if connected_receiver == receiver:
		to_remove.append(key)
		for key in to_remove:
		last_idx = len(self.receivers) - 1
		# enumerate in reverse order so that indexes are valid even
		# after we delete some items
		for idx, (r_key, _) in enumerate(reversed(self.receivers)):
		if r_key == key:
		del self.receivers[last_idx - idx]
		if receiver is not None:
		receiver_id = _make_id(receiver)
		self.receivers[:] = [val for val in self.receivers if val[2] != receiver_id]
		self.sender_receivers_cache.clear()

django/dispatch/saferef.py

deleted100644 → 0

+0 −261

Original line number	Diff line number	Diff line
		"""
		"Safe weakrefs", originally from pyDispatcher.

		Provides a way to safely weakref any function, including bound methods (which
		aren't handled by the core weakref module).
		"""

		import traceback
		import weakref


		def safeRef(target, onDelete=None):
		"""Return a safe weak reference to a callable target

		target -- the object to be weakly referenced, if it's a
		bound method reference, will create a BoundMethodWeakref,
		otherwise creates a simple weakref.
		onDelete -- if provided, will have a hard reference stored
		to the callable to be called after the safe reference
		goes out of scope with the reference object, (either a
		weakref or a BoundMethodWeakref) as argument.
		"""
		if hasattr(target, '__self__'):
		if target.__self__ is not None:
		# Turn a bound method into a BoundMethodWeakref instance.
		# Keep track of these instances for lookup by disconnect().
		assert hasattr(target, '__func__'), """safeRef target %r has __self__, but no __func__, don't know how to create reference""" % (target,)
		reference = get_bound_method_weakref(
		target=target,
		onDelete=onDelete
		)
		return reference
		if callable(onDelete):
		return weakref.ref(target, onDelete)
		else:
		return weakref.ref(target)


		class BoundMethodWeakref(object):
		"""'Safe' and reusable weak references to instance methods

		BoundMethodWeakref objects provide a mechanism for
		referencing a bound method without requiring that the
		method object itself (which is normally a transient
		object) is kept alive. Instead, the BoundMethodWeakref
		object keeps weak references to both the object and the
		function which together define the instance method.

		Attributes:
		key -- the identity key for the reference, calculated
		by the class's calculateKey method applied to the
		target instance method
		deletionMethods -- sequence of callable objects taking
		single argument, a reference to this object which
		will be called when either the target object or
		target function is garbage collected (i.e. when
		this object becomes invalid). These are specified
		as the onDelete parameters of safeRef calls.
		weakSelf -- weak reference to the target object
		weakFunc -- weak reference to the target function

		Class Attributes:
		_allInstances -- class attribute pointing to all live
		BoundMethodWeakref objects indexed by the class's
		calculateKey(target) method applied to the target
		objects. This weak value dictionary is used to
		short-circuit creation so that multiple references
		to the same (object, function) pair produce the
		same BoundMethodWeakref instance.

		"""

		_allInstances = weakref.WeakValueDictionary()

		def __new__(cls, target, onDelete=None, arguments, *named):
		"""Create new instance or return current instance

		Basically this method of construction allows us to
		short-circuit creation of references to already-
		referenced instance methods. The key corresponding
		to the target is calculated, and if there is already
		an existing reference, that is returned, with its
		deletionMethods attribute updated. Otherwise the
		new instance is created and registered in the table
		of already-referenced methods.
		"""
		key = cls.calculateKey(target)
		current = cls._allInstances.get(key)
		if current is not None:
		current.deletionMethods.append(onDelete)
		return current
		else:
		base = super(BoundMethodWeakref, cls).__new__(cls)
		cls._allInstances[key] = base
		base.__init__(target, onDelete, arguments, *named)
		return base

		def __init__(self, target, onDelete=None):
		"""Return a weak-reference-like instance for a bound method

		target -- the instance-method target for the weak
		reference, must have __self__ and __func__ attributes
		and be reconstructable via:
		target.__func__.__get__( target.__self__ )
		which is true of built-in instance methods.
		onDelete -- optional callback which will be called
		when this weak reference ceases to be valid
		(i.e. either the object or the function is garbage
		collected). Should take a single argument,
		which will be passed a pointer to this object.
		"""
		def remove(weak, self=self):
		"""Set self.isDead to true when method or instance is destroyed"""
		methods = self.deletionMethods[:]
		del self.deletionMethods[:]
		try:
		del self.__class__._allInstances[self.key]
		except KeyError:
		pass
		for function in methods:
		try:
		if callable(function):
		function(self)
		except Exception as e:
		try:
		traceback.print_exc()
		except AttributeError:
		print('Exception during saferef %s cleanup function %s: %s' % (
		self, function, e)
		)
		self.deletionMethods = [onDelete]
		self.key = self.calculateKey(target)
		self.weakSelf = weakref.ref(target.__self__, remove)
		self.weakFunc = weakref.ref(target.__func__, remove)
		self.selfName = str(target.__self__)
		self.funcName = str(target.__func__.__name__)

		@classmethod
		def calculateKey(cls, target):
		"""Calculate the reference key for this reference

		Currently this is a two-tuple of the id()'s of the
		target object and the target function respectively.
		"""
		return (id(target.__self__), id(target.__func__))

		def __str__(self):
		"""Give a friendly representation of the object"""
		return """%s( %s.%s )""" % (
		self.__class__.__name__,
		self.selfName,
		self.funcName,
		)

		__repr__ = __str__

		def __hash__(self):
		return hash(self.key)

		def __bool__(self):
		"""Whether we are still a valid reference"""
		return self() is not None

		def __nonzero__(self): # Python 2 compatibility
		return type(self).__bool__(self)

		def __eq__(self, other):
		"""Compare with another reference"""
		if not isinstance(other, self.__class__):
		return self.__class__ == type(other)
		return self.key == other.key

		def __call__(self):
		"""Return a strong reference to the bound method

		If the target cannot be retrieved, then will
		return None, otherwise returns a bound instance
		method for our object and function.

		Note:
		You may call this method any number of times,
		as it does not invalidate the reference.
		"""
		target = self.weakSelf()
		if target is not None:
		function = self.weakFunc()
		if function is not None:
		return function.__get__(target)
		return None


		class BoundNonDescriptorMethodWeakref(BoundMethodWeakref):
		"""A specialized BoundMethodWeakref, for platforms where instance methods
		are not descriptors.

		It assumes that the function name and the target attribute name are the
		same, instead of assuming that the function is a descriptor. This approach
		is equally fast, but not 100% reliable because functions can be stored on an
		attribute named differenty than the function's name such as in:

		class A: pass
		def foo(self): return "foo"
		A.bar = foo

		But this shouldn't be a common use case. So, on platforms where methods
		aren't descriptors (such as Jython) this implementation has the advantage
		of working in the most cases.
		"""
		def __init__(self, target, onDelete=None):
		"""Return a weak-reference-like instance for a bound method

		target -- the instance-method target for the weak
		reference, must have __self__ and __func__ attributes
		and be reconstructable via:
		target.__func__.__get__( target.__self__ )
		which is true of built-in instance methods.
		onDelete -- optional callback which will be called
		when this weak reference ceases to be valid
		(i.e. either the object or the function is garbage
		collected). Should take a single argument,
		which will be passed a pointer to this object.
		"""
		assert getattr(target.__self__, target.__name__) == target, \
		("method %s isn't available as the attribute %s of %s" %
		(target, target.__name__, target.__self__))
		super(BoundNonDescriptorMethodWeakref, self).__init__(target, onDelete)

		def __call__(self):
		"""Return a strong reference to the bound method

		If the target cannot be retrieved, then will
		return None, otherwise returns a bound instance
		method for our object and function.

		Note:
		You may call this method any number of times,
		as it does not invalidate the reference.
		"""
		target = self.weakSelf()
		if target is not None:
		function = self.weakFunc()
		if function is not None:
		# Using partial() would be another option, but it erases the
		# "signature" of the function. That is, after a function is
		# curried, the inspect module can't be used to determine how
		# many arguments the function expects, nor what keyword
		# arguments it supports, and pydispatcher needs this
		# information.
		return getattr(target, function.__name__)
		return None


		def get_bound_method_weakref(target, onDelete):
		"""Instantiates the appropiate BoundMethodWeakRef, depending on the details of
		the underlying class method implementation"""
		if hasattr(target, '__get__'):
		# target method is a descriptor, so the default implementation works:
		return BoundMethodWeakref(target=target, onDelete=onDelete)
		else:
		# no luck, use the alternative implementation:
		return BoundNonDescriptorMethodWeakref(target=target, onDelete=onDelete)

django/dispatch/weakref_backports.py

0 → 100644

+62 −0

Original line number	Diff line number	Diff line
		"""
		weakref_backports is a partial backport of the weakref module for python
		versions below 3.4.

		TODO: LICENSE!
		"""
		from weakref import ref


		class WeakMethod(ref):
		"""
		A custom `weakref.ref` subclass which simulates a weak reference to
		a bound method, working around the lifetime problem of bound methods.
		"""

		__slots__ = "_func_ref", "_meth_type", "_alive", "__weakref__"

		def __new__(cls, meth, callback=None):
		try:
		obj = meth.__self__
		func = meth.__func__
		except AttributeError:
		raise TypeError("argument should be a bound method, not {}"
		.format(type(meth)))
		def _cb(arg):
		# The self-weakref trick is needed to avoid creating a reference
		# cycle.
		self = self_wr()
		if self._alive:
		self._alive = False
		if callback is not None:
		callback(self)
		self = ref.__new__(cls, obj, _cb)
		self._func_ref = ref(func, _cb)
		self._meth_type = type(meth)
		self._alive = True
		self_wr = ref(self)
		return self

		def __call__(self):
		obj = super(WeakMethod, self).__call__()
		func = self._func_ref()
		if obj is None or func is None:
		return None
		return self._meth_type(func, obj)

		def __eq__(self, other):
		if isinstance(other, WeakMethod):
		if not self._alive or not other._alive:
		return self is other
		return ref.__eq__(self, other) and self._func_ref == other._func_ref
		return False

		def __ne__(self, other):
		if isinstance(other, WeakMethod):
		if not self._alive or not other._alive:
		return self is not other
		return ref.__ne__(self, other) or self._func_ref != other._func_ref
		return True

		__hash__ = ref.__hash__

tests/dispatch/tests/test_saferef.py

deleted100644 → 0

+0 −76

Original line number	Diff line number	Diff line
		import unittest

		from django.dispatch.saferef import safeRef
		from django.utils.six.moves import xrange


		class Test1(object):
		def x(self):
		pass


		def test2(obj):
		pass


		class Test2(object):
		def __call__(self, obj):
		pass


		class SaferefTests(unittest.TestCase):
		def setUp(self):
		ts = []
		ss = []
		for x in xrange(5000):
		t = Test1()
		ts.append(t)
		s = safeRef(t.x, self._closure)
		ss.append(s)
		ts.append(test2)
		ss.append(safeRef(test2, self._closure))
		for x in xrange(30):
		t = Test2()
		ts.append(t)
		s = safeRef(t, self._closure)
		ss.append(s)
		self.ts = ts
		self.ss = ss
		self.closureCount = 0

		def tearDown(self):
		del self.ts
		del self.ss

		def testIn(self):
		"""Test the "in" operator for safe references (cmp)"""
		for t in self.ts[:50]:
		self.assertTrue(safeRef(t.x) in self.ss)

		def testValid(self):
		"""Test that the references are valid (return instance methods)"""
		for s in self.ss:
		self.assertTrue(s())

		def testShortCircuit(self):
		"""Test that creation short-circuits to reuse existing references"""
		sd = {}
		for s in self.ss:
		sd[s] = 1
		for t in self.ts:
		if hasattr(t, 'x'):
		self.assertTrue(safeRef(t.x) in sd)
		else:
		self.assertTrue(safeRef(t) in sd)

		def testRepresentation(self):
		"""Test that the reference object's representation works

		XXX Doesn't currently check the results, just that no error
		is raised
		"""
		repr(self.ss[-1])

		def _closure(self, ref):
		"""Dumb utility mechanism to increment deletion counter"""
		self.closureCount += 1