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Thanks!
> On Dec 16, 2020, at 2:21 AM, Jasper Phillips <jasperisja...@gmail.com> wrote:
>
>
>
>
>> On Fri, Dec 11, 2020 at 6:08 AM Jean-Paul Calderone
>> <exar...@twistedmatrix.com> wrote:
>>> On Fri, Dec 11, 2020 at 8:19 AM Jasper Phillips <jasperisja...@gmail.com>
>>> wrote:
>>
>>> I'm using perspective broker to transfer objects in a networked game, which
>>> I'm having trouble unjellying -- the remote versions wind up with dangling
>>> twisted.persisted.crefutil._Dereference instances, so don't match the
>>> original objects.
>>>
>>> I'm seeing this for objects that have circular references to each other.
>>> I've refactored things to mostly avoid circular references and sidestep
>>> this, but have one remaining case where I find circular references mean
>>> clearer code that I'm reluctant to refactor.
>>>
>>> Is there some trick I'm missing to avoid _Dereferences?
>>
>> No, it's supposed to Just Work™ so you've found a bug in some part of the
>> implementation. If you can produce a minimal reproducing example then it
>> may be worth a bug report. But after that, I'd suggest investigating HTTP
>> or AMP as a replacement for PB.
>
> Here's a test case demonstrating the bug:
>
> import sys
> from twisted.persisted.crefutil import _Dereference
> from twisted.spread import pb, jelly
>
> class RemoteCopyable( pb.Copyable, pb.RemoteCopy ): pass
> jelly.globalSecurity.allowInstancesOf( RemoteCopyable )
> pb.setCopierForClassTree( sys.modules[__name__], pb.Copyable )
>
> if __name__ == '__main__':
> # circular object ref
> cell = RemoteCopyable()
> cell.link = RemoteCopyable()
> cell.link.cell = cell
>
> # Mimic sending across network
> broker = pb.Broker()
> serializedCell = broker.serialize( cell )
> remoteCell = broker.unserialize( serializedCell )
>
> print( _Dereference is type(remoteCell.link.cell) )
>
> This bug stems from twisted.spread.flavors.RemoteCopy.setCopyableState(),
> which works fine for Python 2! But the UTF fix for Python 3 broke circular
> references. It looks like this:
>
> def setCopyableState(self, state):
> if _PY3:
> state = {x.decode('utf8') if isinstance(x, bytes)
> else x:y for x,y in state.items()}
> self.__dict__ = state
>
> Here is a simple tweak that fixes the problem:
>
> def setCopyableState(self, state):
> if _PY3:
> for x, y in list(state.items()):
> if isinstance(x, bytes):
> del state[x]
> state[x.decode('utf8')] = y
> self.__dict__ = state
>
>
> Basically the reference unwinding that takes place in
> twisted.spread.jelly._Unjellier._unjelly_reference()'s call to
> ref.resolveDependants() relies upon setCopyableStates()'s passed in state
> being used directly, such that all matching references' __dict__ point to the
> same object.
>
> Hope this helps clarify. Is there some more formal location than this list
> that you'd like a bug report filed?
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