[Twisted-Python] Re: More on PB Copyable Errors

[Justin Johnson]

Submitted Issue844.

On Wed, 29 Dec 2004 08:56:48 -0600, Justin Johnson
<justinjohnson at gmail.com> wrote:
> Attached is a patch with modifications to pb.py and jelly.py.  With
> the patch applied, CopyableFailure.getStateToCopy first checks to see
> if the actual exception instance's class has an unjellyable registered
> so it can be unjellied on the other side.  If it does, the actual
> exception instance is passed back as failure.value.  Otherwise a
> string representation is passed back as it is today.
> 
> I'd like some confirmation that this is an acceptable approach.  If so
> I will gladly submit an enhancement and attach the patch.
> 
> -Justin
> 
> On Tue, 28 Dec 2004 14:34:02 -0600, Justin Johnson
> <justinjohnson at gmail.com> wrote:
> > Whoops... forgot the attachments.  Here they are.
> >
> >
> > On Tue, 28 Dec 2004 14:32:04 -0600, Justin Johnson
> > <justinjohnson at gmail.com> wrote:
> > > I would really like to be able to pass custom exceptions over the wire
> > > in PB.  Previous discussion on this list ended with the conclusion
> > > that it currently isn't possible without hacking a local copy of
> > > Twisted.
> > >
> > > I have done that to get the result I want, with minimal testing, and
> > > would like to get some discussion going around this topic.  Attached
> > > are 3 test files, s.py for the server, c.py for the client, and e.py
> > > for the error definitions which are imported by both s.py and c.py.
> > > If I make the following modification to my local copy of
> > > twisted/spread/pb.py in the CopyableFailure's getStateToCopy method,
> > > the custom error is passed back as I want.
> > >
> > >   #state['value'] = str(self.value) # Exception instance
> > >   state['value'] = self.value # Exception instance
> > >
> > > I was wondering if there is a reason we wouldn't want to change the
> > > code to check for registered unjellyables for the exception, and
> > > return them (or rather go through the jelly/unjelly process) if they
> > > exist, but return the string representation otherwise.  Maybe that is
> > > more complicated than I realize.
> > >
> > > Any thoughts or suggestions on how we might make this possible?
> > > Thanks.
> > > -Justin
> > >
> >
> >
> >
> 
> 
>