[Python-Dev] Pickling failure on Enums

[Ethan Furman]

On 05/14/2013 03:16 PM, Nick Coghlan wrote:
>
> On 15 May 2013 07:38, "Guido van Rossum" <guido at python.org <mailto:guido at python.org>> wrote:
>>
>> On Tue, May 14, 2013 at 2:13 PM, Ethan Furman <ethan at stoneleaf.us <mailto:ethan at stoneleaf.us>> wrote:
>> > On 05/14/2013 01:58 PM, Guido van Rossum wrote:
>> >>
>> >> On Tue, May 14, 2013 at 1:09 PM, Ethan Furman <ethan at stoneleaf.us <mailto:ethan at stoneleaf.us>> wrote:
>> >>> I can get pickle failure on members created using the functional syntax
>> >>> with no module set;
>> >>
>> >>
>> >> That's the case I care most about.
>> >
>> >
>> > Good, 'cause that one is handled.  :)
>>
>> Then we're good.
>>
>> >>> I cannot get pickle failure on those same classes;
>> >>
>> >>
>> >> I suppose you mean "if you create the same enums using class syntax"?
>> >> Sounds fine to me.
>> >
>> >
>> > No.  Example class:
>> >
>> > --> Example = Enum('Example', 'example ie eg')  # no module name given,
>> > frame hack fails
>> >
>> > --> pickle(Example.ie)
>> > # blows up
>> >
>> > --# pickle(Example)
>> > # succeeds here, but unpickle will fail
>>
>> Not great, but (a) few people pickle classes, and (b) there's probably
>> something you can do to the metaclass to sabotage this. But it's fine
>> to punt on this now.
>
> It may be a bug in pickle - it sounds like it is sanity checking type(obj), but not checking for cases where obj itself
> is a class.

Well, it's definitely not calling the metaclass' __reduce__ as that's where I put the bomb (hmm, will I be visited by 
men in dark suits now?) so maybe that's a bug in pickle.

At any rate, I figured it out -- give the class' __module__ a dummy name (I like 'uh uh' ;) and when pickle can't find 
that module it'll blow itself up.

--
~Ethan~