bpo-41052: Optout serialization/deserialization for blake2s/b

[corona10]

https://bugs.python.org/issue41052

[corona10]

Before heap types, serialization/deserialization was failed.

[corona10]

@vstinner This function is very redundant with this issue.
Do you have any ideas with better solution?

[shihai1991]

Maybe a public marco :)

[corona10]

I don't think that exposing it to the public is the proper way.
It's should be a kind of internal utility routine.

[vstinner]

Rather than having to copy/paste such code in each type, would it be possible to have a protocol like:

class NotHashable:
__hash__ = None
obj = NotHashable()
hash(obj)

This code raises TypeError: unhashable type: 'NotHashable'.

cc @pitrou@serhiy-storchaka

[serhiy-storchaka]

By default most extension types are not serializable. blake2b is not serializable. Why is it needed to add explicit __reduce__ method?

[corona10]

@serhiy-storchaka

master (after #21856)

Python3.10.0a0 (heads/master:f76d894dc5, Sep102020, 23:26:39)
[Clang11.0.0 (clang-1100.0.33.12)] ondarwinType"help", "copyright", "credits"or"license"formoreinformation.
>>>importpickle>>>import_blake2>>>pickle.dumps(_blake2.blake2s(), 0)
b'ccopy_reg\n_reconstructor\np0\n(c_blake2\nblake2s\np1\nc__builtin__\nobject\np2\nNtp3\nRp4\n.'>>>pickle.dumps(_blake2.blake2s(), 1)
b'ccopy_reg\n_reconstructor\nq\x00(c_blake2\nblake2s\nq\x01c__builtin__\nobject\nq\x02Ntq\x03Rq\x04.'

before

>>>import_blake2>>>importpickle>>>pickle.dumps(_blake2.blake2s(), 0)
Traceback (mostrecentcalllast):
File"<stdin>", line1, in<module>File"/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/copyreg.py", line65, in_reduce_exraiseTypeError("can't pickle %s objects"%base.__name__)
TypeError: can'tpickleblake2sobjects>>>pickle.dumps(_blake2.blake2s(), 1)
Traceback (mostrecentcalllast):
File"<stdin>", line1, in<module>File"/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/copyreg.py", line65, in_reduce_exraiseTypeError("can't pickle %s objects"%base.__name__)
TypeError: can'tpickleblake2sobjects

[corona10]

I created the issue https://bugs.python.org/issue41052 when I found the issue after porting to heap type.

[serhiy-storchaka]

This is no longer needed, is not?

[corona10]

@serhiy-storchaka Yeah this pr is no needed ;)

[vstinner]

This is no longer needed, is not?

Cool. I like the fact that it's no longer needed thanks to the generic https://bugs.python.org/issue41052 fix :-D Thanks again for the generic fix! It's way better than such copy/paste fix on each type.