gh-99631: Add custom loads and dumps support for the shelve module

[furkanonder]

• Issue: Custom unpickler and pickler for the shelve module  #99631

[merwok]

Could you add docs and tests?

[serhiy-storchaka]

Do we need to specify the pickler and unpickler classes or just dumps() and loads() functions?

[isidentical]

I'd also go fordumps and loads instead of pickler/unpickler classes. With a proper definition (e.g. takes a Python object and returns bytes) I think that should make it much more simpler (it is also similar how other pickle-related APIs work outside of the stdlib)

[furkanonder]

Doc and test have been added. @merwok

The pickler and unpickler classes have been replaced with dumps() and load() functions. @isidentical@serhiy-storchaka

[isidentical]

Thanks a lot for your efforts @furkanonder, I have a few minor suggestions but this already looks great!

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[serhiy-storchaka]

Should we require the serializer to accept the pickle protocol? It does not make sense for other than pickle formats.

What happens if only serializer or only deserializer are passed?

[furkanonder]

What happens if only serializer or only deserializer are passed?

elif (serializerisNoneanddeserializerisnotNone) or (deserializerisNoneandserializerisnotNone):
raiseShelveError("Serializer and deserializer must be defined together.")

In this case, shelve raises an error.

[encukou]

This seems to have been forgotten over end-of-year break in 2022. Do you want to revive it?

The BsdDbShelf class needs to be updated as well; its extra functions should use deserializer rather than Unpickler

[furkanonder]

I accidentally deleted my forked repository, so I can't update my old PRs. So I opened a new PR.