[Python] Null buffers with Pickle protocol

[asfimport]

When underlying buffers are null they populate the buffer protocol ".buf" value with a null value.  In some cases this can violate contracts asserted in cpython.  It might be best to always return an empty non-null buffer when the underlying buffer is null.

Reporter: Micah Kornfield / @emkornfield
Assignee: Antoine Pitrou / @pitrou

PRs and other links:

• GitHub Pull Request #12752

_{Note: This issue was originally created as ARROW-16048. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
Hmm, best would perhaps be to have a dedicated NullBuffer class so that they can be recreated faithfully when unpickling?

[asfimport]

Micah Kornfield / @emkornfield:
I don't think this affect faithfulness.  Another option specifically for pickle could be to modify the condition in __reduce_ex which returns pybytes also when the underlying buffer has size 0?

 

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 12752
#12752