DRAFT Introduce CFFI-based Python bindings

[Floris Bruynooghe]

David Bremner <david at tethera.net> writes:

> Floris Bruynooghe <flub at devork.be> writes:
>
>>
>> Lastly there are some downsides to the choices I made:
>> - I ended up going squarely for CPython 3.6+.  Choosing Python
>>   3 allowed better API design, e.g. with keyword-only parameters
>>   etc.  Choosing CPython 3.4+ restricts the madness that can
>>   happen with __del__ and gives some newer (tho now unused)
>>   features in weakref.finalizer.
>> - This is no longer drop-in compatible.
>> - I haven't got to a stage where my initial goal of speed has
>>   been proven yet.
>
> I guess you'll have to convince the maintainers / users of alot and afew
> that this makes sense before we go much further. I'd point out that
> Debian stable is only at python 3.5, so that makes me a bit wary of this
> (being able to run the test suite on debian stable and similar aged
> distros useful for me, and I suspect other developers).
>
> I know there are issues with memory management in the current bindings,
> so that may be a strong reason to push to python 3.6; it seems to need
> more investigation at the moment.

So on earlier Python versions, sure this is possible at not too much
cost.

- Python 3.4+ would just cost the use of some f-strings.  Not major, was
  just nice to use.
- Python <3.4 afaik would only need a tweak to the Database.tags and
  Message.tags properties.  I *think* swapping the caching of these
  using a weakref should suffice and not break the brittle
  Python-libnotmuch memory management.
  Mind you I think Python 3.0-3.3 are pretty old and not much point in
  supporting them.  But this would also apply for 2.7 support.
- Python 2.7 is probably the worst, in that keyword-only arguments would
  be gone.  If python 2.7 is required I'd be much keener to have another
  go at a drop-in replacement with the memory safety features and then
  build the "notdb" API on top off it.  But for that to be worth it
  people need to be convinced enough that maintaining a CFFI version is
  nicer than a ctypes version I guess.

Kind regards,
Floris