Support serialising to named mappings

[juntyr]

This PR includes four changes:

• Implement PythonizeListType for PyTuple, a small convenience that cannot be achieved outside the crate
• Add support for prebuilding mappings during serialisation, which delays the collection of mapping key-value pairs until all are known
• Add support for named mappings during serialisation, which adds a tiny default-implemented helper trait method to pass forward the struct / tuple / enum name to the mapping type
• Allow deserializing an enum from any mapping instead of just dicts

I have found them to be very useful to serialise to and from class-like Python types (e.g. namedtuple which keep more type information around).

[juntyr]

@davidhewitt what are your thoughts on this?

[juntyr]

@davidhewitt I apologise for pinging again - I'm hoping that this PR could move forward soon-ish as I'm working on publishing a crate of mine (which would need a feature similar to this) for a publication.

[MarshalX]

@juntyr Perhaps he unfollowed this repository or pull request. Maybe try pinging him on X, for example, as he has a few social links on his GitHub profile

[davidhewitt]

Hi @juntyr sorry for the delay! I have seen this PR but haven't had a chance to investigate yet. Please hold on and I'll do my best to get to this soon - I'm trying to wrap up PyO3 0.22 and then let's aim to ship this in pythonize 0.22 👍

[juntyr]

@davidhewitt Congrats on shipping pyo3 v0.22, I'm excited to start using it!

I'm looking forward to collaborating with you to push this PR forward :)

[juntyr]

The merge conflict should now be resolved again :)

[juntyr]

Once #66 is merged, I will very quickly rebase this PR again so that we can hopefully still get it into v0.22

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 75.25773% with 24 lines in your changes missing coverage. Please review.

Project coverage is 83.41%. Comparing base (6c2c3f2) to head (7c18b9f).

Files	Patch %	Lines
src/ser.rs	77.77%	4 Missing and 16 partials :warning:
src/de.rs	42.85%	0 Missing and 4 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #62      +/-   ##
==========================================
- Coverage   83.83%   83.41%   -0.42%     
==========================================
  Files           3        3              
  Lines        1169     1224      +55     
  Branches     1169     1224      +55     
==========================================
+ Hits          980     1021      +41     
- Misses        140      144       +4     
- Partials       49       59      +10     

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:loudspeaker: Have feedback on the report? Share it here.

[juntyr]

GATs were only stabilised in 1.65 but pythonize uses 1.63 … so the builder can’t use a GAT. Perhaps I can inline the builder methods into the main trait itself (hopefully while keeping Map = PyDict)

[juntyr]

I also tried to add a small convenience wrapper type PythonizeUnnamedMappingWrapper so that

1. it is more explicit that type NamedMap = PythonizeUnnamedMappingWrapper<PyDict> discards the name
2. it is reusable for others so you don't need to copy-past two trait impls

[juntyr]

Thanks for your review @davidhewitt!

[juntyr]

I’m unsure if the coverage can be easily improved as all new misses seem to be partial and short-circuiting related

[davidhewitt]

Agreed, I'm very happy to call this as good as it gets! Thanks again 🚀