Render the library more modular for contributors' goodness ✨

[bonjourmauko]

@openfisca/international-contrib what do you think?

Technical improvements

• Render all OpenFisca Core components modular and sandboxed
  • Allows for simpler contribution
  • Allows for better unit testing
  • Allows for dealing with circular dependencies
  • Allows for more explicit contracts between components

Deprecations

• Reorganise formula_helpers, memory_config, rates, simulation_builder.
  • Their functionalities are still there, just moved around
  • Transitional __init__.py files added to make transition smooth

[augusto-herrmann]

I think this proposal seems to make sense, especially considering, as you mentioned, it would avoid cyclic dependency problems.

Unfortunately I can't say anything from a practical point of view, as I am not really using OpenFIsca yet.

[fpagnoux]

900 lines of code per file... phew 😅

Assuming this PR only moves things around without changing any functionality (i didn't look in details), I think leaning towards smaller and more modular files is a great idea. Thanks for the busy work!

[bonjourmauko]

900 lines of code per file... phew 😅

Assuming this PR only moves things around without changing any functionality (i didn't look in details), I think leaning towards smaller and more modular files is a great idea. Thanks for the busy work!

Yes! I took care of keeping exposed all the same functions, classes, and modules, with the original names. I didn't expose protected functions however (the one of the ones _like(this):) but if people are relying on them we can just make them public.

That's basically why I didn't touch the tests at all.

[MattiSG]

Wow, that's impressive! Fingers crossed that such a large changeset passes everywhere 🤞 If it all goes smoothly, I expect this to improve contributors’ navigation in the codebase 👏

[bonjourmauko]

Thanks @MattiSG ! I plan to broadcast this and reach as many users as possible for help and feedback on possible issues. And yes I think this is a big step on making it easier for contributors to navigate and to contribute :)