Add typestub generator

[tobiasdiez]

For automatically generating/checking type stubs for Cython modules. Based on/inspired by https://github.com/Vizonex/CyStub/ (but extended to handle default values, check mode etc)

Pretty basic at the moment, main functionality is to check that the existing stubs contain exactly the methods that we expect them to have.

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview.

⌛ Dependencies

[tobiasdiez]

TODO:

• Fix all issues reported by the check, and then add it to CI.
• Add unit tests
• Improve extraction of typing info from cython annotations
• Consider upstreaming the script to the Cython repo

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@vincentmacri FYI

[github-actions]

Documentation preview for this PR (built with commit 16d468b; changes) is ready! 🎉
This preview will update shortly after each push to this PR.

[vincentmacri]

This needs more documentation/comments before I can review this as I'm not familiar with the Cython libraries in use here (and presumably most other Sage contributors aren't familiar with it either).

Please add:

• A module docstring giving a high-level overview of that this code does and how it works (include links to the documentation of the relevant Cython libraries being used)
• Function docstrings (I don't think we need doctests, just descriptions of each function)

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Do you intend to run this script in this PR and add the autogenerated typestubs as well? Any plans to upstream this to Cython?

[vincentmacri]

Your PR description says this file was taken/adapted from somewhere else? Then it needs to include the relevant copyright info.

[tobiasdiez]

I've added a link. It's really more inspiration than copy & paste of their code. For example, here we extract a list of symbols as an intermediate step while cystub directly translate the ast into a pyi.

[tobiasdiez]

Please add:

Done now. Sorry that it took me so long.

Do you intend to run this script in this PR and add the autogenerated typestubs as well?

No, I want to do this slowly and improve the typegen script along the way. This here is meant as a first working version, not as a complete solution.

Any plans to upstream this to Cython?

Yes, in principle. Depends a bit on how open the cython devs are for this. Alternatively, one could consider making this a separate subproject.

[vincentmacri]

Just letting you know that I'm a bit busy this month (papers, PhD qualifying exam, etc.). I should have time to look at this in early May.