requires-extra not documented for new style metadata

[koubaa]

requires-extra is documented only under the old style metadata
https://flit.pypa.io/en/latest/pyproject_toml.html#module-section

I want to add a requires-extra section to a module that uses the new style metadata, and I'm stuck with trying to migrate from new-style to old-style, which is lossy and I suppose it is not what flit wants its users to do.

[pradyunsg]

You're looking for project.optional-dependencies?

[pradyunsg]

I don't believe there's any bits of information being lost in the translation.

[koubaa]

@pradyunsg ah yes that would be it. I suppose it would be helpful for each old-style metadata attribute to mention what the equivalent new-style metadata attribute is if the name is different - I really couldn't find it.

[takluyver]

I hope not every entry needs this - quite a few of them are exactly the same - but I agree that requires-extra to optional-dependencies is not super obvious, so maybe one or two such 'translations' are worth including, if someone wants to make a PR.