Document self-referential extras now that pip officially supports it

[Trenza1ore]

Using self-referential extras is a more preferable pattern than to manually write, for example, an all extra for all dependencies combined (which is both tedious and easy to fall out of sync with reality).

Following pypa/pip#14157, this is now a documented and tested feature of pip (supported unofficially since v21.2).

Update: check https://github.com/Trenza1ore/Self-Referential-Extras for which installer / dependency manager currently supports installing with self-referential extras.

Closes #2086

---

📚 Documentation preview 📚: https://python-packaging-user-guide--2087.org.readthedocs.build/en/2087/

[henryiii]

Should there also be a "several installers" note in the writing toml page? I think it's not officially a standard, this is just says most installers support it? Getting it standardized is a bigger effort (but maybe a worthwhile one?).

[Trenza1ore]

Should there also be a "several installers" note in the writing toml page? I think it's not officially a standard, this is just says most installers support it?

I'll update the toml page with a list of package installers supporting self-referential extras. Will test a few more and make a list.

Getting it standardized is a bigger effort (but maybe a worthwhile one?).

Totally agree, that should probably be standardized at some point as there are many packages using self-referential extras already.

[henryiii]

You have a note on one of the two pages, having it on the other makes sense too. I think pip + uv is fine, but if you want to add more (Poetry?), the more the merrier (within reason!). :)

[Trenza1ore]

You have a note on one of the two pages, having it on the other makes sense too. I think pip + uv is fine, but if you want to add more (Poetry?), the more the merrier (within reason!). :)

I've updated the list of supported installers/dependency managers, created a test repo to verify. Anything except conda stuffs should work. 👍🏻