Implement "Requires" field in pip show

[ChannyClaus]

Summary

Follow-up for 395be44

adds Requires field to pip show output.

I've aimed to make it behave exactly the same as pip does for now, but there seem to be subtle issues that may require some discussion going forward:

• Should uv pip show support extras? pip has an open issue for it, but currently does not support Add support for outputting a list of extras and their requirements. pypa/pip#4824.
• Relatedly, Requred-by field (not implemented in this PR) in pip show currently doesn't take the extras into account transparently, i.e. when PySocks has been installed as an extra for requests[socks], pip show PySocks doesn't have requests or requests[socks] under Requred-by field. Should uv pip show for now just replicate pip's behavior for now for simplicity and parity or try to cover the extras for completeness?

Test Plan

Added a couple of tests:

1. requests==2.31.0 has four dependencies that would be ordered differently unless sorted. Additionally, it has two dependencies that are optionally included for extras.
2. pandas==2.1.3 depends on different versions of numpy depending on the python version used.

[ChannyClaus]

not super clear why windows doesn't pull tzdata https://github.com/astral-sh/uv/actions/runs/8225296455/job/22490152644; seems like it's not a platform-dependent dependency https://github.com/pandas-dev/pandas/blob/871f01b5582fc737a63f17c1d9027eb6a2099912/pyproject.toml#L37. may continue to look while having this open for review 😭 (probably not a blocking issue?)

[konstin]

We have a windows filter hack in the snapshots for our common test packages:

uv/crates/uv/tests/common/mod.rs

Lines 370 to 376 in 1181aa9

	// The optional leading +/- is for install logs, the optional next line is for lock files
	let windows_only_deps = [
	("( [+-] )?colorama==\\d+(\\.[\\d+])+\n( # via .*\n)?"),
	("( [+-] )?colorama==\\d+(\\.[\\d+])+\\s+(# via .*\n)?"),
	("( [+-] )?tzdata==\\d+(\\.[\\d+])+\n( # via .*\n)?"),
	("( [+-] )?tzdata==\\d+(\\.[\\d+])+\\s+(# via .*\n)?"),
	];

Could you use a pure python package for the test case? Pandas and numpy wheel are big due to their native modules (something like 5-20 MB) and since we run the tests with no cache these add up.

[ChannyClaus]

updated to use click.

$ du -sh /Users/chan.kang/test/uv/venv/lib/python3.12/site-packages/click
824K	/Users/chan.kang/test/uv/venv/lib/python3.12/site-packages/click

[konstin]

Should uv pip show support extras? pip has an open issue for it, but currently does not support pypa/pip#4824.

That would be a nice addition, feel free to make a follow-up PR.

Relatedly, Requred-by field (not implemented in this PR) in pip show currently doesn't take the extras into account transparently, i.e. when PySocks has been installed as an extra for requests[socks], pip show PySocks doesn't have requests or requests[socks] under Requred-by field. Should uv pip show for now just replicate pip's behavior for now for simplicity and parity or try to cover the extras for completeness?

There's unfortunately no tracking for which extras get installed, so we don't know if an extra was activated or not.

[konstin]

Can you try collecting into a BTreeSet instead? There are some cases where names occur twice in the requirements. This would remove those duplicates and skip the sorting step

[ChannyClaus]

Do you happen to remember which particular package has duplicates (was thinking if I should add a test using it)? https://github.com/pypa/pip/blob/fb5f63f0f4c3a204ada8353ce9858d4d4b777c2a/src/pip/_internal/commands/show.py#L104 does seem to suggest the same.