Add xfail tests for case where specifications added as an extra are not honoured

[pelson]

Adds expected failing test cases for #7096.

Essentially pip ignores specifications in the extras if the package has already been specified in the install_requires. #7096 is essentially the same issue, but in that case it doesn't have any install_requires at all, and instead has two distinct but overlapping requirements in the extras.

To be clear: I'm happy for this to not be merged - it would be completely reasonable to have concerns about adding quite so many functional tests (4), each of which comes with a significant execution overhead. I'm happy to receive guidance on where might be a better place for unit-testing of this code.

No news entry added.

[pelson]

Looks like this could use assert_installed as per https://github.com/pypa/pip/pull/7897/files#diff-77dd5d72580d087628f7667b15bbf75dR137.

[uranusjr]

Thanks for the work. The test cases look good to me, but I would prefer putting it in test_new_resolver.py instead, and only run it against the new resolver. The current (“legacy”) implementation is unlikely to receive much work on functional deficiencies, especially this particular issue (I know because I worked on it and gave up). It’s not particularly useful to apply these tests for them.

[pradyunsg]

@pelson Thanks for the PR! ^>^

Would it be possible for you to update the PR, or would your prefer that someone pick this up from here?

[pradyunsg]

Actually, this is covered by https://github.com/pypa/pip/blob/a0fe4112d15ebcb20052c33f8792f237e1ad83e7/tests/yaml/install/extras.yml in our test suite currently, so I'm going to go ahead and close this PR.

[pradyunsg]

OH WAIT. I misjudged this -- we aren't checking root requirements in that test case, which is something that's being done here.