Fix #5889 which occurs when comes_from.link is None

[ircwaves]

fixes issue #5889, which blocks a private-package use case of installing a package C, that requires package B via a direct URL requirement, which requires A via direct URL requirement (a la pep508).

@benoit-pierre said:

• allow calling it with comes_from=None (easier for testing)
• handle the case where comes_from.link is None (which can happen
  if a package using a PEP 508 URL requirement is already installed)

On benoit-pierre's PR #5893, @cjerdonek suggested that a slimmer PR might be better, so here it is. This may be a total faux pas, but I've cherry-picked the commit he made, as it fixes issue #5889.

I see that on the PR #5893 @cjerdonek asked for a unit test, but I'm not familiar enough with pip internals to set up that unit test. The test that benoit-pierre wrote should ensure that there isn't a regression that blocks this use-case again.

[ircwaves]

OK. Now I see that the test has issues.

[benoit-pierre]

Yes, you can't use file:///path/to/package because of a packaging bug (pypa/packaging#115), and the work around using file://localhost/path/to/package does not work on Linux because of a pip bug (see #5892)... Either wait for a new packaging version to be released and vendored, or work on getting #5892 merged, or drop the functional test and add a unit test.

[xavfernandez]

FWIW, pypa/packaging#115, was merged and packaging 19 is now vendored in pip.

[BrownTruck]

Hello!

I am an automated bot and I have noticed that this pull request is not currently able to be merged. If you are able to either merge the master branch into this pull request or rebase this pull request against master then it will be eligible for code review and hopefully merging!

[cjerdonek]

@xavfernandez Can this be closed because of PR #6336 just merged?

[xavfernandez]

Indeed

[xavfernandez]

Thanks @ircwaves for the initial PR though

[ircwaves]

@xavfernandez -- I'll pass those thanks on back to @benoit-pierre, @cjerdonek, and @aloosley. I just wish my bandwidth had allowed me to get more involved and push the fix through. Thanks to all for their efforts, of any measure.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.