Installing dependent wheels in a single command with specified extras is order dependent

[mattnotmitt]

Description

• Given two wheel files for a package called, child and another, parent, which depends on child and with both having a [test] extra (ie {"test": ["pytest"]},
• when pip install child.whl[test] parent.whl[test] is run the install will succeed.
• when pip install parent.whl child.whl is run the install will succeed.
• If the command is instead pip install parent.whl[test] child.whl[test] the install will fail.

Expected behavior

I expect this to work in both orders. I understand it's a bit of an edge case, but would potentially be useful to note in the docs if not fixed as the error message isn't particularly helpful.

pip version

23.0.1

Python version

3.11

OS

Linux

How to Reproduce

I've written a test which reproduces the issue.

Output

ERROR: Could not find a version that satisfies the requirement childpkg (from parent[test]) (from versions: none)
ERROR: No matching distribution found for childpkg

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[uranusjr]

IMO the current behaviour makes sense; child is not a thing until pip “sees” it, so it needs to be specified first. It’s not impossible (probably not too complicated either) to implement the behaviour this is looking for—essentially pip needs to perform an additional pass through the usersupplied requirements and register everything in it before handing things off to resolvelib—but personally I’m not going to bother since this additional pass is not beneficial in general.

[mattnotmitt]

Yeah it's definitely some niche behaviour so it's not too much of an issue for me, however:

IMO the current behaviour makes sense; child is not a thing until pip “sees” it, so it needs to be specified first.

If this is true, why is this only an issue when the extras are set, and works fine without them?