Space in filename in PIP_CONSTRAINTS is interpreted as a new file

Description

The PIP_CONSTRAINTS variable (and likely any other path related variables?) can’t handle a path with a space in it. Something like PIP_CONSTRAINTS="C:\Program Files\..." causes Could not open requirements file: [Errno 2] No such file or directory: 'C:\\Program'. These path variables should probably interpret spaces as part of paths, and use a separator for multiple values (like : or ;).

Also, quotes around the path causes this to fail, too, PIP_CONSTRAINTS="'C:\Program Files\...'" breaks.

See https://github.com/pypa/cibuildwheel/issues/740

Expected behavior

Spaces in paths should not break.

pip version

21.1.3

Python version

All

OS

Windows and macOS, at least, probably all.

How to Reproduce

1. Make a constraints file with a space my constraints.txt
2. Then run PIP_CONSTRAINTS="my constraints.txt" pip install <package>
3. An error occurs.

Output

Could not open requirements file: [Errno 2] No such file or directory: 'C:\\Program'`

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[uranusjr]

I believe since 10.0 the : path separator is purely cosmetic on macOS; it always stores paths with /, and only transforms it to : when showing it in GUI. So as far as Python code (which is run in POSIX mode) is concerned, we can use os.pathsep without issues.

But there are two major downsides here. First, this means the accepted values on POSIX and Windows will be different (os.pathsep is ; on Windows), which will cause user confusion. Another is that most of pip’s path arguments are actually path-or-URL (including PIP_CONSTRAINT!) and obviously you’re going you run into issues parsing /a/local/path:https://rawgithubcontent.com/pypa/pip/requirements.txt. So I think the quoting + space solution is the way to go if we want to do this.

[pfmoore]

Ah, I didn’t know MacOS did that. Cross-platform rules are weird 🙂