pip currently supports invalid PEP-508 specifiers

[pelson]

Description

As mentioned in https://discuss.python.org/t/pip-supporting-non-pep508-dependency-specifiers/23107, pip currently supports a specifier such as numpy>='1.20', but this is not supported in PEP-508, nor is it supported in packaging.requirements.

Expected behavior

pip should not install such invalid version specifiers - it should follow the specs that have been formalised. Since this would be a breaking change, I suspect we would want to raise a good exception, but have a feature flag to re-enable the existing behaviour.

Unfortunately, it is not clear to me whether that feature flag can ever be removed, as this would prohibit existing packages (e.g. flox) from being installed.

pip version

all

Python version

all

OS

all

How to Reproduce

python -m pip install flox==0.6.7

Output

It installs just fine, despite having invalid specifiers.

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[pradyunsg]

Consolidating into #11715

[merwok]

Would help if the specific invalid specifiers would be noted in the ticket! 🙂

[pradyunsg]

They are? (the numpy one)

[merwok]

Ah right, missed it in the first line!

Is the problem with the quotes?