pip does not reinstall an already installed package from a different direct url requirement

What’s the problem this feature will solve?

Assume packaging has been installed with pip install "packaging @ git+https://github.com/pypa/packaging@20.0".

Then try to install from the 20.1 tag: pip install "packaging @ git+https://github.com/pypa/packaging@20.1". The second install does nothing, saying the requirement is already satisfied.

Describe the solution you’d like

The second install should reinstall with the requested requirement.

Alternative Solutions

• Document this as a limitation of direct URL references support in PIP.

Additional context

This requires PEP 610 to implement. This may or may not influence the ongoing reflection about the resolver.

[pfmoore]

https://github.com/pypa/pip/issues/536 has an extensive discussion over whether we should force reinstall explicitly specified locations. Apparently I was ambivalent when it was discussed then, as well 🙂

[sbidoul]

@pfmoore my impression (trying to factor out my own use cases) is that the common use case for direct URLs is very similar to pinning a version. For instance when pointing to a VCS tag, a VCS commit id, an archive with a version number in it, or a local directory, the user says “I want this specific version and not any other one”.

So this could mean direct URL requirements could be handled the same as == version specifiers wrt conflict handling.