pdm loops indefinitely, instead of deciding quickly, that requires-python is set too low

[meop]

• I have searched the issue tracker and believe that this is not a duplicate.

It is similar to these two bugs, although not identical, because they have already been fixed, and I have a version of pdm with those fixes merged.

#627
#744

Make sure you run commands with -v flag before pasting the output.

Steps to reproduce

Case 1:

In an empty project, set:

requires-python = ">=3.7"

Then:

pdm install
pdm add pandas==1.3.4 -v

You can see that the output loops for a little while, mostly on numpy constraints, but pdm ultimately accurately decides that pandas requires Python 3.7.1, not 3.7, and prints this. This is good.

Case 2:

However, if instead of an empty project, you had:

dependencies = [
    "matplotlib==3.4.3",
]
requires-python = ">=3.7"

Then again you do:

pdm install
pdm add pandas==1.3.4 -v

This appears to be too much for pdm. It loops for a few minutes printing again mostly numpy constraints, until I cancel it.

Projects are often much bigger than 1 package, and if only 2 packages are able to confuse the dependency resolver, that is not good.

The workaround is of course, you can find out through external means that certain packages have minimum Python version requirements, and adjust your config accordingly.

Actual behavior

Pdm completes but is a bit slow for Case 1.
Pdm loops indefinitely for Case 2.

Expected behavior

Pdm completes fast for Case 1.
Pdm completes fast for Case 2.

Environment Information

It is actually version 1.11.0 through homebrew, and there is an open bug about 0.0.0 printing.

PDM version:        0.0.0
Python Interpreter: /Users/me/.asdf/installs/python/3.10.0/bin/python (3.10)
Project Root:       /Users/me/source/code/my/project
Project Packages:   /Users/me/source/code/my/project/__pypackages__/3.10
{
  "implementation_name": "cpython",
  "implementation_version": "3.10.0",
  "os_name": "posix",
  "platform_machine": "x86_64",
  "platform_release": "21.1.0",
  "platform_system": "Darwin",
  "platform_version": "Darwin Kernel Version 21.1.0: Wed Oct 13 17:33:23 PDT 2021; root:xnu-8019.41.5~1/RELEASE_X86_64",
  "python_full_version": "3.10.0",
  "platform_python_implementation": "CPython",
  "python_version": "3.10",
  "sys_platform": "darwin"
}

Thanks for working on this tool!