PDM doesn't find Python interpreters when PDM_IGNORE_ACTIVE_VENV is set

[p-rogalski]

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

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

Steps to reproduce

1. Have some Python version >=3.10 installed

2. Use following minimal pyproject.toml

   [project]
   name = "test"
   version = "0.0.1"
   requires-python = ">=3.10"

3. Set environment variable PDM_IGNORE_SAVED_PYTHON and PDM_IGNORE_ACTIVE_VENV.

4. Try to install the project:

   pdm install --verbose

Actual behavior

PDM does not find a Python version to use and errors out:

PS C:\Users\progalski\git\test> pdm install --verbose
WARNING: Lockfile does not exist
Updating the lock file...
[NoPythonVersion]: No Python that satisfies >=3.10 is found on the system.

Expected behavior

According to PDM Docs: Virtualenv auto-detection I would expect that PDM creates a new virtual environment because virtual env auto-detection fails.

Environment Information

# Paste the output of `pdm info && pdm info --env` below:
PS C:\Users\progalski\git\test> pdm info && pdm info --env
[NoPythonVersion]: No Python that satisfies >=3.10 is found on the system.

Environment Information without the problematic environment variables set:

# Paste the output of `pdm info && pdm info --env` below:
PDM version:
  2.13.2
Python Interpreter:
  C:\Users\progalski\git\test\.venv\Scripts\python.exe (3.11)
Project Root:
  C:/Users/progalski/git/test
Local Packages:

{
  "implementation_name": "cpython",
  "implementation_version": "3.11.4",
  "os_name": "nt",
  "platform_machine": "AMD64",
  "platform_release": "10",
  "platform_system": "Windows",
  "platform_version": "10.0.22631",
  "python_full_version": "3.11.4",
  "platform_python_implementation": "CPython",
  "python_version": "3.11",
  "sys_platform": "win32"
}

[p-rogalski]

I had a look into the PDM source code, the logic of getting a valid interpreter can be found here:

pdm/src/pdm/project/core.py

Line 193 in 881cd4e

def resolve_interpreter(self) -> PythonInfo:

If PDM_IGNORE_ACTIVE_VENV is set, the logic which creates a new virtual environment is skipped completely. This is unexpected, because the env var name suggests that it just ignores the currently activated venv.

Instead, I would PDM expect to fall back to creating a new virtual environment when python.use_venv is True.

[noirbizarre]

I just hit the same issue.
Working on a fix