Hi.

As #3426 said, current poetry only checks the python constraint in pyproject.toml when creating a virtualenv.

This PR added a python version check for created virtualenv as well, at each command execution.

Demo

(Supporse python 3.8 and 3.9 are installed)

First, poetry install with pyproject.tom which requires python3.8:

[tool.poetry]
name = "ptry"
version = "0.1.0"
description = ""
authors = ["Your Name <[email protected]>"]

[tool.poetry.dependencies]
python = "~3.8"

[tool.poetry.dev-dependencies]

[build-system]
requires = ["poetry-core>=1.0.0"]
build-backend = "poetry.core.masonry.api"

It creates virtualenv with python 3.8.x executable.

$ poetry run python -V
Python 3.8.10

Then change pyproject.tom to python = "^3.9".

With this PR, now poetry install aborts with error message:

  InvalidCurrentPythonVersionError

  Current Python version (3.8.10) is not allowed by the project (^3.9).
  Please change python executable via the "env use" command.

  at ~/.poetry/lib/poetry/utils/env.py:651 in create_venv
       647│             current_python = Version.parse(
       648│                 ".".join(str(c) for c in env.version_info[:3])
       649│             )
       650│             if not self._poetry.package.python_constraint.allows(current_python):
    →  651│                 raise InvalidCurrentPythonVersionError(
       652│                     self._poetry.package.python_versions, current_python
       653│                 )
       654│             return env
       655│ 

As above message suggests, by running poetry env use python3.9 , poetry install will work again.

I expect this PR covers all commands which should check python version, like uninstall, run, shell etc.

Pull Request Check List

Resolves: #3426

• Added tests for changed code.
• [ ] Updated documentation for changed code.