`.python-version` file is not used to establish the python version

Description: v4.1.0 introduced a regression where the repo-root .python-version file is no longer used by default to select the python version to install. The regression was introduced by https://github.com/actions/setup-python/pull/450/

Reading from .python-version when the python-version input is unset is documented in action.yml - https://github.com/actions/setup-python/blob/00a5248c77bed9280afb34f891aa24a152490ab5/action.yml#L6-L7

Action version: v4.1.0 (regression from v4.0.0)

Platform:

• Ubuntu
• macOS
• Windows

Runner type:

• Hosted
• Self-hosted

Tools version: N/A

Repro steps:
Create a repository with a .python-version file containing 3.10.4 and a workflow containing a setup-python step, e.g.:

name: CI
on: [push]
jobs:
  python:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Install python
        uses: actions/setup-python@v4.0.0

Expected behavior: setup-python should install 3.10.4 as it is listed in the .python-version file, i.e. the step logs:

Run actions/setup-python@v4
  with:
    token: ***
Resolved  as 3.10.4

This is the behaviour with v4.0.0.

Actual behavior: setup-python ignores the .python-version file and logs:

Run actions/setup-python@v4
Warning: Neither 'python-version' nor 'python-version-file' inputs were supplied.
Warning: The `python-version` input is not set.  The version of Python currently in `PATH` will be used.

[IvanZosimov]

Hi, @gg-kialo and @rs-garrick 👋 Thank you for your questions, we took them into consideration and decided to update behavior of the action, take a look at this PR.

[IvanZosimov]

Hi, @OmeGak 👋 Sorry for the long delay, the new version of setup-python is released.