Revert to supporting simple Python factors (#2849)

Co-authored-by: Bernát Gábor <bgabor8@bloomberg.net>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Fixes https://github.com/tox-dev/tox/issues/2657
Fixes https://github.com/tox-dev/tox/issues/2848

9 files changed, 72 insertions, 39 deletions

diff --git a/.github/ISSUE_TEMPLATE/feature-request.md b/.github/ISSUE_TEMPLATE/feature-request.md
index d065c219..3d35f697 100644
--- a/.github/ISSUE_TEMPLATE/feature-request.md
+++ b/.github/ISSUE_TEMPLATE/feature-request.md
@@ -18,7 +18,8 @@ assignees: ""
 
 ## Alternative Solutions
 
-<!-- Have you tried to workaround the problem using tox or other tools? Or a different approach to solving this issue? Please elaborate here. -->
+<!-- Have you tried to workaround the problem using tox or other tools? Or a different approach to solving this issue?
+Please elaborate here. -->
 
 ## Additional context
 
diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 43c6d09c..4a25b76c 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -40,18 +40,10 @@ jobs:
         uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.py }}
-      - name: Pick environment to run
-        run: |
-          import os; import platform; import sys; from pathlib import Path
-          env = f'TOXENV=py{"" if platform.python_implementation() == "CPython" else "py"}3{sys.version_info.minor}'
-          print(f"Picked: {env} for {sys.version} based of {sys.executable}")
-          with Path(os.environ["GITHUB_ENV"]).open("ta") as file_handler:
-               file_handler.write(env)
-        shell: python
       - name: Setup test suite
-        run: tox r -vv --notest
+        run: tox r -e py${{ matrix.py }} -vv --notest
       - name: Run test suite
-        run: tox r --skip-pkg-install
+        run: tox r -e py${{ matrix.py }} --skip-pkg-install
         env:
           CI_RUN: "yes"
           DIFF_AGAINST: HEAD
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index d153df00..ebccbdc3 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -43,7 +43,7 @@ repos:
     hooks:
       - id: rst-backticks
   - repo: https://github.com/tox-dev/tox-ini-fmt
-    rev: "0.5.2"
+    rev: "0.6.0"
     hooks:
       - id: tox-ini-fmt
         args: ["-p", "fix"]
@@ -69,7 +69,7 @@ repos:
           - "@prettier/plugin-xml@2.2"
         args: ["--print-width=120", "--prose-wrap=always"]
   - repo: https://github.com/igorshubovych/markdownlint-cli
-    rev: v0.32.2
+    rev: v0.33.0
     hooks:
       - id: markdownlint
   - repo: local
diff --git a/docs/changelog/2848.bugfix.rst b/docs/changelog/2848.bugfix.rst
new file mode 100644
index 00000000..9220c483
--- /dev/null
+++ b/docs/changelog/2848.bugfix.rst
@@ -0,0 +1,6 @@
+tox has reverted support for Python factors that include PATCH release info (e.g. ``py3.10.1``), build architecture
+(e.g. ``pypy3-64``) or do not define a ``py`` prefix or other supported prefix (e.g. ``3.10``). These complex factors
+were initially supported with the release of tox 4.0 but has proven complicated to support. Instead, the simple factors
+supported by tox 3 e.g. (``py310``, ``pypy3``) or period-separated equivalent (``py3.10``) introduced in tox 4 should be
+used. Users who wish to specify more specific Python version information should configure the :ref:`base_python` setting
+- by :user:`stephenfin`.
diff --git a/pyproject.toml b/pyproject.toml
index e4d5ad96..e8be85ac 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [build-system]
 build-backend = "hatchling.build"
-requires = ["hatchling>=1.12", "hatch-vcs>=0.3"]
+requires = ["hatchling>=1.12.2", "hatch-vcs>=0.3"]
 
 [project]
 name = "tox"
@@ -22,24 +22,24 @@ maintainers = [
 ]
 requires-python = ">=3.7"
 dependencies = [
-  "cachetools>=5.2",
+  "cachetools>=5.2.1",
   "chardet>=5.1",
   "colorama>=0.4.6",
-  "packaging>=22",
+  "packaging>=23",
   "platformdirs>=2.6.2",
   "pluggy>=1",
-  "pyproject-api>=1.2.1",
+  "pyproject-api>=1.4",
   'tomli>=2.0.1; python_version < "3.11"',
   "virtualenv>=20.17.1",
   "filelock>=3.9",
-  'importlib-metadata>=5.2; python_version < "3.8"',
+  'importlib-metadata>=6; python_version < "3.8"',
   'typing-extensions>=4.4; python_version < "3.8"',
 ]
 optional-dependencies.docs = [
   "furo>=2022.12.7",
-  "sphinx>=6",
-  "sphinx-argparse-cli>=1.10",
-  "sphinx-autodoc-typehints>=1.19.5",
+  "sphinx>=6.1.3",
+  "sphinx-argparse-cli>=1.11",
+  "sphinx-autodoc-typehints>=1.20.1",
   "sphinx-copybutton>=0.5.1",
   "sphinx-inline-tabs>=2022.1.2b11",
   "sphinxcontrib-towncrier>=0.2.1a0",
@@ -53,7 +53,7 @@ optional-dependencies.testing = [
   "distlib>=0.3.6",
   "flaky>=3.7",
   "hatch-vcs>=0.3",
-  "hatchling>=1.12",
+  "hatchling>=1.12.2",
   "psutil>=5.9.4",
   "pytest>=7.2",
   "pytest-cov>=4",
diff --git a/src/tox/tox_env/python/api.py b/src/tox/tox_env/python/api.py
index 271a3803..da9e435f 100644
--- a/src/tox/tox_env/python/api.py
+++ b/src/tox/tox_env/python/api.py
@@ -4,12 +4,12 @@ Declare the abstract base class for tox environments that handle the Python lang
 from __future__ import annotations
 
 import logging
+import re
 import sys
 from abc import ABC, abstractmethod
 from pathlib import Path
 from typing import Any, List, NamedTuple, cast
 
-from packaging.tags import INTERPRETER_SHORT_NAMES
 from virtualenv.discovery.py_spec import PythonSpec
 
 from tox.config.main import Config
@@ -47,6 +47,16 @@ class PythonInfo(NamedTuple):
         return f"{self.version_info.major}.{self.version_info.minor}"
 
 
+PY_FACTORS_RE = re.compile(
+    r"""
+    ^(?!py$)                                               # don't match 'py' as it doesn't provide any info
+    (?P<impl>py|pypy|cpython|jython|rustpython|ironpython) # the interpeter; most users will simply use 'py'
+    (?P<version>[2-9]\.?[0-9]?[0-9]?)?$                    # the version; one of: MAJORMINOR, MAJOR.MINOR
+    """,
+    re.VERBOSE,
+)
+
+
 class Python(ToxEnv, ABC):
     def __init__(self, create_args: ToxEnvCreateArgs) -> None:
         self._base_python: PythonInfo | None = None
@@ -131,9 +141,8 @@ class Python(ToxEnv, ABC):
     def extract_base_python(cls, env_name: str) -> str | None:
         candidates: list[str] = []
         for factor in env_name.split("-"):
-            spec = PythonSpec.from_string_spec(factor)
-            impl = spec.implementation or "python"
-            if impl.lower() in INTERPRETER_SHORT_NAMES and env_name is not None and spec.path is None:
+            match = PY_FACTORS_RE.match(factor)
+            if match:
                 candidates.append(factor)
         if candidates:
             if len(candidates) > 1:
diff --git a/tests/tox_env/python/test_python_api.py b/tests/tox_env/python/test_python_api.py
index 725eab05..3348acda 100644
--- a/tests/tox_env/python/test_python_api.py
+++ b/tests/tox_env/python/test_python_api.py
@@ -71,6 +71,36 @@ def test_diff_msg_no_diff() -> None:
     assert Python._diff_msg({}, {}) == "python "
 
 
+@pytest.mark.parametrize(
+    ("env", "base_python"),
+    [
+        ("py3", "py3"),
+        ("py311", "py311"),
+        ("py3.12", "py3.12"),
+        ("pypy2", "pypy2"),
+        ("rustpython3", "rustpython3"),
+        ("cpython3.8", "cpython3.8"),
+        ("ironpython2.7", "ironpython2.7"),
+        ("functional-py310", "py310"),
+        ("bar-pypy2-foo", "pypy2"),
+        ("py", None),
+        ("django-32", None),
+        ("eslint-8.3", None),
+        ("py-310", None),
+        ("py3000", None),
+        ("4.foo", None),
+        ("310", None),
+        ("5", None),
+        ("2000", None),
+        ("4000", None),
+    ],
+    ids=lambda a: "|".join(a) if isinstance(a, list) else str(a),
+)
+def test_extract_base_python(env: str, base_python: str | None) -> None:
+    result = Python.extract_base_python(env)
+    assert result == base_python
+
+
 @pytest.mark.parametrize("ignore_conflict", [True, False])
 @pytest.mark.parametrize(
     ("env", "base_python"),
@@ -89,7 +119,6 @@ def test_base_python_env_no_conflict(env: str, base_python: list[str], ignore_co
 @pytest.mark.parametrize(
     ("env", "base_python", "expected", "conflict"),
     [
-        ("cpython", ["pypy"], "cpython", ["pypy"]),
         ("pypy", ["cpython"], "pypy", ["cpython"]),
         ("pypy2", ["pypy3"], "pypy2", ["pypy3"]),
         ("py3", ["py2"], "py3", ["py2"]),
@@ -97,8 +126,7 @@ def test_base_python_env_no_conflict(env: str, base_python: list[str], ignore_co
         ("py38", ["py38", "py39"], "py38", ["py39"]),
         ("py38", ["python3"], "py38", ["python3"]),
         ("py310", ["py38", "py39"], "py310", ["py38", "py39"]),
-        ("py3.11.1", ["py3.11.2"], "py3.11.1", ["py3.11.2"]),
-        ("py3-64", ["py3-32"], "py3-64", ["py3-32"]),
+        ("py3.11", ["py310"], "py3.11", ["py310"]),
         ("py310-magic", ["py39"], "py310", ["py39"]),
     ],
     ids=lambda a: "|".join(a) if isinstance(a, list) else str(a),
@@ -110,9 +138,6 @@ def test_base_python_env_conflict(
     conflict: list[str],
     ignore_conflict: bool,
 ) -> None:
-    if env == "py3-64":
-        raise pytest.skip("bug #2657")
-
     if ignore_conflict:
         result = Python._validate_base_python(env, base_python, ignore_conflict)
         assert result == [expected]
diff --git a/tests/tox_env/python/virtual_env/test_virtualenv_api.py b/tests/tox_env/python/virtual_env/test_virtualenv_api.py
index 2d84dafd..cd57fd05 100644
--- a/tests/tox_env/python/virtual_env/test_virtualenv_api.py
+++ b/tests/tox_env/python/virtual_env/test_virtualenv_api.py
@@ -33,10 +33,10 @@ def virtualenv_opt(monkeypatch: MonkeyPatch, mocker: MockerFixture) -> VirtualEn
 
 def test_virtualenv_default_settings(tox_project: ToxProjectCreator, virtualenv_opt: VirtualEnvOptions) -> None:
     proj = tox_project({"tox.ini": "[testenv]\npackage=skip"})
-    result = proj.run("r", "-e", "py", "--discover", sys.executable, str(proj.path / "a"))
+    result = proj.run("r", "-e", "py3", "--discover", sys.executable, str(proj.path / "a"))
     result.assert_success()
 
-    conf = result.env_conf("py")
+    conf = result.env_conf("py3")
     assert conf["system_site_packages"] is False
     assert conf["always_copy"] is False
     assert conf["download"] is False
@@ -46,7 +46,7 @@ def test_virtualenv_default_settings(tox_project: ToxProjectCreator, virtualenv_
     assert virtualenv_opt.download is False
     assert virtualenv_opt.copies is False
     assert virtualenv_opt.no_periodic_update is True
-    assert virtualenv_opt.python == ["py"]
+    assert virtualenv_opt.python == ["py3"]
     assert virtualenv_opt.try_first_with == [str(sys.executable), str(proj.path / "a")]
 
 
@@ -60,10 +60,10 @@ def test_virtualenv_flipped_settings(
     )
     monkeypatch.setenv("VIRTUALENV_CLEAR", "0")
 
-    result = proj.run("r", "-e", "py")
+    result = proj.run("r", "-e", "py3")
     result.assert_success()
 
-    conf = result.env_conf("py")
+    conf = result.env_conf("py3")
     assert conf["system_site_packages"] is True
     assert conf["always_copy"] is True
     assert conf["download"] is True
@@ -72,7 +72,7 @@ def test_virtualenv_flipped_settings(
     assert virtualenv_opt.system_site is True
     assert virtualenv_opt.download is True
     assert virtualenv_opt.copies is True
-    assert virtualenv_opt.python == ["py"]
+    assert virtualenv_opt.python == ["py3"]
 
 
 def test_virtualenv_env_ignored_if_set(
diff --git a/tox.ini b/tox.ini
index d7bbdf47..2f803f23 100644
--- a/tox.ini
+++ b/tox.ini
@@ -83,7 +83,7 @@ description = do a release, required posarg of the version number
 skip_install = true
 deps =
     gitpython>=3.1.30
-    packaging>=22
+    packaging>=23
     towncrier>=22.12
 commands =
     python {toxinidir}/tasks/release.py --version {posargs}