From fdc9eb0355f3f58ca700147dc15e4c6894595bdf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bern=C3=A1t=20G=C3=A1bor?= <gaborjbernat@gmail.com>
Date: Wed, 7 Aug 2024 10:15:57 -0700
Subject: [PATCH] Restore limited <major>.<minor> environment name support
 (#3319)

---
 docs/changelog.rst                      |  8 ++++----
 docs/changelog/2849.bugfix.rst          |  1 +
 src/tox/tox_env/python/api.py           | 13 +++++++++----
 tests/tox_env/python/test_python_api.py |  3 +++
 4 files changed, 17 insertions(+), 8 deletions(-)
 create mode 100644 docs/changelog/2849.bugfix.rst

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 5cfedf69b..ce8275571 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -9,7 +9,7 @@ v4.17.0 (2024-08-05)
 
 Features - 4.17.0
 ~~~~~~~~~~~~~~~~~
-- Add "graalpy" prefix as a supported base python (:issue:`3312`)
+- Add ``graalpy`` prefix as a supported base python (:issue:`3312`)
 - Add :ref:`on_platform` core configuration holding the tox platform and do not install package when exec an environment
   - by :user:`gaborbernat`. (:issue:`3315`)
 
@@ -69,7 +69,7 @@ Bugfixes - 4.14.2
 
 Improved Documentation - 4.14.2
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Removed unused line from the 'fresh_subprocess' documentation. (:issue:`3241`)
+- Removed unused line from the ``fresh_subprocess`` documentation. (:issue:`3241`)
 
 v4.14.1 (2024-03-06)
 --------------------
@@ -216,9 +216,9 @@ v4.7.0 (2023-08-08)
 
 Features - 4.7.0
 ~~~~~~~~~~~~~~~~
-- Make --hashseed default to PYTHONHASHSEED, if defined - by :user:`paravoid`.
+- Make ``--hashseed`` default to ``PYTHONHASHSEED``, if defined - by :user:`paravoid`.
   The main motivation for this is to able to set the hash seed when building the
-  documentation with "tox -e docs", and thus avoid embedding a random value in
+  documentation with ``tox -e docs``, and thus avoid embedding a random value in
   the tox documentation for --help. This caused documentation builds to fail to
   build reproducibly. (:issue:`2942`)
 
diff --git a/docs/changelog/2849.bugfix.rst b/docs/changelog/2849.bugfix.rst
new file mode 100644
index 000000000..7e5b2101f
--- /dev/null
+++ b/docs/changelog/2849.bugfix.rst
@@ -0,0 +1 @@
+Support for running ``-e <major>.<minor>`` has been lost, fixing it - by :user:`gaborbernat`.
diff --git a/src/tox/tox_env/python/api.py b/src/tox/tox_env/python/api.py
index ed8ba8ece..1f9141790 100644
--- a/src/tox/tox_env/python/api.py
+++ b/src/tox/tox_env/python/api.py
@@ -56,6 +56,7 @@ def version_dot(self) -> str:
     """,
     re.VERBOSE,
 )
+PY_FACTORS_RE_EXPLICIT_VERSION = re.compile(r"^(?P<version>[2-9]\.[0-9]+)$")
 
 
 class Python(ToxEnv, ABC):
@@ -142,10 +143,14 @@ def default_base_python(self, conf: Config, env_name: str | None) -> list[str]:
     @classmethod
     def extract_base_python(cls, env_name: str) -> str | None:
         candidates: list[str] = []
-        for factor in env_name.split("-"):
-            match = PY_FACTORS_RE.match(factor)
-            if match:
-                candidates.append(factor)
+        match = PY_FACTORS_RE_EXPLICIT_VERSION.match(env_name)
+        if match:
+            candidates.append(env_name)
+        else:
+            for factor in env_name.split("-"):
+                match = PY_FACTORS_RE.match(factor)
+                if match:
+                    candidates.append(factor)
         if candidates:
             if len(candidates) > 1:
                 msg = f"conflicting factors {', '.join(candidates)} in {env_name}"
diff --git a/tests/tox_env/python/test_python_api.py b/tests/tox_env/python/test_python_api.py
index da3628f4c..8690cc838 100644
--- a/tests/tox_env/python/test_python_api.py
+++ b/tests/tox_env/python/test_python_api.py
@@ -100,6 +100,9 @@ def test_diff_msg_no_diff() -> None:
         ("5", None),
         ("2000", None),
         ("4000", None),
+        ("3.10", "3.10"),
+        ("3.9", "3.9"),
+        ("2.7", "2.7"),
     ],
     ids=lambda a: "|".join(a) if isinstance(a, list) else str(a),
 )