From 7639ecb7a4483605bad9565f826daba139b80f29 Mon Sep 17 00:00:00 2001
From: reginaldalfret <reginaldalfret@gmail.com>
Date: Tue, 27 Oct 2026 22:49:23 +0530
Subject: [PATCH] fix: handle VCS checkout CPython versions with trailing '+'
 in config

CPython builds from a VCS checkout append '+' to the version string (e.g.
'3.13.15+'). When running on such builds, packaging.version.Version rejects
the bare trailing '+' with an InvalidVersion exception, causing merge_configs
and default Config instantiation to fail on every file.

Introduce current_python_version() helper that strips any trailing '+' from
platform.python_version() before parsing as a Version, ensuring compatibility
with development builds while strictly preserving user configuration validation.

Closes #576

Signed-off-by: reginaldalfret <reginaldalfret@gmail.com>
---
 src/fixit/config.py       |  4 ++--
 src/fixit/ftypes.py       | 14 +++++++++++---
 src/fixit/tests/config.py | 12 ++++++++++++
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/fixit/config.py b/src/fixit/config.py
index 64b0d096..3f832d5f 100644
--- a/src/fixit/config.py
+++ b/src/fixit/config.py
@@ -10,7 +10,6 @@
 import platform
 import sys
 from contextlib import contextmanager, ExitStack
-
 from pathlib import Path
 from types import ModuleType
 from typing import (
@@ -35,6 +34,7 @@
 from .format import FORMAT_STYLES
 from .ftypes import (
     Config,
+    current_python_version,
     is_collection,
     is_sequence,
     Options,
@@ -415,7 +415,7 @@ def merge_configs(
     enable_rules: Set[QualifiedRule] = {QualifiedRule("fixit.rules")}
     disable_rules: Set[QualifiedRule] = set()
     rule_options: RuleOptionsTable = {}
-    target_python_version: Optional[Version] = Version(platform.python_version())
+    target_python_version: Optional[Version] = current_python_version()
     target_formatter: Optional[str] = None
     output_format: OutputFormat = OutputFormat.fixit
     output_template: str = ""
diff --git a/src/fixit/ftypes.py b/src/fixit/ftypes.py
index 1e3c1d8a..3bd07239 100644
--- a/src/fixit/ftypes.py
+++ b/src/fixit/ftypes.py
@@ -206,6 +206,16 @@ class LSPOptions:
     debounce_interval: float = 0.5
 
 
+def current_python_version() -> Version:
+    """
+    Return the running Python version as a packaging Version object.
+
+    Strips any trailing '+' from VCS checkout builds (e.g. '3.13.15+')
+    to ensure compatibility with PEP 440 version parsing.
+    """
+    return Version(platform.python_version().rstrip("+"))
+
+
 @dataclass
 class Config:
     """
@@ -226,9 +236,7 @@ class Config:
     options: RuleOptionsTable = field(default_factory=dict)
 
     # filtering criteria
-    python_version: Optional[Version] = field(
-        default_factory=lambda: Version(platform.python_version())
-    )
+    python_version: Optional[Version] = field(default_factory=current_python_version)
     tags: Tags = field(default_factory=Tags)
 
     # post-run processing
diff --git a/src/fixit/tests/config.py b/src/fixit/tests/config.py
index 04729734..33997c66 100644
--- a/src/fixit/tests/config.py
+++ b/src/fixit/tests/config.py
@@ -9,6 +9,7 @@
 from textwrap import dedent
 from typing import List, Sequence, Tuple, Type
 from unittest import TestCase
+from unittest.mock import patch
 
 from click.testing import CliRunner
 
@@ -351,6 +352,17 @@ def test_merge_configs(self) -> None:
                 actual = config.merge_configs(target, raw_configs)
                 self.assertEqual(expected, actual)
 
+    def test_merge_configs_vcs_python_version(self) -> None:
+        target = self.tdp / "foo.py"
+        with patch("platform.python_version", return_value="3.13.15+"):
+            cfg = config.merge_configs(target, [])
+            self.assertEqual(cfg.python_version, Version("3.13.15"))
+
+    def test_config_default_vcs_python_version(self) -> None:
+        with patch("platform.python_version", return_value="3.13.15+"):
+            cfg = Config()
+            self.assertEqual(cfg.python_version, Version("3.13.15"))
+
     def test_generate_config(self) -> None:
         for name, path, root, options, expected in (
             (