From 5deffeb55c65f11536498674723fdd6eb6146b06 Mon Sep 17 00:00:00 2001
From: Artur Shiriev <lesnik512@gmail.com>
Date: Sat, 3 Oct 2026 23:25:01 +0300
Subject: [PATCH] feat!: drop Python 3.10 and use typing.assert_never

Closes #33
---
 .github/workflows/_checks.yml                     |  6 ++----
 docs/adr/0002-keep-py310-vendored-assert-never.md | 12 ------------
 docs/agents/domain.md                             |  2 +-
 eof_fixer/fixer.py                                |  9 ++-------
 pyproject.toml                                    |  3 +--
 5 files changed, 6 insertions(+), 26 deletions(-)
 delete mode 100644 docs/adr/0002-keep-py310-vendored-assert-never.md

diff --git a/.github/workflows/_checks.yml b/.github/workflows/_checks.yml
index b6bd0d5..1b37473 100644
--- a/.github/workflows/_checks.yml
+++ b/.github/workflows/_checks.yml
@@ -12,8 +12,8 @@ jobs:
         with:
           enable-cache: true
           cache-dependency-glob: "**/pyproject.toml"
-      - run: uv python install 3.10
-      - run: uv python pin 3.10
+      - run: uv python install 3.11
+      - run: uv python pin 3.11
       - run: just install lint-ci
       - run: just adr-check
 
@@ -23,7 +23,6 @@ jobs:
       fail-fast: false
       matrix:
         python-version:
-          - "3.10"
           - "3.11"
           - "3.12"
           - "3.13"
@@ -54,7 +53,6 @@ jobs:
       fail-fast: false
       matrix:
         python-version:
-          - "3.10"
           - "3.11"
           - "3.12"
           - "3.13"
diff --git a/docs/adr/0002-keep-py310-vendored-assert-never.md b/docs/adr/0002-keep-py310-vendored-assert-never.md
deleted file mode 100644
index 773babb..0000000
--- a/docs/adr/0002-keep-py310-vendored-assert-never.md
+++ /dev/null
@@ -1,12 +0,0 @@
-# Keep Python 3.10, with a vendored `_assert_never`
-
-`requires-python` floors at `>=3.10` and CI runs the matrix from 3.10 to 3.14t, so the exhaustive
-`match` over `_EofAction` in `fixer.py` cannot use `typing.assert_never`, which is 3.11+, and
-`typing_extensions` would become a new direct dependency. The original plan leaned on the return
-type and was dropped: `fix_file` is typed `-> bool`, so a lost `match` arm falls through to an
-implicit `None` that ty already rejects, but the error surfaces on the return type not the `match`,
-and it vanishes for any future consumer of `_EofAction` that legitimately returns `None`. The
-two-line vendored `_assert_never(value: NoReturn) -> NoReturn` pins the error at the `case _:` arm
-on every supported version for no dependency, and dropping 3.10 to save it would be an
-outward-facing breaking change. Python 3.10 reaches end of life on 2026-10-31, which is when the
-floor moves to 3.11 and the helper becomes `from typing import assert_never`.
diff --git a/docs/agents/domain.md b/docs/agents/domain.md
index 45a5ff4..eb07f35 100644
--- a/docs/agents/domain.md
+++ b/docs/agents/domain.md
@@ -18,7 +18,7 @@ Single-context repo:
 ├── CONTEXT.md
 ├── docs/adr/
 │   ├── 0001-build-on-pathspec-for-nested-gitignore.md
-│   └── 0002-keep-py310-vendored-assert-never.md
+│   └── 0003-fix-directory-returns-a-path-list-and-writes-nothing.md
 └── eof_fixer/
 ```
 
diff --git a/eof_fixer/fixer.py b/eof_fixer/fixer.py
index ef97917..79cbb2e 100644
--- a/eof_fixer/fixer.py
+++ b/eof_fixer/fixer.py
@@ -2,7 +2,7 @@
 import os
 import pathlib
 from collections.abc import Iterator, Sequence
-from typing import IO, NoReturn
+from typing import IO, assert_never
 
 from eof_fixer.discovery import iter_text_files
 
@@ -11,11 +11,6 @@
 _BINARY_SAMPLE_SIZE = 1024
 
 
-def _assert_never(value: NoReturn) -> NoReturn:
-    """Static-exhaustiveness guard: ty errors if any union member can reach here."""
-    raise AssertionError(value)  # pragma: no cover - ty proves every call unreachable (ADR-0002)
-
-
 @dataclasses.dataclass(frozen=True)
 class Noop:
     """No change: the file is empty or already ends with exactly one terminator."""
@@ -100,7 +95,7 @@ def fix_file(file_obj: IO[bytes], *, check: bool) -> bool:
                 file_obj.truncate()
             return True
         case _:  # pragma: no cover - exhaustiveness guard; ty verifies every _EofAction is matched
-            _assert_never(action)
+            assert_never(action)
 
 
 def fix_directory(
diff --git a/pyproject.toml b/pyproject.toml
index 2d7eda0..d4ef8db 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,7 +3,7 @@ name = "eof-fixer"
 description = "CLI tool that ensures text files end with exactly one newline"
 license = "MIT"
 readme = "README.md"
-requires-python = ">=3.10,<4"
+requires-python = ">=3.11,<4"
 dependencies = [
     "pathspec>=0.12",
 ]
@@ -22,7 +22,6 @@ classifiers = [
     "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
     "Typing :: Typed",
-    "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",