feat!: drop Python 3.10 and use typing.assert_never

.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"

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/
 ```
 

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(

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",