Raise NotImplementedError if using wrong class (#135)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Bernát Gábor <bgabor8@bloomberg.net>

docs/changelog.rst

@@ -1,6 +1,13 @@
 Changelog
 =========
 
+v3.6.0 (2022-02-17)
+-------------------
+- Fix pylint warning "Abstract class :class:`WindowsFileLock <filelock.WindowsFileLock>` with abstract methods instantiated"
+  :pr:`135` - by :user:`vonschultz`
+- Fix pylint warning "Abstract class :class:`UnixFileLock <filelock.UnixFileLock>` with abstract methods instantiated"
+  :pr:`135` - by :user:`vonschultz`
+
 v3.5.1 (2022-02-16)
 -------------------
 - Use ``time.monotonic`` instead of ``time.time`` for calculating timeouts.

src/filelock/_unix.py

@@ -2,7 +2,6 @@
 
 import os
 import sys
-from abc import ABC
 from typing import cast
 
 from ._api import BaseFileLock
@@ -11,9 +10,15 @@
 has_fcntl = False
 if sys.platform == "win32":  # pragma: win32 cover
 
-    class UnixFileLock(BaseFileLock, ABC):
+    class UnixFileLock(BaseFileLock):
         """Uses the :func:`fcntl.flock` to hard lock the lock file on unix systems."""
 
+        def _acquire(self) -> None:
+            raise NotImplementedError
+
+        def _release(self) -> None:
+            raise NotImplementedError
+
 else:  # pragma: win32 no cover
     try:
         import fcntl

src/filelock/_windows.py

@@ -2,7 +2,6 @@
 
 import os
 import sys
-from abc import ABC
 from errno import ENOENT
 from typing import cast
 
@@ -49,9 +48,15 @@ def _release(self) -> None:
 
 else:  # pragma: win32 no cover
 
-    class WindowsFileLock(BaseFileLock, ABC):
+    class WindowsFileLock(BaseFileLock):
         """Uses the :func:`msvcrt.locking` function to hard lock the lock file on windows systems."""
 
+        def _acquire(self) -> None:
+            raise NotImplementedError
+
+        def _release(self) -> None:
+            raise NotImplementedError
+
 
 __all__ = [
     "WindowsFileLock",

tests/test_filelock.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import inspect
 import logging
 import sys
 import threading
@@ -13,7 +14,7 @@
 import pytest
 from _pytest.logging import LogCaptureFixture
 
-from filelock import BaseFileLock, FileLock, SoftFileLock, Timeout
+from filelock import BaseFileLock, FileLock, SoftFileLock, Timeout, UnixFileLock, WindowsFileLock
 
 
 @pytest.mark.parametrize(
@@ -382,3 +383,17 @@ def decorated_method() -> None:
     assert not lock.is_locked
     decorated_method()
     assert not lock.is_locked
+
+
+def test_wrong_platform(tmp_path: Path) -> None:
+    assert not inspect.isabstract(UnixFileLock)
+    assert not inspect.isabstract(WindowsFileLock)
+    assert inspect.isabstract(BaseFileLock)
+
+    lock_type = UnixFileLock if sys.platform == "win32" else WindowsFileLock
+    lock = lock_type(str(tmp_path / "lockfile"))
+
+    with pytest.raises(NotImplementedError):
+        lock.acquire()
+    with pytest.raises(NotImplementedError):
+        lock._release()

whitelist.txt

@@ -15,6 +15,7 @@ fmt
 fspath
 intersphinx
 intervall
+isabstract
 iwgrp
 iwoth
 iwusr