from __future__ import annotations import os import sys from contextlib import suppress from errno import EACCES, EEXIST from pathlib import Path from ._api import BaseFileLock from ._util import ensure_directory_exists, raise_on_not_writable_file class SoftFileLock(BaseFileLock): """Simply watches the existence of the lock file.""" def _acquire(self) -> None: raise_on_not_writable_file(self.lock_file) ensure_directory_exists(self.lock_file) # first check for exists and read-only mode as the open will mask this case as EEXIST flags = ( os.O_WRONLY # open for writing only | os.O_CREAT | os.O_EXCL # together with above raise EEXIST if the file specified by filename exists | os.O_TRUNC # truncate the file to zero byte ) try: file_handler = os.open(self.lock_file, flags, self._context.mode) except OSError as exception: # re-raise unless expected exception if not ( exception.errno == EEXIST # lock already exist or (exception.errno == EACCES and sys.platform == "win32") # has no access to this lock ): # pragma: win32 no cover raise else: self._context.lock_file_fd = file_handler def _release(self) -> None: assert self._context.lock_file_fd is not None # noqa: S101 os.close(self._context.lock_file_fd) # the lock file is definitely not None self._context.lock_file_fd = None with suppress(OSError): # the file is already deleted and that's what we want Path(self.lock_file).unlink() __all__ = [ "SoftFileLock", ]