v4.0.0

4.0.0:

• Fixed open_atomic() replacing a destination created while its context
  was open on POSIX; publication now raises FileExistsError and preserves
  the concurrent winner (#114)
• Python 3.10 or later is now required; Python 3.9 (EOL) support dropped
• pywin32 is no longer installed by default on Windows; the msvcrt-based
  locker is the default and works dependency-free for exclusive locks.
  Shared locks on Windows require portalocker[win32], and an informative
  ImportError is raised otherwise (#104)
• POSIX lock exceptions now populate .strerror and pass the message as
  a second positional argument, matching the Windows exception contract.
  This changes the str() output of these exceptions on POSIX from the
  bare OSError text to a 2-tuple repr
• LockBase is now generic over the acquire return type (typing-only
  change; downstream Lock subclasses are unaffected)
• Added PidFileLock for pidfile-based locking (#106)
• Added PidFileLock.fail_closed() for ownership-only contexts; contention
  raises AlreadyLocked before entering the body and exposes the competing
  PID through AlreadyLocked.holder_pid when readable (#118)
• Packaging switched to the uv_build backend; releases are published to
  PyPI through GitHub Actions Trusted Publishing
• python -m portalocker combine: --output-file now opens lazily;
  the vendored single-file output correctly includes RedisLock (it was
  always None before); the smoke-run now uses sys.executable
  (fixes Windows)
• Fixed PidFileLock ignoring timeout when fail_when_locked=False;
  all PID-publication failures now transactionally release the sidecar and
  preserve the publication error if cleanup also fails (#116)
• Fixed a TemporaryFileLock/PidFileLock unlock-then-unlink race that
  could let two processes hold the same lock (split-brain); release now
  unlinks before unlocking on POSIX and acquire re-verifies file identity
  (inode) after locking (#115)
• Fixed BoundedSemaphore staying permanently "Already locked" after a
  non-contention error (e.g. a missing directory)
• Fixed RedisLock crashed-holder detection: the liveness check was
  always satisfied by its own subscribe confirmation, so dead holders were
  never reaped; the ping is now published only after the subscription is
  confirmed active, pubsub connections no longer leak on the reap path,
  fail_when_locked=True fails fast instead of polling the full timeout,
  internally-created connections are closed on release, and a failed
  acquire() rolls back cleanly so the lock can be retried
• Added shared RedisLock readers through LockFlags.SHARED. Waiting
  writers gate new readers to prevent starvation, holder-specific heartbeats
  preserve stale-client cleanup, and legacy Redis lock responses are treated
  as exclusive for mixed-version safety (#124)
• Fixed FlockLocker/LockfLocker on POSIX to use their named syscall
  (previously silently used the global LOCKER); the module-level
  lock()/unlock() on POSIX now accept all documented LOCKER
  forms (tuple/instance/class)
• Fixed the Windows msvcrt locker locking from the current file position
  instead of byte 0 for raw file descriptors, which could break mutual
  exclusion on files larger than 64KiB; unexpected Win32 errors now raise
  LockException per the documented contract
• RedisLock tests now run everywhere via fakeredis, with a live
  Redis server still tested in CI
• Lock.release() continues suppressing unlock and close errors by default;
  closing is always attempted and the file handle reference is cleared.
  Callers can opt into reporting cleanup failures with
  Lock(..., raise_on_release_error=True) (#117)
• TemporaryFileLock.release() and PidFileLock.release() are now
  no-ops when the object does not hold the lock, so a stale object (double
  release, or garbage collection of a failed acquire) can no longer unlink
  the lock file out from under the current holder
• TemporaryFileLock no longer keeps a strong atexit reference to
  itself, so unused instances can be garbage collected; cleanup at
  interpreter exit still happens via a weak reference
• NamedBoundedSemaphore is now exported from the top-level
  portalocker namespace