🐛 fix(unix): auto-fallback to SoftFileLock on ENOSYS#480
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gaborbernat merged 1 commit intotox-dev:mainfrom Feb 14, 2026
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🐛 fix(unix): auto-fallback to SoftFileLock on ENOSYS#480gaborbernat merged 1 commit intotox-dev:mainfrom
gaborbernat merged 1 commit intotox-dev:mainfrom
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On platforms like Android/Termux and network filesystems (NFS, CIFS), fcntl imports fine but flock() fails at runtime with ENOSYS. Previously this raised NotImplementedError, leaving users no recourse except monkey-patching filelock.FileLock before any other imports. Now UnixFileLock catches ENOSYS, cleans up the leftover lock file, and swaps __class__ to SoftFileLock (or AsyncSoftFileLock for async instances). Both classes share the same BaseFileLock layout with no extra instance state, so the swap is safe and preserves all context. Subsequent acquire/release calls go straight through the soft path. Fixes tox-dev#289, fixes tox-dev#349
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On platforms like Android/Termux and network filesystems (NFS, CIFS),
fcntlimports fine butflock()fails at runtime withENOSYS. 💥 Previously this raisedNotImplementedError, leaving users no recourse except monkey-patchingfilelock.FileLock = filelock.SoftFileLockbefore any other import — fragile and easy to get wrong.This catches
ENOSYSinUnixFileLock._acquire(), cleans up the leftover lock file, and transparently swapsself.__class__toSoftFileLock(orAsyncSoftFileLockfor async instances). Both classes share the sameBaseFileLocklayout with no extra instance state, so the swap is safe and preserves all context. ✨ Subsequent acquire/release cycles go straight through the soft path with no repeatedflock()attempts.The soft fallback relies on
O_CREAT | O_EXCLwhich is atomic on NFSv3+ with Linux kernel 2.6+ and endorsed by CERT as secure against TOCTOU. Symlink attacks are mitigated byO_NOFOLLOWalready used inSoftFileLock._acquire(). On Android/Termux the local filesystem (ext4/f2fs) provides fullO_EXCLguarantees. The__class__swap is validated by CPython'scompatible_for_assignment()when both types share the same base layout.Fixes #289, fixes #349