[sivadaboi]

A regression from #100, on Windows: restoring a snapshot of a save that has subfolders fails most of the time, and a game deleting one of its own save folders can be refused in the same way.

Seen as:

• TestAdversarial_AwkwardFilenamesSurviveASnapshotRoundTrip and TestAdversarial_RepeatedRollbackIsIdempotent fail 7 runs in 10 on dev-public, with restore snapshot …: clear target dir: unlinkat …\saves\b: The process cannot access the file because it is being used by another process.
• Bisecting dev-public's merges with those two tests: 0 failures up to e2e: branchHolds reads a branch's newest snapshot, as it says #98, failures from watcher: a subfolder missed when it was created is watched on the next change in its parent #100 on. The restore is safe either way: it puts the save back and says so.
• By hand, with a scratch daemon built from dev-public: restoring Terraria (saves in Players\) failed 2 times in 5. A script standing in for the game, deleting Players\Backups while OpenSave watched, was refused ("Device or resource busy").

Why. Since #100, a Write on a watched folder makes the watcher list that folder (checkFolders), to find subfolders whose Create was missed. On Windows, os.ReadDir opens the folder without FILE_SHARE_DELETE, and while it is open the folder can't be removed. Every file a restore deletes is a Write on its folder, so the watcher was listing the very folders the restore was about to remove. A game emptying a folder of its own is the same race.

The change. fsx.ReadDirShared lists a folder through a handle opened with FILE_SHARE_DELETE, falling back to os.ReadDir if that open fails, as fsx.OpenShared does for files. checkFolders uses it. Nothing else changes: on other systems an open folder never blocked removing it, and there it is os.ReadDir.

Measured before writing it: a folder held by os.Open can't be removed (the error above), while one held by the shared handle can, and the listing is the same.

Tests:

• fsx/readdirshared_windows_test.go: a folder being listed can be removed; the listing matches os.ReadDir; a missing folder is "not exist".
• The two e2e tests above: 0 failures in 20 runs with this change, against 7 in 10 without it.
• watcher: a subfolder missed when it was created is watched on the next change in its parent #100's own TestSubfolder_* tests and the watcher, fsx and snapshot packages pass.

Checks:

• With Games from your other devices set themselves up again; trust your own devices to choose folders #132, Device settings take the catalogue once it is indexed, without a restart #133 and Watcher: list a folder without blocking its removal (restores failing since #100) #134 merged onto dev-public (951cee6), the full Windows unit and e2e suites pass, with one exception: TestBuildManifest_SurvivesFilesVanishingDuringTheWalk (delta), which fails in over half of runs on this PC on dev-public and dev alike and isn't touched here. After Games from your other devices set themselves up again; trust your own devices to choose folders #132's last commit (a fix to how the catalogue check reads the index after a rebuild), presets, p2p, daemon and api and the folder, offer and rollback e2e tests were run again, and pass.
• -race on Linux (WSL Ubuntu) passes for presets, daemon, p2p/..., api, store, cliapp, fsx, watcher and snapshot, and for the folder, offer and rollback e2e tests. TestSignIn_AnOldAttemptsTimerLeavesTheNewListener once reported a data race in its cleanup; it does the same on plain dev-public.
• go vet for Linux and macOS.
• Merged one at a time with every open PR, it adds no conflict. sync: a game being played is held back from syncing until the session ends #117 and sessions: see protected games and games installed anywhere; a safety net for the rest #128 also change watcher.go, but nowhere near checkFolders.

cc @ChakraFusion, since it's #100's check. The folder check itself is untouched; only how it reads the folder changes.

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Project	Deployment	Actions	Updated
open-save	Ready	Preview	Oct 27, 2026 9:50pm UTC