[wan9chi]

Motivation

A task that stats or lists a folder holding only its own outputs pins that folder as an input. TypeScript 7's tsc, for example, stats dist while emitting into it. Removing the folder, as on every clean checkout in CI, is then a miss, although the task writes every file in it. A task that cleans its output folder before writing a new one, like tsdown listing dist and removing what it holds, pins it the same way once it runs over an existing output.

Changes

After the run, vt climbs from the written paths through their parent folders and lists each folder once, deepest first. A folder is rebuildable when it isn't empty, every file or symlink in it was written by the task, and every folder in it is rebuildable. A folder that's gone by then, like Astro's dist/.prerender, plays no part. A rebuildable folder the task read gets no inferred-input fingerprint. Only those fingerprints ask about folders, so a task with no inferred reads skips the climb. A hit restores the folder's files if they're among the task's outputs, which recreates it; explicit output config can leave them out. vt_path gets RelativePath::parent.

E2E cases: stat_own_output_folder (synthetic) and typescript_out_dir (TypeScript 7 emitting to dist): removing the output folder misses today and hits with the folder restored after. clean_and_rebuild_output_folder (synthetic) and tsdown_rebuild_after_edit (tsdown): a task that cleans its output folder and writes a new one misses today after the folder is removed, and hits after.

Part of a stack that lets automatic tracking cache tasks which read their own outputs and list the folders holding them, so they also hit on a clean checkout.

🤖 Generated with Claude Code

---

Note

Medium Risk
Changes core task-cache fingerprinting for directory reads; incorrect rebuildable detection could cause stale cache hits or miss legitimate invalidations.

Overview
Tasks that stat or list an output directory (e.g. tsc on dist, or a bundler that wipes dist before writing) no longer miss the cache when that folder is gone on a clean checkout. After a run, vt walks parent directories of everything the task wrote and treats a directory as rebuildable when every entry is task output (nested rebuildable dirs included); those paths are omitted from post-run input fingerprints, so a later run can still hit and replay archived outputs to recreate the tree.

Implementation centers on an expanded Rebuildable (with_folders, is_rebuildable_folder), wiring in observe_fspy / PostRunFingerprint::create, plus RelativePath::parent for the climb. Docs and changelog describe the behavior; vtt fs rm supports synthetic e2e scenarios, with new snapshot fixtures (and tsdown / tsc cases, some marked ignore).

^{Reviewed by Cursor Bugbot for commit 3bd9097. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

fspy benchmark

linux

dynamic/launch             change  +0.65%  [ -4.48% ..  +6.50%]  overhead   +59.21%
dynamic/access             change  -0.72%  [ -9.78% ..  +9.01%]  overhead   +25.34%
dynamic/access-relative    change  -0.52%  [ -4.96% ..  +2.76%]  overhead   +71.47%
dynamic/access-contended   change  -3.12%  [-14.14% .. +13.76%]  overhead    -3.17%
static/launch              change  +1.05%  [ -3.49% ..  +5.93%]  overhead  +190.65%
static/access              change  -0.02%  [ -8.95% .. +15.66%]  overhead +1320.26%
static/access-relative     change  +0.23%  [-14.48% ..  +8.09%]  overhead +1770.54%
static/access-contended    change  +0.22%  [ -1.81% ..  +3.15%]  overhead +1266.76%

macos

dynamic/launch             change  -0.23%  [ -3.97% ..  +3.44%]  overhead  +217.55%
dynamic/access             change  +0.00%  [ -4.12% ..  +3.30%]  overhead    +1.96%
dynamic/access-relative    change  +0.22%  [ -5.47% ..  +6.41%]  overhead  +276.46%
dynamic/access-contended   change  -0.95%  [ -8.02% ..  +4.53%]  overhead    +3.47%

windows

dynamic/launch             change  -0.31%  [ -4.33% ..  +4.47%]  overhead   +27.24%
dynamic/access             change  +0.34%  [ -1.91% ..  +2.67%]  overhead    +1.74%
dynamic/access-relative    change  +0.00%  [ -1.07% ..  +1.23%]  overhead    +1.93%
dynamic/access-contended   change  +0.17%  [ -1.20% ..  +5.15%]  overhead    +1.56%

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	npm/​tsdown@​0.23.3

View full report