[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 a hit restores every file in it.

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 gets no inferred-input fingerprint; restoring its files recreates it. 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.

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

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Note

Medium Risk
Changes post-run input fingerprinting and cache-hit rules for auto-tracked directory reads; incorrect rebuildable classification could hide real input changes or allow stale hits.

Overview
Tasks that stat or list an output directory (e.g. tsc on dist) no longer treat that folder as a tracked input when every entry in it is something the task wrote. Post-run fingerprinting skips those “rebuildable” directories, so a clean checkout with the folder gone can still cache hit and restore archived outputs, recreating the tree.

Rebuildable now walks parent paths from fspy’s unfiltered writes after the run, classifies directories whose live listing contains only written files/symlinks and already-known rebuildable subfolders (ignoring .DS_Store, ignoring dirs removed before classification), and exposes is_rebuildable_folder. PostRunFingerprint::create filters those paths out alongside prerun globs. RelativePath::parent supports the climb.

Docs/changelog and e2e fixtures cover a synthetic stat out case and TypeScript emitting to dist (typescript fixture marked ignore in snapshots.toml).

^{Reviewed by Cursor Bugbot for commit 9ad3c84. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

fspy benchmark

linux

dynamic/launch             change  +0.84%  [ -5.19% ..  +8.09%]  overhead   +62.95%
dynamic/access             change  +0.37%  [ -8.61% .. +17.54%]  overhead   +23.59%
dynamic/access-relative    change  -0.21%  [ -6.52% ..  +5.94%]  overhead   +75.97%
dynamic/access-contended   change  +0.93%  [ -8.15% .. +11.44%]  overhead    +7.02%
static/launch              change  +0.66%  [ -5.07% ..  +6.39%]  overhead  +193.73%
static/access              change  +0.34%  [ -2.06% ..  +4.84%]  overhead +1477.63%
static/access-relative     change  -0.26%  [-12.65% .. +12.14%]  overhead +1904.69%
static/access-contended    change  +1.76%  [ -3.85% ..  +8.57%]  overhead +1161.38%

macos

dynamic/launch             change  +0.77%  [ -3.85% ..  +4.03%]  overhead  +229.11%
dynamic/access             change  -0.68%  [ -5.23% ..  +4.14%]  overhead    +4.94%
dynamic/access-relative    change  +1.17%  [ -5.43% ..  +6.79%]  overhead  +259.74%
dynamic/access-contended   change  -0.66%  [ -8.41% ..  +3.69%]  overhead    +3.03%

windows

dynamic/launch             change  +0.19%  [ -1.51% ..  +1.89%]  overhead   +25.35%
dynamic/access             change  +0.00%  [ -0.77% ..  +0.59%]  overhead    +0.96%
dynamic/access-relative    change  -0.18%  [ -0.94% ..  +0.56%]  overhead    +1.16%
dynamic/access-contended   change  +0.00%  [ -0.71% ..  +0.73%]  overhead    +1.65%