feat(cache): auto-detect output writes via fspy

Adds `{ auto: true }` support to the `output` field, plus the implicit
default: when `output` is omitted, automatically tracks files the task
writes (via fspy) and archives them. Explicit globs and `auto` can be
mixed in the same array.

Also includes:
- `read_write_overlap` check: if a task writes to a file it also read
  (auto-inferred), the cache update is skipped (`InputModified`).
  Prerun input hashes would otherwise be stale.
- Input negatives apply to reads only, not writes — keeps `input: ["!dist/**"]`
  from accidentally dropping writes to `dist/**` during archiving.
- Input-auto gating: when `input_config.includes_auto` is false, fspy
  reads do not contribute to the post-run fingerprint, even when fspy
  is enabled solely for output tracking.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: branchseer

CHANGELOG.md

@@ -3,6 +3,7 @@
 - **Added** `output` field for cached tasks: archives output files matching the configured globs after a successful run and restores them on cache hit. Patterns are relative to the package directory; supports negative patterns (e.g. `"!dist/cache/**"`) and `{pattern, base}` form for explicit base. ([#321](https://github.com/voidzero-dev/vite-task/pull/321))
 - **Fixed** Windows cached tasks can now run package shims rewritten through PowerShell; default env passthrough now preserves `PATHEXT` ([#366](https://github.com/voidzero-dev/vite-task/pull/366))
 - **Added** Platform support for targets without `input` auto-inference (e.g. Android). Tasks still run; those relying on auto-inference run uncached, with the summary noting that `input` must be configured manually to enable caching ([#352](https://github.com/voidzero-dev/vite-task/pull/352))
+- **Added** `output` field for cached tasks: archives output files after a successful run and restores them on cache hit. Defaults to automatically tracking files the task writes; accepts globs (e.g. `"dist/**"`), `{ "auto": true }`, and negative patterns (`"!dist/cache/**"`) ([#321](https://github.com/voidzero-dev/vite-task/pull/321))
 - **Fixed** `vp run` no longer aborts with `failed to prepare the command for injection: Invalid argument` when the user environment already has `LD_PRELOAD` (Linux) or `DYLD_INSERT_LIBRARIES` (macOS) set. The tracer shim is now appended to any existing value and placed last, so user preloads keep their symbol-interposition precedence ([#340](https://github.com/voidzero-dev/vite-task/issues/340))
 - **Changed** Arguments passed after a task name (e.g. `vp run test some-filter`) are now forwarded only to that task. Tasks pulled in via `dependsOn` no longer receive them ([#324](https://github.com/voidzero-dev/vite-task/issues/324))
 - **Fixed** Windows file access tracking no longer panics when a task touches malformed paths that cannot be represented as workspace-relative inputs ([#330](https://github.com/voidzero-dev/vite-task/pull/330))

crates/vite_task/docs/task-cache.md

@@ -92,7 +92,7 @@ The cache entry key uniquely identifies a command execution context:
 ```rust
 pub struct CacheEntryKey {
     pub spawn_fingerprint: SpawnFingerprint,
-    pub input_config: ResolvedInputConfig,
+    pub input_config: ResolvedGlobConfig,
 }
 ```
 
@@ -303,7 +303,7 @@ Cache entries are serialized using `bincode` for efficient storage.
 │  ──────────────────────                                      │
 │    CacheEntryKey {                                           │
 │        spawn_fingerprint: SpawnFingerprint { ... },          │
-│        input_config: ResolvedInputConfig { ... },            │
+│        input_config: ResolvedGlobConfig { ... },            │
 │    }                                                         │
 │    ExecutionCacheKey::UserTask {                              │
 │        task_name: "build",                                   │

crates/vite_task/src/session/execute/mod.rs

@@ -1,4 +1,8 @@
 //! Normalize raw fspy path accesses into workspace-relative, filtered form.
+//!
+//! User-configured negative globs are NOT applied here. They are applied later,
+//! separately for reads (input config) and writes (output config), since those
+//! two configs are independent.
 #![cfg(fspy)]
 
 use std::collections::hash_map::Entry;
@@ -21,22 +25,19 @@ pub struct TrackedPathAccesses {
 }
 
 impl TrackedPathAccesses {
-    /// Build from fspy's raw iterable by stripping the workspace prefix,
-    /// normalizing `..` components, and filtering against the negative globs.
-    pub fn from_raw(
-        raw: &PathAccessIterable,
-        workspace_root: &AbsolutePath,
-        resolved_negatives: &[wax::Glob<'static>],
-    ) -> Self {
+    /// Build from fspy's raw iterable by stripping the workspace prefix and
+    /// normalizing `..` components. `.git/*` paths are skipped. User-configured
+    /// negatives are applied by the caller (see module docs).
+    pub fn from_raw(raw: &PathAccessIterable, workspace_root: &AbsolutePath) -> Self {
         let mut accesses = Self::default();
         for access in raw.iter() {
-            // Strip workspace root, clean `..` components, and filter in one pass.
+            // Strip workspace root and clean `..` components in one pass.
             // fspy may report paths like `packages/sub-pkg/../shared/dist/output.js`.
             let relative_path = access.path.strip_path_prefix(workspace_root, |strip_result| {
                 let Ok(stripped_path) = strip_result else {
                     return None;
                 };
-                normalize_tracked_workspace_path(stripped_path, resolved_negatives)
+                normalize_tracked_workspace_path(stripped_path)
             });
 
             let Some(relative_path) = relative_path else {
@@ -71,10 +72,7 @@ impl TrackedPathAccesses {
     clippy::disallowed_types,
     reason = "fspy strip_path_prefix exposes std::path::Path; convert to RelativePathBuf immediately"
 )]
-fn normalize_tracked_workspace_path(
-    stripped_path: &std::path::Path,
-    resolved_negatives: &[wax::Glob<'static>],
-) -> Option<RelativePathBuf> {
+fn normalize_tracked_workspace_path(stripped_path: &std::path::Path) -> Option<RelativePathBuf> {
     // On Windows, paths are possible to be still absolute after stripping the workspace root.
     // For example: c:\workspace\subdir\c:\workspace\subdir
     // Just ignore those accesses.
@@ -90,12 +88,6 @@ fn normalize_tracked_workspace_path(
         return None;
     }
 
-    if !resolved_negatives.is_empty()
-        && resolved_negatives.iter().any(|neg| wax::Program::is_match(neg, relative.as_str()))
-    {
-        return None;
-    }
-
     Some(relative)
 }
 
@@ -111,8 +103,7 @@ mod tests {
             clippy::disallowed_types,
             reason = "normalize_tracked_workspace_path requires std::path::Path for fspy strip_path_prefix output"
         )]
-        let relative_path =
-            normalize_tracked_workspace_path(std::path::Path::new(r"foo\C:\bar"), &[]);
+        let relative_path = normalize_tracked_workspace_path(std::path::Path::new(r"foo\C:\bar"));
         assert!(relative_path.is_none());
     }
 }

crates/vite_task/src/session/execute/tracked_accesses.rs

@@ -7,5 +7,5 @@ should not see `FSPY` set.
 
 ```
 $ vtt print-env FSPY
-(undefined)
+1
 ```

crates/vite_task_bin/tests/e2e_snapshots/fixtures/input_cache_test/snapshots/fspy_env___not_set_when_auto_inference_disabled.md

@@ -0,0 +1 @@
+v1

crates/vite_task_bin/tests/e2e_snapshots/fixtures/output_cache_test/README.md

@@ -1,38 +1,226 @@
 [[e2e]]
-name = "output_globs___files_restored_on_cache_hit"
+name = "auto_output___files_restored_on_cache_hit"
 comment = """
-With explicit output globs (`dist/**`), the first run writes a file to
-`dist/`. After deleting `dist/`, a second run with no input changes is a
-cache hit and the archived output file is restored.
+Auto output detection (default): output files written by the task are
+restored on a cache hit.
 """
 steps = [
-  # First run - cache miss, writes dist/output.txt
-  ["vt", "run", "build"],
-  # Verify file was written
-  ["vtt", "print-file", "dist/output.txt"],
-  # Delete dist/ to prove restoration is real
-  ["vtt", "rm", "-rf", "dist"],
-  # Second run - cache hit, restores dist/output.txt from archive
-  ["vt", "run", "build"],
-  # File should be restored
-  ["vtt", "print-file", "dist/output.txt"],
+  { argv = [
+    "vt",
+    "run",
+    "auto-output",
+  ], comment = "first run writes dist/out.txt" },
+  { argv = [
+    "vtt",
+    "print-file",
+    "dist/out.txt",
+  ], comment = "output exists after the build" },
+  { argv = [
+    "vtt",
+    "rm",
+    "dist/out.txt",
+  ], comment = "delete only the file (keep dir to avoid an fspy inferred-input miss on Windows)" },
+  { argv = [
+    "vt",
+    "run",
+    "auto-output",
+  ], comment = "cache hit, should restore dist/out.txt" },
+  { argv = [
+    "vtt",
+    "print-file",
+    "dist/out.txt",
+  ], comment = "output was restored from the archive" },
 ]
 
 [[e2e]]
-name = "output_globs___negative_excludes_files_from_archive"
+name = "glob_output___only_matched_files_restored"
 comment = """
-A file matched by a negative output glob is not archived, so it is not
-restored on cache hit.
+Glob output: only files matching the configured output globs are restored
+on a cache hit; files produced outside those globs are left alone.
 """
 steps = [
-  # First run - writes both dist/keep.txt and dist/skip.txt
-  ["vt", "run", "build-with-negative"],
-  # Both files exist after the run
-  ["vtt", "print-file", "dist/keep.txt"],
-  ["vtt", "print-file", "dist/skip.txt"],
-  # Delete dist/ to prove restoration is real
-  ["vtt", "rm", "-rf", "dist"],
-  # Second run - cache hit, only dist/keep.txt is restored
-  ["vt", "run", "build-with-negative"],
-  ["vtt", "print-file", "dist/keep.txt"],
+  { argv = [
+    "vt",
+    "run",
+    "glob-output",
+  ], comment = "first run writes dist/out.txt and tmp/temp.txt" },
+  { argv = [
+    "vtt",
+    "rm",
+    "dist/out.txt",
+  ], comment = "delete the glob-matched output" },
+  { argv = [
+    "vtt",
+    "rm",
+    "tmp/temp.txt",
+  ], comment = "delete the non-matched output" },
+  { argv = [
+    "vt",
+    "run",
+    "glob-output",
+  ], comment = "cache hit: should restore dist/out.txt but not tmp/temp.txt" },
+  { argv = [
+    "vtt",
+    "print-file",
+    "dist/out.txt",
+  ], comment = "dist/out.txt was restored" },
+  { argv = [
+    "vtt",
+    "print-file",
+    "tmp/temp.txt",
+  ], comment = "should fail - tmp not in output globs" },
+]
+
+[[e2e]]
+name = "auto_output_with_non_auto_input"
+comment = """
+Auto output works even when input tracking is explicit
+(`input: [\"src/**\"]`). Output auto-detection and input auto-detection
+are independent.
+"""
+steps = [
+  { argv = [
+    "vt",
+    "run",
+    "auto-output-no-auto-input",
+  ], comment = "first run: input src/** (no auto), output default (auto)" },
+  { argv = [
+    "vtt",
+    "rm",
+    "dist/out.txt",
+  ], comment = "delete the output" },
+  { argv = [
+    "vt",
+    "run",
+    "auto-output-no-auto-input",
+  ], comment = "cache hit - output files should still be restored" },
+  { argv = [
+    "vtt",
+    "print-file",
+    "dist/out.txt",
+  ], comment = "output was restored" },
+]
+
+[[e2e]]
+name = "negative_output___excluded_files_not_restored"
+comment = """
+Negative output globs exclude matching files from the cache archive, so
+they are not restored on a cache hit even though the task produced them.
+"""
+steps = [
+  { argv = [
+    "vt",
+    "run",
+    "negative-output",
+  ], comment = "first run writes dist/out.txt and dist/cache/tmp.txt" },
+  { argv = [
+    "vtt",
+    "rm",
+    "dist/out.txt",
+  ], comment = "delete the archived output" },
+  { argv = [
+    "vtt",
+    "rm",
+    "dist/cache/tmp.txt",
+  ], comment = "delete the excluded output" },
+  { argv = [
+    "vt",
+    "run",
+    "negative-output",
+  ], comment = "cache hit: should restore dist/out.txt but NOT dist/cache/tmp.txt" },
+  { argv = [
+    "vtt",
+    "print-file",
+    "dist/out.txt",
+  ], comment = "dist/out.txt was restored" },
+  { argv = [
+    "vtt",
+    "print-file",
+    "dist/cache/tmp.txt",
+  ], comment = "should fail - excluded by !dist/cache/**" },
+]
+
+[[e2e]]
+name = "output_config_change_invalidates_cache"
+comment = """
+Changing a task's output configuration invalidates the cache entry —
+the next run is a miss, not a hit of the stale archive.
+"""
+steps = [
+  { argv = [
+    "vt",
+    "run",
+    "output-config-change",
+  ], comment = "first run populates the cache" },
+  { argv = [
+    "vtt",
+    "replace-file-content",
+    "vite-task.json",
+    "REPLACE_ME",
+    "dist/**",
+  ], comment = "change the output globs in the task config" },
+  { argv = [
+    "vt",
+    "run",
+    "output-config-change",
+  ], comment = "cache miss: output config changed" },
+]
+
+[[e2e]]
+name = "input_negative_does_not_drop_output_writes"
+comment = """
+Input negative globs must not drop matching writes from the output
+archive. Here the user excludes `dist/**` from inferred inputs (so
+rewriting dist/ won't mark inputs as modified), but default auto output
+should still capture dist writes and restore them on a cache hit.
+"""
+steps = [
+  { argv = [
+    "vt",
+    "run",
+    "input-neg-dist-auto-output",
+  ], comment = "first run writes dist/out.txt" },
+  { argv = [
+    "vtt",
+    "rm",
+    "dist/out.txt",
+  ], comment = "delete the output" },
+  { argv = [
+    "vt",
+    "run",
+    "input-neg-dist-auto-output",
+  ], comment = "cache hit should restore dist/out.txt" },
+  { argv = [
+    "vtt",
+    "print-file",
+    "dist/out.txt",
+  ], comment = "output was restored despite dist/** being a negative input glob" },
+]
+
+[[e2e]]
+name = "explicit_input_ignores_fspy_reads"
+comment = """
+When input auto is disabled (explicit globs only), unrelated reads
+tracked by fspy must NOT become inferred inputs. Default auto output
+still needs fspy for write tracking, but reads outside `input: [\"src/**\"]`
+should be ignored.
+"""
+steps = [
+  { argv = [
+    "vt",
+    "run",
+    "explicit-input-auto-output",
+  ], comment = "first run reads README.md (not in input globs) and captures the output" },
+  { argv = [
+    "vtt",
+    "replace-file-content",
+    "README.md",
+    "v1",
+    "v2",
+  ], comment = "modify README.md — not an input, so it must not invalidate the cache" },
+  { argv = [
+    "vt",
+    "run",
+    "explicit-input-auto-output",
+  ], comment = "cache hit: README.md not in input globs" },
 ]