internal/pkg: scrub for dangling status

These cause build to fail to start.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg.go

@@ -665,6 +665,9 @@ type ScrubError struct {
 	// Dangling identifier symlinks. This can happen if the content-addressed
 	// entry was removed while scrubbing due to a checksum mismatch.
 	DanglingIdentifiers []ID
+	// Dangling status files. This can happen if a dangling status symlink was
+	// removed while scrubbing.
+	DanglingStatus []ID
 	// Miscellaneous errors, including [os.ReadDir] on checksum and identifier
 	// directories, [Decode] on entry names and [os.RemoveAll] on inconsistent
 	// entries.
@@ -716,6 +719,13 @@ func (e *ScrubError) Error() string {
 		}
 		segments = append(segments, s)
 	}
+	if len(e.DanglingStatus) > 0 {
+		s := "dangling status:\n"
+		for _, id := range e.DanglingStatus {
+			s += Encode(id) + "\n"
+		}
+		segments = append(segments, s)
+	}
 	if len(e.Errs) > 0 {
 		s := "errors during scrub:\n"
 		for pathname, errs := range e.errs {
@@ -894,6 +904,36 @@ func (c *Cache) Scrub(checks int) error {
 		wg.Wait()
 	}
 
+	dir = c.base.Append(dirStatus)
+	if entries, readdirErr := os.ReadDir(dir.String()); readdirErr != nil {
+		if !errors.Is(readdirErr, os.ErrNotExist) {
+			addErr(dir, readdirErr)
+		}
+	} else {
+		wg.Add(len(entries))
+		for _, ent := range entries {
+			w <- checkEntry{ent, func(ent os.DirEntry, want *Checksum) bool {
+				got := p.Get().(*Checksum)
+				defer p.Put(got)
+
+				if _, err := os.Stat(c.base.Append(
+					dirIdentifier,
+					ent.Name(),
+				).String()); err != nil {
+					if !errors.Is(err, os.ErrNotExist) {
+						addErr(dir.Append(ent.Name()), err)
+					}
+					seMu.Lock()
+					se.DanglingStatus = append(se.DanglingStatus, *want)
+					seMu.Unlock()
+					return false
+				}
+				return true
+			}}
+		}
+		wg.Wait()
+	}
+
 	if len(c.identPending) > 0 {
 		addErr(c.base, errors.New(
 			"scrub began with pending artifacts",
@@ -924,6 +964,7 @@ func (c *Cache) Scrub(checks int) error {
 
 	if len(se.ChecksumMismatches) > 0 ||
 		len(se.DanglingIdentifiers) > 0 ||
+		len(se.DanglingStatus) > 0 ||
 		len(se.Errs) > 0 {
 		slices.SortFunc(se.ChecksumMismatches, func(a, b ChecksumMismatchError) int {
 			return bytes.Compare(a.Want[:], b.Want[:])
@@ -931,6 +972,9 @@ func (c *Cache) Scrub(checks int) error {
 		slices.SortFunc(se.DanglingIdentifiers, func(a, b ID) int {
 			return bytes.Compare(a[:], b[:])
 		})
+		slices.SortFunc(se.DanglingStatus, func(a, b ID) int {
+			return bytes.Compare(a[:], b[:])
+		})
 		return &se
 	} else {
 		return nil