Add sanity check to fsnotify paths (#31)

internal/pipeline/watch.go

@@ -38,6 +38,7 @@ func Watch(
 
 		proc := &watchProcess{
 			verbose:      verbose,
+			rootDirs:     dirs,
 			watcher:      watcher,
 			watchFilter:  watchFilter,
 			trackedPaths: ds.NewSet[string](1024),
@@ -68,6 +69,7 @@ func Watch(
 
 type watchProcess struct {
 	verbose     bool
+	rootDirs    []string
 	watcher     *fsnotify.Watcher
 	watchFilter *filesystem.FilterTree
 
@@ -109,6 +111,10 @@ func (proc *watchProcess) handleEvent(event fsnotify.Event) *ds.Set[string] {
 }
 
 func (proc *watchProcess) startWatching(root string) *ds.Set[string] {
+	if !proc.isSanePath(root) {
+		return nil
+	}
+
 	result := ds.NewSet[string](1)
 
 	filesystem.Traverse(root, func(p string, isDir bool, err error) error {
@@ -150,6 +156,10 @@ func (proc *watchProcess) startWatching(root string) *ds.Set[string] {
 }
 
 func (proc *watchProcess) stopWatching(root string) *ds.Set[string] {
+	if !proc.isSanePath(root) {
+		return nil
+	}
+
 	result := ds.NewSet[string](1)
 
 	for p := range proc.trackedPaths.Unbox() {
@@ -186,6 +196,18 @@ func (proc *watchProcess) isTracked(path string) bool {
 	return proc.trackedPaths.Contains(path)
 }
 
+// isSanePath returns whether the path appears to be legit, since fsnotify
+// has issues on some platforms where after a Remove it starts emitting
+// empty paths or ones relative to root.
+func (proc *watchProcess) isSanePath(path string) bool {
+	for _, root := range proc.rootDirs {
+		if strings.HasPrefix(path, root) {
+			return true
+		}
+	}
+	return false
+}
+
 func (proc *watchProcess) logFSWatchEvent(event fsnotify.Event) {
 	if proc.verbose {
 		log.Printf("Filesystem watch event: %s", event)