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fix: Watch dirs recursively and dynamically
Automatically start watching created directories. Automatically stop watching removed/renamed directories.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,206 @@ | ||
| package watcher | ||
|
|
||
| import ( | ||
| "context" | ||
| "errors" | ||
| "fmt" | ||
| "os" | ||
| "path/filepath" | ||
| "strings" | ||
| "sync" | ||
|
|
||
| "github.com/fsnotify/fsnotify" | ||
| ) | ||
|
|
||
| // Watcher is a recursive file watcher. | ||
| type Watcher struct { | ||
| lock sync.Mutex | ||
| closed bool | ||
| watchedDirs map[string]struct{} // dir path -> closer channel | ||
| onChange func(ctx context.Context, e fsnotify.Event) | ||
| watcher *fsnotify.Watcher | ||
| } | ||
|
|
||
| // New creates a new file watcher that executes onChange for any | ||
| // remove/create/change/chmod filesystem event. | ||
| // onChange will receive the ctx that was passed to Run. | ||
| func New(onChange func(ctx context.Context, e fsnotify.Event)) (*Watcher, error) { | ||
| watcher, err := fsnotify.NewWatcher() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return &Watcher{ | ||
| watchedDirs: make(map[string]struct{}), | ||
| onChange: onChange, | ||
| watcher: watcher, | ||
| }, nil | ||
| } | ||
|
|
||
| var ErrClosed = errors.New("closed") | ||
|
|
||
| // RangeWatchedDirs calls fn for every currently watched directory. | ||
| // Noop if the watcher is closed. | ||
| func (w *Watcher) RangeWatchedDirs(fn func(path string) (continueIter bool)) { | ||
| w.lock.Lock() | ||
| defer w.lock.Unlock() | ||
| if w.closed { | ||
| return | ||
| } | ||
| for p := range w.watchedDirs { | ||
| if !fn(p) { | ||
| return | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // Close stops watching everything and closes the watcher. | ||
| // Noop if the watcher is closed. | ||
| func (w *Watcher) Close() error { | ||
| w.lock.Lock() | ||
| defer w.lock.Unlock() | ||
| if w.closed { | ||
| return nil | ||
| } | ||
| w.closed = true | ||
| return w.watcher.Close() | ||
| } | ||
|
|
||
| // Run runs the watcher. | ||
| // Returns ErrClosed if already closed. | ||
| func (w *Watcher) Run(ctx context.Context) error { | ||
| w.lock.Lock() | ||
| if w.closed { | ||
| w.lock.Unlock() | ||
| return ErrClosed | ||
| } | ||
| w.lock.Unlock() | ||
|
|
||
| defer w.Close() | ||
| for { | ||
| select { | ||
| case <-ctx.Done(): | ||
| return ctx.Err() // Watching canceled | ||
| case e := <-w.watcher.Events: | ||
| switch e.Op { | ||
| case fsnotify.Create, fsnotify.Remove, fsnotify.Rename: | ||
| if w.isDirEvent(e) { | ||
| switch e.Op { | ||
| case fsnotify.Create: | ||
| // New sub-directory was created, start watching it. | ||
| if err := w.Add(e.Name); err != nil { | ||
| return fmt.Errorf("adding created directory: %w", err) | ||
| } | ||
| case fsnotify.Remove, fsnotify.Rename: | ||
| // Sub-directory was removed or renamed, stop watching it. | ||
| // A new create notification will readd it. | ||
| if err := w.Remove(e.Name); err != nil { | ||
| return fmt.Errorf("removing directory: %w", err) | ||
| } | ||
| } | ||
| } | ||
| case 0: | ||
| continue | ||
| } | ||
| w.onChange(ctx, e) | ||
| case err := <-w.watcher.Errors: | ||
| if err != nil { | ||
| return fmt.Errorf("watching: %w", err) | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // Add starts watching the directory and all of its subdirectories recursively. | ||
| // Returns ErrClosed if the watcher is already closed. | ||
| func (w *Watcher) Add(dir string) error { | ||
| w.lock.Lock() | ||
| defer w.lock.Unlock() | ||
| if w.closed { | ||
| return ErrClosed | ||
| } | ||
| err := forEachDir(dir, func(dir string) error { | ||
| if _, ok := w.watchedDirs[dir]; ok { | ||
| return errAlreadyWatched // Directory already watched | ||
| } | ||
| w.watchedDirs[dir] = struct{}{} | ||
| return w.watcher.Add(dir) | ||
| }) | ||
| if err == errAlreadyWatched { | ||
| return nil | ||
| } | ||
| return err | ||
| } | ||
|
|
||
| var errAlreadyWatched = errors.New("directory already watched") | ||
|
|
||
| // Remove stops watching the directory and all of its subdirectories recursively. | ||
| // Returns ErrClosed if the watcher is already closed. | ||
| func (w *Watcher) Remove(dir string) error { | ||
| w.lock.Lock() | ||
| defer w.lock.Unlock() | ||
| if w.closed { | ||
| return ErrClosed | ||
| } | ||
|
|
||
| if _, ok := w.watchedDirs[dir]; !ok { | ||
| return nil | ||
| } | ||
| delete(w.watchedDirs, dir) | ||
| if err := w.removeWatcher(dir); err != nil { | ||
| return err | ||
| } | ||
|
|
||
| // Stop all sub-directory watchers | ||
| for p := range w.watchedDirs { | ||
| if strings.HasPrefix(p, dir) { | ||
| delete(w.watchedDirs, p) | ||
| if err := w.removeWatcher(dir); err != nil { | ||
| return err | ||
| } | ||
| } | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| // removeWatcher ignores ErrNonExistentWatch when removing a watcher. | ||
| func (w *Watcher) removeWatcher(dir string) error { | ||
| if err := w.watcher.Remove(dir); err != nil { | ||
| if !errors.Is(err, fsnotify.ErrNonExistentWatch) { | ||
| return err | ||
| } | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| func (w *Watcher) isDirEvent(e fsnotify.Event) bool { | ||
| switch e.Op { | ||
| case fsnotify.Create, fsnotify.Write, fsnotify.Chmod: | ||
| fileInfo, err := os.Stat(e.Name) | ||
| if err != nil { | ||
| return false | ||
| } | ||
| return fileInfo.IsDir() | ||
| } | ||
| _, ok := w.watchedDirs[e.Name] | ||
| return ok | ||
| } | ||
|
|
||
| // forEachDir executes fn for every subdirectory of pathDir, | ||
| // including pathDir itself, recursively. | ||
| func forEachDir(pathDir string, fn func(dir string) error) error { | ||
| // Use filepath.Walk to traverse directories | ||
| err := filepath.Walk(pathDir, func(path string, info os.FileInfo, err error) error { | ||
| if err != nil { | ||
| return err // Stop walking the directory tree. | ||
| } | ||
| if !info.IsDir() { | ||
| return nil // Continue walking. | ||
| } | ||
| if err = fn(path); err != nil { | ||
| return err | ||
| } | ||
| return nil | ||
| }) | ||
| return err | ||
| } |
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