Close methods only unregister fs once

dropboxfs/dropboxfs.go

@@ -392,6 +392,10 @@ func (dbfs *fileSystem) Remove(filePath string) error {
 }
 
 func (dbfs *fileSystem) Close() error {
+	if dbfs.id == "" {
+		return nil // already closed
+	}
 	fs.Unregister(dbfs)
+	dbfs.id = ""
 	return nil
 }

ftpfs/ftpfs.go

@@ -415,6 +415,11 @@ func (f *fileSystem) Remove(filePath string) error {
 }
 
 func (f *fileSystem) Close() error {
+	if f.conn == nil {
+		return nil // already closed
+	}
 	fs.Unregister(f)
-	return f.conn.Quit()
+	err := f.conn.Quit()
+	f.conn = nil
+	return err
 }

memfilesystem.go

@@ -90,8 +90,15 @@ func NewMemFileSystem(separator string, rootFiles ...MemFile) (*MemFileSystem, e
 }
 
 func (fs *MemFileSystem) Close() error {
+	fs.mtx.Lock()
+	if fs.id == "" {
+		fs.mtx.Unlock()
+		return nil // already closed
+	}
+	fs.id = ""
+	clear(fs.root.Dir)
+	fs.mtx.Unlock() // Unlock before Unregister to avoid deadlock
 	Unregister(fs)
-	fs.Clear()
 	return nil
 }
 
@@ -250,17 +257,23 @@ func (fs *MemFileSystem) WithID(id string) *MemFileSystem {
 	if id == "" {
 		panic("empty id")
 	}
-	Unregister(fs)
-	fs.id = id
-	Register(fs)
+	if id != fs.id {
+		if fs.id != "" {
+			Unregister(fs)
+		}
+		fs.id = id
+		Register(fs)
+	}
 	return fs
 }
 
 // This method is not thread-safe!
 func (fs *MemFileSystem) WithVolume(volume string) *MemFileSystem {
-	Unregister(fs)
-	fs.volume = volume
-	Register(fs)
+	if volume != fs.volume {
+		Unregister(fs)
+		fs.volume = volume
+		Register(fs)
+	}
 	return fs
 }
 

s3fs/s3fs.go

@@ -475,6 +475,10 @@ func (s *fileSystem) Watch(filePath string, onEvent func(fs.File, fs.Event)) (ca
 }
 
 func (s *fileSystem) Close() error {
+	if s.client == nil {
+		return nil // already closed
+	}
 	fs.Unregister(s)
+	s.client = nil
 	return nil
 }

sftpfs/sftpfs.go

@@ -396,6 +396,10 @@ func (f *fileSystem) Remove(filePath string) error {
 }
 
 func (f *fileSystem) Close() error {
+	if f.client == nil {
+		return nil // already closed
+	}
 	fs.Unregister(f)
-	return f.client.Close()
+	f.client = nil
+	return nil
 }