Use fsnotify for watching file updates (#1667)

* Add watch option

* Implement directory changes

* Implement file changes

* Fix for dircounts

* Remove test code

* fix dircounts

* Set watches on cd instead of select

* Set watches on startup too

* Watch newly created directories

* Add chmod events

* Avoid using multiple threads

Seems to cause issues if there are multiple threads and each one of them
is loading the same new file, in which case there is a race condition.

* Reduce logic when updating files

* Throttle write updates

* Use timer instead of ticker

* Fix file write out-of-band timing issue

* Fix cursor when renaming

* Prevent file showing at bottom during rename

* Watch new directory when created

* Revert "Watch new directory when created"

This reverts commit 6856804.

* Reapply "Watch new directory when created"

This reverts commit 1c29f34.

* Try batching renew updates

* Big rewrite

* Reload individual directories

* Change delay to 100 milliseconds

* Use separate goroutine for loading files/dirs

* Fix filter resetting

* Add documentation

app.go

@@ -34,6 +34,7 @@ type app struct {
 	menuComps      []string
 	menuCompInd    int
 	selectionOut   []string
+	watch          *watch
 }
 
 func newApp(ui *ui, nav *nav) *app {
@@ -44,6 +45,7 @@ func newApp(ui *ui, nav *nav) *app {
 		nav:      nav,
 		ticker:   new(time.Ticker),
 		quitChan: quitChan,
+		watch:    newWatch(nav.dirChan, nav.fileChan),
 	}
 
 	sigChan := make(chan os.Signal, 1)
@@ -382,6 +384,8 @@ func (app *app) loop() {
 				if ok {
 					d.ind = prev.ind
 					d.pos = prev.pos
+					d.filter = prev.filter
+					d.sort()
 					d.sel(prev.name(), app.nav.height)
 				}
 
@@ -414,6 +418,8 @@ func (app *app) loop() {
 				}
 			}
 
+			app.setWatchPaths()
+
 			app.ui.draw(app.nav)
 		case r := <-app.nav.regChan:
 			app.nav.regCache[r.path] = r
@@ -425,6 +431,31 @@ func (app *app) loop() {
 				}
 			}
 
+			app.ui.draw(app.nav)
+		case f := <-app.nav.fileChan:
+			dirs := app.nav.dirs
+			if app.ui.dirPrev != nil {
+				dirs = append(dirs, app.ui.dirPrev)
+			}
+
+			for _, dir := range dirs {
+				if dir.path != filepath.Dir(f.path) {
+					continue
+				}
+
+				for i := range dir.allFiles {
+					if dir.allFiles[i].path == f.path {
+						dir.allFiles[i] = f
+						break
+					}
+				}
+
+				name := dir.name()
+				dir.sort()
+				dir.sel(name, app.nav.height)
+			}
+
+			app.ui.loadFile(app, false)
 			app.ui.draw(app.nav)
 		case ev := <-app.ui.evChan:
 			e := app.ui.readEvent(ev, app.nav)
@@ -591,3 +622,22 @@ func (app *app) runShell(s string, args []string, prefix string) {
 		}()
 	}
 }
+
+func (app *app) setWatchPaths() {
+	if !gOpts.watch || len(app.nav.dirs) == 0 {
+		return
+	}
+
+	paths := make(map[string]bool)
+	for _, dir := range app.nav.dirs {
+		paths[dir.path] = true
+	}
+
+	for _, file := range app.nav.currDir().allFiles {
+		if file.IsDir() {
+			paths[file.path] = true
+		}
+	}
+
+	app.watch.set(paths)
+}

doc.md

@@ -202,6 +202,7 @@ The following options can be used to customize the behavior of lf:
 	truncatechar        string    (default '~')
 	truncatepct         int       (default 100)
 	waitmsg             string    (default 'Press any key to continue')
+	watch               bool      (default false)
 	wrapscan            bool      (default true)
 	wrapscroll          bool      (default false)
 	user_{option}       string    (default none)
@@ -1016,6 +1017,11 @@ while a value of 0 will only show the end of the filename, e.g.:
 
 String shown after commands of shell-wait type.
 
+## watch (bool) (default false)
+
+Watch the filesystem for changes using `fsnotify` to automatically refresh file information.
+FUSE is currently not supported due to limitations in `fsnotify`.
+
 ## wrapscan (bool) (default true)
 
 Searching can wrap around the file list.

eval.go

@@ -196,6 +196,16 @@ func (e *setExpr) eval(app *app, args []string) {
 			app.ui.sort()
 			app.ui.loadFile(app, true)
 		}
+	case "watch", "nowatch", "watch!":
+		err = applyBoolOpt(&gOpts.watch, e)
+		if err == nil {
+			if gOpts.watch {
+				app.watch.start()
+				app.setWatchPaths()
+			} else {
+				app.watch.stop()
+			}
+		}
 	case "wrapscan", "nowrapscan", "wrapscan!":
 		err = applyBoolOpt(&gOpts.wrapscan, e)
 	case "wrapscroll", "nowrapscroll", "wrapscroll!":
@@ -563,6 +573,7 @@ func preChdir(app *app) {
 
 func onChdir(app *app) {
 	app.nav.addJumpList()
+	app.setWatchPaths()
 	if cmd, ok := gOpts.cmds["on-cd"]; ok {
 		cmd.eval(app, nil)
 	}

go.mod

@@ -4,6 +4,7 @@ go 1.18
 
 require (
 	github.com/djherbis/times v1.6.0
+	github.com/fsnotify/fsnotify v1.7.0
 	github.com/gdamore/tcell/v2 v2.7.4
 	github.com/mattn/go-runewidth v0.0.15
 	golang.org/x/sys v0.21.0

go.sum

@@ -1,5 +1,7 @@
 github.com/djherbis/times v1.6.0 h1:w2ctJ92J8fBvWPxugmXIv7Nz7Q3iDMKNx9v5ocVH20c=
 github.com/djherbis/times v1.6.0/go.mod h1:gOHeRAz2h+VJNZ5Gmc/o7iD9k4wW7NMVqieYCY99oc0=
+github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
+github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
 github.com/gdamore/encoding v1.0.0 h1:+7OoQ1Bc6eTm5niUzBa0Ctsh6JbMW6Ra+YNuAtDBdko=
 github.com/gdamore/encoding v1.0.0/go.mod h1:alR0ol34c49FCSBLjhosxzcPHQbf2trDkoo5dl+VrEg=
 github.com/gdamore/tcell/v2 v2.7.4 h1:sg6/UnTM9jGpZU+oFYAsDahfchWAFW8Xx2yFinNSAYU=

nav.go

@@ -39,6 +39,84 @@ type file struct {
 	err        error
 }
 
+func newFile(path string) *file {
+	lstat, err := os.Lstat(path)
+
+	if err != nil {
+		log.Printf("getting file information: %s", err)
+		return &file{
+			FileInfo:   &fakeStat{name: filepath.Base(path)},
+			linkState:  notLink,
+			linkTarget: "",
+			path:       path,
+			dirCount:   -1,
+			dirSize:    -1,
+			accessTime: time.Unix(0, 0),
+			changeTime: time.Unix(0, 0),
+			ext:        "",
+			err:        err,
+		}
+	}
+
+	var linkState linkState
+	var linkTarget string
+
+	if lstat.Mode()&os.ModeSymlink != 0 {
+		stat, err := os.Stat(path)
+		if err == nil {
+			linkState = working
+			lstat = stat
+		} else {
+			linkState = broken
+		}
+		linkTarget, err = os.Readlink(path)
+		if err != nil {
+			log.Printf("reading link target: %s", err)
+		}
+	}
+
+	ts := times.Get(lstat)
+	at := ts.AccessTime()
+	var ct time.Time
+	// from times docs: ChangeTime() panics unless HasChangeTime() is true
+	if ts.HasChangeTime() {
+		ct = ts.ChangeTime()
+	} else {
+		// fall back to ModTime if ChangeTime cannot be determined
+		ct = lstat.ModTime()
+	}
+
+	dirCount := -1
+	if lstat.IsDir() && gOpts.dircounts {
+		d, err := os.Open(path)
+		if err != nil {
+			dirCount = -2
+		} else {
+			names, err := d.Readdirnames(1000)
+			d.Close()
+
+			if names == nil && err != io.EOF {
+				dirCount = -2
+			} else {
+				dirCount = len(names)
+			}
+		}
+	}
+
+	return &file{
+		FileInfo:   lstat,
+		linkState:  linkState,
+		linkTarget: linkTarget,
+		path:       path,
+		dirCount:   dirCount,
+		dirSize:    -1,
+		accessTime: at,
+		changeTime: ct,
+		ext:        getFileExtension(lstat),
+		err:        nil,
+	}
+}
+
 func (file *file) TotalSize() int64 {
 	if file.IsDir() {
 		if file.dirSize >= 0 {
@@ -70,87 +148,7 @@ func readdir(path string) ([]*file, error) {
 
 	files := make([]*file, 0, len(names))
 	for _, fname := range names {
-		fpath := filepath.Join(path, fname)
-
-		lstat, err := os.Lstat(fpath)
-
-		if os.IsNotExist(err) {
-			continue
-		}
-		if err != nil {
-			log.Printf("getting file information: %s", err)
-			files = append(files, &file{
-				FileInfo:   &fakeStat{name: fname},
-				linkState:  notLink,
-				linkTarget: "",
-				path:       fpath,
-				dirCount:   -1,
-				dirSize:    -1,
-				accessTime: time.Unix(0, 0),
-				changeTime: time.Unix(0, 0),
-				ext:        "",
-				err:        err,
-			})
-			continue
-		}
-
-		var linkState linkState
-		var linkTarget string
-
-		if lstat.Mode()&os.ModeSymlink != 0 {
-			stat, err := os.Stat(fpath)
-			if err == nil {
-				linkState = working
-				lstat = stat
-			} else {
-				linkState = broken
-			}
-			linkTarget, err = os.Readlink(fpath)
-			if err != nil {
-				log.Printf("reading link target: %s", err)
-			}
-		}
-
-		ts := times.Get(lstat)
-		at := ts.AccessTime()
-		var ct time.Time
-		// from times docs: ChangeTime() panics unless HasChangeTime() is true
-		if ts.HasChangeTime() {
-			ct = ts.ChangeTime()
-		} else {
-			// fall back to ModTime if ChangeTime cannot be determined
-			ct = lstat.ModTime()
-		}
-
-		dirCount := -1
-		if lstat.IsDir() && gOpts.dircounts {
-			d, err := os.Open(fpath)
-			if err != nil {
-				dirCount = -2
-			} else {
-				names, err := d.Readdirnames(1000)
-				d.Close()
-
-				if names == nil && err != io.EOF {
-					dirCount = -2
-				} else {
-					dirCount = len(names)
-				}
-			}
-		}
-
-		files = append(files, &file{
-			FileInfo:   lstat,
-			linkState:  linkState,
-			linkTarget: linkTarget,
-			path:       fpath,
-			dirCount:   dirCount,
-			dirSize:    -1,
-			accessTime: at,
-			changeTime: ct,
-			ext:        getFileExtension(lstat),
-			err:        nil,
-		})
+		files = append(files, newFile(filepath.Join(path, fname)))
 	}
 
 	return files, err
@@ -440,6 +438,7 @@ type nav struct {
 	dirPreviewChan  chan *dir
 	dirChan         chan *dir
 	regChan         chan *reg
+	fileChan        chan *file
 	dirCache        map[string]*dir
 	regCache        map[string]*reg
 	saves           map[string]bool
@@ -530,8 +529,6 @@ func (nav *nav) checkDir(dir *dir) {
 		dir.loadTime = now
 		go func() {
 			nd := newDir(dir.path)
-			nd.filter = dir.filter
-			nd.sort()
 			if gOpts.dirpreviews {
 				nav.dirPreviewChan <- nd
 			}
@@ -587,6 +584,7 @@ func newNav(height int) *nav {
 		dirPreviewChan:  make(chan *dir, 1024),
 		dirChan:         make(chan *dir),
 		regChan:         make(chan *reg),
+		fileChan:        make(chan *file),
 		dirCache:        make(map[string]*dir),
 		regCache:        make(map[string]*reg),
 		saves:           make(map[string]bool),
@@ -1564,7 +1562,13 @@ func (nav *nav) rename() error {
 	dir := nav.loadDir(filepath.Dir(newPath))
 
 	if dir.loading {
-		dir.files = append(dir.files, &file{FileInfo: lstat})
+		for i := range dir.allFiles {
+			if dir.allFiles[i].path == oldPath {
+				dir.allFiles[i] = &file{FileInfo: lstat}
+				break
+			}
+		}
+		dir.sort()
 	}
 
 	dir.sel(lstat.Name(), nav.height)

opts.go

@@ -66,6 +66,7 @@ var gOpts struct {
 	smartcase          bool
 	smartdia           bool
 	waitmsg            string
+	watch              bool
 	wrapscan           bool
 	wrapscroll         bool
 	findlen            int
@@ -213,6 +214,7 @@ func init() {
 	gOpts.smartcase = true
 	gOpts.smartdia = false
 	gOpts.waitmsg = "Press any key to continue"
+	gOpts.watch = false
 	gOpts.wrapscan = true
 	gOpts.wrapscroll = false
 	gOpts.findlen = 1