Guarantee preview/previewClear ordering (gokcehan#537)

* Use chan struct{} in place of chan bool

* Revert "nav.checkReg now returns a boolean instead of calling nav.preview"

* Guarantee preview/previewClear ordering

* Pass the file path to the cleaner script

app.go

@@ -25,7 +25,7 @@ type app struct {
 	ui            *ui
 	nav           *nav
 	ticker        *time.Ticker
-	quitChan      chan bool
+	quitChan      chan struct{}
 	cmd           *exec.Cmd
 	cmdIn         io.WriteCloser
 	cmdOutBuf     []byte
@@ -38,7 +38,7 @@ func newApp(screen tcell.Screen) *app {
 	ui := newUI(screen)
 	nav := newNav(ui.wins[0].h)
 
-	quitChan := make(chan bool, 1)
+	quitChan := make(chan struct{}, 1)
 
 	app := &app{
 		ui:       ui,
@@ -213,7 +213,7 @@ func (app *app) loop() {
 				continue
 			}
 
-			go app.nav.previewClear()
+			app.nav.previewChan <- ""
 
 			log.Print("bye!")
 
@@ -312,10 +312,7 @@ func (app *app) loop() {
 
 			app.ui.draw(app.nav)
 		case r := <-app.nav.regChan:
-			if app.nav.checkReg(r) {
-				win := app.ui.wins[len(app.ui.wins)-1]
-				go app.nav.preview(r.path, win)
-			}
+			app.nav.checkReg(r)
 
 			app.nav.regCache[r.path] = r
 
@@ -407,7 +404,7 @@ func (app *app) runShell(s string, args []string, prefix string) {
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
 
-		go app.nav.previewClear()
+		app.nav.previewChan <- ""
 		app.ui.pause()
 		defer app.ui.resume()
 		defer app.nav.renew()

client.go

@@ -42,6 +42,7 @@ func run() {
 		app.ui.echoerrf("reading history file: %s", err)
 	}
 
+	go app.nav.previewLoop(app.ui)
 	app.loop()
 	app.ui.screen.Fini()
 }

doc.go

@@ -601,6 +601,7 @@ Preview filtering is disabled and files are displayed as they are when the value
 
 Set the path of a cleaner file. This file will be called if previewing is enabled, the previewer is set, and the previously selected file had its preview cache disabled.
 The file should be executable.
+One argument is passed to the file; the path to the file whose preview should be cleaned.
 Preview clearing is disabled when the value of this option is left empty.
 
     promptfmt      string    (default "\033[32;1m%u@%h\033[0m:\033[34;1m%w/\033[0m\033[1m%f\033[0m")

eval.go

@@ -699,7 +699,7 @@ func (e *callExpr) eval(app *app, args []string) {
 				log.Printf("writing selection file: %s", err)
 			}
 
-			app.quitChan <- true
+			app.quitChan <- struct{}{}
 
 			return
 		}
@@ -708,7 +708,7 @@ func (e *callExpr) eval(app *app, args []string) {
 			cmd.eval(app, e.args)
 		}
 	case "quit":
-		app.quitChan <- true
+		app.quitChan <- struct{}{}
 	case "top":
 		app.nav.top()
 		app.ui.loadFile(app.nav)

lf.1

@@ -719,7 +719,7 @@ Set the path of a previewer file to filter the content of regular files for prev
     cleaner        string    (default '') (not called if empty)
 .EE
 .PP
-Set the path of a cleaner file. This file will be called if previewing is enabled, the previewer is set, and the previously selected file had its preview cache disabled. The file should be executable. Preview clearing is disabled when the value of this option is left empty.
+Set the path of a cleaner file. This file will be called if previewing is enabled, the previewer is set, and the previously selected file had its preview cache disabled. The file should be executable. One argument is passed to the file; the path to the file whose preview should be cleaned. Preview clearing is disabled when the value of this option is left empty.
 .PP
 .EX
     promptfmt      string    (default "\e033[32;1m%u@%h\e033[0m:\e033[34;1m%w/\e033[0m\e033[1m%f\e033[0m")

nav.go

@@ -285,6 +285,7 @@ type nav struct {
 	moveTotalChan   chan int
 	deleteCountChan chan int
 	deleteTotalChan chan int
+	previewChan     chan string
 	dirChan         chan *dir
 	regChan         chan *reg
 	dirCache        map[string]*dir
@@ -398,6 +399,7 @@ func newNav(height int) *nav {
 		moveTotalChan:   make(chan int, 1024),
 		deleteCountChan: make(chan int, 1024),
 		deleteTotalChan: make(chan int, 1024),
+		previewChan:     make(chan string, 1024),
 		dirChan:         make(chan *dir),
 		regChan:         make(chan *reg),
 		dirCache:        make(map[string]*dir),
@@ -457,6 +459,27 @@ func (nav *nav) position() {
 	}
 }
 
+func (nav *nav) previewLoop(ui *ui) {
+	var path string
+	for {
+		p, ok := <-nav.previewChan
+		if !ok {
+			return
+		}
+		if len(p) != 0 {
+			win := ui.wins[len(ui.wins)-1]
+			nav.preview(p, win)
+			path = p
+		} else if len(gOpts.previewer) != 0 && len(gOpts.cleaner) != 0 && nav.volatilePreview {
+			cmd := exec.Command(gOpts.cleaner, path)
+			if err := cmd.Run(); err != nil {
+				log.Printf("cleaning preview: %s", err)
+			}
+			nav.volatilePreview = false
+		}
+	}
+}
+
 func (nav *nav) preview(path string, win *win) {
 	reg := &reg{loadTime: time.Now(), path: path}
 	defer func() { nav.regChan <- reg }()
@@ -487,8 +510,8 @@ func (nav *nav) preview(path string, win *win) {
 			if err := cmd.Wait(); err != nil {
 				if e, ok := err.(*exec.ExitError); ok {
 					if e.ExitCode() != 0 {
-						nav.volatilePreview = true
 						reg.volatile = true
+						nav.volatilePreview = true
 					}
 				} else {
 					log.Printf("loading file: %s", err)
@@ -525,53 +548,38 @@ func (nav *nav) preview(path string, win *win) {
 	}
 }
 
-func (nav *nav) previewClear() {
-	if len(gOpts.cleaner) != 0 && nav.volatilePreview {
-		nav.volatilePreview = false
-
-		cmd := exec.Command(gOpts.cleaner)
-		if err := cmd.Run(); err != nil {
-			log.Printf("cleaning preview: %s", err)
-		}
-	}
-}
-
-func (nav *nav) loadReg(path string, win *win) *reg {
+func (nav *nav) loadReg(path string) *reg {
 	r, ok := nav.regCache[path]
 	if !ok || r.volatile {
 		r := &reg{loading: true, loadTime: time.Now(), path: path, volatile: true}
 		nav.regCache[path] = r
-		go nav.preview(path, win)
+		nav.previewChan <- path
 		return r
 	}
 
-	if nav.checkReg(r) {
-		go nav.preview(path, win)
-	}
+	nav.checkReg(r)
 
 	return r
 }
 
-func (nav *nav) checkReg(reg *reg) bool {
+func (nav *nav) checkReg(reg *reg) {
 	s, err := os.Stat(reg.path)
 	if err != nil {
-		return false
+		return
 	}
 
 	now := time.Now()
 
 	// XXX: Linux builtin exFAT drivers are able to predict modifications in the future
 	// https://bugs.launchpad.net/ubuntu/+source/ubuntu-meta/+bug/1872504
 	if s.ModTime().After(now) {
-		return false
+		return
 	}
 
 	if s.ModTime().After(reg.loadTime) {
 		reg.loadTime = now
-		return true
+		nav.previewChan <- reg.path
 	}
-
-	return false
 }
 
 func (nav *nav) sort() {

server.go

@@ -13,7 +13,7 @@ var (
 	gCopyFile bool
 	gFileList []string
 	gConnList = make(map[int]net.Conn)
-	gQuitChan = make(chan bool, 1)
+	gQuitChan = make(chan struct{}, 1)
 	gListener net.Listener
 )
 
@@ -115,7 +115,7 @@ Loop:
 				}
 			}
 		case "quit":
-			gQuitChan <- true
+			gQuitChan <- struct{}{}
 			for _, c := range gConnList {
 				fmt.Fprintln(c, "echo server is quitting...")
 				c.Close()

ui.go

@@ -625,12 +625,11 @@ func (ui *ui) loadFile(nav *nav) {
 		return
 	}
 
-	go nav.previewClear()
+	nav.previewChan <- ""
 	if curr.IsDir() {
 		ui.dirPrev = nav.loadDir(curr.path)
 	} else if curr.Mode().IsRegular() {
-		win := ui.wins[len(ui.wins)-1]
-		ui.regPrev = nav.loadReg(curr.path, win)
+		ui.regPrev = nav.loadReg(curr.path)
 	}
 }