execute: Open separate handles to /dev/tty (in, out, err)

# This will no longer cause 'Vim: Warning: Output is not to a terminal'
  fzf --bind 'enter:execute:vim {}' > /tmp/foo

src/tui/light.go

@@ -127,11 +127,7 @@ type LightWindow struct {
 	bg       Color
 }
 
-func NewLightRenderer(theme *ColorTheme, forceBlack bool, mouse bool, tabstop int, clearOnExit bool, fullscreen bool, maxHeightFunc func(int) int) (Renderer, error) {
-	in, err := openTtyIn()
-	if err != nil {
-		return nil, err
-	}
+func NewLightRenderer(ttyin *os.File, theme *ColorTheme, forceBlack bool, mouse bool, tabstop int, clearOnExit bool, fullscreen bool, maxHeightFunc func(int) int) (Renderer, error) {
 	out, err := openTtyOut()
 	if err != nil {
 		out = os.Stderr
@@ -142,7 +138,7 @@ func NewLightRenderer(theme *ColorTheme, forceBlack bool, mouse bool, tabstop in
 		forceBlack:    forceBlack,
 		mouse:         mouse,
 		clearOnExit:   clearOnExit,
-		ttyin:         in,
+		ttyin:         ttyin,
 		ttyout:        out,
 		yoffset:       0,
 		tabstop:       tabstop,

src/tui/light_unix.go

@@ -7,7 +7,6 @@ import (
 	"os"
 	"os/exec"
 	"strings"
-	"sync"
 	"syscall"
 
 	"github.com/junegunn/fzf/src/util"
@@ -15,13 +14,6 @@ import (
 	"golang.org/x/term"
 )
 
-var (
-	tty    string
-	ttyin  *os.File
-	ttyout *os.File
-	mutex  sync.Mutex
-)
-
 func IsLightRendererSupported() bool {
 	return true
 }
@@ -53,15 +45,13 @@ func (r *LightRenderer) initPlatform() error {
 }
 
 func (r *LightRenderer) closePlatform() {
-	// NOOP
+	r.ttyout.Close()
 }
 
 func openTty(mode int) (*os.File, error) {
 	in, err := os.OpenFile(consoleDevice, mode, 0)
 	if err != nil {
-		if len(tty) == 0 {
-			tty = ttyname()
-		}
+		tty := ttyname()
 		if len(tty) > 0 {
 			if in, err := os.OpenFile(tty, mode, 0); err == nil {
 				return in, nil
@@ -73,31 +63,11 @@ func openTty(mode int) (*os.File, error) {
 }
 
 func openTtyIn() (*os.File, error) {
-	mutex.Lock()
-	defer mutex.Unlock()
-
-	if ttyin != nil {
-		return ttyin, nil
-	}
-	in, err := openTty(syscall.O_RDONLY)
-	if err == nil {
-		ttyin = in
-	}
-	return in, err
+	return openTty(syscall.O_RDONLY)
 }
 
 func openTtyOut() (*os.File, error) {
-	mutex.Lock()
-	defer mutex.Unlock()
-
-	if ttyout != nil {
-		return ttyout, nil
-	}
-	out, err := openTty(syscall.O_WRONLY)
-	if err == nil {
-		ttyout = out
-	}
-	return out, err
+	return openTty(syscall.O_WRONLY)
 }
 
 func (r *LightRenderer) setupTerminal() {

src/tui/tcell_test.go

@@ -3,6 +3,7 @@
 package tui
 
 import (
+	"os"
 	"testing"
 
 	"github.com/gdamore/tcell/v2"
@@ -20,7 +21,7 @@ func assert(t *testing.T, context string, got interface{}, want interface{}) boo
 
 // Test the handling of the tcell keyboard events.
 func TestGetCharEventKey(t *testing.T) {
-	if util.ToTty() {
+	if util.IsTty(os.Stdout) {
 		// This test is skipped when output goes to terminal, because it causes
 		// some glitches:
 		// - output lines may not start at the beginning of a row which makes

src/tui/ttyname_unix.go

@@ -4,12 +4,19 @@ package tui
 
 import (
 	"os"
+	"sync/atomic"
 	"syscall"
 )
 
 var devPrefixes = [...]string{"/dev/pts/", "/dev/"}
 
+var tty atomic.Value
+
 func ttyname() string {
+	if cached := tty.Load(); cached != nil {
+		return cached.(string)
+	}
+
 	var stderr syscall.Stat_t
 	if syscall.Fstat(2, &stderr) != nil {
 		return ""
@@ -27,17 +34,21 @@ func ttyname() string {
 				continue
 			}
 			if stat, ok := info.Sys().(*syscall.Stat_t); ok && stat.Rdev == stderr.Rdev {
-				return prefix + file.Name()
+				value := prefix + file.Name()
+				tty.Store(value)
+				return value
 			}
 		}
 	}
 	return ""
 }
 
-// TtyIn returns terminal device to be used as STDIN, falls back to os.Stdin
-func TtyIn() *os.File {
-	if in, err := openTtyIn(); err == nil {
-		return in
-	}
-	return os.Stdin
+// TtyIn returns terminal device to read user input
+func TtyIn() (*os.File, error) {
+	return openTtyIn()
+}
+
+// TtyIn returns terminal device to write to
+func TtyOut() (*os.File, error) {
+	return openTtyOut()
 }

src/tui/ttyname_windows.go

@@ -2,13 +2,20 @@
 
 package tui
 
-import "os"
+import (
+	"os"
+)
 
 func ttyname() string {
 	return ""
 }
 
 // TtyIn on Windows returns os.Stdin
-func TtyIn() *os.File {
-	return os.Stdin
+func TtyIn() (*os.File, error) {
+	return os.Stdin, nil
+}
+
+// TtyIn on Windows returns nil
+func TtyOut() (*os.File, error) {
+	return nil, nil
 }