feat(output): add unsafe option

This disables any TTY checks including IOCTL and unix calls.
Useful for mocking console output and querying the terminal over SSH.

output.go

@@ -26,6 +26,7 @@ type Output struct {
 	tty     io.Writer
 	environ Environ
 
+	unsafe  bool
 	cache   bool
 	fgSync  *sync.Once
 	fgColor Color
@@ -105,6 +106,17 @@ func WithColorCache(v bool) OutputOption {
 	}
 }
 
+// WithUnsafe returns a new Output with unsafe mode enabled. Unsafe mode doesn't
+// check whether or not the terminal is a TTY.
+//
+// This is useful when mocking console output and enforcing ANSI escape output
+// e.g. on SSH sessions.
+func WithUnsafe() OutputOption {
+	return func(o *Output) {
+		o.unsafe = true
+	}
+}
+
 // ForegroundColor returns the terminal's default foreground color.
 func (o *Output) ForegroundColor() Color {
 	f := func() {

termenv.go

@@ -25,6 +25,9 @@ const (
 )
 
 func (o *Output) isTTY() bool {
+	if o.unsafe {
+		return true
+	}
 	if len(o.environ.Getenv("CI")) > 0 {
 		return false
 	}

termenv_unix.go

@@ -109,7 +109,8 @@ func (o Output) backgroundColor() Color {
 	return ANSIColor(0)
 }
 
-func waitForData(fd uintptr, timeout time.Duration) error {
+func (o *Output) waitForData(timeout time.Duration) error {
+	fd := o.TTY().Fd()
 	tv := unix.NsecToTimeval(int64(timeout))
 	var readfds unix.FdSet
 	readfds.Set(int(fd))
@@ -132,13 +133,15 @@ func waitForData(fd uintptr, timeout time.Duration) error {
 	return nil
 }
 
-func readNextByte(f File) (byte, error) {
-	if err := waitForData(f.Fd(), OSCTimeout); err != nil {
-		return 0, err
+func (o *Output) readNextByte() (byte, error) {
+	if !o.unsafe {
+		if err := o.waitForData(OSCTimeout); err != nil {
+			return 0, err
+		}
 	}
 
 	var b [1]byte
-	n, err := f.Read(b[:])
+	n, err := o.TTY().Read(b[:])
 	if err != nil {
 		return 0, err
 	}
@@ -153,15 +156,15 @@ func readNextByte(f File) (byte, error) {
 // readNextResponse reads either an OSC response or a cursor position response:
 //   - OSC response: "\x1b]11;rgb:1111/1111/1111\x1b\\"
 //   - cursor position response: "\x1b[42;1R"
-func readNextResponse(fd File) (response string, isOSC bool, err error) {
-	start, err := readNextByte(fd)
+func (o *Output) readNextResponse() (response string, isOSC bool, err error) {
+	start, err := o.readNextByte()
 	if err != nil {
 		return "", false, err
 	}
 
 	// first byte must be ESC
 	for start != ESC {
-		start, err = readNextByte(fd)
+		start, err = o.readNextByte()
 		if err != nil {
 			return "", false, err
 		}
@@ -170,7 +173,7 @@ func readNextResponse(fd File) (response string, isOSC bool, err error) {
 	response += string(start)
 
 	// next byte is either '[' (cursor position response) or ']' (OSC response)
-	tpe, err := readNextByte(fd)
+	tpe, err := o.readNextByte()
 	if err != nil {
 		return "", false, err
 	}
@@ -188,7 +191,7 @@ func readNextResponse(fd File) (response string, isOSC bool, err error) {
 	}
 
 	for {
-		b, err := readNextByte(fd)
+		b, err := o.readNextByte()
 		if err != nil {
 			return "", false, err
 		}
@@ -229,23 +232,25 @@ func (o Output) termStatusReport(sequence int) (string, error) {
 		return "", ErrStatusReport
 	}
 
-	fd := int(tty.Fd())
-	// if in background, we can't control the terminal
-	if !isForeground(fd) {
-		return "", ErrStatusReport
-	}
+	if !o.unsafe {
+		fd := int(tty.Fd())
+		// if in background, we can't control the terminal
+		if !isForeground(fd) {
+			return "", ErrStatusReport
+		}
 
-	t, err := unix.IoctlGetTermios(fd, tcgetattr)
-	if err != nil {
-		return "", fmt.Errorf("%s: %s", ErrStatusReport, err)
-	}
-	defer unix.IoctlSetTermios(fd, tcsetattr, t) //nolint:errcheck
+		t, err := unix.IoctlGetTermios(fd, tcgetattr)
+		if err != nil {
+			return "", fmt.Errorf("%s: %s", ErrStatusReport, err)
+		}
+		defer unix.IoctlSetTermios(fd, tcsetattr, t) //nolint:errcheck
 
-	noecho := *t
-	noecho.Lflag = noecho.Lflag &^ unix.ECHO
-	noecho.Lflag = noecho.Lflag &^ unix.ICANON
-	if err := unix.IoctlSetTermios(fd, tcsetattr, &noecho); err != nil {
-		return "", fmt.Errorf("%s: %s", ErrStatusReport, err)
+		noecho := *t
+		noecho.Lflag = noecho.Lflag &^ unix.ECHO
+		noecho.Lflag = noecho.Lflag &^ unix.ICANON
+		if err := unix.IoctlSetTermios(fd, tcsetattr, &noecho); err != nil {
+			return "", fmt.Errorf("%s: %s", ErrStatusReport, err)
+		}
 	}
 
 	// first, send OSC query, which is ignored by terminal which do not support it
@@ -255,7 +260,7 @@ func (o Output) termStatusReport(sequence int) (string, error) {
 	fmt.Fprintf(tty, CSI+"6n")
 
 	// read the next response
-	res, isOSC, err := readNextResponse(tty)
+	res, isOSC, err := o.readNextResponse()
 	if err != nil {
 		return "", fmt.Errorf("%s: %s", ErrStatusReport, err)
 	}
@@ -266,7 +271,7 @@ func (o Output) termStatusReport(sequence int) (string, error) {
 	}
 
 	// read the cursor query response next and discard the result
-	_, _, err = readNextResponse(tty)
+	_, _, err = o.readNextResponse()
 	if err != nil {
 		return "", err
 	}