Fix Windows terminal handling

Fix some issues with Windows terminal handling with respect to TTYs that came up as part of the
code that adds support for terminal resizing.

pkg/util/term/resize.go

@@ -32,10 +32,11 @@ type Size struct {
 // GetSize returns the current size of the user's terminal. If it isn't a terminal,
 // nil is returned.
 func (t TTY) GetSize() *Size {
-	if !t.IsTerminalOut() {
+	outFd, isTerminal := term.GetFdInfo(t.Out)
+	if !isTerminal {
 		return nil
 	}
-	return GetSize(t.Out.(fd).Fd())
+	return GetSize(outFd)
 }
 
 // GetSize returns the current size of the terminal associated with fd.
@@ -57,7 +58,8 @@ func SetSize(fd uintptr, size Size) error {
 // MonitorSize monitors the terminal's size. It returns a TerminalSizeQueue primed with
 // initialSizes, or nil if there's no TTY present.
 func (t *TTY) MonitorSize(initialSizes ...*Size) TerminalSizeQueue {
-	if !t.IsTerminalOut() {
+	outFd, isTerminal := term.GetFdInfo(t.Out)
+	if !isTerminal {
 		return nil
 	}
 
@@ -69,7 +71,7 @@ func (t *TTY) MonitorSize(initialSizes ...*Size) TerminalSizeQueue {
 		stopResizing: make(chan struct{}),
 	}
 
-	t.sizeQueue.monitorSize(initialSizes...)
+	t.sizeQueue.monitorSize(outFd, initialSizes...)
 
 	return t.sizeQueue
 }
@@ -94,7 +96,7 @@ var _ TerminalSizeQueue = &sizeQueue{}
 
 // monitorSize primes resizeChan with initialSizes and then monitors for resize events. With each
 // new event, it sends the current terminal size to resizeChan.
-func (s *sizeQueue) monitorSize(initialSizes ...*Size) {
+func (s *sizeQueue) monitorSize(outFd uintptr, initialSizes ...*Size) {
 	// send the initial sizes
 	for i := range initialSizes {
 		if initialSizes[i] != nil {
@@ -104,7 +106,7 @@ func (s *sizeQueue) monitorSize(initialSizes ...*Size) {
 
 	resizeEvents := make(chan Size, 1)
 
-	monitorResizeEvents(s.t.Out.(fd).Fd(), resizeEvents, s.stopResizing)
+	monitorResizeEvents(outFd, resizeEvents, s.stopResizing)
 
 	// listen for resize events in the background
 	go func() {

pkg/util/term/resizeevents_windows.go

@@ -29,7 +29,11 @@ func monitorResizeEvents(fd uintptr, resizeEvents chan<- Size, stop chan struct{
 	go func() {
 		defer runtime.HandleCrash()
 
-		var lastSize Size
+		size := GetSize(fd)
+		if size == nil {
+			return
+		}
+		lastSize := *size
 
 		for {
 			// see if we need to stop running

pkg/util/term/term.go

@@ -52,11 +52,6 @@ type TTY struct {
 	sizeQueue *sizeQueue
 }
 
-// fd returns a file descriptor for a given object.
-type fd interface {
-	Fd() uintptr
-}
-
 // IsTerminalIn returns true if t.In is a terminal. Does not check /dev/tty
 // even if TryDev is set.
 func (t TTY) IsTerminalIn() bool {
@@ -71,8 +66,8 @@ func (t TTY) IsTerminalOut() bool {
 
 // IsTerminal returns whether the passed object is a terminal or not
 func IsTerminal(i interface{}) bool {
-	file, ok := i.(fd)
-	return ok && term.IsTerminal(file.Fd())
+	_, terminal := term.GetFdInfo(i)
+	return terminal
 }
 
 // Safe invokes the provided function and will attempt to ensure that when the
@@ -82,22 +77,16 @@ func IsTerminal(i interface{}) bool {
 // If the input file descriptor is not a TTY and TryDev is true, the /dev/tty file
 // will be opened (if available).
 func (t TTY) Safe(fn SafeFunc) error {
-	in := t.In
+	inFd, isTerminal := term.GetFdInfo(t.In)
 
-	var hasFd bool
-	var inFd uintptr
-	if desc, ok := in.(fd); ok && in != nil {
-		inFd = desc.Fd()
-		hasFd = true
-	}
-	if t.TryDev && (!hasFd || !term.IsTerminal(inFd)) {
+	if !isTerminal && t.TryDev {
 		if f, err := os.Open("/dev/tty"); err == nil {
 			defer f.Close()
 			inFd = f.Fd()
-			hasFd = true
+			isTerminal = term.IsTerminal(inFd)
 		}
 	}
-	if !hasFd || !term.IsTerminal(inFd) {
+	if !isTerminal {
 		return fn()
 	}