review comments

main.go

@@ -196,7 +196,7 @@ func wrappedMain() int {
 			Reader:      os.Stdin,
 			Writer:      os.Stdout,
 			ErrorWriter: os.Stdout,
-			PB:          &packer.UiProgressBar{},
+			PB:          &packer.NoopProgressTracker{},
 		}
 		ui = basicUi
 		if !inPlugin {
@@ -208,12 +208,11 @@ func wrappedMain() int {
 			}
 			if backgrounded {
 				fmt.Fprint(os.Stderr, "Running in background, not using a TTY\n")
-				basicUi.PB = &packer.NoopProgressTracker{}
 			} else if TTY, err := openTTY(); err != nil {
 				fmt.Fprintf(os.Stderr, "No tty available: %s\n", err)
-				basicUi.PB = &packer.NoopProgressTracker{}
 			} else {
 				basicUi.TTY = TTY
+				basicUi.PB = &packer.UiProgressBar{}
 				defer TTY.Close()
 			}
 		}

packer/progressbar.go

@@ -15,14 +15,8 @@ func ProgressBarConfig(bar *pb.ProgressBar, prefix string) {
 	bar.Prefix(prefix)
 }
 
-var defaultUiProgressBar = &UiProgressBar{}
-
-// UiProgressBar is a self managed progress bar singleton.
-// decorate your struct with a *UiProgressBar to
-// give it TrackProgress capabilities.
-// In TrackProgress if UiProgressBar is nil
-// defaultUiProgressBar will be used as
-// the progress bar.
+// UiProgressBar is a progress bar compatible with go-getter used in our
+// UI structs.
 type UiProgressBar struct {
 	Noop bool
 	lock sync.Mutex
@@ -30,10 +24,9 @@ type UiProgressBar struct {
 	pbs  int
 }
 
+var noOpProgressBar *UiProgressBar = nil
+
 func (p *UiProgressBar) TrackProgress(src string, currentSize, totalSize int64, stream io.ReadCloser) io.ReadCloser {
-	if p == nil {
-		return defaultUiProgressBar.TrackProgress(src, currentSize, totalSize, stream)
-	}
 	if p.Noop {
 		return stream
 	}

packer/ui_test.go

@@ -49,7 +49,7 @@ func (tty *testTTY) ReadString() (string, error) {
 
 func TestColoredUi(t *testing.T) {
 	bufferUi := testUi()
-	ui := &ColoredUi{UiColorYellow, UiColorRed, bufferUi, defaultUiProgressBar}
+	ui := &ColoredUi{UiColorYellow, UiColorRed, bufferUi, &UiProgressBar{}}
 
 	if !ui.supportsColors() {
 		t.Skip("skipping for ui without color support")
@@ -81,7 +81,7 @@ func TestColoredUi(t *testing.T) {
 
 func TestColoredUi_noColorEnv(t *testing.T) {
 	bufferUi := testUi()
-	ui := &ColoredUi{UiColorYellow, UiColorRed, bufferUi, defaultUiProgressBar}
+	ui := &ColoredUi{UiColorYellow, UiColorRed, bufferUi, &UiProgressBar{}}
 
 	// Set the env var to get rid of the color
 	oldenv := os.Getenv("PACKER_NO_COLOR")