Switch to explicitly declaring TrackProgress on UI, using an underlying progress bar specifically stored on the struct. Export UiProgressTracker. These changes allow us to optionaly switch to the NoopProgressTracker when no TTY is set.

go.mod

@@ -96,6 +96,7 @@ require (
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/mitchellh/go-testing-interface v1.0.3 // indirect
 	github.com/mitchellh/go-vnc v0.0.0-20150629162542-723ed9867aed
+	github.com/mitchellh/gox v1.0.1 // indirect
 	github.com/mitchellh/iochan v1.0.0
 	github.com/mitchellh/mapstructure v1.2.3
 	github.com/mitchellh/panicwrap v0.0.0-20170106182340-fce601fe5557

go.sum

@@ -351,6 +351,7 @@ github.com/hashicorp/go-uuid v1.0.1 h1:fv1ep09latC32wFoVwnqcnKJGnMSdBanPczbHAYm1
 github.com/hashicorp/go-uuid v1.0.1/go.mod h1:6SBZvOh/SIDV7/2o3Jml5SYk/TvGqwFJ/bN7x4byOro=
 github.com/hashicorp/go-uuid v1.0.2 h1:cfejS+Tpcp13yd5nYHWDI6qVCny6wyX2Mt5SGur2IGE=
 github.com/hashicorp/go-uuid v1.0.2/go.mod h1:6SBZvOh/SIDV7/2o3Jml5SYk/TvGqwFJ/bN7x4byOro=
+github.com/hashicorp/go-version v1.0.0/go.mod h1:fltr4n8CU8Ke44wwGCBoEymUuxUHl09ZGVZPK5anwXA=
 github.com/hashicorp/go-version v1.1.0 h1:bPIoEKD27tNdebFGGxxYwcL4nepeY4j1QP23PFRGzg0=
 github.com/hashicorp/go-version v1.1.0/go.mod h1:fltr4n8CU8Ke44wwGCBoEymUuxUHl09ZGVZPK5anwXA=
 github.com/hashicorp/go-version v1.2.0 h1:3vNe/fWF5CBgRIguda1meWhsZHy3m8gCJ5wx+dIzX/E=
@@ -487,6 +488,8 @@ github.com/mitchellh/go-wordwrap v0.0.0-20150314170334-ad45545899c7/go.mod h1:ZX
 github.com/mitchellh/go-wordwrap v1.0.0 h1:6GlHJ/LTGMrIJbwgdqdl2eEH8o+Exx/0m8ir9Gns0u4=
 github.com/mitchellh/go-wordwrap v1.0.0/go.mod h1:ZXFpozHsX6DPmq2I0TCekCxypsnAUbP2oI0UX1GXzOo=
 github.com/mitchellh/gox v0.4.0/go.mod h1:Sd9lOJ0+aimLBi73mGofS1ycjY8lL3uZM3JPS42BGNg=
+github.com/mitchellh/gox v1.0.1 h1:x0jD3dcHk9a9xPSDN6YEL4xL6Qz0dvNYm8yZqui5chI=
+github.com/mitchellh/gox v1.0.1/go.mod h1:ED6BioOGXMswlXa2zxfh/xdd5QhwYliBFn9V18Ap4z4=
 github.com/mitchellh/iochan v1.0.0 h1:C+X3KsSTLFVBr/tK1eYN/vs4rJcvsiLU338UhYPJWeY=
 github.com/mitchellh/iochan v1.0.0/go.mod h1:JwYml1nuB7xOzsp52dPpHFffvOCDupsG0QubkSMEySY=
 github.com/mitchellh/mapstructure v0.0.0-20160808181253-ca63d7c062ee/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=

main.go

@@ -196,6 +196,7 @@ func wrappedMain() int {
 			Reader:      os.Stdin,
 			Writer:      os.Stdout,
 			ErrorWriter: os.Stdout,
+			PB:          &packer.UiProgressBar{},
 		}
 		ui = basicUi
 		if !inPlugin {
@@ -207,8 +208,10 @@ 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
 				defer TTY.Close()

packer/progressbar.go

@@ -15,26 +15,28 @@ func ProgressBarConfig(bar *pb.ProgressBar, prefix string) {
 	bar.Prefix(prefix)
 }
 
-var defaultUiProgressBar = &uiProgressBar{}
+var defaultUiProgressBar = &UiProgressBar{}
 
-// uiProgressBar is a self managed progress bar singleton.
+// UiProgressBar is a self managed progress bar singleton.
-// decorate your struct with a *uiProgressBar to
+// decorate your struct with a *UiProgressBar to
 // give it TrackProgress capabilities.
-// In TrackProgress if uiProgressBar is nil
+// In TrackProgress if UiProgressBar is nil
 // defaultUiProgressBar will be used as
 // the progress bar.
-type uiProgressBar struct {
+type UiProgressBar struct {
+	Noop bool
 	lock sync.Mutex
-
 	pool *pb.Pool
-
 	pbs  int
 }
 
-func (p *uiProgressBar) TrackProgress(src string, currentSize, totalSize int64, stream io.ReadCloser) io.ReadCloser {
+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
+	}
 	p.lock.Lock()
 	defer p.lock.Unlock()
 

packer/progressbar_solaris.go

@@ -1,3 +1,3 @@
 package packer
 
-type uiProgressBar = NoopProgressTracker
+type UiProgressBar = NoopProgressTracker

packer/progressbar_test.go

@@ -11,7 +11,7 @@ import (
 // The following tests rarelly just happen. So we run them 100 times.
 
 func TestProgressTracking_open_close(t *testing.T) {
-	var bar *uiProgressBar
+	var bar *UiProgressBar
 
 	tracker := bar.TrackProgress("1,", 1, 42, ioutil.NopCloser(nil))
 	tracker.Close()
@@ -21,7 +21,7 @@ func TestProgressTracking_open_close(t *testing.T) {
 }
 
 func TestProgressTracking_multi_open_close(t *testing.T) {
-	var bar *uiProgressBar
+	var bar *UiProgressBar
 	g := errgroup.Group{}
 
 	for i := 0; i < 100; i++ {
@@ -36,7 +36,7 @@ func TestProgressTracking_multi_open_close(t *testing.T) {
 }
 
 func TestProgressTracking_races(t *testing.T) {
-	var bar *uiProgressBar
+	var bar *UiProgressBar
 	g := errgroup.Group{}
 
 	for i := 0; i < 100; i++ {

packer/ui.go

@@ -40,11 +40,12 @@ type Ui interface {
 	Message(string)
 	Error(string)
 	Machine(string, ...string)
+	// TrackProgress(src string, currentSize, totalSize int64, stream io.ReadCloser) (body io.ReadCloser)
 	getter.ProgressTracker
 }
 
 type NoopUi struct {
-	NoopProgressTracker
+	PB NoopProgressTracker
 }
 
 var _ Ui = new(NoopUi)
@@ -54,13 +55,16 @@ func (*NoopUi) Say(string)                 { return }
 func (*NoopUi) Message(string)             { return }
 func (*NoopUi) Error(string)               { return }
 func (*NoopUi) Machine(string, ...string)  { return }
+func (u *NoopUi) TrackProgress(src string, currentSize, totalSize int64, stream io.ReadCloser) io.ReadCloser {
+	return u.PB.TrackProgress(src, currentSize, totalSize, stream)
+}
 
 // ColoredUi is a UI that is colored using terminal colors.
 type ColoredUi struct {
 	Color      UiColor
 	ErrorColor UiColor
 	Ui         Ui
-	*uiProgressBar
+	PB         getter.ProgressTracker
 }
 
 var _ Ui = new(ColoredUi)
@@ -189,7 +193,7 @@ type BasicUi struct {
 	l           sync.Mutex
 	interrupted bool
 	TTY         TTY
-	*uiProgressBar
+	PB          getter.ProgressTracker
 }
 
 var _ Ui = new(BasicUi)
@@ -304,11 +308,15 @@ func (rw *BasicUi) Machine(t string, args ...string) {
 	log.Printf("machine readable: %s %#v", t, args)
 }
 
+func (rw *BasicUi) TrackProgress(src string, currentSize, totalSize int64, stream io.ReadCloser) (body io.ReadCloser) {
+	return rw.PB.TrackProgress(src, currentSize, totalSize, stream)
+}
+
 // MachineReadableUi is a UI that only outputs machine-readable output
 // to the given Writer.
 type MachineReadableUi struct {
 	Writer io.Writer
-	NoopProgressTracker
+	PB     NoopProgressTracker
 }
 
 var _ Ui = new(MachineReadableUi)
@@ -366,11 +374,15 @@ func (u *MachineReadableUi) Machine(category string, args ...string) {
 	log.Printf("%d,%s,%s,%s\n", now.Unix(), target, category, argsString)
 }
 
+func (u *MachineReadableUi) TrackProgress(src string, currentSize, totalSize int64, stream io.ReadCloser) (body io.ReadCloser) {
+	return u.PB.TrackProgress(src, currentSize, totalSize, stream)
+}
+
 // TimestampedUi is a UI that wraps another UI implementation and
 // prefixes each message with an RFC3339 timestamp
 type TimestampedUi struct {
 	Ui Ui
-	*uiProgressBar
+	PB getter.ProgressTracker
 }
 
 var _ Ui = new(TimestampedUi)
@@ -395,6 +407,10 @@ func (u *TimestampedUi) Machine(message string, args ...string) {
 	u.Ui.Machine(message, args...)
 }
 
+func (u *TimestampedUi) TrackProgress(src string, currentSize, totalSize int64, stream io.ReadCloser) (body io.ReadCloser) {
+	return u.Ui.TrackProgress(src, currentSize, totalSize, stream)
+}
+
 func (u *TimestampedUi) timestampLine(string string) string {
 	return fmt.Sprintf("%v: %v", time.Now().Format(time.RFC3339), string)
 }
@@ -404,7 +420,7 @@ func (u *TimestampedUi) timestampLine(string string) string {
 type SafeUi struct {
 	Sem chan int
 	Ui  Ui
-	*uiProgressBar
+	PB  getter.ProgressTracker
 }
 
 var _ Ui = new(SafeUi)
@@ -440,3 +456,11 @@ func (u *SafeUi) Machine(t string, args ...string) {
 	u.Ui.Machine(t, args...)
 	<-u.Sem
 }
+
+func (u *SafeUi) TrackProgress(src string, currentSize, totalSize int64, stream io.ReadCloser) (body io.ReadCloser) {
+	u.Sem <- 1
+	ret := u.Ui.TrackProgress(src, currentSize, totalSize, stream)
+	<-u.Sem
+
+	return ret
+}