restic: introduce Counter interface to decouple from ui/progress (#21861)

decouple restic and ui/progress packages

internal/ui/progress/counter.go

@@ -3,6 +3,8 @@ package progress
 import (
 	"sync/atomic"
 	"time"
+
+	"github.com/restic/restic/internal/restic"
 )
 
 // A Func is a callback for a Counter.
@@ -20,6 +22,8 @@ type Counter struct {
 	value, max atomic.Uint64
 }
 
+var _ restic.Counter = (*Counter)(nil)
+
 // NewCounter starts a new Counter.
 func NewCounter(interval time.Duration, total uint64, report Func) *Counter {
 	c := new(Counter)
@@ -35,16 +39,12 @@ func NewCounter(interval time.Duration, total uint64, report Func) *Counter {
 
 // Add v to the Counter. This method is concurrency-safe.
 func (c *Counter) Add(v uint64) {
-	if c != nil {
-		c.value.Add(v)
-	}
+	c.value.Add(v)
 }
 
 // SetMax sets the maximum expected counter value. This method is concurrency-safe.
 func (c *Counter) SetMax(max uint64) {
-	if c != nil {
-		c.max.Store(max)
-	}
+	c.max.Store(max)
 }
 
 // Get returns the current value and the maximum of c.
@@ -54,7 +54,5 @@ func (c *Counter) Get() (v, max uint64) {
 }
 
 func (c *Counter) Done() {
-	if c != nil {
-		c.Updater.Done()
-	}
+	c.Updater.Done()
 }

internal/ui/progress/counter_test.go

@@ -58,11 +58,3 @@ func TestCounter(t *testing.T) {
 
 	t.Log("number of calls:", ncalls)
 }
-
-func TestCounterNil(_ *testing.T) {
-	// Shouldn't panic.
-	var c *progress.Counter
-	c.Add(1)
-	c.SetMax(42)
-	c.Done()
-}

internal/ui/progress/printer.go

@@ -1,14 +1,18 @@
 package progress
 
+import (
+	"github.com/restic/restic/internal/restic"
+)
+
 // A Printer can can return a new counter or print messages
 // at different log levels.
 // It must be safe to call its methods from concurrent goroutines.
 type Printer interface {
 	// NewCounter returns a new progress counter. It is not shown if --quiet or --json is specified.
-	NewCounter(description string) *Counter
+	NewCounter(description string) restic.Counter
 	// NewCounterTerminalOnly returns a new progress counter that is only shown if stdout points to a
 	// terminal. It is not shown if --quiet or --json is specified.
-	NewCounterTerminalOnly(description string) *Counter
+	NewCounterTerminalOnly(description string) restic.Counter
 
 	// E reports an error. This message is always printed to stderr.
 	// Appends a newline if not present.
@@ -42,12 +46,12 @@ func NewNoopPrinter() Printer {
 	return &noopPrinter{}
 }
 
-func (*noopPrinter) NewCounter(_ string) *Counter {
-	return nil
+func (*noopPrinter) NewCounter(_ string) restic.Counter {
+	return restic.NoopCounter
 }
 
-func (*noopPrinter) NewCounterTerminalOnly(_ string) *Counter {
-	return nil
+func (*noopPrinter) NewCounterTerminalOnly(_ string) restic.Counter {
+	return restic.NoopCounter
 }
 
 func (*noopPrinter) E(_ string, _ ...interface{}) {}

internal/ui/progress/terminal.go

@@ -6,6 +6,7 @@ import (
 	"strconv"
 	"time"
 
+	"github.com/restic/restic/internal/restic"
 	"github.com/restic/restic/internal/ui"
 )
 
@@ -27,9 +28,9 @@ func CalculateProgressInterval(show bool, json bool, canUpdateStatus bool) time.
 }
 
 // newProgressMax returns a progress.Counter that prints to terminal if provided.
-func newProgressMax(show bool, max uint64, description string, term ui.Terminal) *Counter {
+func newProgressMax(show bool, max uint64, description string, term ui.Terminal) restic.Counter {
 	if !show {
-		return nil
+		return restic.NoopCounter
 	}
 	interval := CalculateProgressInterval(show, false, term.CanUpdateStatus())
 
@@ -57,11 +58,11 @@ type terminalPrinter struct {
 	v    uint
 }
 
-func (t *terminalPrinter) NewCounter(description string) *Counter {
+func (t *terminalPrinter) NewCounter(description string) restic.Counter {
 	return newProgressMax(t.v > 0, 0, description, t.term)
 }
 
-func (t *terminalPrinter) NewCounterTerminalOnly(description string) *Counter {
+func (t *terminalPrinter) NewCounterTerminalOnly(description string) restic.Counter {
 	return newProgressMax(t.v > 0 && t.term.OutputIsTerminal(), 0, description, t.term)
 }