fix race condition in (*Spinner).Print

manager.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"os/signal"
 	"runtime"
+	"sync"
 	"time"
 
 	"github.com/chelnak/ysmrr/pkg/animations"
@@ -32,7 +33,9 @@ type SpinnerManager interface {
 }
 
 type spinnerManager struct {
-	spinners      []*Spinner
+	spinners []*Spinner
+	mutex    sync.RWMutex
+
 	chars         []string
 	frameDuration time.Duration
 	spinnerColor  colors.Color
@@ -58,12 +61,18 @@ func (sm *spinnerManager) AddSpinner(message string) *Spinner {
 		HasUpdate:     sm.hasUpdate,
 	}
 	spinner := NewSpinner(opts)
+
+	sm.mutex.Lock()
+	defer sm.mutex.Unlock()
 	sm.spinners = append(sm.spinners, spinner)
+
 	return spinner
 }
 
 // GetSpinners returns the spinners managed by the manager.
 func (sm *spinnerManager) GetSpinners() []*Spinner {
+	sm.mutex.RLock()
+	defer sm.mutex.RUnlock()
 	return sm.spinners
 }
 
@@ -96,6 +105,8 @@ func (sm *spinnerManager) Stop() {
 	sm.ticks.Stop()
 
 	// Persist the final frame for each spinner.
+	sm.mutex.Lock()
+	defer sm.mutex.Unlock()
 	for _, s := range sm.spinners {
 		tput.ClearLine(sm.writer)
 		s.Print(sm.writer, sm.chars[sm.frame])
@@ -173,11 +184,13 @@ func (sm *spinnerManager) renderFrame(animate bool) {
 		return
 	}
 
-	tput.BufScreen(sm.writer, len(sm.spinners))
-	tput.Cuu(sm.writer, len(sm.spinners))
+	spinners := sm.GetSpinners()
+
+	tput.BufScreen(sm.writer, len(spinners))
+	tput.Cuu(sm.writer, len(spinners))
 	tput.Sc(sm.writer)
 
-	for _, s := range sm.spinners {
+	for _, s := range spinners {
 		tput.ClearLine(sm.writer)
 		s.Print(sm.writer, sm.chars[sm.frame])
 	}

manager_test.go

@@ -2,6 +2,7 @@ package ysmrr_test
 
 import (
 	"bytes"
+	"sync"
 	"testing"
 	"time"
 
@@ -105,3 +106,24 @@ func TestGetMessageColor(t *testing.T) {
 
 	assert.Equal(t, colors.FgHiBlue, spinnerManager.GetMessageColor())
 }
+
+func TestManagerConcurrentSpinnerUsage(t *testing.T) {
+	var out bytes.Buffer
+	spinnerManager := ysmrr.NewSpinnerManager(ysmrr.WithWriter(&out))
+	spinnerManager.Start()
+
+	var wg sync.WaitGroup
+	for _, msg := range []string{"test-1", "test-2", "test-3"} {
+		wg.Add(1)
+		go func(wg *sync.WaitGroup, msg string) {
+			defer wg.Done()
+
+			s := spinnerManager.AddSpinner(msg)
+			s.UpdateMessage(msg + "-update")
+			s.Complete()
+		}(&wg, msg)
+	}
+	wg.Wait()
+
+	spinnerManager.Stop()
+}

spinner.go

@@ -85,6 +85,8 @@ func (s *Spinner) Print(w io.Writer, char string) {
 		print(w, char, s.spinnerColor)
 	}
 
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
 	message := fmt.Sprintf(" %s\r\n", s.message)
 	print(w, message, s.messageColor)
 }