fix(concurrency): add mutex to protect repoFailList and out in updateCharts

Signed-off-by: Suleiman Dibirov <idsulik@gmail.com>

cmd/helm/repo_update.go

@@ -116,15 +116,22 @@ func (o *repoUpdateOptions) run(out io.Writer) error {
 
 func updateCharts(repos []*repo.ChartRepository, out io.Writer, failOnRepoUpdateFail bool) error {
 	fmt.Fprintln(out, "Hang tight while we grab the latest from your chart repositories...")
-	var wg sync.WaitGroup
-	var repoFailList []string
+
+	var (
+		wg           sync.WaitGroup
+		mu           sync.Mutex
+		repoFailList []string
+	)
+
 	for _, re := range repos {
 		wg.Add(1)
 		go func(re *repo.ChartRepository) {
 			defer wg.Done()
 			if _, err := re.DownloadIndexFile(); err != nil {
+				mu.Lock()
 				fmt.Fprintf(out, "...Unable to get an update from the %q chart repository (%s):\n\t%s\n", re.Config.Name, re.Config.URL, err)
 				repoFailList = append(repoFailList, re.Config.URL)
+				mu.Unlock()
 			} else {
 				fmt.Fprintf(out, "...Successfully got an update from the %q chart repository\n", re.Config.Name)
 			}

cmd/helm/repo_update_test.go

@@ -205,7 +205,14 @@ func TestUpdateChartsFailWithError(t *testing.T) {
 	defer ts.Stop()
 
 	var invalidURL = ts.URL() + "55"
-	r, err := repo.NewChartRepository(&repo.Entry{
+	r1, err := repo.NewChartRepository(&repo.Entry{
+		Name: "charts",
+		URL:  invalidURL,
+	}, getter.All(settings))
+	if err != nil {
+		t.Error(err)
+	}
+	r2, err := repo.NewChartRepository(&repo.Entry{
 		Name: "charts",
 		URL:  invalidURL,
 	}, getter.All(settings))
@@ -214,7 +221,7 @@ func TestUpdateChartsFailWithError(t *testing.T) {
 	}
 
 	b := bytes.NewBuffer(nil)
-	err = updateCharts([]*repo.ChartRepository{r}, b, true)
+	err = updateCharts([]*repo.ChartRepository{r1, r2}, b, true)
 	if err == nil {
 		t.Error("Repo update should return error because update of repository fails and 'fail-on-repo-update-fail' flag set")
 		return