feat: If the required chart is already cached, there is no need to download it again

Signed-off-by: ithrael <wh01096045@gmail.com>

pkg/downloader/chart_downloader.go

@@ -97,11 +97,6 @@ func (c *ChartDownloader) DownloadTo(ref, version, dest string) (string, *proven
 		return "", nil, err
 	}
 
-	data, err := g.Get(u.String(), c.Options...)
-	if err != nil {
-		return "", nil, err
-	}
-
 	name := filepath.Base(u.Path)
 	if u.Scheme == registry.OCIScheme {
 		idx := strings.LastIndexByte(name, ':')
@@ -109,9 +104,23 @@ func (c *ChartDownloader) DownloadTo(ref, version, dest string) (string, *proven
 	}
 
 	destfile := filepath.Join(dest, name)
+	_, err = os.Stat(destfile)
+
+	// If the required chart is already cached, there is no need to download it again
+	if err != nil {
+		if os.IsNotExist(err) {
+			data, err := g.Get(u.String(), c.Options...)
+			if err != nil {
+				return "", nil, err
+			}
+
 			if err := fileutil.AtomicWriteFile(destfile, data, 0644); err != nil {
 				return destfile, nil, err
 			}
+		} else {
+			return destfile, nil, err
+		}
+	}
 
 	// If provenance is requested, verify it.
 	ver := &provenance.Verification{}

pkg/downloader/chart_downloader_test.go

@@ -197,7 +197,9 @@ func TestDownloadTo(t *testing.T) {
 		},
 	}
 	cname := "/signtest-0.1.0.tgz"
-	dest := srv.Root()
+	dest := srv.Root() + "/dest"
+	os.Mkdir(dest, 0755)
+
 	where, v, err := c.DownloadTo(srv.URL()+cname, "", dest)
 	if err != nil {
 		t.Fatal(err)
@@ -248,7 +250,8 @@ func TestDownloadTo_TLS(t *testing.T) {
 		Options: []getter.Option{},
 	}
 	cname := "test/signtest"
-	dest := srv.Root()
+	dest := srv.Root() + "/dest"
+	os.Mkdir(dest, 0755)
 	where, v, err := c.DownloadTo(cname, "", dest)
 	if err != nil {
 		t.Fatal(err)