fix: fall back after image transport init failure

pkg/deckoder/extractor/image/image.go

@@ -116,7 +116,12 @@ func newSource(ctx context.Context, imageName string, transports []string, sys *
 		var src imageTypes.ImageCloser
 		src, err = image.FromSource(ctx, sys, rawSource)
 		if err != nil {
-			return nil, nil, fmt.Errorf("failed to initialize: %w", err)
+			err = fmt.Errorf("failed to initialize: %w", err)
+			if closeErr := rawSource.Close(); closeErr != nil {
+				err = fmt.Errorf("%w; failed to close source: %v", err, closeErr)
+			}
+			// try next transport
+			continue
 		}
 
 		return rawSource, src, nil

pkg/deckoder/extractor/image/image_test.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 	"testing"
 
+	imageTypes "github.com/containers/image/v5/types"
 	"github.com/goodwithtech/dockle/pkg/types"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -172,6 +173,41 @@ func TestNewImage(t *testing.T) {
 	}
 }
 
+func TestNewSourceFallsBackAfterInitializationFailure(t *testing.T) {
+	invalid := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "application/vnd.docker.distribution.manifest.v2+json")
+		_, _ = w.Write([]byte(`{invalid}`))
+	}))
+	defer invalid.Close()
+
+	manifest, err := ioutil.ReadFile("testdata/manifest.json")
+	require.NoError(t, err)
+	valid := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "application/vnd.docker.distribution.manifest.v2+json")
+		_, _ = w.Write(manifest)
+	}))
+	defer valid.Close()
+
+	transports := []string{
+		fmt.Sprintf("docker://%s/", strings.TrimPrefix(invalid.URL, "http://")),
+		fmt.Sprintf("docker://%s/", strings.TrimPrefix(valid.URL, "http://")),
+	}
+	sys := &imageTypes.SystemContext{
+		DockerDisableV1Ping:         true,
+		DockerInsecureSkipTLSVerify: imageTypes.OptionalBoolTrue,
+	}
+
+	rawSource, source, err := newSource(
+		context.Background(),
+		"foobar:latest",
+		transports,
+		sys,
+	)
+	require.NoError(t, err)
+	require.NoError(t, source.Close())
+	require.NoError(t, rawSource.Close())
+}
+
 func TestRealImage_LayerIDs(t *testing.T) {
 	tests := []struct {
 		name      string