encoder/filename: Wrap scsu package

lib/encoder/filename/decode.go

@@ -7,7 +7,6 @@ import (
 	"errors"
 	"sync"
 
-	"github.com/dop251/scsu"
 	"github.com/klauspost/compress/huff0"
 )
 
@@ -51,7 +50,7 @@ func DecodeBytes(table byte, data []byte) (string, error) {
 	case tableReserved:
 		return "", ErrUnsupported
 	case tableSCSUPlain:
-		return scsu.Decode(data)
+		return scsuDecode(data)
 	case tableRLE:
 		if len(data) < 2 {
 			return "", ErrCorrupted
@@ -88,7 +87,7 @@ func DecodeBytes(table byte, data []byte) (string, error) {
 			return "", ErrCorrupted
 		}
 		if table == tableSCSU {
-			return scsu.Decode(name)
+			return scsuDecode(name)
 		}
 		return string(name), nil
 	}

lib/encoder/filename/decode_test.go

@@ -1,6 +1,9 @@
 package filename
 
-import "testing"
+import (
+	"runtime"
+	"testing"
+)
 
 func TestDecode(t *testing.T) {
 	tests := []struct {
@@ -117,6 +120,10 @@ func TestDecode(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			got, err := Decode(tt.encoded)
 			if (err != nil) != tt.wantErr {
+				if err != nil && err.Error() == scsuNotEnabled && runtime.Version() < "go1.13" {
+					t.Skip(err.Error())
+					return
+				}
 				if tt.encoded == "" && tt.want != "" {
 					proposed := Encode(tt.want)
 					table := decodeMap[proposed[0]] - 1

lib/encoder/filename/encode.go

@@ -4,7 +4,6 @@ import (
 	"encoding/base64"
 	"encoding/binary"
 
-	"github.com/dop251/scsu"
 	"github.com/klauspost/compress/huff0"
 )
 
@@ -38,7 +37,7 @@ func EncodeBytes(s string) (table byte, payload []byte) {
 		if i == tableSCSU {
 			var err error
 			olen := len(org)
-			org, err = scsu.EncodeStrict(s, make([]byte, 0, len(org)))
+			org, err = scsuEncodeStrict(s, make([]byte, 0, len(org)))
 			if err != nil || olen <= len(org) {
 				continue
 			}

lib/encoder/filename/scsu.go

@@ -0,0 +1,16 @@
+package filename
+
+import "errors"
+
+const scsuNotEnabled = "scsu encoding not enabled in this build due to old go version"
+
+// Functions wrap scsu package, since it doesn't build on old Go versions.
+// Remove once v1.13 is minimum supported version.
+
+var scsuDecode = func(b []byte) (string, error) {
+	return "", errors.New(scsuNotEnabled)
+}
+
+var scsuEncodeStrict = func(src string, dst []byte) ([]byte, error) {
+	return nil, errors.New(scsuNotEnabled)
+}

lib/encoder/filename/scsu_go113.go

@@ -0,0 +1,10 @@
+// +build go1.13
+
+package filename
+
+import "github.com/dop251/scsu"
+
+func init() {
+	scsuDecode = scsu.Decode
+	scsuEncodeStrict = scsu.EncodeStrict
+}