common/helpers: fix decoding of strings as slice

We use the previous version of the function from upstream.

common/helpers/mapstructure.go

@@ -36,12 +36,33 @@ func GetMapStructureDecoderConfig(config interface{}, hooks ...mapstructure.Deco
 				mapstructure.ComposeDecodeHookFunc(mapstructureUnmarshallerHookFuncs...),
 				mapstructure.TextUnmarshallerHookFunc(),
 				mapstructure.StringToTimeDurationHookFunc(),
-				mapstructure.StringToSliceHookFunc(","),
+				StringToSliceHookFunc(","),
 			),
 		),
 	}
 }
 
+// StringToSliceHookFunc returns a DecodeHookFunc that converts
+// string to []string by splitting on the given sep.
+func StringToSliceHookFunc(sep string) mapstructure.DecodeHookFunc {
+	return func(
+		f reflect.Kind,
+		t reflect.Kind,
+		data interface{},
+	) (interface{}, error) {
+		if f != reflect.String || t != reflect.Slice {
+			return data, nil
+		}
+
+		raw := data.(string)
+		if raw == "" {
+			return []string{}, nil
+		}
+
+		return strings.Split(raw, sep), nil
+	}
+}
+
 // ProtectedDecodeHookFunc wraps a DecodeHookFunc to recover and returns an error on panic.
 func ProtectedDecodeHookFunc(hook mapstructure.DecodeHookFunc) mapstructure.DecodeHookFunc {
 	return func(from, to reflect.Value) (v interface{}, err error) {

common/helpers/mapstructure_test.go

@@ -37,6 +37,28 @@ func TestMapStructureMatchName(t *testing.T) {
 	}
 }
 
+func TestStringToSliceHookFunc(t *testing.T) {
+	type Configuration struct {
+		A []string
+		B []int
+	}
+	TestConfigurationDecode(t, ConfigurationDecodeCases{
+		{
+			Initial: func() interface{} { return Configuration{} },
+			Configuration: func() interface{} {
+				return gin.H{
+					"a": "blip,blop",
+					"b": "1,2,3,4",
+				}
+			},
+			Expected: Configuration{
+				A: []string{"blip", "blop"},
+				B: []int{1, 2, 3, 4},
+			},
+		},
+	})
+}
+
 func TestProtectedDecodeHook(t *testing.T) {
 	var configuration struct {
 		A string