encoding/xml: unmarshal allow empty, non-string values

When unmarshaling, if an element is empty, eg. '<tag></tag>', and
destination type is int, uint, float or bool, do not attempt to parse
value (""). Set to its zero value instead.

Fixes #13417

Change-Id: I2d79f6d8f39192bb277b1a9129727d5abbb2dd1f
Reviewed-on: https://go-review.googlesource.com/38386
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/src/encoding/xml/read.go b/src/encoding/xml/read.go
index b90271fed3..000d9fbd0e 100644
--- a/src/encoding/xml/read.go
+++ b/src/encoding/xml/read.go
@@ -120,6 +120,9 @@ import (
 // Unmarshal maps an XML element to a pointer by setting the pointer
 // to a freshly allocated value and then mapping the element to that value.
 //
+// A missing element or empty attribute value will be unmarshaled as a zero value.
+// If the field is a slice, a zero value will be appended to the field. Otherwise, the
+// field will be set to its zero value.
 func Unmarshal(data []byte, v interface{}) error {
 	return NewDecoder(bytes.NewReader(data)).Decode(v)
 }
@@ -607,24 +610,40 @@ func copyValue(dst reflect.Value, src []byte) (err error) {
 	default:
 		return errors.New("cannot unmarshal into " + dst0.Type().String())
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		if len(src) == 0 {
+			dst.SetInt(0)
+			return nil
+		}
 		itmp, err := strconv.ParseInt(string(src), 10, dst.Type().Bits())
 		if err != nil {
 			return err
 		}
 		dst.SetInt(itmp)
 	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		if len(src) == 0 {
+			dst.SetUint(0)
+			return nil
+		}
 		utmp, err := strconv.ParseUint(string(src), 10, dst.Type().Bits())
 		if err != nil {
 			return err
 		}
 		dst.SetUint(utmp)
 	case reflect.Float32, reflect.Float64:
+		if len(src) == 0 {
+			dst.SetFloat(0)
+			return nil
+		}
 		ftmp, err := strconv.ParseFloat(string(src), dst.Type().Bits())
 		if err != nil {
 			return err
 		}
 		dst.SetFloat(ftmp)
 	case reflect.Bool:
+		if len(src) == 0 {
+			dst.SetBool(false)
+			return nil
+		}
 		value, err := strconv.ParseBool(strings.TrimSpace(string(src)))
 		if err != nil {
 			return err