encoding/xml: add support for the omitempty flag
This also changes the behavior of attribute marshalling so
that strings and byte slices are marshalled even if empty.
The omitempty flag may be used to obtain the previous behavior.
Fixes #2899.
R=rsc
CC=golang-dev
https://golang.org/cl/5645050
diff --git a/src/pkg/encoding/xml/marshal.go b/src/pkg/encoding/xml/marshal.go
index 7a05a1b..a2e47cf 100644
--- a/src/pkg/encoding/xml/marshal.go
+++ b/src/pkg/encoding/xml/marshal.go
@@ -52,6 +52,10 @@
// - a field with tag ",comment" is written as an XML comment, not
// subject to the usual marshalling procedure. It must not contain
// the "--" string within it.
+// - a field with a tag including the "omitempty" option is omitted
+// if the field value is empty. The empty values are false, 0, any
+// nil pointer or interface value, and any array, slice, map, or
+// string of length zero.
//
// If a field uses a tag "a>b>c", then the element c will be nested inside
// parent elements a and b. Fields that appear next to each other that name
@@ -63,6 +67,8 @@
// FirstName string `xml:"person>name>first"`
// LastName string `xml:"person>name>last"`
// Age int `xml:"person>age"`
+// Height float `xml:"person>height,omitempty"`
+// Married bool `xml:"person>married"`
// }
//
// xml.Marshal(&Result{Id: 13, FirstName: "John", LastName: "Doe", Age: 42})
@@ -76,6 +82,7 @@
// <last>Doe</last>
// </name>
// <age>42</age>
+// <married>false</married>
// </person>
// </result>
//
@@ -116,6 +123,9 @@
if !val.IsValid() {
return nil
}
+ if finfo != nil && finfo.flags&fOmitEmpty != 0 && isEmptyValue(val) {
+ return nil
+ }
kind := val.Kind()
typ := val.Type()
@@ -183,12 +193,8 @@
continue
}
fv := val.FieldByIndex(finfo.idx)
- switch fv.Kind() {
- case reflect.String, reflect.Array, reflect.Slice:
- // TODO: Should we really do this once ,omitempty is in?
- if fv.Len() == 0 {
- continue
- }
+ if finfo.flags&fOmitEmpty != 0 && isEmptyValue(fv) {
+ continue
}
p.WriteByte(' ')
p.WriteString(finfo.name)
@@ -378,3 +384,21 @@
func (e *UnsupportedTypeError) Error() string {
return "xml: unsupported type: " + e.Type.String()
}
+
+func isEmptyValue(v reflect.Value) bool {
+ switch v.Kind() {
+ case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+ return v.Len() == 0
+ case reflect.Bool:
+ return !v.Bool()
+ case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+ return v.Int() == 0
+ case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+ return v.Uint() == 0
+ case reflect.Float32, reflect.Float64:
+ return v.Float() == 0
+ case reflect.Interface, reflect.Ptr:
+ return v.IsNil()
+ }
+ return false
+}
