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
+}
diff --git a/src/pkg/encoding/xml/marshal_test.go b/src/pkg/encoding/xml/marshal_test.go
index 0f6c0f0..ce51ea8 100644
--- a/src/pkg/encoding/xml/marshal_test.go
+++ b/src/pkg/encoding/xml/marshal_test.go
@@ -38,14 +38,14 @@
type Port struct {
XMLName struct{} `xml:"port"`
- Type string `xml:"type,attr"`
+ Type string `xml:"type,attr,omitempty"`
Comment string `xml:",comment"`
Number string `xml:",chardata"`
}
type Domain struct {
XMLName struct{} `xml:"domain"`
- Country string `xml:",attr"`
+ Country string `xml:",attr,omitempty"`
Name []byte `xml:",chardata"`
Comment []byte `xml:",comment"`
}
@@ -149,11 +149,33 @@
type AttrTest struct {
Int int `xml:",attr"`
- Lower int `xml:"int,attr"`
+ Named int `xml:"int,attr"`
Float float64 `xml:",attr"`
Uint8 uint8 `xml:",attr"`
Bool bool `xml:",attr"`
Str string `xml:",attr"`
+ Bytes []byte `xml:",attr"`
+}
+
+type OmitAttrTest struct {
+ Int int `xml:",attr,omitempty"`
+ Named int `xml:"int,attr,omitempty"`
+ Float float64 `xml:",attr,omitempty"`
+ Uint8 uint8 `xml:",attr,omitempty"`
+ Bool bool `xml:",attr,omitempty"`
+ Str string `xml:",attr,omitempty"`
+ Bytes []byte `xml:",attr,omitempty"`
+}
+
+type OmitFieldTest struct {
+ Int int `xml:",omitempty"`
+ Named int `xml:"int,omitempty"`
+ Float float64 `xml:",omitempty"`
+ Uint8 uint8 `xml:",omitempty"`
+ Bool bool `xml:",omitempty"`
+ Str string `xml:",omitempty"`
+ Bytes []byte `xml:",omitempty"`
+ Ptr *PresenceTest `xml:",omitempty"`
}
type AnyTest struct {
@@ -549,13 +571,65 @@
{
Value: &AttrTest{
Int: 8,
- Lower: 9,
+ Named: 9,
Float: 23.5,
Uint8: 255,
Bool: true,
- Str: "s",
+ Str: "str",
+ Bytes: []byte("byt"),
},
- ExpectXML: `<AttrTest Int="8" int="9" Float="23.5" Uint8="255" Bool="true" Str="s"></AttrTest>`,
+ ExpectXML: `<AttrTest Int="8" int="9" Float="23.5" Uint8="255"` +
+ ` Bool="true" Str="str" Bytes="byt"></AttrTest>`,
+ },
+ {
+ Value: &AttrTest{Bytes: []byte{}},
+ ExpectXML: `<AttrTest Int="0" int="0" Float="0" Uint8="0"` +
+ ` Bool="false" Str="" Bytes=""></AttrTest>`,
+ },
+ {
+ Value: &OmitAttrTest{
+ Int: 8,
+ Named: 9,
+ Float: 23.5,
+ Uint8: 255,
+ Bool: true,
+ Str: "str",
+ Bytes: []byte("byt"),
+ },
+ ExpectXML: `<OmitAttrTest Int="8" int="9" Float="23.5" Uint8="255"` +
+ ` Bool="true" Str="str" Bytes="byt"></OmitAttrTest>`,
+ },
+ {
+ Value: &OmitAttrTest{},
+ ExpectXML: `<OmitAttrTest></OmitAttrTest>`,
+ },
+
+ // omitempty on fields
+ {
+ Value: &OmitFieldTest{
+ Int: 8,
+ Named: 9,
+ Float: 23.5,
+ Uint8: 255,
+ Bool: true,
+ Str: "str",
+ Bytes: []byte("byt"),
+ Ptr: &PresenceTest{},
+ },
+ ExpectXML: `<OmitFieldTest>` +
+ `<Int>8</Int>` +
+ `<int>9</int>` +
+ `<Float>23.5</Float>` +
+ `<Uint8>255</Uint8>` +
+ `<Bool>true</Bool>` +
+ `<Str>str</Str>` +
+ `<Bytes>byt</Bytes>` +
+ `<Ptr></Ptr>` +
+ `</OmitFieldTest>`,
+ },
+ {
+ Value: &OmitFieldTest{},
+ ExpectXML: `<OmitFieldTest></OmitFieldTest>`,
},
// Test ",any"
diff --git a/src/pkg/encoding/xml/read_test.go b/src/pkg/encoding/xml/read_test.go
index 833eafc..a3b0b1d 100644
--- a/src/pkg/encoding/xml/read_test.go
+++ b/src/pkg/encoding/xml/read_test.go
@@ -97,7 +97,7 @@
}
type Link struct {
- Rel string `xml:"rel,attr"`
+ Rel string `xml:"rel,attr,omitempty"`
Href string `xml:"href,attr"`
}
@@ -109,7 +109,7 @@
}
type Text struct {
- Type string `xml:"type,attr"`
+ Type string `xml:"type,attr,omitempty"`
Body string `xml:",chardata"`
}
diff --git a/src/pkg/encoding/xml/typeinfo.go b/src/pkg/encoding/xml/typeinfo.go
index 5475f29..8e2e450 100644
--- a/src/pkg/encoding/xml/typeinfo.go
+++ b/src/pkg/encoding/xml/typeinfo.go
@@ -36,8 +36,7 @@
fComment
fAny
- // TODO:
- //fOmitEmpty
+ fOmitEmpty
fMode = fElement | fAttr | fCharData | fInnerXml | fComment | fAny
)
@@ -133,20 +132,28 @@
finfo.flags |= fComment
case "any":
finfo.flags |= fAny
+ case "omitempty":
+ finfo.flags |= fOmitEmpty
}
}
// Validate the flags used.
+ valid := true
switch mode := finfo.flags & fMode; mode {
case 0:
finfo.flags |= fElement
case fAttr, fCharData, fInnerXml, fComment, fAny:
- if f.Name != "XMLName" && (tag == "" || mode == fAttr) {
- break
+ if f.Name == "XMLName" || tag != "" && mode != fAttr {
+ valid = false
}
- fallthrough
default:
// This will also catch multiple modes in a single field.
+ valid = false
+ }
+ if finfo.flags&fOmitEmpty != 0 && finfo.flags&(fElement|fAttr) == 0 {
+ valid = false
+ }
+ if !valid {
return nil, fmt.Errorf("xml: invalid tag in field %s of type %s: %q",
f.Name, typ, f.Tag.Get("xml"))
}
