encoding/xml: Add CDATA-wrapper output support to xml.Marshal.

Fixes #12963

Change-Id: Icc50dfb6130fe1e189d45f923c2f7408d3cf9401
Reviewed-on: https://go-review.googlesource.com/16047Reviewed-by: Russ Cox <rsc@golang.org>

src/encoding/xml/marshal.go

@@ -768,7 +768,11 @@ func (p *printer) marshalStruct(tinfo *typeInfo, val reflect.Value) error {
 		}
 
 		switch finfo.flags & fMode {
-		case fCharData:
+		case fCDATA, fCharData:
+			emit := EscapeText
+			if finfo.flags&fMode == fCDATA {
+				emit = emitCDATA
+			}
 			if err := s.trim(finfo.parents); err != nil {
 				return err
 			}
@@ -777,7 +781,9 @@ func (p *printer) marshalStruct(tinfo *typeInfo, val reflect.Value) error {
 				if err != nil {
 					return err
 				}
-				Escape(p, data)
+				if err := emit(p, data); err != nil {
+					return err
+				}
 				continue
 			}
 			if vf.CanAddr() {
@@ -787,27 +793,37 @@ func (p *printer) marshalStruct(tinfo *typeInfo, val reflect.Value) error {
 					if err != nil {
 						return err
 					}
-					Escape(p, data)
+					if err := emit(p, data); err != nil {
+						return err
+					}
 					continue
 				}
 			}
 			var scratch [64]byte
 			switch vf.Kind() {
 			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-				Escape(p, strconv.AppendInt(scratch[:0], vf.Int(), 10))
+				if err := emit(p, strconv.AppendInt(scratch[:0], vf.Int(), 10)); err != nil {
+					return err
+				}
 			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-				Escape(p, strconv.AppendUint(scratch[:0], vf.Uint(), 10))
+				if err := emit(p, strconv.AppendUint(scratch[:0], vf.Uint(), 10)); err != nil {
+					return err
+				}
 			case reflect.Float32, reflect.Float64:
-				Escape(p, strconv.AppendFloat(scratch[:0], vf.Float(), 'g', -1, vf.Type().Bits()))
+				if err := emit(p, strconv.AppendFloat(scratch[:0], vf.Float(), 'g', -1, vf.Type().Bits())); err != nil {
+					return err
+				}
 			case reflect.Bool:
-				Escape(p, strconv.AppendBool(scratch[:0], vf.Bool()))
+				if err := emit(p, strconv.AppendBool(scratch[:0], vf.Bool())); err != nil {
+					return err
+				}
 			case reflect.String:
-				if err := EscapeText(p, []byte(vf.String())); err != nil {
+				if err := emit(p, []byte(vf.String())); err != nil {
 					return err
 				}
 			case reflect.Slice:
 				if elem, ok := vf.Interface().([]byte); ok {
-					if err := EscapeText(p, elem); err != nil {
+					if err := emit(p, elem); err != nil {
 						return err
 					}
 				}

src/encoding/xml/marshal_test.go

@@ -356,6 +356,15 @@ type NestedAndComment struct {
 	Comment string   `xml:",comment"`
 }
 
+type CDataTest struct {
+	Chardata string `xml:",cdata"`
+}
+
+type NestedAndCData struct {
+	AB    []string `xml:"A>B"`
+	CDATA string   `xml:",cdata"`
+}
+
 func ifaceptr(x interface{}) interface{} {
 	return &x
 }
@@ -978,6 +987,42 @@ var marshalTests = []struct {
 			MyInt: 42,
 		},
 	},
+	// Test outputting CDATA-wrapped text.
+	{
+		ExpectXML: `<CDataTest></CDataTest>`,
+		Value:     &CDataTest{},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[http://example.com/tests/1?foo=1&bar=baz]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "http://example.com/tests/1?foo=1&bar=baz",
+		},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[Literal <![CDATA[Nested]]]]><![CDATA[>!]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "Literal <![CDATA[Nested]]>!",
+		},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[<![CDATA[Nested]]]]><![CDATA[> Literal!]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "<![CDATA[Nested]]> Literal!",
+		},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[<![CDATA[Nested]]]]><![CDATA[> Literal! <![CDATA[Nested]]]]><![CDATA[> Literal!]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "<![CDATA[Nested]]> Literal! <![CDATA[Nested]]> Literal!",
+		},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[<![CDATA[<![CDATA[Nested]]]]><![CDATA[>]]]]><![CDATA[>]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "<![CDATA[<![CDATA[Nested]]>]]>",
+		},
+	},
+
 	// Test omitempty with parent chain; see golang.org/issue/4168.
 	{
 		ExpectXML: `<Strings><A></A></Strings>`,
@@ -1016,6 +1061,10 @@ var marshalTests = []struct {
 		ExpectXML: `<NestedAndComment><A><B></B><B></B></A><!--test--></NestedAndComment>`,
 		Value:     &NestedAndComment{AB: make([]string, 2), Comment: "test"},
 	},
+	{
+		ExpectXML: `<NestedAndCData><A><B></B><B></B></A><![CDATA[test]]></NestedAndCData>`,
+		Value:     &NestedAndCData{AB: make([]string, 2), CDATA: "test"},
+	},
 }
 
 func TestMarshal(t *testing.T) {

src/encoding/xml/read.go

@@ -431,7 +431,7 @@ func (p *Decoder) unmarshal(val reflect.Value, start *StartElement) error {
 					}
 				}
 
-			case fCharData:
+			case fCDATA, fCharData:
 				if !saveData.IsValid() {
 					saveData = finfo.value(sv)
 				}

src/encoding/xml/typeinfo.go

@@ -31,6 +31,7 @@ type fieldFlags int
 const (
 	fElement fieldFlags = 1 << iota
 	fAttr
+	fCDATA
 	fCharData
 	fInnerXml
 	fComment
@@ -38,7 +39,7 @@ const (
 
 	fOmitEmpty
 
-	fMode = fElement | fAttr | fCharData | fInnerXml | fComment | fAny
+	fMode = fElement | fAttr | fCDATA | fCharData | fInnerXml | fComment | fAny
 )
 
 var tinfoMap = make(map[reflect.Type]*typeInfo)
@@ -130,6 +131,8 @@ func structFieldInfo(typ reflect.Type, f *reflect.StructField) (*fieldInfo, erro
 			switch flag {
 			case "attr":
 				finfo.flags |= fAttr
+			case "cdata":
+				finfo.flags |= fCDATA
 			case "chardata":
 				finfo.flags |= fCharData
 			case "innerxml":
@@ -148,7 +151,7 @@ func structFieldInfo(typ reflect.Type, f *reflect.StructField) (*fieldInfo, erro
 		switch mode := finfo.flags & fMode; mode {
 		case 0:
 			finfo.flags |= fElement
-		case fAttr, fCharData, fInnerXml, fComment, fAny:
+		case fAttr, fCDATA, fCharData, fInnerXml, fComment, fAny:
 			if f.Name == "XMLName" || tag != "" && mode != fAttr {
 				valid = false
 			}

src/encoding/xml/xml.go

@@ -1943,6 +1943,46 @@ func Escape(w io.Writer, s []byte) {
 	EscapeText(w, s)
 }
 
+var (
+	cdataStart  = []byte("<![CDATA[")
+	cdataEnd    = []byte("]]>")
+	cdataEscape = []byte("]]]]><![CDATA[>")
+)
+
+// emitCDATA writes to w the CDATA-wrapped plain text data s.
+// It escapes CDATA directives nested in s.
+func emitCDATA(w io.Writer, s []byte) error {
+	if len(s) == 0 {
+		return nil
+	}
+	if _, err := w.Write(cdataStart); err != nil {
+		return err
+	}
+	for {
+		i := bytes.Index(s, cdataEnd)
+		if i >= 0 && i+len(cdataEnd) <= len(s) {
+			// Found a nested CDATA directive end.
+			if _, err := w.Write(s[:i]); err != nil {
+				return err
+			}
+			if _, err := w.Write(cdataEscape); err != nil {
+				return err
+			}
+			i += len(cdataEnd)
+		} else {
+			if _, err := w.Write(s); err != nil {
+				return err
+			}
+			break
+		}
+		s = s[i:]
+	}
+	if _, err := w.Write(cdataEnd); err != nil {
+		return err
+	}
+	return nil
+}
+
 // procInst parses the `param="..."` or `param='...'`
 // value out of the provided string, returning "" if not found.
 func procInst(param, s string) string {