Use xml Marshal to encode attribute values in encodeOpenTag

xmltree/example_test.go

@@ -190,7 +190,7 @@ func ExampleMarshal() {
 	      <number>2</number>
 	    </chapter>
 	    <chapter>
-	      <title>A Good Going-over.Grace Triumphant."One of Tom Sawyers's Lies".</title>
+	      <title>A Good Going-over.Grace Triumphant.&quot;One of Tom Sawyers's Lies&quot;.</title>
 	      <number>3</number>
 	    </chapter>
 	    <chapter>
@@ -220,7 +220,7 @@ func ExampleMarshal() {
 	// <toc>
 	//   <chapter>Civilizing Huck.Miss Watson.Tom Sawyer Waits.</chapter>
 	//   <chapter>The Boys Escape Jim.Torn Sawyer's Gang.Deep-laid Plans.</chapter>
-	//   <chapter>A Good Going-over.Grace Triumphant."One of Tom Sawyers's Lies".</chapter>
+	//   <chapter>A Good Going-over.Grace Triumphant.&quot;One of Tom Sawyers's Lies&quot;.</chapter>
 	//   <chapter>Huck and the Judge.Superstition.</chapter>
 	// </toc>
 }

xmltree/marshal.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/xml"
 	"io"
+	"strings"
 	"text/template"
 )
 
@@ -22,6 +23,48 @@ var tagTmpl = template.Must(template.New("Marshal XML tags").Parse(
 	{{define "end" -}}
 	</{{.Prefix .Name}}>{{end}}`))
 
+type vContentMapping struct {
+	Decoded string
+	Encoded string
+}
+
+var vContentMappings = []vContentMapping{
+	{Decoded: `&`, Encoded: `&amp;`},
+	{Decoded: `<`, Encoded: `&lt;`},
+	{Decoded: `>`, Encoded: `&gt;`},
+	{Decoded: `"`, Encoded: `&quot;`},
+}
+
+// XML encode any special characters in a plain string.
+// For example & will be encoded as &amp;
+
+func xmlEncodeString(strToEncode string) (string, error) {
+	strEncoded := strToEncode
+
+	for _, mapping := range vContentMappings {
+		strEncoded = strings.Replace(strEncoded, mapping.Decoded, mapping.Encoded, -1)
+	}
+
+	//fmt.Printf("xmlEncodeString([%s]) -> [%s]\n", strToEncode, strEncoded)
+
+	return strEncoded, nil
+}
+
+// XML decode escaped characters in a string.
+// For example &quot; will be encoded as "
+
+func xmlDecodeString(strToDecode string) (string, error) {
+	strDecoded := strToDecode
+
+	for _, mapping := range vContentMappings {
+		strDecoded = strings.Replace(strDecoded, mapping.Encoded, mapping.Decoded, -1)
+	}
+
+	//fmt.Printf("xmlDecodeString([%s]) -> [%s]\n", strToDecode, strDecoded)
+
+	return strDecoded, nil
+}
+
 // Marshal produces the XML encoding of an Element as a self-contained
 // document. The xmltree package may adjust the declarations of XML
 // namespaces if the Element has been modified, or is part of a larger scope,
@@ -96,7 +139,11 @@ func (e *encoder) encode(el, parent *Element, visited map[*Element]struct{}) err
 	}
 	if len(el.Children) == 0 {
 		if len(el.Content) > 0 {
-			e.w.Write(el.Content)
+			mStr, mErr := xmlEncodeString(string(el.Content))
+			if mErr != nil {
+				return mErr
+			}
+			e.w.Write([]byte(mStr))
 		} else {
 			return nil
 		}
@@ -139,10 +186,42 @@ func (e *encoder) encodeOpenTag(el *Element, scope Scope, depth int) error {
 			io.WriteString(e.w, e.indent)
 		}
 	}
+	// Note that a copy of el is used here so that XML encoded attributes are generated
+	var elCopy *Element = &Element{}
+	elCopy.StartElement = xml.StartElement{}
+	elCopy.StartElement.Name = el.StartElement.Name
+	elCopy.StartElement.Attr = make([]xml.Attr, len(el.StartElement.Attr))
+	for i := 0; i < len(el.StartElement.Attr); i++ {
+		elCopy.StartElement.Attr[i] = el.StartElement.Attr[i]
+	}
+	elCopy.Scope = el.Scope
+	// Escape node contents
+	{
+		mStr, mErr := xmlEncodeString(string(el.Content))
+		if mErr != nil {
+			return mErr
+		}
+		elCopy.Content = []byte(mStr)
+	}
+	elCopy.Children = el.Children
+
 	var tag = struct {
 		*Element
 		NS []xml.Name
-	}{Element: el, NS: scope.ns}
+	}{Element: elCopy, NS: scope.ns}
+
+	// XML escape attribute strings held in copy
+	attrs := tag.StartElement.Attr
+	for i := 0; i < len(attrs); i++ {
+		attrStr := attrs[i].Value
+		mStr, mErr := xmlEncodeString(attrStr)
+		if mErr != nil {
+			return mErr
+		}
+		attrs[i].Value = mStr
+	}
+	tag.StartElement.Attr = attrs
+
 	if err := tagTmpl.ExecuteTemplate(e.w, "start", tag); err != nil {
 		return err
 	}