private/protocol/xml/xmlutil: Updated XML encoding

CHANGELOG_PENDING.md

@@ -1,5 +1,6 @@
 ### SDK Features
 
 ### SDK Enhancements
+* `private/protocol/xml/xmlutil`: XML encoding has been updated to include encoding line feed character. ([#3881](https://github.com/aws/aws-sdk-go/pull/3881))
 
 ### SDK Bugs

private/protocol/xml/xmlutil/build.go

@@ -308,6 +308,8 @@ func (b *xmlBuilder) buildScalar(value reflect.Value, current *XMLNode, tag refl
 	if tag.Get("xmlAttribute") != "" { // put into current node's attribute list
 		attr := xml.Attr{Name: xname, Value: str}
 		current.Attr = append(current.Attr, attr)
+	} else if len(xname.Local) == 0 {
+		current.Text = str
 	} else { // regular text node
 		current.AddChild(&XMLNode{Name: xname, Text: str})
 	}

private/protocol/xml/xmlutil/build_test.go

@@ -153,6 +153,12 @@ func TestBuildXML(t *testing.T) {
 			Input:  &namedEmptyPayload{},
 			Expect: "<namedEmptyPayload></namedEmptyPayload>",
 		},
+		"escape line feed and carriage return": {
+			Input: &implicitPayload{
+				StrVal: aws.String("this\nstring\rhas\r\nescapable\n\rcharacters"),
+			},
+			Expect: "<StrVal>this&#xA;string&#xD;has&#xD;&#xA;escapable&#xA;&#xD;characters</StrVal>",
+		},
 	}
 
 	for name, c := range cases {

private/protocol/xml/xmlutil/xml_to_struct.go

@@ -18,6 +18,14 @@ type XMLNode struct {
 	parent     *XMLNode
 }
 
+// textEncoder is a string type alias that implemnts the TextMarshaler interface.
+// This alias type is used to ensure that the line feed (\n) (U+000A) is escaped.
+type textEncoder string
+
+func (t textEncoder) MarshalText() ([]byte, error) {
+	return []byte(t), nil
+}
+
 // NewXMLElement returns a pointer to a new XMLNode initialized to default values.
 func NewXMLElement(name xml.Name) *XMLNode {
 	return &XMLNode{
@@ -130,11 +138,16 @@ func StructToXML(e *xml.Encoder, node *XMLNode, sorted bool) error {
 		attrs = sortedAttrs
 	}
 
-	e.EncodeToken(xml.StartElement{Name: node.Name, Attr: attrs})
+	startElement := xml.StartElement{Name: node.Name, Attr: attrs}
 
 	if node.Text != "" {
-		e.EncodeToken(xml.CharData([]byte(node.Text)))
-	} else if sorted {
+		e.EncodeElement(textEncoder(node.Text), startElement)
+		return e.Flush()
+	}
+
+	e.EncodeToken(startElement)
+
+	if sorted {
 		sortedNames := []string{}
 		for k := range node.Children {
 			sortedNames = append(sortedNames, k)
@@ -154,6 +167,7 @@ func StructToXML(e *xml.Encoder, node *XMLNode, sorted bool) error {
 		}
 	}
 
-	e.EncodeToken(xml.EndElement{Name: node.Name})
+	e.EncodeToken(startElement.End())
+
 	return e.Flush()
 }