encoding/xml: check for exported fields in embedded structs

Addresses issue #12367.

Must be checked in before CL 14010.

Change-Id: I4523a1de112ed02371504e27882659bce8028a9f
Reviewed-on: https://go-review.googlesource.com/14012Reviewed-by: Russ Cox <rsc@golang.org>

src/encoding/xml/marshal_test.go

@@ -139,6 +139,7 @@ type EmbedA struct {
 	EmbedC
 	EmbedB EmbedB
 	FieldA string
+	embedD
 }
 
 type EmbedB struct {
@@ -153,6 +154,11 @@ type EmbedC struct {
 	FieldC  string
 }
 
+type embedD struct {
+	fieldD string
+	FieldE string // Promoted and visible when embedD is embedded.
+}
+
 type NameCasing struct {
 	XMLName struct{} `xml:"casing"`
 	Xy      string
@@ -711,6 +717,9 @@ var marshalTests = []struct {
 				},
 			},
 			FieldA: "A.A",
+			embedD: embedD{
+				FieldE: "A.D.E",
+			},
 		},
 		ExpectXML: `<EmbedA>` +
 			`<FieldB>A.C.B</FieldB>` +
@@ -724,6 +733,7 @@ var marshalTests = []struct {
 			`<FieldC>A.B.C.C</FieldC>` +
 			`</EmbedB>` +
 			`<FieldA>A.A</FieldA>` +
+			`<FieldE>A.D.E</FieldE>` +
 			`</EmbedA>`,
 	},
 

src/encoding/xml/typeinfo.go

@@ -60,7 +60,7 @@ func getTypeInfo(typ reflect.Type) (*typeInfo, error) {
 		n := typ.NumField()
 		for i := 0; i < n; i++ {
 			f := typ.Field(i)
-			if f.PkgPath != "" || f.Tag.Get("xml") == "-" {
+			if (f.PkgPath != "" && !f.Anonymous) || f.Tag.Get("xml") == "-" {
 				continue // Private field
 			}