Un-resolve xml attribute namespaces

encoding/xml/xml_decoder.go

@@ -38,14 +38,44 @@ func (d NodeDecoder) Token() (t xml.StartElement, done bool, err error) {
 		}
 
 		if t, ok := token.(xml.StartElement); ok {
-			return t, false, err
+			return restoreAttrNamespaces(t), false, err
 		}
 
 		// skip token if it is a comment or preamble or empty space value due to indentation
 		// or if it's a value and is not expected
 	}
 }
 
+// restoreAttrNamespaces update XML attributes to restore the short namespaces found within
+// the raw XML document.
+func restoreAttrNamespaces(node xml.StartElement) xml.StartElement {
+	if len(node.Attr) == 0 {
+		return node
+	}
+
+	// Generate a mapping of XML namespace values to their short names.
+	ns := map[string]string{}
+	for _, a := range node.Attr {
+		if a.Name.Space == "xmlns" {
+			ns[a.Value] = a.Name.Local
+			break
+		}
+	}
+
+	for i, a := range node.Attr {
+		if a.Name.Space == "xmlns" {
+			continue
+		}
+		// By default, xml.Decoder will fully resolve these namespaces. So if you had <foo xmlns:bar=baz bar:bin=hi/>
+		// then by default the second attribute would have the `Name.Space` resolved to `baz`. But we need it to
+		// continue to resolve as `bar` so we can easily identify it later on.
+		if v, ok := ns[node.Attr[i].Name.Space]; ok {
+			node.Attr[i].Name.Space = v
+		}
+	}
+	return node
+}
+
 // GetElement looks for the given tag name at the current level, and returns the element if found, and
 // skipping over non-matching elements. Returns an error if the node is not found, or if an error occurs while walking
 // the document.

encoding/xml/xml_decoder_test.go

@@ -52,6 +52,30 @@ func TestXMLNodeDecoder_Token(t *testing.T) {
 				Attr: []xml.Attr{},
 			},
 		},
+		"attr with namespace": {
+			responseBody: bytes.NewReader([]byte(`<Response><Grantee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="CanonicalUser"></Grantee></Response>`)),
+			expectedStartElement: xml.StartElement{
+				Name: xml.Name{
+					Local: "Grantee",
+				},
+				Attr: []xml.Attr{
+					{
+						Name: xml.Name{
+							Space: "xmlns",
+							Local: "xsi",
+						},
+						Value: "http://www.w3.org/2001/XMLSchema-instance",
+					},
+					{
+						Name: xml.Name{
+							Space: "xsi",
+							Local: "type",
+						},
+						Value: "CanonicalUser",
+					},
+				},
+			},
+		},
 	}
 
 	for name, c := range cases {