xml-ns-workaround.go

package main

import (
	"encoding/xml"
	"fmt"
	"strings"
)

func main() {

	// f := os.Stdin

	f := strings.NewReader(`<rdf:RDF
  xmlns="http://purl.org/rss/1.0/"
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:content="http://purl.org/rss/1.0/modules/content/"
  xmlns:media="http://search.yahoo.com/mrss/"
  xml:lang="en-US">
  <media:thumbnail height="30" width="30"
    url="https://avatars.githubusercontent.com/u/1024025?s=30&amp;v=4" />
</rdf:RDF>`)

	var s struct {
		XMLName    xml.Name
		Attributes []xml.Attr `xml:",any,attr,omitempty"`

		Thumbnail *struct {
			XMLName    xml.Name
			Attributes []xml.Attr `xml:",any,attr,omitempty"`
		} `xml:"thumbnail"`

		// XMLNs   *xml.Attr `xml:"xmlns,attr,omitempty"`
		// Language *xml.Attr `xml:"lang,attr,omitempty"`
		// Media   *xml.Attr `xml:"xmlns media,attr,omitempty"`
		// RDF     *xml.Attr `xml:"xmlns rdf,attr,omitempty"`
		// DC      *xml.Attr `xml:"xmlns dc,attr,omitempty"`
		// Content *xml.Attr `xml:"xmlns content,attr,omitempty"`
	}

	err := xml.NewDecoder(f).Decode(&s)
	if err != nil {
		panic(err)
	}

	fmt.Printf("%+v\n", s)

	{

		var nsMap = make(map[string]string)

		for i := range s.Attributes {
			if s.Attributes[i].Name.Space == "xmlns" && s.Attributes[i].Name.Local != "" {
				nsMap[s.Attributes[i].Value] = s.Attributes[i].Name.Local
				s.Attributes[i].Name.Local = s.Attributes[i].Name.Space + ":" + s.Attributes[i].Name.Local
				s.Attributes[i].Name.Space = ""
			}
		}

		if local, ok := nsMap[s.XMLName.Space]; ok {
			s.XMLName.Local = local + ":" + s.XMLName.Local
			s.XMLName.Space = ""
		}

		if s.Thumbnail != nil {
			if local, ok := nsMap[s.Thumbnail.XMLName.Space]; ok {
				s.Thumbnail.XMLName.Local = local + ":" + s.Thumbnail.XMLName.Local
				s.Thumbnail.XMLName.Space = ""
			}
		}

		b, err := xml.Marshal(s)
		if err != nil {
			panic(err)
		}

		fmt.Println(string(b))
	}
}