How to get both the chardata and the value of the attributes of an XML tag when decoding it in Golang

My XML file resembles to something like this:

<page>
    <title>Antoine Meillet</title>
    <ns>0</ns>
    <id>3</id>
    <revision>
      <id>178204512</id>
      <parentid>178097574</parentid>
      <timestamp>2020-12-30T10:12:14Z</timestamp>
      <contributor>
        <username>Rovo</username>
        <id>34820</id>
      </contributor>
      <minor />
      <model>wikitext</model>
      <format>text/x-wiki</format>
      <text bytes="11274" xml:space="preserve">
        a lot of text
      </text>
      <sha1>ikqy1f9ppwo8eo38a0hh817eynr40vg</sha1>
    </revision>
  </page>

My goal is to filter out a lot of those tags and only keep the page tag and those inner tags: title, id, text.

So far, I have been able to successfully extract the page tag with title and id having the right value.
This is what I get:

<page>
 <title>Antoine Meillet</title>
 <id>3</id>
 <text bytes="0" xml:space=""></text>
</page>
<page>
 <title>Algèbre linéaire</title>
 <id>7</id>
 <text bytes="0" xml:space=""></text>
</page>

So the problem here as you can see is that the text tag doesn't have the right values for its attributes and the absence of text in it.

I have achieved this using this piece of code:

package main

import (
	"encoding/xml"
	"fmt"
	"io"
	"os"
)

type Page struct {
	XMLName xml.Name `xml:"page"`
	Title   string   `xml:"title"`
	Id      int64    `xml:"id"`
	Text    struct {
		Key   float32 `xml:"bytes,attr"`
		Space string  `xml:"xml:space,attr"`
	} `xml:"text"`
}

func main() {
	frwikiXML, err := os.Open("frwiki10000.xml")
	if err != nil {
		fmt.Println(err)
	}
	cleanedWikiXML, err := os.Create("cleaned_fr_wiki.xml")
	if err != nil {
		fmt.Println(err)
	}

	cleanXMLEncoder := xml.NewEncoder(cleanedWikiXML)
	cleanXMLEncoder.Indent("", " ")

	frwikiDecoder := xml.NewDecoder(frwikiXML)
	for {
		t, tokenErr := frwikiDecoder.Token()
		if tokenErr != nil {
			if tokenErr == io.EOF {
				break
			}
			fmt.Errorf("decoding token: %w", tokenErr)
		}
		switch t := t.(type) {
		case xml.StartElement:
			if t.Name.Local == "page" {
				var page Page
				if err := frwikiDecoder.DecodeElement(&page, &t); err != nil {
					fmt.Errorf("decoding element %q: %v", t.Name.Local, err)
				}
				fmt.Println("Element was decoded successfully.")
				fmt.Printf("Page title: %v\n Page id: %d\n", page.Title, page.Id)
				fmt.Printf("Text: %v", page.Text)
				cleanXMLEncoder.Encode(page)
			}
		}
	}

	defer frwikiXML.Close()
	defer cleanedWikiXML.Close()
}

How would I be able to solve this problem, please?

Thanks.

To parse huge file xml file, use the standard xml Decoder.

Call Token to read tokens one by one. When a start element with required name is found ("page"), call DecodeElement to decode the element and prepare result to next actions.

type Page struct {
XMLName  xml.Name `xml:"page"`
Title    string   `xml:"title"`
Id       int64    `xml:"id"`
Revision struct {
Text struct {
Key   float32 `xml:"bytes,attr"`
Space string  `xml:"xml:space,attr"`
} `xml:"text"`
} `xml:"revision"`
}
type PageTarget struct {
XMLName xml.Name `xml:"page"`
Title   string   `xml:"title"`
Id      int64    `xml:"id"`
Text    struct {
Key   float32 `xml:"bytes,attr"`
Space string  `xml:"xml:space,attr"`
} `xml:"text"`
}

	dec := xml.NewDecoder(strings.NewReader(sample))
loop:
for {
tok, err := dec.Token()
switch {
case err != nil && err != io.EOF:
panic(err)
case err == io.EOF:
break loop
case tok == nil:
fmt.Println("token is nill")
}
switch se := tok.(type) {
case xml.StartElement:
if se.Name.Local == "page" {
var page Page
if err := dec.DecodeElement(&page, &se); err != nil {
panic(err)
}
target := PageTarget{
XMLName: page.XMLName,
Id:      page.Id,
Title:   page.Title,
Text:    page.Revision.Text,
}
out, err := xml.MarshalIndent(target, " ", "  ")
if err != nil {
panic(err)
}
fmt.Println(string(out))
}
}
}

<kbd>PLAYGROUND</kbd>

Simply decoding to the struct and encoding again will satisfy your goal.

Please check this: https://go.dev/play/p/69vjlve4P6p