encoding/xml: add omitzero option

// This program demonstrates the new omitzero option in encoding/xml.
// It shows that a field with omitzero is omitted when its value is zero.
// The program runs under Go 1.27.1, which already includes the change.

package main

import (
	"encoding/xml"
	"fmt"
)

type Example struct {
	// The omitzero tag causes this field to be omitted when empty.
	Name string `xml:"Name,omitempty,omitzero"`
	// A slice that is nil will be omitted, but a zero-length slice will be emitted.
	Items []int `xml:"Item,omitempty,omitzero"`
}

func main() {
	// Create a value with zero fields.
	e := Example{}

	// Marshal to XML.
	data, err := xml.MarshalIndent(e, "", "  ")
	if err != nil {
		panic(err)
	}

	// Print the resulting XML. The Name element is omitted because it is zero.
	// The Items element is omitted because the slice is nil.
	fmt.Println(string(data))
}