CDATA support

[estronnom]

Hi! I was wondering is there any way to use CDATA element with your lib?
Thanks

[twpayne]

What exactly do you want to achieve? Could you give an exact example with code and example output?

[estronnom]

The KML structure I'm trying to get should look like this:

<ExtendedData>
    <Data name="extraImage">
        <![CDATA[files/image_1.jpg]]>
    </Data>
</ExtendedData>

So, the code example to generate it with go-kml may look like this:

kml.ExtendedData(
		kml.Data(
			"extraImage",
			kml.CharacterData("files/image_1.jpg"), //CDATA
		),
	)

Also, an xml struct to parse such structure should utilize chardata encoding/xml tag:

type DataWithCDATA struct {
    ChardataValue string   `xml:",chardata"`
}

[twpayne]

Thanks for the follow-up.

CDATA elements are used to escape character data. The standard library's encoding/xml (on which github.com/twpayne/go-kml is based) automatically escapes character data if needed, so, as a user you never need to think about whether you have to use CDATA.

As files/image_1.jpg does not need escaping, the following two XML documents are equivalent:

<ExtendedData>
    <Data name="extraImage">
        <![CDATA[files/image_1.jpg]]>
    </Data>
</ExtendedData>

<ExtendedData>
    <Data name="extraImage">files/image_1.jpg</Data>
</ExtendedData>

However, if the KML you are generated is consumed by a broken code that expects a CDATA directive, then you can pass any Go value that implements encoding/xml.Marshaler as a KML child element, so you can force use of a CDATA directive.

For example:

package main

import (
	"encoding/xml"
	"os"

	"github.com/twpayne/go-kml/v3"
)

type CData string

func (c CData) MarshalXML(e *xml.Encoder, startElement xml.StartElement) error {
	directive := xml.Directive([]byte("[CDATA[" + string(c) + "]]"))
	return e.EncodeToken(directive)
}

func main() {
	extendedData := kml.ExtendedData(
		kml.Data(
			"extraImage",
			CData("files/image1.jpg"),
		),
	)

	e := xml.NewEncoder(os.Stdout)
	e.Indent("", "\t")
	e.Encode(extendedData)
}

which outputs:

<ExtendedData>
	<Data name="extraImage"><![CDATA[files/image1.jpg]]></Data>
</ExtendedData>

You can see this example in the Go playground.

If you can avoid using a broken XML parser then you don't need CDATA.

[estronnom]

Thank you! That does exactly what I needed, closing this.