How to unmarshal XML attributes with colons?

Question

Some SVG/XML files I'm working with have dashes and colons in attribute names - for example:

<g>
  <a xlink:href="http://example.com" data-bind="121">...</a>
</g>

I'm trying to figure out how to unmarshal these attributes using golang's encoding/xml package. While the dashed attributes works, the ones with the colon doesn't:

[See here for a live example]

package main

import (
    "encoding/xml"
    "fmt"
)

var data = `
<g>
    <a xlink:href="http://example.com" data-bind="121">lala</a>
</g>
`

type Anchor struct {
    DataBind  int    `xml:"data-bind,attr"`  // this works
    XlinkHref string `xml:"xlink:href,attr"` // this fails
}

type Group struct {
    A Anchor `xml:"a"`
}

func main() {
    group := Group{}
    _ = xml.Unmarshal([]byte(data), &group)

    fmt.Printf("%#v\n", group.A)
}

These are seemingly legal attribute names; any idea how to extract the xlink:href one? thanks.

Minorite

Answer 1

Your example fragment is not quite correct, since it does not include an XML namespace binding for the xlink: prefix. What you probably want is:

<g xmlns:xlink="http://www.w3.org/1999/xlink">
  <a xlink:href="http://example.com" data-bind="121">lala</a>
</g>

You can unmarshal this attribute using the namespace URL:

XlinkHref string `xml:"http://www.w3.org/1999/xlink href,attr"`

Here is an updated copy of your example program with the namespace fix.

Fragonard

Just to add, I had trouble getting attributes prefixed with "xml", like xml:lang="eng", but seems like since xml is default(?) you can just use `xml:"lang,attr"` as usual. – Igniter

Well, the xml: prefix for attributes doesn't actually identify an XML namespace. It was defined before the XML Namespace spec. – Fragonard

An example for what localhost is referring to above, that failing line would change to xml:"href,attr" .. like so play.golang.org/p/30p2ebQMD0 – Hemminger