transform.Unmarshal for XML docs needs clarification

[faraixyz]

I'm excited for the XML support but I was wondering how things like attributes, tags with a namespace and multiple tags of the same type are handled as they aren't covered in the docs . From the little work I've done, I've found that

• multiple tags of the same name return a map with each instance,
• attributes start with a -. Given that, you need to use the index function,
• it looks like the namespaces are stripped out.

[jmooring]

Please provide a small example with attributes, tags with a namespace, and multiple tags of the same type.

[faraixyz]

With an RSS XML feed like this:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
    <channel>
        <title>RSS Feed</title>
        <link>/</link>
        <atom:id>tag:an.example,2020-01-10:/</atom:id>
        <atom:link href="/feed.rss.xml" rel="self" type="application/rss+xml" />
        <item>
            <title>A</title>
            <link>/a</link>
            <guid>/a</guid>
            <description>Some Stuff</description>
        </item>
        <item>
            <title>B</title>
            <link>/b</link>
            <guid>/b</guid>
            <description>Some More Stuff</description>
        </item>
        <item>
            <title>C</title>
            <link>/c</link>
            <guid>/c</guid>
            <description>Some Stuff Again</description>
        </item>
    </channel>
</rss>

This is dumped

map[-atom:http://www.w3.org/2005/Atom -version:2.0 channel:map[item:[map[description:Some Stuff guid:/a link:/a title:A] map[description:Some More Stuff guid:/b link:/b title:B] map[description:Some Stuff Again guid:/c link:/c title:C]] link:[/ map[-href:/feed.rss.xml -rel:self -type:application/rss+xml]] title:RSS Feed]] 

Accessing things will go like this

{{ $feed.-atom }} => error
{{ index $feed "-atom" }} => http://www.w3.org/2005/Atom
{{ $feed.channel.title }} => RSS Feed
{{ $feed.channel.item }} => [map[...] map[...] map[...]]
{{ $feed.channel.id }} => tag:an.example,2020-01-10:/
{{ index $feed.channel "atom:id" }} => 
{{ index $feed.channel "id" }} => tag:an.example,2020-01-10:/
{{ $feed.link }} => [/ map[-href:/feed.rss.xml -rel:self -type:application/rss+xml]] 

[wgroeneveld]

@jmooring led me here via https://discourse.gohugo.io/t/parsing-xml-in-data-with-hugos-new-xml-support-attributes/36654/2 -- I discovered the same shortcomings in the docs.
Here's my attempt to fix it: #1637