XML Unmarshal被并行标记绊倒了

Question

I'm working on an RSS reader application and running into an issue with The New York Times RSS feed. I've narrowed the issue down to the following XML (unnecessary fields omitted):

<item>
  <link>https://www.nytimes.com/2017/09/25/briefing/nfl-angela-merkel-iraqi-kurdistan.html?partner=rss&amp;emc=rss</link>
  <atom:link rel="standout" href="https://www.nytimes.com/2017/09/25/briefing/nfl-angela-merkel-iraqi-kurdistan.html?partner=rss&amp;emc=rss"/>
  <pubDate>Mon, 25 Sep 2017 13:36:07 GMT</pubDate>
</item>

I'm trying to parse it into the following structure:

type item struct {
    Link    string `xml:"link"`
    PubDate string `xml:"pubDate"`
}

When parsed, the Link field is blank. However, by deleting the atom:link field it works fine. I think the similarity in the tags names is confusing the parser. I have a go playground that demonstrates the issue, and that removing that line fixes it: https://play.golang.org/p/fUbLhSbo5K How can I work around this issue? It's not really feasible to special case it because there could be other feeds that do this too.

Answer 1

This is a long-standing documentation bug in Go's encoding/xml package. Basically, when you don't specify a namespace, the field will match any namespace instead of no namespace. In fact, there is no way to make a field match only when there is no namespace. If your XML has a namespace, the solution is to explicitly set it:

<item xmlns="foo">
  <link>https://www.nytimes.com/2017/09/25/briefing/nfl-angela-merkel-iraqi-kurdistan.html?partner=rss&amp;emc=rss</link>
  <atom:link rel="standout" href="https://www.nytimes.com/2017/09/25/briefing/nfl-angela-merkel-iraqi-kurdistan.html?partner=rss&amp;emc=rss"/>
  <pubDate>Mon, 25 Sep 2017 13:36:07 GMT</pubDate>
</item>

type item struct {
    Link    string `xml:"foo link"`
    PubDate string `xml:"pubDate"`
}

Playground: https://play.golang.org/p/L9WOhixTKa.

If your link element explicitly doesn't have a namespace, you'll probably have to roll out your own UnmarshalXML method.