encode/xml: Support XML namespaces

[gopherbot]

by oltoko:

http://play.golang.org/p/J98usiO91P

If you look at this code you expect that Data of the "pers:on"-Tag is
unmarshaled into the Customer struct.
But if you run the code this doesn't happen, because there is a colon in the Tag-Name.
To prove that this code isn't wrong just remove the colon
or use this link:

http://play.golang.org/p/OyDM87mzVh

[davecheney]

Comment 1:

colon is a reserved character in the XML spec[1], it denotes a namespace. The go XML
package does not handle namespaces so your example is equivalent to
http://play.golang.org/p/UbFjiHRhZt
[1] http://www.w3.org/TR/REC-xml/#NT-Name

[gopherbot]

Comment 2 by oltoko:

Thank you for your answer. Sorry for the inconvenience because of this fault.
Are there any plans to improve the go XML package in the future to handle namespaces?

[rsc]

Comment 4:

XML name spaces are already supported.
golang.org/pkg/encoding/xml
"Package xml implements a simple XML 1.0 parser that understands XML name spaces."
However, your example at http://play.golang.org/p/J98usiO91P is not valid XML. In
<ns:tag>, the ns is not an absolute name. It is a relative reference to a URL
defined earlier in the XML. For example, these two stanzas are semantically equivalent
XML
<outer xmlns:pers="http://my.url/">
  <pers:on>Hello</pers:on>
</outer>
<outer xmlns:foo="http://my.url/">
  <foo:on>Hello</foo:on>
</outer>
A corrected version of the example is http://play.golang.org/p/lqxkM3MDeD.
If you must pass malformed XML to the parser, it will cope and assume that the "URL" is
the prefix itself, in which case you can do something like
http://play.golang.org/p/DXosg_tjfj. However, that is more fragile, because it does not
understand alternate encodings of the same XML (using different prefixes but the same
underlying URL) and I don't recommend it.

Status changed to WorkingAsIntended.