Creating invalid XML: Undefined prefix xsi found

[onli]

At https://www.onli-blogging.de/feeds/index.rss2, I have an RSS feed with an empty description:

<description></description>

OXML produces this hash element from that:

channel: {
    ...
    description: nil

Sound so far, but when then building XML from that has, the XML builder is adding xsi:nil

<description xsi:nil="true">

(And also seems to switch to a non-closed element, which would be a separate problem). The resulting XML now can not be parsed by the RSS gem, I get this error:

RSS::NotWellFormedError: This is not well formed XML
Undefined prefix xsi found

I think the RSS gem is correct here, the xsi namespace is indeed not defined and the attribute should not have been added like this.

oxml/lib/oxml/builder.rb

Line 37 in 5fa61c1

builder.element(Utils.camelize(key), 'xsi:nil': 'true')

is the responsible line, already part of cf663ff, but I'm missing the context here why this was added.

I would propose that OXML should not add the xsi attribute at all.