keyValueXml5.groovy

def kvmap = [
  key1: "value1",
  key2: "value2",
  key3: [
    "key3-1" : "value3-1",
    "key3-2" : "value3-2",
  ],
]

LinkedHashMap.metaClass.toXml = { builder ->
  delegate.each { k, v ->
    builder."$k" {
      v in String ? builder.mkp.yield(v) : v.toXml(builder)
    }
  }
}

def expect = '''\
<langs type="current">
  <key1>value1</key1>
  <key2>value2</key2>
  <key3>
    <key3-1>value3-1</key3-1>
    <key3-2>value3-2</key3-2>
  </key3>
</langs>'''

assert new StringWriter().with {
  new groovy.xml.MarkupBuilder(delegate).with {
    doubleQuotes = true
    langs(type: 'current') {
      kvmap.toXml(delegate)
    }
  }
  delegate.toString()
} == expect