ポリモーフィズムで再帰的なXMLを生成する

KeyValue.scala

package com.example.kvxml2

import _root_.scala.xml.{Elem, MetaData, Node, NodeSeq, Null, Text, TopScope, UnprefixedAttribute}


sealed abstract class Value {
  def nodes: NodeSeq
}

case class StringValue(str: String) extends Value {
  def nodes = Text(str)
}

case class ValueSeq(seq: Seq[Value]) extends Value {
  def nodes = seq flatMap (_.nodes)
}

case class KeyValue(key: String, attributes: Map[String, String], value: Value) extends Value {
  def this(key: String, value: Value) = this(key, Map.empty, value)

  def xml: Node = Elem(null, key, meta, TopScope, value.nodes: _*)

  def meta = ((Null: MetaData) /: attributes){ (meta, attr) =>
    new UnprefixedAttribute(attr._1, attr._2, meta)
  }

  def nodes = xml
}

KeyValueSpec.scala

package com.example.kvxml2

import org.specs2._
import scala.xml.PrettyPrinter

class KeyValueSpec extends Specification { def is =
  "ポリモーフィズム版KeyValueのテスト"                  ^
    "XMLリテラルと一致する"                             ! S.example1 ^
    "PrettyPrinterで生成したStringが一致する"           ! S.example2 ^
    "改行とインデント込みでXMLリテラルに一致する"       ! S.example3 ^
                                                        end

  object S {
    implicit def string2value(str: String): Value = StringValue(str)
    implicit def seq2value(seq: Seq[Value]): Value = ValueSeq(seq)

    val kv =
      KeyValue("langs", Map("type" -> "current"), Seq(
        new KeyValue("key1", "value1"),
        new KeyValue("key2", "value2"),
        new KeyValue("key3", Seq(
          new KeyValue("key3-1", "value3-1"),
          new KeyValue("key3-2", "value3-2")
        ))
      ))

    def example1 = kv.xml must_==
      <langs type="current"><key1>value1</key1><key2>value2</key2><key3><key3-1>value3-1</key3-1><key3-2>value3-2</key3-2></key3></langs>

    def example2 = {
      val 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>""".stripMargin

      new PrettyPrinter(80, 2).format(kv.xml) must_== expect
    }


    val kv2 = {
      val nl = "\n"
      val indent = "  "
      KeyValue("langs", Map("type" -> "current"), Seq[Value](
        nl + indent,
        new KeyValue("key1", "value1"),
        nl + indent,
        new KeyValue("key2", "value2"),
        nl + indent,
        new KeyValue("key3", Seq[Value](
          nl + indent * 2,
          new KeyValue("key3-1", "value3-1"),
          nl + indent * 2,
          new KeyValue("key3-2", "value3-2"),
          nl + indent
        )),
        nl
      ))
    }

    def example3 = kv2.xml must_==
<langs type="current">
  <key1>value1</key1>
  <key2>value2</key2>
  <key3>
    <key3-1>value3-1</key3-1>
    <key3-2>value3-2</key3-2>
  </key3>
</langs>
  }

}