Scala - how to print case classes like (pretty printed) tree

Question

I\'m making a parser with Scala Combinators. It is awesome. What I end up with is a long list of entagled case classes, like: ClassDecl(Complex,List(VarDecl(Real,float

Answer 1

This is a shamless copy paste of @F. P Freely, but

• I've added an indentation feature
• slight modifications so that the output will be of correct Scala style (and will compile for all primative types)
• Fixed string literal bug
• Added support for java.sql.Timestamp (as I use this with Spark a lot)

Tada!

// Recursively get all the fields; this will grab vals declared in parents of case classes.
  def getFields(cls: Class[_]): List[Field] =
    Option(cls.getSuperclass).map(getFields).getOrElse(Nil) ++
      cls.getDeclaredFields.toList.filterNot(f =>
        f.isSynthetic || java.lang.reflect.Modifier.isStatic(f.getModifiers))

  // FIXME fix bug where indent seems to increase too much
  def prettyfy(a: Any, indentSize: Int = 0): String = {
    val indent = List.fill(indentSize)(" ").mkString

    val newIndentSize = indentSize + 2
    (a match {
      // Make Strings look similar to their literal form.
      case string: String =>
        val conversionMap = Map('\n' -> "\\n", '\r' -> "\\r", '\t' -> "\\t", '\"' -> "\\\"", '\\' -> "\\\\")
        string.map(c => conversionMap.getOrElse(c, c)).mkString("\"", "", "\"")
      case xs: Seq[_] =>
        xs.map(prettyfy(_, newIndentSize)).toString
      case xs: Array[_] =>
        s"Array(${xs.map(prettyfy(_, newIndentSize)).mkString(", ")})"
      case map: Map[_, _] =>
        s"Map(\n" + map.map {
          case (key, value) => "  " + prettyfy(key, newIndentSize) + " -> " + prettyfy(value, newIndentSize)
        }.mkString(",\n") + "\n)"
      case None => "None"
      case Some(x) => "Some(" + prettyfy(x, newIndentSize) + ")"
      case timestamp: Timestamp => "new Timestamp(" + timestamp.getTime + "L)"
      case p: Product =>
        s"${p.productPrefix}(\n${
          getFields(p.getClass)
            .map { f =>
              f.setAccessible(true)
              s"  ${f.getName} = ${prettyfy(f.get(p), newIndentSize)}"
            }
            .mkString(",\n")
        }\n)"
      // General objects and primitives end up here.
      case q =>
        Option(q).map(_.toString).getOrElse("null")
    })
      .split("\n", -1).mkString("\n" + indent)
  }

E.g.

case class Foo(bar: String, bob: Int)

case class Alice(foo: Foo, opt: Option[String], opt2: Option[String])

scala> prettyPrint(Alice(Foo("hello world", 10), Some("asdf"), None))
res6: String =
Alice(
  foo = Foo(
    bar = "hello world",
    bob = 10
  ),
  opt = Some("asdf"),
  opt2 = None
)