ProductPPrinter.scala

import pprint.PPrinter._

/**
 * Pretty printer support for products where field names are rendered.
 * @author sfitch
 * @since 9/14/16
 */
object ProductPPrinter {
  /** Pretty Printer adding 'key = value' field rendering. */
  implicit def ProductWithFieldsPPrinter[P <: Product] = new pprint.PPrinter[P] {
    import Internals._
    override def render0(t: P, c: pprint.Config): Iterator[String] = {
      val values = asFields(t)

      pprint.Internals.handleChunks(t.productPrefix, c, { conf ⇒
        values.iterator.map { case (name, value) ⇒
            Iterator(s"$name = ") ++ implicitly[pprint.PPrint[Any]].pprinter.render(value, c)
        }
      })
    }
  }

  implicit class HasPPString(val p: Product) extends AnyVal {
    def toPPString(implicit c: pprint.Config = pprint.Config.Defaults.PPrintConfig): String = pprint.tokenize(p).mkString
  }

  object Internals {
    /** This allows for recursive invocation of the ProductWithFieldsPPrinter based on dynamic type introspection. */
    implicit object AnyReifiedRepr extends pprint.PPrinter[Any] {
      override def render0(t: Any, c: pprint.Config): Iterator[String] = {
        implicit val anyPrinter = this
        t match {
          case Some(stuff) ⇒ anyPrinter.render(stuff, c)
          case p: Product ⇒ ProductWithFieldsPPrinter.render(p, c)
          case a: Array[Any @unchecked] ⇒ ArrayRepr[Any].render(a, c)
          case s: Seq[_] ⇒ SeqRepr[Any, Seq].render(s, c)
          case m: Map[Any @unchecked, _] ⇒ MapRepr[Any, Any].render(m, c)
          case f: Float ⇒ FloatRepr.render(f, c)
          case d: Double ⇒ DoubleRepr.render(d, c)
          case i: Int ⇒ IntRepr.render(i, c)
          case l: Long ⇒ LongRepr.render(l, c)
          case b: Boolean ⇒ BooleanRepr.render(b, c)
          case o ⇒ StringRepr.render(o.toString, c) // cop-out
        }
      }
    }

    // NB: This is brittle. Presumes field order and productIterator are the same.
    private[ProductPPrinter] def asFields[P <: Product](p: P) = {
      p.getClass.getDeclaredFields.map(_.getName).zip(p.productIterator.to)
    }
  }
}