DateTimeFormatter interpolator

date_time_format.sc

import $ivy.`com.propensive::contextual-core:3.0.1`

import java.time.format.DateTimeFormatter

import scala.language.experimental.macros

import contextual._

object dateTimeFormat {
  object DateTimeFormatInterpolator extends Interpolator {
    def contextualize(interpolation: StaticInterpolation): Seq[ContextType] = {
      interpolation.parts.foreach {
        case lit @ Literal(_, str) =>
          try DateTimeFormatter.ofPattern(str) catch {
            case ia: IllegalArgumentException =>
              interpolation.error(lit, 0, ia.getMessage)
          }
        case hole @ Hole(_, _) =>
          interpolation.abort(hole, "substitution is not supported")
      }

      Nil
    }

    def evaluate(interpolation: RuntimeInterpolation): DateTimeFormatter =
      DateTimeFormatter.ofPattern(interpolation.parts.mkString)
  }

  implicit class ProtoStringContext(sc: StringContext) {
    def dateTimeFormat(expressions: String*): DateTimeFormatter =
      macro Macros.contextual[DateTimeFormatInterpolator.type]
  }
}

@

import dateTimeFormat._

val fmt = dateTimeFormat"dd-MM-yyyy"

println(fmt)