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StringInterpolation.scala
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StringInterpolation.scala
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/*
* Copyright (c) 2021 Typelevel
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package cats.parse
import scala.reflect.macros.whitebox
object StringInterpolation {
implicit class Helper(val sc: StringContext) extends AnyVal {
def parser(args: Any*): Parser0[Any] = macro StringInterpolationMacros.parser
}
}
class StringInterpolationMacros(val c: whitebox.Context) {
import c.universe._
private def lit(s: String) = q"_root_.cats.parse.Parser.string($s)"
final def parser(args: c.Expr[Any]*) =
c.prefix.tree match {
case Apply(_, Apply(_, parts) :: Nil) =>
val stringParts = parts.collect { case Literal(Constant(s: String)) => s }
val (matched, last) = stringParts.splitAt(args.length)
val parsers: List[Tree] = matched.zip(args).map { case (a, b) =>
if (a.isEmpty) b.tree else q"${lit(a)} *> $b"
}
val trailing = last.filter(_.nonEmpty).headOption.map(lit)
(parsers, trailing) match {
case (Nil, None) => q"_root_.cats.parse.Parser.unit"
case (Nil, Some(t)) => t
case (x :: Nil, Some(t)) => q"$x <* $t"
case (x :: Nil, None) => x
case (xs, t) =>
val tupled = Apply(
Select(q"_root_.cats.Semigroupal", TermName(s"tuple${parsers.length}")),
xs
)
t.map(p => q"$tupled <* $p").getOrElse(tupled)
}
case _ => c.abort(c.enclosingPosition, "Must be called as string interpolator")
}
}