Add tests for PartialTransformer#contramap

scalalandio · Aug 31, 2024 · 0733e9a · 0733e9a
1 parent b6882c6
commit 0733e9a
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diff --git a/chimney/src/main/scala/io/scalaland/chimney/PartialTransformer.scala b/chimney/src/main/scala/io/scalaland/chimney/PartialTransformer.scala
@@ -180,54 +180,54 @@ object PartialTransformer extends PartialTransformerCompanionPlatform {
     def transform(src: From, failFast: Boolean): partial.Result[To]
 
     /** Creates a new [[io.scalaland.chimney.PartialTransformer PartialTransformer]] by applying a pure function to a
-      * [[io.scalaland.chimney.partial.Result Result]] of transforming `From` to `To`. See an example:
+      * source of type `A` before transforming it to `To`. See an example:
       * {{{
       *   val stringTransformer: PartialTransformer[String, Int] =
       *     PartialTransformer.fromFunction(_.length)
       *
-      *   case class Length(length: Int)
+      *   case class Id(id: String)
       *
-      *   implicit val toLengthTransformer: PartialTransformer[String, Length] =
-      *     stringTransformer.map(id => Length(id))
+      *   implicit val idTransformer: PartialTransformer[Id, Int] =
+      *     stringTransformer.contramap(_.id)
       * }}}
       *
       * @param f
-      *   a pure function that maps a value of `To` to `A`
+      *   a pure function that maps a value of `A` to `From`
       * @return
       *   new [[io.scalaland.chimney.PartialTransformer PartialTransformer]]
       *
       * @since 1.5.0
       */
-    final def map[A](f: To => A): PartialTransformer[From, A] = new PartialTransformer[From, A] {
-      override def transform(src: From, failFast: Boolean): partial.Result[A] =
-        self.transform(src, failFast) match {
-          case partial.Result.Value(to)    => partial.Result.Value(f(to))
-          case errs: partial.Result.Errors => errs.asInstanceOf[partial.Result[A]]
-        }
+    final def contramap[A](f: A => From): PartialTransformer[A, To] = new PartialTransformer[A, To] {
+      override def transform(src: A, failFast: Boolean): partial.Result[To] =
+        self.transform(f(src), failFast)
     }
 
     /** Creates a new [[io.scalaland.chimney.PartialTransformer PartialTransformer]] by applying a pure function to a
-      * source of type `A` before transforming it to `To`. See an example:
+      * [[io.scalaland.chimney.partial.Result Result]] of transforming `From` to `To`. See an example:
       * {{{
       *   val stringTransformer: PartialTransformer[String, Int] =
       *     PartialTransformer.fromFunction(_.length)
       *
-      *   case class Id(id: String)
+      *   case class Length(length: Int)
       *
-      *   implicit val idTransformer: PartialTransformer[Id, Int] =
-      *     stringTransformer.contramap(_.id)
+      *   implicit val toLengthTransformer: PartialTransformer[String, Length] =
+      *     stringTransformer.map(id => Length(id))
       * }}}
       *
       * @param f
-      *   a pure function that maps a value of `A` to `From`
+      *   a pure function that maps a value of `To` to `A`
       * @return
       *   new [[io.scalaland.chimney.PartialTransformer PartialTransformer]]
       *
       * @since 1.5.0
       */
-    final def contramap[A](f: A => From): PartialTransformer[A, To] = new PartialTransformer[A, To] {
-      override def transform(src: A, failFast: Boolean): partial.Result[To] =
-        self.transform(f(src), failFast)
+    final def map[A](f: To => A): PartialTransformer[From, A] = new PartialTransformer[From, A] {
+      override def transform(src: From, failFast: Boolean): partial.Result[A] =
+        self.transform(src, failFast) match {
+          case partial.Result.Value(to)    => partial.Result.Value(f(to))
+          case errs: partial.Result.Errors => errs.asInstanceOf[partial.Result[A]]
+        }
     }
   }
 }

diff --git a/chimney/src/test/scala/io/scalaland/chimney/PartialTransformerSpec.scala b/chimney/src/test/scala/io/scalaland/chimney/PartialTransformerSpec.scala
@@ -114,4 +114,34 @@ class PartialTransformerSpec extends ChimneySpec {
     id.intoPartial[Length].transform ==> partial.Result.fromValue(Length(id.toInt))
     id.intoPartial[Prefix].transform ==> partial.Result.fromValue(Prefix.BarPrefix)
   }
+
+  test("contramap") {
+    case class Id(id: String)
+
+    trait Prefix {
+      def value: String
+    }
+
+    object Prefix {
+      case object FooPrefix extends Prefix {
+        override def value: String = "1"
+      }
+
+      case object BarPrefix extends Prefix {
+        override def value: String = "2"
+      }
+    }
+
+    implicit val idTransformer: PartialTransformer[Id, Int] =
+      pt1.contramap(_.id)
+
+    implicit val prefixTransformer: PartialTransformer[Prefix, Int] =
+      pt1.contramap(_.value)
+
+    val id = "1"
+    Id(id).intoPartial[Int].transform ==> partial.Result.fromValue(id.toInt)
+
+    val prefix: Prefix = Prefix.FooPrefix
+    prefix.intoPartial[Int].transform ==> partial.Result.fromValue(id.toInt)
+  }
 }