Add support for refined

Author: Luc DUZAN

build.sbt

@@ -112,6 +112,17 @@ lazy val tapirCats: Project = (project in file("cats"))
   )
   .dependsOn(core)
 
+lazy val tapirRefined: Project = (project in file("refined"))
+  .settings(commonSettings)
+  .settings(
+    name := "tapir-refined",
+    libraryDependencies ++= Seq(
+      "eu.timepit" %% "refined" % Versions.refined,
+      scalaTest % "test"
+    )
+  )
+  .dependsOn(core)
+
 // json
 
 lazy val circeJson: Project = (project in file("json/circe"))

project/Versions.scala

@@ -15,4 +15,5 @@ object Versions {
   val sprayJson = "1.3.5"
   val scalaCheck = "1.14.1"
   val scalaTest = "3.0.8"
+  val refined = "0.9.12"
 }

refined/src/main/scala/sttp/tapir/codec/refined/TapirCodecRefined.scala

@@ -0,0 +1,17 @@
+package sttp.tapir.codec.refined
+
+import sttp.tapir._
+import eu.timepit.refined.api.{Refined, Validate}
+import eu.timepit.refined.refineV
+
+trait TapirCodecRefined {
+  implicit def codecForRefined[V, P, CF <: CodecFormat, R](implicit tm: Codec[V, CF, R], validator: Validate[V, P]): Codec[V Refined P, CF, R] =
+    implicitly[Codec[V, CF, R]]
+      .mapDecode { v: V =>
+        refineV[P](v) match {
+          case Right(refined) => DecodeResult.Value(refined)
+          //TODO: exploit error
+          case Left(_) => DecodeResult.InvalidValue(List())
+        }
+      }(_.value)
+}

refined/src/main/scala/sttp/tapir/codec/refined/package.scala

@@ -0,0 +1,3 @@
+package sttp.tapir.codec
+
+package object refined extends TapirCodecRefined

refined/src/test/scala/sttp/tapir/codec/refined/TapirCodecRefinedTest.scala

@@ -0,0 +1,21 @@
+package sttp.tapir.codec.refined
+
+import eu.timepit.refined.collection.NonEmpty
+import eu.timepit.refined.refineMV
+import eu.timepit.refined.types.string.NonEmptyString
+import org.scalatest.{FlatSpec, Matchers}
+import sttp.tapir.Codec.PlainCodec
+import sttp.tapir.DecodeResult
+
+class TapirCodecRefinedTest extends FlatSpec with Matchers with TapirCodecRefined {
+
+  val nonEmptyStringCodec = implicitly[PlainCodec[NonEmptyString]]
+
+  it should "return DecodResult.Invalid if subtype can't be refined" in {
+    nonEmptyStringCodec.decode("") should matchPattern{case DecodeResult.InvalidValue(_) =>}
+  }
+
+  it should "correctly delegate to raw parser and refine it" in {
+    nonEmptyStringCodec.decode("vive le fromage") shouldBe DecodeResult.Value(refineMV[NonEmpty]("vive le fromage"))
+  }
+}