Circe KeyEncoder/KeyDecoder for String Enum (#178)

* Enable Circe string enums to be used as keys of a map. * Test JSON serialization of String Enum as map key
lloydmeta · Mar 14, 2018 · fea39d6 · fea39d6
1 parent d328c23
commit fea39d6
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Showing 4 changed files with 40 additions and 4 deletions.
diff --git a/enumeratum-circe/src/main/scala/enumeratum/values/Circe.scala b/enumeratum-circe/src/main/scala/enumeratum/values/Circe.scala
@@ -42,4 +42,15 @@ object Circe {
         }
     }
   }
+
+  def keyEncoder[EntryType <: ValueEnumEntry[String]](
+    enum: ValueEnum[String, EntryType]
+  ): KeyEncoder[EntryType] =
+    KeyEncoder.instance(_.value)
+
+  def keyDecoder[EntryType <: ValueEnumEntry[String]](
+    enum: ValueEnum[String, EntryType]
+  ): KeyDecoder[EntryType] =
+    KeyDecoder.instance(enum.withValueOpt)
+
 }
diff --git a/enumeratum-circe/src/main/scala/enumeratum/values/CirceValueEnum.scala b/enumeratum-circe/src/main/scala/enumeratum/values/CirceValueEnum.scala
@@ -1,6 +1,6 @@
 package enumeratum.values
 
-import io.circe.{Decoder, Encoder}
+import io.circe.{Decoder, Encoder, KeyDecoder, KeyEncoder}
 
 /**
   * Created by Lloyd on 4/14/16.
@@ -81,6 +81,9 @@ trait StringCirceEnum[EntryType <: StringEnumEntry] extends CirceValueEnum[Strin
   this: ValueEnum[String, EntryType] =>
   implicit val circeEncoder: Encoder[EntryType] = Circe.encoder(this)
   implicit val circeDecoder: Decoder[EntryType] = Circe.decoder(this)
+
+  implicit val circeKeyEncoder: KeyEncoder[EntryType] = Circe.keyEncoder(this)
+  implicit val circeKeyDecoder: KeyDecoder[EntryType] = Circe.keyDecoder(this)
 }
 
 /**

diff --git a/enumeratum-circe/src/test/scala/enumeratum/values/CirceValueEnumSpec.scala b/enumeratum-circe/src/test/scala/enumeratum/values/CirceValueEnumSpec.scala
@@ -2,7 +2,7 @@ package enumeratum.values
 
 import org.scalatest.{FunSpec, Matchers}
 import cats.syntax.either._
-import io.circe.{Decoder, Encoder, Json}
+import io.circe.{Decoder, Encoder, KeyDecoder, KeyEncoder, Json}
 import io.circe.syntax._
 
 /**
@@ -16,6 +16,7 @@ class CirceValueEnumSpec extends FunSpec with Matchers {
   testCirceEnum("ShortCirceEnum", CirceDrinks)
   testCirceEnum("IntCirceEnum", CirceLibraryItem)
   testCirceEnum("StringCirceEnum", CirceOperatingSystem)
+  testCirceKeyEnum("StringCirceEnum", CirceOperatingSystem)
   testCirceEnum("CharEnum", CirceAlphabet)
   testCirceEnum("ByteEnum", CirceBites)
   testCirceEnum("IntCirceEnum with val value members", CirceMovieGenre)
@@ -60,6 +61,27 @@ class CirceValueEnumSpec extends FunSpec with Matchers {
     }
   }
 
+  private def testCirceKeyEnum[EntryType <: ValueEnumEntry[String]: KeyEncoder: KeyDecoder](
+    enumKind: String,
+    enum: ValueEnum[String, EntryType] with CirceValueEnum[String, EntryType]
+  ): Unit = {
+    describe(s"$enumKind as Key") {
+      describe("to JSON") {
+        it("should work") {
+          val map = enum.values.toStream.zip(Stream.from(1)).toMap
+          map.asJson.as[Map[EntryType, Int]] shouldBe Right(map)
+        }
+      }
+
+      describe("from JSON") {
+        it("should fail to parse random JSON into a map") {
+          val invalidJsonMap = Stream.from(1).map(_.toString).take(10).toStream.zip(Stream.from(1)).toMap.asJson
+          invalidJsonMap.as[Map[EntryType, Int]].isLeft shouldBe true
+        }
+      }
+    }
+  }
+
 }
 
 sealed abstract class CirceContentType(val value: Long, name: String) extends LongEnumEntry

diff --git a/project/plugins.sbt b/project/plugins.sbt
@@ -2,7 +2,7 @@ resolvers ++= Seq(
   Classpaths.sbtPluginReleases
 )
 
-lazy val neoScalafmtVersion = "1.14"
+lazy val neoScalafmtVersion = "1.15"
 
 addSbtPlugin("com.lucidchart" % "sbt-scalafmt" % neoScalafmtVersion)
 
@@ -24,4 +24,4 @@ addSbtPlugin("org.wartremover" % "sbt-wartremover" % "2.2.0")
 
 addSbtPlugin("com.github.tkawachi" % "sbt-doctest" % "0.7.1")
 
-addSbtPlugin("com.jsuereth" % "sbt-pgp" % "1.1.0")
+addSbtPlugin("com.jsuereth" % "sbt-pgp" % "1.1.0")