Hello, Scala3 🎉

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        scala: [2.12.14, 2.13.6]
+        scala: [2.12.14, 2.13.6, 3.0.0]
         java: [[email protected]]
     runs-on: ${{ matrix.os }}
     steps:
@@ -77,7 +77,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        scala: [2.13.6]
+        scala: [3.0.0]
         java: [[email protected]]
     runs-on: ${{ matrix.os }}
     steps:
@@ -123,6 +123,16 @@ jobs:
           tar xf targets.tar
           rm targets.tar
 
+      - name: Download target directories (3.0.0)
+        uses: actions/download-artifact@v2
+        with:
+          name: target-${{ matrix.os }}-3.0.0-${{ matrix.java }}
+
+      - name: Inflate target directories (3.0.0)
+        run: |
+          tar xf targets.tar
+          rm targets.tar
+
       - env:
           PGP_PASSPHRASE: ${{ secrets.PGP_PASSPHRASE }}
           PGP_SECRET: ${{ secrets.PGP_SECRET }}

build.sbt

@@ -1,22 +1,36 @@
+val isScala3 = Def.setting(
+  CrossVersion.partialVersion(scalaVersion.value).exists(_._1 == 3)
+)
+
 name := "sangria-marshalling-api"
 organization := "org.sangria-graphql"
-mimaPreviousArtifacts := Set("org.sangria-graphql" %% "sangria-marshalling-api" % "1.0.5")
+mimaPreviousArtifacts := {
+  if (isScala3.value)
+    Set.empty
+  else
+    Set("org.sangria-graphql" %% "sangria-marshalling-api" % "1.0.5")
+}
 
 description := "Sangria Marshalling API"
 homepage := Some(url("https://sangria-graphql.github.io/"))
-licenses := Seq("Apache License, ASL Version 2.0" → url("https://www.apache.org/licenses/LICENSE-2.0"))
+licenses := Seq(
+  "Apache License, ASL Version 2.0" → url("https://www.apache.org/licenses/LICENSE-2.0"))
 
 // sbt-github-actions needs configuration in `ThisBuild`
-ThisBuild / crossScalaVersions := Seq("2.12.14", "2.13.6")
+ThisBuild / crossScalaVersions := Seq("2.12.14", "2.13.6", "3.0.0")
 ThisBuild / scalaVersion := crossScalaVersions.value.last
 ThisBuild / githubWorkflowPublishTargetBranches := List()
 ThisBuild / githubWorkflowBuildPreamble ++= List(
   WorkflowStep.Sbt(List("mimaReportBinaryIssues"), name = Some("Check binary compatibility")),
   WorkflowStep.Sbt(List("scalafmtCheckAll"), name = Some("Check formatting"))
 )
 scalacOptions ++= Seq("-deprecation", "-feature")
-
-scalacOptions += "-target:jvm-1.8"
+scalacOptions ++= {
+  if (isScala3.value)
+    Seq("-Xtarget:8")
+  else
+    Seq("-target:jvm-1.8")
+}
 javacOptions ++= Seq("-source", "8", "-target", "8")
 
 libraryDependencies ++= Seq(
@@ -42,11 +56,16 @@ ThisBuild / githubWorkflowPublish := Seq(
 
 startYear := Some(2016)
 organizationHomepage := Some(url("https://github.com/sangria-graphql"))
-developers := Developer("OlegIlyenko", "Oleg Ilyenko", "", url("https://github.com/OlegIlyenko")) :: Nil
-scmInfo := Some(ScmInfo(
-  browseUrl = url("https://github.com/sangria-graphql/sangria-marshalling-api"),
-  connection = "scm:git:[email protected]:sangria-graphql/sangria-marshalling-api.git"
-))
+developers := Developer(
+  "OlegIlyenko",
+  "Oleg Ilyenko",
+  "",
+  url("https://github.com/OlegIlyenko")) :: Nil
+scmInfo := Some(
+  ScmInfo(
+    browseUrl = url("https://github.com/sangria-graphql/sangria-marshalling-api"),
+    connection = "scm:git:[email protected]:sangria-graphql/sangria-marshalling-api.git"
+  ))
 
 // nice *magenta* prompt!
 ThisBuild / shellPrompt := { state =>

src/main/scala/sangria/marshalling/FromInput.scala

@@ -12,14 +12,14 @@ trait FromInput[Val] {
 
 object FromInput {
   private object ScalarFromInput extends FromInput[Any] {
-    val marshaller = CoercedScalaResultMarshaller.default
-    def fromResult(node: marshaller.Node) = node
+    val marshaller: CoercedScalaResultMarshaller = CoercedScalaResultMarshaller.default
+    def fromResult(node: marshaller.Node): marshaller.Node = node
   }
 
   class SeqFromInput[T](delegate: FromInput[T]) extends FromInput[Seq[T]] {
-    val marshaller = delegate.marshaller
+    val marshaller: ResultMarshaller = delegate.marshaller
 
-    def fromResult(node: marshaller.Node) =
+    def fromResult(node: marshaller.Node): Seq[T] =
       node
         .asInstanceOf[Seq[Any]]
         .map {
@@ -33,14 +33,17 @@ object FromInput {
 
   import sangria.util.tag._
 
-  implicit def coercedScalaInput[T] =
+  implicit def coercedScalaInput[T]: FromInput[T @@ CoercedScalaResult] =
     ScalarFromInput.asInstanceOf[FromInput[T @@ CoercedScalaResult]]
-  implicit def defaultInput[T] = ScalarFromInput.asInstanceOf[FromInput[Map[String, Any]]]
-  implicit def inputObjectResultInput[T](implicit ev: FromInput[T]) =
+  implicit def defaultInput[T]: FromInput[Map[String, Any]] =
+    ScalarFromInput.asInstanceOf[FromInput[Map[String, Any]]]
+  implicit def inputObjectResultInput[T](implicit
+      ev: FromInput[T]): FromInput[T @@ InputObjectResult] =
     ev.asInstanceOf[FromInput[T @@ InputObjectResult]]
 
-  implicit def optionInput[T](implicit ev: FromInput[T]) = ev.asInstanceOf[FromInput[Option[T]]]
-  implicit def seqInput[T](implicit ev: FromInput[T]) = new SeqFromInput[T](ev)
+  implicit def optionInput[T](implicit ev: FromInput[T]): FromInput[Option[T]] =
+    ev.asInstanceOf[FromInput[Option[T]]]
+  implicit def seqInput[T](implicit ev: FromInput[T]): SeqFromInput[T] = new SeqFromInput[T](ev)
 
   trait CoercedScalaResult
   trait InputObjectResult

src/main/scala/sangria/marshalling/InputUnmarshaller.scala

@@ -1,6 +1,7 @@
 package sangria.marshalling
 
 import sangria.util.tag
+import sangria.util.tag.@@
 
 import scala.annotation.implicitNotFound
 
@@ -54,5 +55,6 @@ object InputUnmarshaller {
 
   def emptyMapVars = tag[ScalaInput](Map.empty[String, Any])
 
-  implicit def scalaInputUnmarshaller[T] = scalaMarshalling.scalaInputUnmarshaller[T]
+  implicit def scalaInputUnmarshaller[T]: InputUnmarshaller[T @@ ScalaInput] =
+    scalaMarshalling.scalaInputUnmarshaller[T]
 }

src/main/scala/sangria/marshalling/MarshallingUtil.scala

@@ -20,8 +20,8 @@ object MarshallingUtil {
         rm.mapNode(builder)
       case list if iu.isListNode(list) =>
         rm.mapAndMarshal(iu.getListValue(list), (elem: In) => convert(elem).asInstanceOf[rm.Node])
-      case enum if iu.isEnumNode(enum) && iu.getScalaScalarValue(enum).isInstanceOf[String] =>
-        rm.enumNode(iu.getScalaScalarValue(enum).asInstanceOf[String], "Conversion")
+      case enums if iu.isEnumNode(enums) && iu.getScalaScalarValue(enums).isInstanceOf[String] =>
+        rm.enumNode(iu.getScalaScalarValue(enums).asInstanceOf[String], "Conversion")
       case scalar if iu.isScalarNode(scalar) =>
         rm.scalarNode(iu.getScalaScalarValue(scalar), "Conversion", Set.empty)
       case variable if iu.isVariableNode(variable) =>

src/main/scala/sangria/marshalling/ResultMarshaller.scala

@@ -56,7 +56,8 @@ trait ResultMarshaller {
 }
 
 object ResultMarshaller {
-  implicit val defaultResultMarshaller = scalaMarshalling.scalaResultMarshaller
+  implicit val defaultResultMarshaller: ScalaResultMarshaller =
+    scalaMarshalling.scalaResultMarshaller
 }
 
 /** Alters the behaviour of the executor and marshals raw (in-scala coerced representation) or scalar values and enums.

src/main/scala/sangria/marshalling/ToInput.scala

@@ -13,18 +13,21 @@ trait ToInput[Val, Raw] {
 
 object ToInput {
   class ScalarToInput[T] extends ToInput[T, T @@ ScalaInput] {
-    def toInput(value: T) = (ScalaInput.scalaInput(value), InputUnmarshaller.scalaInputUnmarshaller)
+    def toInput(value: T): (T @@ ScalaInput, InputUnmarshaller[T @@ ScalaInput]) =
+      (ScalaInput.scalaInput(value), InputUnmarshaller.scalaInputUnmarshaller)
   }
 
-  implicit def normalScalaInput[T] = new ToInput[T @@ ScalaInput, T @@ ScalaInput] {
-    def toInput(value: T @@ ScalaInput) = (value, InputUnmarshaller.scalaInputUnmarshaller)
-  }
+  implicit def normalScalaInput[T]: ToInput[T @@ ScalaInput, T @@ ScalaInput] =
+    new ToInput[T @@ ScalaInput, T @@ ScalaInput] {
+      def toInput(value: T @@ ScalaInput): (T @@ ScalaInput, InputUnmarshaller[T @@ ScalaInput]) =
+        (value, InputUnmarshaller.scalaInputUnmarshaller)
+    }
 
-  implicit val intInput = new ScalarToInput[Int]
-  implicit val bigDecimalInput = new ScalarToInput[BigDecimal]
-  implicit val bigIntInput = new ScalarToInput[BigInt]
-  implicit val longInput = new ScalarToInput[Long]
-  implicit val floatInput = new ScalarToInput[Double]
-  implicit val booleanInput = new ScalarToInput[Boolean]
-  implicit val stringInput = new ScalarToInput[String]
+  implicit val intInput: ScalarToInput[Int] = new ScalarToInput[Int]
+  implicit val bigDecimalInput: ScalarToInput[BigDecimal] = new ScalarToInput[BigDecimal]
+  implicit val bigIntInput: ScalarToInput[BigInt] = new ScalarToInput[BigInt]
+  implicit val longInput: ScalarToInput[Long] = new ScalarToInput[Long]
+  implicit val floatInput: ScalarToInput[Double] = new ScalarToInput[Double]
+  implicit val booleanInput: ScalarToInput[Boolean] = new ScalarToInput[Boolean]
+  implicit val stringInput: ScalarToInput[String] = new ScalarToInput[String]
 }

src/main/scala/sangria/marshalling/scalaMarshalling.scala

@@ -7,7 +7,7 @@ import scala.collection.immutable.ListMap
 
 object scalaMarshalling {
   private val scalaScalaUnmarshallerGen = new ScalaInputUnmarshaller[Any]
-  implicit val scalaResultMarshaller = new ScalaResultMarshaller
+  implicit val scalaResultMarshaller: ScalaResultMarshaller = new ScalaResultMarshaller
 
   implicit object ScalaMarshallerForType extends ResultMarshallerForType[Any @@ ScalaInput] {
     val marshaller = scalaResultMarshaller