codec (feature): Support Scala 3 Enum

airframe-codec/src/test/scala-3/wvlet/airframe/codec/Scala3EnumCodecTest.scala

@@ -0,0 +1,30 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package wvlet.airframe.codec
+
+import wvlet.airspec.AirSpec
+
+object Scala3EnumCodecTest extends AirSpec:
+  enum Color:
+    case Red, Green, Blue
+
+  test("pack Scala 3 Enum") {
+    val codec = MessageCodec.of[Color]
+    Color.values.foreach { c =>
+      val packed = codec.pack(c)
+      debug(packed)
+      val unpacked = codec.unpack(packed)
+      unpacked shouldBe c
+    }
+  }

airframe-surface/src/main/scala-2/wvlet/airframe/surface/Surface.scala

@@ -33,6 +33,11 @@ trait Surface extends Serializable {
   def isMap: Boolean   = classOf[Map[_, _]].isAssignableFrom(rawType)
   def isArray: Boolean = this.isInstanceOf[ArraySurface]
 
+  /**
+   * True if this surface is a Scala3 enum. In Scala 2, it always returns false
+   */
+  def isEnum: Boolean = false
+
   def objectFactory: Option[ObjectFactory] = None
   def withOuter(outer: AnyRef): Surface    = this
 }

airframe-surface/src/main/scala-3/wvlet/airframe/surface/CompileTimeSurfaceFactory.scala

@@ -432,6 +432,44 @@ private[surface] class CompileTimeSurfaceFactory[Q <: Quotes](using quotes: Q) {
       '{ new GenericSurface(${ clsOf(a1) }, typeArgs = ${ Expr.ofSeq(typeArgs) }.toIndexedSeq) }
     case r: Refinement =>
       newGenericSurfaceOf(r.info)
+    case t if t <:< TypeRepr.of[scala.reflect.Enum] =>
+      /**
+        * Build a code for finding Enum instance from an input string value: {{ (cl: Class[_], s: String) =>
+        * Try(EnumType.valueOf(s)).toOption }}
+        */
+      val enumType = t.typeSymbol.companionModule
+      val valueOfMethod = enumType.methodMember("valueOf").headOption match {
+        case Some(m) => m
+        case None =>
+          sys.error(s"valueOf method not found in ${t}")
+      }
+      val newFn = Lambda(
+        owner = Symbol.spliceOwner,
+        tpe = MethodType(List("cl", "s"))(
+          _ => List(TypeRepr.of[Class[_]], TypeRepr.of[String]),
+          _ => TypeRepr.of[Option[Any]]
+        ),
+        rhsFn = (sym: Symbol, paramRefs: List[Tree]) => {
+          val strVarRef = paramRefs(1).asExprOf[String].asTerm
+          val expr: Term =
+            Select
+              .unique(
+                Apply(Select.unique(Ref(t.typeSymbol.companionModule), "valueOf"), List(strVarRef)),
+                "asInstanceOf"
+              ).appliedToType(TypeRepr.of[Any])
+          val expr2 = ('{
+            scala.util.Try(${ expr.asExprOf[Any] }).toOption
+          }).asExprOf[Option[Any]].asTerm
+          expr2.changeOwner(sym)
+        }
+      )
+
+      '{
+        EnumSurface(
+          ${ clsOf(t) },
+          ${ newFn.asExprOf[(Class[_], String) => Option[Any]] }
+        )
+      }
     case t if hasStringUnapply(t) =>
       // Build EnumSurface.apply code
       // EnumSurface(classOf[t], { (cl: Class[_], s: String) => (companion object).unapply(s).asInstanceOf[Option[Any]] }
@@ -447,7 +485,6 @@ private[surface] class CompileTimeSurfaceFactory[Q <: Quotes](using quotes: Q) {
           val strVarRef = paramRefs(1).asExprOf[String].asTerm
           val expr = Select.unique(Apply(m, List(strVarRef)), "asInstanceOf").appliedToType(TypeRepr.of[Option[Any]])
           expr.changeOwner(sym)
-
         }
       )
       '{

airframe-surface/src/main/scala/wvlet/airframe/surface/Surfaces.scala

@@ -256,6 +256,11 @@ case class OptionSurface(override val rawType: Class[_], elementSurface: Surface
 }
 case class JavaEnumSurface(override val rawType: Class[_]) extends GenericSurface(rawType)
 
+/**
+  * Enum-like surface for Scala 2.x and Scala 3
+  * @param rawType
+  * @param stringExtractor
+  */
 case class EnumSurface(override val rawType: Class[_], stringExtractor: (Class[_], String) => Option[Any])
     extends GenericSurface(rawType)