add-scala3-enum-put-get-derivation

Author: drewfeelsblue

modules/core/src/main/scala-3/doobie/util/GetPlatform.scala

@@ -4,4 +4,22 @@
 
 package doobie.util
 
-trait GetPlatform {}
+import scala.deriving.Mirror
+import scala.compiletime.constValue
+
+trait GetPlatform {
+  private def of[A](name: String, cases: List[A], labels: List[String]): Get[A] =
+    Get[String].temap { caseName =>
+      labels.indexOf(caseName) match {
+        case -1 => Left(s"enum $name does not contain case: $caseName")
+        case i  => Right(cases(i))
+      }
+    }
+
+  inline final def deriveEnumString[A](using mirror: Mirror.SumOf[A]): Get[A] =
+    of(
+      constValue[mirror.MirroredLabel],
+      summonSingletonCases[mirror.MirroredElemTypes, A](constValue[mirror.MirroredLabel]),
+      summonLabels[mirror.MirroredElemLabels]
+    )
+}

modules/core/src/main/scala-3/doobie/util/PutPlatform.scala

@@ -4,4 +4,13 @@
 
 package doobie.util
 
-trait PutPlatform
+import scala.compiletime.constValue
+import scala.deriving.Mirror
+
+trait PutPlatform {
+  inline final def deriveEnumString[A](using mirror: Mirror.SumOf[A]): Put[A] =
+    val _ = summonSingletonCases[mirror.MirroredElemTypes, A](constValue[mirror.MirroredLabel])
+    val labels = summonLabels[mirror.MirroredElemLabels]
+
+    Put[String].contramap(a => labels(mirror.ordinal(a)))
+}

modules/core/src/main/scala-3/doobie/util/package.scala

@@ -0,0 +1,22 @@
+// Copyright (c) 2013-2020 Rob Norris and Contributors
+// This software is licensed under the MIT License (MIT).
+// For more information see LICENSE or https://opensource.org/licenses/MIT
+
+package doobie.util
+
+import scala.compiletime.{codeOf, constValue, erasedValue, error, summonInline}
+import scala.deriving.Mirror
+
+private[util] inline final def summonLabels[T <: Tuple]: List[String] =
+  inline erasedValue[T] match
+    case _: EmptyTuple => Nil
+    case _: (t *: ts)  => constValue[t].asInstanceOf[String] :: summonLabels[ts]
+
+private[util] inline final def summonSingletonCases[T <: Tuple, A](inline typeName: Any): List[A] =
+  inline erasedValue[T] match
+    case _: EmptyTuple => Nil
+    case _: (h *: t) =>
+      inline summonInline[Mirror.Of[h]] match
+        case m: Mirror.Singleton => m.fromProduct(EmptyTuple).asInstanceOf[A] :: summonSingletonCases[t, A](typeName)
+        case m: Mirror =>
+          error("Enum " + codeOf(typeName) + " contains non singleton case " + codeOf(constValue[m.MirroredLabel]))