From 8d7998ebddcbb76c6f264d1148fdade1a3a00ba7 Mon Sep 17 00:00:00 2001
From: Jisoo Park <jisoo.park@doomoolmori.com>
Date: Tue, 17 Sep 2024 17:47:10 +0900
Subject: [PATCH] Respect discriminators of object enums in Scala 3

---
 .../shared/src/main/scala-3/zio/json/macros.scala    |  4 ++--
 .../test/scala-3/zio/json/DerivedDecoderSpec.scala   | 12 ++++++++++++
 .../test/scala-3/zio/json/DerivedEncoderSpec.scala   | 11 +++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/zio-json/shared/src/main/scala-3/zio/json/macros.scala b/zio-json/shared/src/main/scala-3/zio/json/macros.scala
index 3392d476..f5f04c4c 100644
--- a/zio-json/shared/src/main/scala-3/zio/json/macros.scala
+++ b/zio-json/shared/src/main/scala-3/zio/json/macros.scala
@@ -409,7 +409,7 @@ object DeriveJsonDecoder extends Derivation[JsonDecoder] { self =>
 
     def discrim = ctx.annotations.collectFirst { case jsonDiscriminator(n) => n }
 
-    if (isEnumeration) {
+    if (isEnumeration && discrim.isEmpty) {
       new JsonDecoder[A] {
         def unsafeDecode(trace: List[JsonError], in: RetractReader): A = {
           val typeName = Lexer.string(trace, in).toString()
@@ -656,7 +656,7 @@ object DeriveJsonEncoder extends Derivation[JsonEncoder] { self =>
         case jsonDiscriminator(n) => n
       }
 
-    if (isEnumeration) {
+    if (isEnumeration && discrim.isEmpty) {
       new JsonEncoder[A] {
         def unsafeEncode(a: A, indent: Option[Int], out: Write): Unit = {
           val typeName = ctx.choose(a) { sub =>
diff --git a/zio-json/shared/src/test/scala-3/zio/json/DerivedDecoderSpec.scala b/zio-json/shared/src/test/scala-3/zio/json/DerivedDecoderSpec.scala
index b7b6379f..b99dd7cd 100644
--- a/zio-json/shared/src/test/scala-3/zio/json/DerivedDecoderSpec.scala
+++ b/zio-json/shared/src/test/scala-3/zio/json/DerivedDecoderSpec.scala
@@ -36,6 +36,18 @@ object DerivedDecoderSpec extends ZIOSpecDefault {
     
       assertTrue(result == Right(Foo.Qux))
     },
+    test("Derives for a sum sealed trait Enumeration type with discriminator") {
+      @jsonDiscriminator("$type")
+      sealed trait Foo derives JsonDecoder
+      object Foo:
+        case object Bar extends Foo
+        case object Baz extends Foo
+        case object Qux extends Foo
+
+      val result = """{"$type":"Qux"}""".fromJson[Foo]
+    
+      assertTrue(result == Right(Foo.Qux))
+    },
     test("Derives for a sum ADT type") {
       enum Foo derives JsonDecoder:
         case Bar
diff --git a/zio-json/shared/src/test/scala-3/zio/json/DerivedEncoderSpec.scala b/zio-json/shared/src/test/scala-3/zio/json/DerivedEncoderSpec.scala
index 2eb329c4..05e28dd6 100644
--- a/zio-json/shared/src/test/scala-3/zio/json/DerivedEncoderSpec.scala
+++ b/zio-json/shared/src/test/scala-3/zio/json/DerivedEncoderSpec.scala
@@ -24,6 +24,17 @@ object DerivedEncoderSpec extends ZIOSpecDefault {
 
       assertTrue(json == """"Qux"""")
     },
+    test("Derives for a sum enum Enumeration type with discriminator") {
+      @jsonDiscriminator("$type")
+      enum Foo derives JsonEncoder:
+        case Bar
+        case Baz
+        case Qux
+
+      val json = (Foo.Qux: Foo).toJson
+
+      assertTrue(json == """{"$type":"Qux"}""")
+    },
     test("Derives for a sum sealed trait Enumeration type") {
       sealed trait Foo derives JsonEncoder
       object Foo: