From b6a2f96233bbad1a218e3b0fbeeead10b4c98252 Mon Sep 17 00:00:00 2001
From: Nabil Abdel-Hafeez <7283535+987Nabil@users.noreply.github.com>
Date: Tue, 30 Jan 2024 10:16:37 +0100
Subject: [PATCH] Accept empty object for optional json values (#647)

---
 .../scala/zio/schema/codec/JsonCodec.scala    | 32 +++++++++++++++++--
 .../zio/schema/codec/JsonCodecSpec.scala      |  7 ++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/zio-schema-json/shared/src/main/scala/zio/schema/codec/JsonCodec.scala b/zio-schema-json/shared/src/main/scala/zio/schema/codec/JsonCodec.scala
index 823d4bce5..49bc02e7d 100644
--- a/zio-schema-json/shared/src/main/scala/zio/schema/codec/JsonCodec.scala
+++ b/zio-schema-json/shared/src/main/scala/zio/schema/codec/JsonCodec.scala
@@ -3,7 +3,7 @@ package zio.schema.codec
 import java.nio.CharBuffer
 import java.nio.charset.StandardCharsets
 
-import scala.annotation.tailrec
+import scala.annotation.{ switch, tailrec }
 import scala.collection.immutable.ListMap
 
 import zio.json.JsonCodec._
@@ -549,10 +549,38 @@ object JsonCodec {
       case _: ZJsonDecoder[_] =>
     }
 
+    private[schema] def option[A](implicit A: ZJsonDecoder[A]): ZJsonDecoder[Option[A]] =
+      new ZJsonDecoder[Option[A]] { self =>
+        private[this] val ull: Array[Char] = "ull".toCharArray
+
+        override def unsafeDecodeMissing(trace: List[JsonError]): Option[A] =
+          Option.empty
+
+        def unsafeDecode(trace: List[JsonError], in: RetractReader): Option[A] =
+          (in.nextNonWhitespace(): @switch) match {
+            case 'n' =>
+              Lexer.readChars(trace, in, ull, "null")
+              None
+            case '{' =>
+              Lexer.readChars(trace, in, "}".toCharArray, "{}")
+              None
+            case _ =>
+              in.retract()
+              Some(A.unsafeDecode(trace, in))
+          }
+
+        final override def unsafeFromJsonAST(trace: List[JsonError], json: Json): Option[A] =
+          json match {
+            case Json.Null         => None
+            case Json.Obj(Chunk()) => None
+            case _                 => Some(A.unsafeFromJsonAST(trace, json))
+          }
+      }
+
     //scalafmt: { maxColumn = 400, optIn.configStyleArguments = false }
     private[codec] def schemaDecoder[A](schema: Schema[A], discriminator: Int = -1): ZJsonDecoder[A] = schema match {
       case Schema.Primitive(standardType, _)     => primitiveCodec(standardType).decoder
-      case Schema.Optional(codec, _)             => ZJsonDecoder.option(schemaDecoder(codec, discriminator))
+      case Schema.Optional(codec, _)             => option(schemaDecoder(codec, discriminator)).orElse(Json.decoder.mapOrFail(ast => if (ast.asObject.exists(_.isEmpty)) Right(None) else Left("None empty object")))
       case Schema.Tuple2(left, right, _)         => ZJsonDecoder.tuple2(schemaDecoder(left, -1), schemaDecoder(right, -1))
       case Schema.Transform(c, f, _, a, _)       => schemaDecoder(a.foldLeft(c)((s, a) => s.annotate(a)), discriminator).mapOrFail(f)
       case Schema.Sequence(codec, f, _, _, _)    => ZJsonDecoder.chunk(schemaDecoder(codec, -1)).map(f)
diff --git a/zio-schema-json/shared/src/test/scala-2/zio/schema/codec/JsonCodecSpec.scala b/zio-schema-json/shared/src/test/scala-2/zio/schema/codec/JsonCodecSpec.scala
index 60a5091f6..208aa9d02 100644
--- a/zio-schema-json/shared/src/test/scala-2/zio/schema/codec/JsonCodecSpec.scala
+++ b/zio-schema-json/shared/src/test/scala-2/zio/schema/codec/JsonCodecSpec.scala
@@ -556,6 +556,13 @@ object JsonCodecSpec extends ZIOSpecDefault {
           WithOptionFields(Some("s"), None),
           charSequenceToByteChunk("""{"a":"s"}""")
         )
+      },
+      test("case class with option fields accept empty json object as value") {
+        assertDecodes(
+          WithOptionFields.schema,
+          WithOptionFields(Some("s"), None),
+          charSequenceToByteChunk("""{"a":"s", "b":{}}""")
+        )
       }
     ),
     suite("enums")(