From 0ef6321b880102bc583834d7af35f70c89c2e53a Mon Sep 17 00:00:00 2001
From: Antonio Morales <antonio.morales1990@gmail.com>
Date: Tue, 17 Sep 2024 00:29:53 -0700
Subject: [PATCH] Add JsonCodec.Config.explicitNulls option (#740)

---
 .../scala/zio/schema/codec/JsonCodec.scala    |  8 +++-
 .../zio/schema/codec/JsonCodecSpec.scala      | 47 +++++++++++--------
 2 files changed, 33 insertions(+), 22 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 38ea34ff6..ee9c14a3d 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
@@ -26,7 +26,11 @@ import zio.{ Cause, Chunk, ChunkBuilder, ZIO, ZNothing }
 
 object JsonCodec {
 
-  final case class Config(ignoreEmptyCollections: Boolean, treatStreamsAsArrays: Boolean = false)
+  final case class Config(
+    ignoreEmptyCollections: Boolean,
+    treatStreamsAsArrays: Boolean = false,
+    explicitNulls: Boolean = false
+  )
 
   object Config {
     val default: Config = Config(ignoreEmptyCollections = false)
@@ -1089,7 +1093,7 @@ object JsonCodec {
                 case e: Throwable => throw new RuntimeException(s"Failed to encode field '${s.name}' in $schema'", e)
               }
             val value = s.get(a)
-            if (!enc.isNothing(value) && !isEmptyOptionalValue(s, value, cfg)) {
+            if (!isEmptyOptionalValue(s, value, cfg) && (!enc.isNothing(value) || cfg.explicitNulls)) {
               if (first)
                 first = false
               else {
diff --git a/zio-schema-json/shared/src/test/scala/zio/schema/codec/JsonCodecSpec.scala b/zio-schema-json/shared/src/test/scala/zio/schema/codec/JsonCodecSpec.scala
index 23d46c157..0d3e37175 100644
--- a/zio-schema-json/shared/src/test/scala/zio/schema/codec/JsonCodecSpec.scala
+++ b/zio-schema-json/shared/src/test/scala/zio/schema/codec/JsonCodecSpec.scala
@@ -118,34 +118,42 @@ object JsonCodecSpec extends ZIOSpecDefault {
     suite("empty collections config")(
       test("list empty") {
         assertEncodesJson(
-          Schema[ListAndMap],
-          ListAndMap(Nil, Map("foo" -> 1)),
-          """{"map":{"foo":1}}""",
-          JsonCodec.Config(ignoreEmptyCollections = true)
+          Schema[ListAndMapAndOption],
+          ListAndMapAndOption(Nil, Map("foo" -> 1), Some("foo")),
+          """{"map":{"foo":1},"option":"foo"}""",
+          JsonCodec.Config(ignoreEmptyCollections = true, explicitNulls = false)
         )
       },
       test("map empty") {
         assertEncodesJson(
-          Schema[ListAndMap],
-          ListAndMap(List("foo"), Map.empty),
-          """{"list":["foo"]}""",
-          JsonCodec.Config(ignoreEmptyCollections = true)
+          Schema[ListAndMapAndOption],
+          ListAndMapAndOption(List("foo"), Map.empty, Some("foo")),
+          """{"list":["foo"],"option":"foo"}""",
+          JsonCodec.Config(ignoreEmptyCollections = true, explicitNulls = false)
+        )
+      },
+      test("option empty") {
+        assertEncodesJson(
+          Schema[ListAndMapAndOption],
+          ListAndMapAndOption(List("foo"), Map("foo" -> 1), None),
+          """{"list":["foo"],"map":{"foo":1}}""",
+          JsonCodec.Config(ignoreEmptyCollections = true, explicitNulls = false)
         )
       },
       test("all empty") {
         assertEncodesJson(
-          Schema[ListAndMap],
-          ListAndMap(Nil, Map.empty),
+          Schema[ListAndMapAndOption],
+          ListAndMapAndOption(Nil, Map.empty, None),
           """{}""",
-          JsonCodec.Config(ignoreEmptyCollections = true)
+          JsonCodec.Config(ignoreEmptyCollections = true, explicitNulls = false)
         )
       },
       test("all empty, but don't ignore empty collections") {
         assertEncodesJson(
-          Schema[ListAndMap],
-          ListAndMap(Nil, Map.empty),
-          """{"list":[],"map":{}}""",
-          JsonCodec.Config(ignoreEmptyCollections = false)
+          Schema[ListAndMapAndOption],
+          ListAndMapAndOption(Nil, Map.empty, None),
+          """{"list":[],"map":{},"option":null}""",
+          JsonCodec.Config(ignoreEmptyCollections = false, explicitNulls = true)
         )
       }
     ),
@@ -1510,8 +1518,7 @@ object JsonCodecSpec extends ZIOSpecDefault {
           Enumeration3(StringValue3("foo"))
         ) &> assertEncodesThenDecodes(
           Schema[Enumeration3],
-          Enumeration3(StringValue3Multi("foo", "bar")),
-          print = true
+          Enumeration3(StringValue3Multi("foo", "bar"))
         )
       },
       test("of case classes with discriminator") {
@@ -2159,10 +2166,10 @@ object JsonCodecSpec extends ZIOSpecDefault {
     implicit lazy val schema: Schema[WithOptField] = DeriveSchema.gen[WithOptField]
   }
 
-  final case class ListAndMap(list: List[String], map: Map[String, Int])
+  final case class ListAndMapAndOption(list: List[String], map: Map[String, Int], option: Option[String])
 
-  object ListAndMap {
-    implicit lazy val schema: Schema[ListAndMap] = DeriveSchema.gen[ListAndMap]
+  object ListAndMapAndOption {
+    implicit lazy val schema: Schema[ListAndMapAndOption] = DeriveSchema.gen[ListAndMapAndOption]
   }
 
   final case class KeyWrapper(key: String)