Fixes #691 - when decoding json payload using decoder derived from a …

zio-schema-json/jvm/src/test/scala-2/zio/schema/codec/JsonCodecJVMSpec.scala

@@ -20,6 +20,18 @@ object JsonCodecJVMSpec extends ZIOSpecDefault {
     ) @@ TestAspect.jvmOnly @@ timeout(180.seconds)
 
   private val decoderSuite = suite("decoding")(
+    suite("decode record with more than 22 fields")(
+      test("missing fields in the json payload are populated with their default values") {
+        val exampleSchema = zio.schema.DeriveSchema.gen[RecordExample]
+        val string        = """{"f1": "test"}"""
+        assertDecodesJson(exampleSchema, RecordExample(Some("test")), string)
+      },
+      test("fail if a field with no default value is missing in the json payload") {
+        val exampleSchema = zio.schema.DeriveSchema.gen[RecordExample2]
+        val string        = """{"f1": "test"}"""
+        assertDecodesJsonFailure(exampleSchema, string)
+      }
+    ),
     suite("case class")(
       test("case class with empty option field is decoded by stream") {
         val names     = Gen.option(Gen.elements("John", "Jane", "Jermaine", "Jasmine"))
@@ -50,6 +62,16 @@ object JsonCodecJVMSpec extends ZIOSpecDefault {
     )
   )
 
+  private def assertDecodesJson[A](schema: Schema[A], value: A, jsonString: String) = {
+    val either = JsonCodec.jsonDecoder(schema).decodeJson(jsonString)
+    zio.test.assert(either)(isRight(equalTo(value)))
+  }
+
+  private def assertDecodesJsonFailure[A](schema: Schema[A], jsonString: String) = {
+    val either = JsonCodec.jsonDecoder(schema).decodeJson(jsonString)
+    zio.test.assertTrue(either.isLeft)
+  }
+
   private def assertDecodesJsonStream[A](
     schema: Schema[A],
     value: Chunk[A],
@@ -64,4 +86,57 @@ object JsonCodecJVMSpec extends ZIOSpecDefault {
       .either
     assertZIO(result)(isRight(equalTo(value)))
   }
+
+  case class RecordExample(
+    f1: Option[String],
+    f2: Option[String] = None,
+    f3: Option[String] = None,
+    f4: Option[String] = None,
+    f5: Option[String] = None,
+    f6: Option[String] = None,
+    f7: Option[String] = None,
+    f8: Option[String] = None,
+    f9: Option[String] = None,
+    f10: Option[String] = None,
+    f11: Option[String] = None,
+    f12: Option[String] = None,
+    f13: Option[String] = None,
+    f14: Option[String] = None,
+    f15: Option[String] = None,
+    f16: Option[String] = None,
+    f17: Option[String] = None,
+    f18: Option[String] = None,
+    f19: Option[String] = None,
+    f20: Option[String] = None,
+    f21: Option[String] = None,
+    f22: Option[String] = None,
+    f23: Option[String] = None
+  )
+
+  case class RecordExample2(
+    f1: Option[String],
+    f2: Option[String],
+    f3: Option[String] = None,
+    f4: Option[String] = None,
+    f5: Option[String] = None,
+    f6: Option[String] = None,
+    f7: Option[String] = None,
+    f8: Option[String] = None,
+    f9: Option[String] = None,
+    f10: Option[String] = None,
+    f11: Option[String] = None,
+    f12: Option[String] = None,
+    f13: Option[String] = None,
+    f14: Option[String] = None,
+    f15: Option[String] = None,
+    f16: Option[String] = None,
+    f17: Option[String] = None,
+    f18: Option[String] = None,
+    f19: Option[String] = None,
+    f20: Option[String] = None,
+    f21: Option[String] = None,
+    f22: Option[String] = None,
+    f23: Option[String] = None
+  )
+
 }

zio-schema-json/shared/src/main/scala/zio/schema/codec/JsonCodec.scala

@@ -830,7 +830,18 @@ object JsonCodec {
               ()
             }
           }
-          (ListMap.newBuilder[String, Any] ++= builder.result()).result()
+          val tuples                       = builder.result()
+          val collectedFields: Set[String] = tuples.map { case (fieldName, _) => fieldName }.toSet
+          val resultBuilder                = ListMap.newBuilder[String, Any]
+
+          // add fields with default values if they are not present in the JSON
+          structure.foreach { field =>
+            if (!collectedFields.contains(field.name) && field.optional && field.defaultValue.isDefined) {
+              val value = field.name -> field.defaultValue.get
+              resultBuilder += value
+            }
+          }
+          (resultBuilder ++= tuples).result()
         }
     }
 

zio-schema-json/shared/src/test/scala-2/zio/schema/codec/JsonCodecSpec.scala

@@ -219,6 +219,13 @@ object JsonCodecSpec extends ZIOSpecDefault {
       }
     ),
     suite("record")(
+      test("missing fields should be replaced by default values") {
+        assertDecodes(
+          recordSchema,
+          ListMap[String, Any]("foo" -> "s", "bar" -> 1),
+          charSequenceToByteChunk("""{"foo":"s"}""")
+        )
+      },
       test("of primitives") {
         assertEncodes(
           recordSchema,
@@ -435,6 +442,13 @@ object JsonCodecSpec extends ZIOSpecDefault {
           ListMap[String, Any]("foo" -> "s", "bar" -> 1),
           charSequenceToByteChunk("""{"foo":"s","bar":1,"baz":2}""")
         )
+      },
+      test("with missing fields") {
+        assertDecodes(
+          RecordExample.schema,
+          RecordExample(f1 = Some("test"), f2 = None),
+          charSequenceToByteChunk("""{"f1":"test"}""")
+        )
       }
     ),
     suite("transform")(
@@ -1636,6 +1650,7 @@ object JsonCodecSpec extends ZIOSpecDefault {
       .Field(
         "bar",
         Schema.Primitive(StandardType.IntType),
+        annotations0 = Chunk(fieldDefaultValue(1)),
         get0 = (p: ListMap[String, _]) => p("bar").asInstanceOf[Int],
         set0 = (p: ListMap[String, _], v: Int) => p.updated("bar", v)
       )
@@ -1867,4 +1882,35 @@ object JsonCodecSpec extends ZIOSpecDefault {
   object AllOptionalFields {
     implicit lazy val schema: Schema[AllOptionalFields] = DeriveSchema.gen[AllOptionalFields]
   }
+
+  case class RecordExample(
+    f1: Option[String], // the only field that does not have a default value
+    f2: Option[String] = None,
+    f3: Option[String] = None,
+    f4: Option[String] = None,
+    f5: Option[String] = None,
+    f6: Option[String] = None,
+    f7: Option[String] = None,
+    f8: Option[String] = None,
+    f9: Option[String] = None,
+    f10: Option[String] = None,
+    f11: Option[String] = None,
+    f12: Option[String] = None,
+    f13: Option[String] = None,
+    f14: Option[String] = None,
+    f15: Option[String] = None,
+    f16: Option[String] = None,
+    f17: Option[String] = None,
+    f18: Option[String] = None,
+    f19: Option[String] = None,
+    f20: Option[String] = None,
+    f21: Option[String] = None,
+    f22: Option[String] = None,
+    f23: Option[String] = None
+  )
+
+  object RecordExample {
+    implicit lazy val schema: Schema[RecordExample] = DeriveSchema.gen[RecordExample]
+  }
+
 }