Merge pull request #450 from erikvanoosten/option-plus-sum-types

Support Option of sum types
fd4s · Nov 23, 2022 · bef0f4e · bef0f4e
2 parents 1d937ff + 4e935f4
commit bef0f4e
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Showing 4 changed files with 48 additions and 5 deletions.
diff --git a/modules/core/src/main/scala/vulcan/Codec.scala b/modules/core/src/main/scala/vulcan/Codec.scala
@@ -976,9 +976,34 @@ object Codec extends CodecCompanionCompat {
     * @group General
     */
   implicit final def option[A](implicit codec: Codec[A]): Codec[Option[A]] =
-    Codec
-      .union[Option[A]](alt => alt[None.type] |+| alt[Some[A]])
+    OptionCodec(codec)
       .withTypeName("Option")
+  private[vulcan] final case class OptionCodec[A](codec: Codec[A]) extends Codec[Option[A]] {
+    type AvroType = Any
+    override def encode(a: Option[A]): Either[AvroError, Any] = {
+      a match {
+        case Some(value) => codec.encode(value)
+        case None        => Codec.none.encode(None)
+      }
+    }
+
+    override def decode(value: Any, schema: Schema): Either[AvroError, Option[A]] = {
+      if (value == null) {
+        Right(None)
+      } else if (schema.isUnion) {
+        codec.schema.flatMap(codec.decode(value, _).map(Some.apply))
+      } else {
+        codec.decode(value, schema).map(Some.apply)
+      }
+    }
+
+    val schema = AvroError.catchNonFatal {
+      codec.schema.map { schema =>
+        val schemaTypes = if (schema.isUnion) schema.getTypes.asScala.toList else List(schema)
+        Schema.createUnion((Schema.create(Schema.Type.NULL) :: schemaTypes).asJava)
+      }
+    }
+  }
 
   /**
     * Returns a new record [[Codec]] for type `A`.

diff --git a/modules/core/src/test/scala/vulcan/CodecSpec.scala b/modules/core/src/test/scala/vulcan/CodecSpec.scala
@@ -1560,7 +1560,7 @@ final class CodecSpec extends BaseSpec with CodecSpecHelpers {
 
         it("should capture errors on nested unions") {
           assertSchemaError[Option[Option[Int]]] {
-            """org.apache.avro.AvroRuntimeException: Nested union: ["null",["null","int"]]"""
+            """org.apache.avro.AvroRuntimeException: Duplicate in union:null"""
           }
         }
       }
@@ -1586,7 +1586,7 @@ final class CodecSpec extends BaseSpec with CodecSpecHelpers {
           assertDecodeError[Option[Int]](
             unsafeEncode(Option(1)),
             unsafeSchema[String],
-            "Error decoding Option: Error decoding union: Exhausted alternatives for type java.lang.Integer"
+            "Error decoding Option: Error decoding Int: Got unexpected schema type STRING, expected schema type INT"
           )
         }
 
@@ -2454,7 +2454,7 @@ final class CodecSpec extends BaseSpec with CodecSpecHelpers {
 
       it("should show the error if schema is unavailable") {
         assert {
-          Codec[Option[Option[Int]]].show == """AvroError(org.apache.avro.AvroRuntimeException: Nested union: ["null",["null","int"]])"""
+          Codec[Option[Option[Int]]].show == """AvroError(org.apache.avro.AvroRuntimeException: Duplicate in union:null)"""
         }
       }
 

diff --git a/modules/generic/src/test/scala/vulcan/generic/GenericDerivationCodecSpec.scala b/modules/generic/src/test/scala/vulcan/generic/GenericDerivationCodecSpec.scala
@@ -69,6 +69,14 @@ final class GenericDerivationCodecSpec extends CodecBase {
             }
           }
 
+          it(
+            "should support optional field of a sum type"
+          ) {
+            assertSchemaIs[CaseClassOptionOfSumType] {
+              """{"type":"record","name":"CaseClassOptionOfSumType","namespace":"vulcan.generic.examples","fields":[{"name":"field1","type":["null",{"type":"record","name":"FirstInSealedTraitCaseClassCustom","fields":[{"name":"value","type":"int"}]},"string"]}]}""".stripMargin
+            }
+          }
+
         }
 
         describe("encode") {

diff --git a/modules/generic/src/test/scala/vulcan/generic/examples/CaseClassOptionOfSumType.scala b/modules/generic/src/test/scala/vulcan/generic/examples/CaseClassOptionOfSumType.scala
@@ -0,0 +1,10 @@
+package vulcan.generic.examples
+
+import vulcan.Codec
+import vulcan.generic._
+
+case class CaseClassOptionOfSumType(field1: Option[SealedTraitCaseClassCustom])
+
+object CaseClassOptionOfSumType {
+  implicit val codec: Codec[CaseClassOptionOfSumType] = Codec.derive
+}