fix-polymorphic-value-class-union-schema-name

core/src/main/kotlin/com/github/avrokotlin/avro4k/internal/PolymorphicResolver.kt

@@ -1,6 +1,8 @@
 package com.github.avrokotlin.avro4k.internal
 
 import com.github.avrokotlin.avro4k.AvroAlias
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.descriptors.PrimitiveKind
 import kotlinx.serialization.descriptors.SerialDescriptor
 import kotlinx.serialization.modules.SerializersModule
 
@@ -12,12 +14,46 @@ internal class PolymorphicResolver(private val serializersModule: SerializersMod
             descriptor.possibleSerializationSubclasses(serializersModule)
                 .flatMap {
                     sequence {
-                        yield(it.nonNullSerialName to it.nonNullSerialName)
+                        yield(it.avroUnionSchemaFullName() to it.nonNullSerialName)
                         it.findAnnotation<AvroAlias>()?.value?.forEach { alias ->
                             yield(alias to it.nonNullSerialName)
                         }
                     }
                 }.toMap()
         }
     }
-}
+}
+
+/**
+ * Returns the Avro schema full name that this descriptor produces when used inside a union.
+ *
+ * For value/inline classes, the Avro schema is the unwrapped inner type's schema, so the union
+ * lookup key must match that inner schema's full name (e.g. "string" for a String-backed value class)
+ * rather than the value class's own serial name.
+ *
+ * For all other types the serial name is used directly, matching how [ClassVisitor] and [ValueVisitor]
+ * produce named Avro schemas.
+ */
+@OptIn(ExperimentalSerializationApi::class)
+private fun SerialDescriptor.avroUnionSchemaFullName(): String {
+    if (!isInline) return nonNullSerialName
+    val innerDescriptor = getElementDescriptor(0)
+    return when (val kind = innerDescriptor.kind) {
+        is PrimitiveKind -> kind.avroTypeName()
+        else -> innerDescriptor.avroUnionSchemaFullName()
+    }
+}
+
+private fun PrimitiveKind.avroTypeName(): String =
+    when (this) {
+        PrimitiveKind.BOOLEAN -> "boolean"
+        PrimitiveKind.BYTE,
+        PrimitiveKind.SHORT,
+        PrimitiveKind.INT,
+        PrimitiveKind.CHAR,
+        -> "int"
+        PrimitiveKind.LONG -> "long"
+        PrimitiveKind.FLOAT -> "float"
+        PrimitiveKind.DOUBLE -> "double"
+        PrimitiveKind.STRING -> "string"
+    }

core/src/test/kotlin/com/github/avrokotlin/avro4k/encoding/SealedClassEncodingTest.kt

@@ -7,6 +7,7 @@ import com.github.avrokotlin.avro4k.recordWithSchema
 import com.github.avrokotlin.avro4k.schema
 import io.kotest.core.spec.style.StringSpec
 import kotlinx.serialization.Serializable
+import org.apache.avro.generic.GenericData
 
 internal class SealedClassEncodingTest : StringSpec({
     "encode/decode sealed classes" {
@@ -15,6 +16,13 @@ internal class SealedClassEncodingTest : StringSpec({
         AvroAssertions.assertThat<Operation>(Operation.Binary.Add(1, 2))
             .isEncodedAs(recordWithSchema(Avro.schema<Operation.Binary.Add>(), 1, 2))
     }
+    "encode/decode sealed class union with value class primitive, enum and record subtypes" {
+        val shapeSchema = Avro.schema<Shape>()
+        val colorSchema = shapeSchema.types.first { it.name == "Color" }
+        AvroAssertions.assertThat<Shape>(Shape.Label("hello")).isEncodedAs("hello")
+        AvroAssertions.assertThat<Shape>(Shape.Color.RED).isEncodedAs(GenericData.get().createEnum("RED", colorSchema))
+        AvroAssertions.assertThat<Shape>(Shape.Circle(5)).isEncodedAs(recordWithSchema(Avro.schema<Shape.Circle>(), 5))
+    }
     "encode/decode nullable sealed classes" {
         AvroAssertions.assertThat(ReferencingNullableSealedClass(Operation.Binary.Add(1, 2)))
             .isEncodedAs(record(recordWithSchema(Avro.schema<Operation.Binary.Add>(), 1, 2)))
@@ -27,6 +35,19 @@ internal class SealedClassEncodingTest : StringSpec({
             .isEncodedAs(null)
     }
 }) {
+    @Serializable
+    private sealed interface Shape {
+        @JvmInline
+        @Serializable
+        value class Label(val value: String) : Shape
+
+        @Serializable
+        enum class Color : Shape { RED, BLUE }
+
+        @Serializable
+        data class Circle(val radius: Int) : Shape
+    }
+
     @Serializable
     private data class ReferencingSealedClass(
         val notNullable: Operation,

kotlin-generator/src/main/kotlin/com/github/avrokotlin/avro4k/KotlinGenerator.kt

@@ -332,6 +332,7 @@ public class KotlinGenerator(
      * ```kotlin
      * @Serializable
      * sealed interface <potentialAnonymousBaseName>Union {
+     *     @AvroAlias("<Type full name>")
      *     @JvmInline
      *     @Serializable
      *     value class For<Type name>(val value: <Type full name>) : <potentialAnonymousBaseName>Union
@@ -356,6 +357,7 @@ public class KotlinGenerator(
                         TypeSpec.classBuilder(unionSubTypeNameFormatter(if (hasSimilarNames) subSchema.fullName else subSchema.simpleName.toPascalCase()))
                             .addSuperinterface(ClassName.fromFullName(className))
                             .addModifiers(KModifier.VALUE)
+                            .addAnnotationIfNotNull(buildAvroAliasAnnotation(listOf(subSchema.fullName)))
                             .addAnnotation(JvmInline::class)
                             .addAnnotation(Serializable::class)
                             .addPrimaryProperty(

kotlin-generator/src/test/expected-sources/complex-union-in-record/ComplexUnionInRecord.kt

@@ -3,6 +3,7 @@
     ExperimentalAvro4kApi::class,
 )
 
+import com.github.avrokotlin.avro4k.AvroAlias
 import com.github.avrokotlin.avro4k.AvroDefault
 import com.github.avrokotlin.avro4k.ExperimentalAvro4kApi
 import com.github.avrokotlin.avro4k.InternalAvro4kApi
@@ -25,18 +26,21 @@ public data class ComplexUnionInRecord(
     @Serializable
     @AvroGenerated("""["null",{"type":"record","name":"NestedRecord","fields":[{"name":"id","type":"string"},{"name":"value","type":"int"}]},{"type":"enum","name":"Status","symbols":["ACTIVE","INACTIVE","PENDING"]},{"type":"array","items":"string"}]""")
     public sealed interface TheFieldUnion {
+        @AvroAlias("NestedRecord")
         @JvmInline
         @Serializable
         public value class ForNestedRecord(
             public val `value`: NestedRecord,
         ) : TheFieldUnion
 
+        @AvroAlias("Status")
         @JvmInline
         @Serializable
         public value class ForStatus(
             public val `value`: Status,
         ) : TheFieldUnion
 
+        @AvroAlias("array")
         @JvmInline
         @Serializable
         public value class ForArray(

kotlin-generator/src/test/expected-sources/field-naming-camel-case/ns/CamelCaseRecord.kt

@@ -48,12 +48,14 @@ public data class CamelCaseRecord(
     @Serializable
     @AvroGenerated("""["string",{"type":"enum","name":"StatusFlag","namespace":"ns","symbols":["ACTIVE","INACTIVE"]},"null"]""")
     public sealed interface AccountStatusUnion {
+        @AvroAlias("string")
         @JvmInline
         @Serializable
         public value class ForString(
             public val `value`: String,
         ) : AccountStatusUnion
 
+        @AvroAlias("ns.StatusFlag")
         @JvmInline
         @Serializable
         public value class ForStatusFlag(

kotlin-generator/src/test/expected-sources/root-complex-union/TestSchema.kt

@@ -3,6 +3,7 @@
     ExperimentalAvro4kApi::class,
 )
 
+import com.github.avrokotlin.avro4k.AvroAlias
 import com.github.avrokotlin.avro4k.AvroFixed
 import com.github.avrokotlin.avro4k.ExperimentalAvro4kApi
 import com.github.avrokotlin.avro4k.InternalAvro4kApi
@@ -20,43 +21,50 @@ import kotlinx.serialization.Serializable
 @Serializable
 @AvroGenerated("""["null","string","int",{"type":"record","name":"NestedRecord","fields":[{"name":"field","type":"string","doc":"field doc"}]},{"type":"enum","name":"AnEnum","symbols":["A","B","C"]},{"type":"fixed","name":"AFixed","size":5},{"type":"array","items":"int"},{"type":"map","values":["null","double"]}]""")
 public sealed interface TestSchema {
+    @AvroAlias("string")
     @JvmInline
     @Serializable
     public value class ForString(
         public val `value`: String,
     ) : TestSchema
 
+    @AvroAlias("int")
     @JvmInline
     @Serializable
     public value class ForInt(
         public val `value`: Int,
     ) : TestSchema
 
+    @AvroAlias("NestedRecord")
     @JvmInline
     @Serializable
     public value class ForNestedRecord(
         public val `value`: NestedRecord,
     ) : TestSchema
 
+    @AvroAlias("AnEnum")
     @JvmInline
     @Serializable
     public value class ForAnEnum(
         public val `value`: AnEnum,
     ) : TestSchema
 
+    @AvroAlias("AFixed")
     @JvmInline
     @Serializable
     public value class ForAFixed(
         @AvroFixed(size = 5)
         public val `value`: ByteArray,
     ) : TestSchema
 
+    @AvroAlias("array")
     @JvmInline
     @Serializable
     public value class ForArray(
         public val `value`: List<Int>,
     ) : TestSchema
 
+    @AvroAlias("map")
     @JvmInline
     @Serializable
     public value class ForMap(

kotlin-generator/src/test/expected-sources/root-map/TestSchemaMapUnion.kt

@@ -3,6 +3,7 @@
     ExperimentalAvro4kApi::class,
 )
 
+import com.github.avrokotlin.avro4k.AvroAlias
 import com.github.avrokotlin.avro4k.ExperimentalAvro4kApi
 import com.github.avrokotlin.avro4k.InternalAvro4kApi
 import com.github.avrokotlin.avro4k.`internal`.AvroGenerated
@@ -15,12 +16,14 @@ import kotlinx.serialization.Serializable
 @Serializable
 @AvroGenerated("""["double","null","int"]""")
 public sealed interface TestSchemaMapUnion {
+    @AvroAlias("double")
     @JvmInline
     @Serializable
     public value class ForDouble(
         public val `value`: Double,
     ) : TestSchemaMapUnion
 
+    @AvroAlias("int")
     @JvmInline
     @Serializable
     public value class ForInt(

kotlin-generator/src/test/expected-sources/root-union-with-nested-map-and-array-unions/TestSchema.kt

@@ -3,6 +3,7 @@
     ExperimentalAvro4kApi::class,
 )
 
+import com.github.avrokotlin.avro4k.AvroAlias
 import com.github.avrokotlin.avro4k.ExperimentalAvro4kApi
 import com.github.avrokotlin.avro4k.InternalAvro4kApi
 import com.github.avrokotlin.avro4k.`internal`.AvroGenerated
@@ -17,18 +18,21 @@ import kotlinx.serialization.Serializable
 @Serializable
 @AvroGenerated("""["int","null",{"type":"map","values":["string","null",{"type":"array","items":["long","null",{"type":"map","values":["boolean","null"]}]}]},{"type":"array","items":["long","null","double"]}]""")
 public sealed interface TestSchema {
+    @AvroAlias("int")
     @JvmInline
     @Serializable
     public value class ForInt(
         public val `value`: Int,
     ) : TestSchema
 
+    @AvroAlias("map")
     @JvmInline
     @Serializable
     public value class ForMap(
         public val `value`: Map<String, TestSchemaMapUnion?>,
     ) : TestSchema
 
+    @AvroAlias("array")
     @JvmInline
     @Serializable
     public value class ForArray(

kotlin-generator/src/test/expected-sources/root-union-with-nested-map-and-array-unions/TestSchemaArrayUnion.kt

@@ -3,6 +3,7 @@
     ExperimentalAvro4kApi::class,
 )
 
+import com.github.avrokotlin.avro4k.AvroAlias
 import com.github.avrokotlin.avro4k.ExperimentalAvro4kApi
 import com.github.avrokotlin.avro4k.InternalAvro4kApi
 import com.github.avrokotlin.avro4k.`internal`.AvroGenerated
@@ -15,12 +16,14 @@ import kotlinx.serialization.Serializable
 @Serializable
 @AvroGenerated("""["long","null","double"]""")
 public sealed interface TestSchemaArrayUnion {
+    @AvroAlias("long")
     @JvmInline
     @Serializable
     public value class ForLong(
         public val `value`: Long,
     ) : TestSchemaArrayUnion
 
+    @AvroAlias("double")
     @JvmInline
     @Serializable
     public value class ForDouble(

kotlin-generator/src/test/expected-sources/root-union-with-nested-map-and-array-unions/TestSchemaMapArrayUnion.kt

@@ -3,6 +3,7 @@
     ExperimentalAvro4kApi::class,
 )
 
+import com.github.avrokotlin.avro4k.AvroAlias
 import com.github.avrokotlin.avro4k.ExperimentalAvro4kApi
 import com.github.avrokotlin.avro4k.InternalAvro4kApi
 import com.github.avrokotlin.avro4k.`internal`.AvroGenerated
@@ -17,12 +18,14 @@ import kotlinx.serialization.Serializable
 @Serializable
 @AvroGenerated("""["long","null",{"type":"map","values":["boolean","null"]}]""")
 public sealed interface TestSchemaMapArrayUnion {
+    @AvroAlias("long")
     @JvmInline
     @Serializable
     public value class ForLong(
         public val `value`: Long,
     ) : TestSchemaMapArrayUnion
 
+    @AvroAlias("map")
     @JvmInline
     @Serializable
     public value class ForMap(

kotlin-generator/src/test/expected-sources/root-union-with-nested-map-and-array-unions/TestSchemaMapUnion.kt

@@ -3,6 +3,7 @@
     ExperimentalAvro4kApi::class,
 )
 
+import com.github.avrokotlin.avro4k.AvroAlias
 import com.github.avrokotlin.avro4k.ExperimentalAvro4kApi
 import com.github.avrokotlin.avro4k.InternalAvro4kApi
 import com.github.avrokotlin.avro4k.`internal`.AvroGenerated
@@ -15,12 +16,14 @@ import kotlinx.serialization.Serializable
 @Serializable
 @AvroGenerated("""["string","null",{"type":"array","items":["long","null",{"type":"map","values":["boolean","null"]}]}]""")
 public sealed interface TestSchemaMapUnion {
+    @AvroAlias("string")
     @JvmInline
     @Serializable
     public value class ForString(
         public val `value`: String,
     ) : TestSchemaMapUnion
 
+    @AvroAlias("array")
     @JvmInline
     @Serializable
     public value class ForArray(

kotlin-generator/src/test/expected-sources/types-across-multiple-files/Union.kt

@@ -3,6 +3,7 @@
     ExperimentalAvro4kApi::class,
 )
 
+import com.github.avrokotlin.avro4k.AvroAlias
 import com.github.avrokotlin.avro4k.AvroFixed
 import com.github.avrokotlin.avro4k.ExperimentalAvro4kApi
 import com.github.avrokotlin.avro4k.InternalAvro4kApi
@@ -18,37 +19,43 @@ import ns2.Enum
 @Serializable
 @AvroGenerated("""[{"type":"record","name":"Record","namespace":"ns","fields":[{"name":"field","type":"int"}]},{"type":"record","name":"RecordWithoutNamespace","fields":[{"name":"field","type":"int"}]},{"type":"enum","name":"Enum","namespace":"ns2","symbols":["FIRST","SECOND"]},{"type":"fixed","name":"FixedType","size":12},"string","bytes"]""")
 public sealed interface Union {
+    @AvroAlias("ns.Record")
     @JvmInline
     @Serializable
     public value class ForRecord(
         public val `value`: Record,
     ) : Union
 
+    @AvroAlias("RecordWithoutNamespace")
     @JvmInline
     @Serializable
     public value class ForRecordWithoutNamespace(
         public val `value`: RecordWithoutNamespace,
     ) : Union
 
+    @AvroAlias("ns2.Enum")
     @JvmInline
     @Serializable
     public value class ForEnum(
         public val `value`: Enum,
     ) : Union
 
+    @AvroAlias("FixedType")
     @JvmInline
     @Serializable
     public value class ForFixedType(
         @AvroFixed(size = 12)
         public val `value`: ByteArray,
     ) : Union
 
+    @AvroAlias("string")
     @JvmInline
     @Serializable
     public value class ForString(
         public val `value`: String,
     ) : Union
 
+    @AvroAlias("bytes")
     @JvmInline
     @Serializable
     public value class ForBytes(