Support nullable types

Author: lauzadis

hll/dynamodb-mapper/dynamodb-mapper-codegen/src/main/kotlin/aws/sdk/kotlin/hll/dynamodbmapper/codegen/model/MapperTypes.kt

@@ -78,6 +78,7 @@ public object MapperTypes {
     public object Values {
         public fun valueConverter(value: Type): TypeRef = TypeRef(MapperPkg.Hl.Values, "ValueConverter", genericArgs = listOf(value))
         public val ItemToValueConverter: TypeRef = TypeRef(MapperPkg.Hl.Values, "ItemToValueConverter")
+        public val NullableConverter: TypeRef = TypeRef(MapperPkg.Hl.Values, "NullableConverter")
 
         public object Collections {
             public val ListConverter: TypeRef = TypeRef(MapperPkg.Hl.CollectionValues, "ListConverter")

hll/dynamodb-mapper/dynamodb-mapper-schema-codegen/src/main/kotlin/aws/sdk/kotlin/hll/dynamodbmapper/codegen/annotations/rendering/SchemaRenderer.kt

@@ -195,6 +195,12 @@ internal class SchemaRenderer(
 
             type.isGenericFor(Types.Kotlin.Collections.Set) -> writeInline("#T", ksType.singleArgument().setValueConverter)
 
+            type.nullable -> {
+                writeInline("#T(", MapperTypes.Values.NullableConverter)
+                renderValueConverter(ksType.makeNotNullable())
+                writeInline(")")
+            }
+
             else -> writeInline(
                 "#T",
                 when (type) {
@@ -218,7 +224,7 @@ internal class SchemaRenderer(
                     Types.Kotlin.UShort -> MapperTypes.Values.Scalars.UShortConverter
                     Types.Kotlin.ULong -> MapperTypes.Values.Scalars.ULongConverter
 
-                    else -> error("Unsupported attribute type $this")
+                    else -> error("Unsupported attribute type $type")
                 },
             )
         }

hll/dynamodb-mapper/dynamodb-mapper-schema-generator-plugin/src/test/kotlin/aws/sdk/kotlin/hll/dynamodbmapper/plugins/SchemaGeneratorPluginTest.kt

@@ -448,6 +448,33 @@ class SchemaGeneratorPluginTest {
         assertContains(setOf(TaskOutcome.SUCCESS, TaskOutcome.UP_TO_DATE), testResult.task(":test")?.outcome)
     }
 
+    @Test
+    fun testNullableTypes() {
+        buildFile.appendText(
+            """
+            dependencies {
+                implementation("aws.smithy.kotlin:runtime-core:$smithyKotlinVersion")
+                testImplementation(kotlin("test")) 
+            }
+            """.trimIndent(),
+        )
+
+        createClassFile("standard-item-converters/src/NullableItem")
+
+        val buildResult = runner.build()
+        assertContains(setOf(TaskOutcome.SUCCESS, TaskOutcome.UP_TO_DATE), buildResult.task(":build")?.outcome)
+        val schemaFile = File(testProjectDir, "build/generated/ksp/main/kotlin/org/example/dynamodbmapper/generatedschemas/NullableItemSchema.kt")
+        assertTrue(schemaFile.exists())
+
+        val testFile = File(testProjectDir, "src/test/kotlin/org/example/standard-item-converters/test/NullableItemTest.kt")
+        testFile.ensureParentDirsCreated()
+        testFile.createNewFile()
+        testFile.writeText(getResource("/standard-item-converters/test/NullableItemTest.kt"))
+
+        val testResult = runner.withArguments("test").build()
+        assertContains(setOf(TaskOutcome.SUCCESS, TaskOutcome.UP_TO_DATE), testResult.task(":test")?.outcome)
+    }
+
     @Test
     fun testLists() {
         buildFile.appendText(

hll/dynamodb-mapper/dynamodb-mapper-schema-generator-plugin/src/test/resources/standard-item-converters/src/NullableItem.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.example
+
+import aws.sdk.kotlin.hll.dynamodbmapper.DynamoDbItem
+import aws.sdk.kotlin.hll.dynamodbmapper.DynamoDbPartitionKey
+import aws.smithy.kotlin.runtime.time.Instant
+
+@DynamoDbItem
+public data class NullableItem(
+    @DynamoDbPartitionKey var id: Int,
+
+    /**
+     * A selection of nullable types
+     */
+    var string: String?,
+    var byte: Byte?,
+    var int: Int?,
+    var instant: Instant?,
+) {
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is NullableItem) return false
+
+        if (id != other.id) return false
+        if (string != other.string) return false
+        if (byte != other.byte) return false
+        if (int != other.int) return false
+        if (instant?.epochSeconds != other.instant?.epochSeconds) return false
+
+        return true
+    }
+}

hll/dynamodb-mapper/dynamodb-mapper-schema-generator-plugin/src/test/resources/standard-item-converters/test/NullableItemTest.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.example
+
+import aws.smithy.kotlin.runtime.ExperimentalApi
+import aws.smithy.kotlin.runtime.time.Instant
+import org.example.dynamodbmapper.generatedschemas.NullableItemConverter
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+@OptIn(ExperimentalApi::class)
+public class NullableItemTest {
+    @Test
+    fun converterTest() {
+        val nullable = NullableItem(
+            id = 1,
+            string = null,
+            byte = null,
+            int = 5,
+            instant = Instant.now(),
+        )
+
+        val item = NullableItemConverter.convertTo(nullable)
+        val converted = NullableItemConverter.convertFrom(item)
+        assertEquals(nullable, converted)
+    }
+}