Bug: empty string serde and Kotlin in 2.8.2

There is an issue in 2.8.2 when serializing an empty string to a non-null field in Kotlin.

This works in 2.8.1, and was exposed by the eclipsestore guide https://github.com/micronaut-projects/micronaut-guides/pull/1443\#commits-pushed-0276ab1

doc-examples/example-java/build.gradle.kts

@@ -10,10 +10,13 @@ micronaut {
 
 dependencies {
     annotationProcessor(projects.micronautSerdeProcessor)
+    annotationProcessor(mnValidation.micronaut.validation.processor)
 
     implementation(projects.micronautSerdeJackson)
     implementation(mn.micronaut.http.client)
     implementation(libs.oci.aidocument)
+    implementation(mnValidation.micronaut.validation)
+    implementation("jakarta.validation:jakarta.validation-api")
 
     runtimeOnly(mnLogging.logback.classic)
 

doc-examples/example-java/src/main/java/example/FruitCommand.java

@@ -0,0 +1,10 @@
+package example;
+
+import io.micronaut.core.annotation.Nullable;
+import io.micronaut.serde.annotation.Serdeable;
+import jakarta.validation.constraints.NotEmpty;
+
+@Serdeable
+record FruitCommand(
+    @NotEmpty String name, @Nullable String description
+) {}

doc-examples/example-java/src/main/resources/logback.xml

@@ -11,4 +11,4 @@
     <root level="info">
         <appender-ref ref="STDOUT" />
     </root>
-</configuration>
+</configuration>

doc-examples/example-java/src/test/java/example/FruitCommandTest.java

@@ -0,0 +1,49 @@
+package example;
+
+import io.micronaut.context.annotation.Property;
+import io.micronaut.context.annotation.Requires;
+import io.micronaut.http.HttpRequest;
+import io.micronaut.http.annotation.Body;
+import io.micronaut.http.annotation.Controller;
+import io.micronaut.http.annotation.Post;
+import io.micronaut.http.client.HttpClient;
+import io.micronaut.http.client.exceptions.HttpClientResponseException;
+import io.micronaut.runtime.server.EmbeddedServer;
+import io.micronaut.test.extensions.junit5.annotation.MicronautTest;
+import jakarta.validation.Valid;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+@MicronautTest
+@Property(name = "spec.name", value = "FruitCommandTest")
+class FruitCommandTest {
+
+    @Test
+    void testCommandPost(EmbeddedServer embeddedServer) {
+        try(var client = embeddedServer.getApplicationContext().createBean(HttpClient.class, embeddedServer.getURL())) {
+            var ex = assertThrows(
+                HttpClientResponseException.class,
+                () -> client.toBlocking().exchange(HttpRequest.POST("/fruits", new FruitCommand("", "")), String.class)
+            );
+            Map<String, Object> embedded = (Map<String, Object>) ex.getResponse().getBody(Map.class).get().get("_embedded");
+            Object message = ((Map<String, Object>) ((List) embedded.get("errors")).get(0)).get("message");
+
+            assertEquals("fruitCommand.name: must not be empty", message);
+        }
+    }
+
+    @Controller("/fruits")
+    @Requires(property = "spec.name", value = "FruitCommandTest")
+    static class FruitCommandController {
+
+        @Post
+        FruitCommand save(@Valid @Body FruitCommand fruitCommand) {
+            return fruitCommand;
+        }
+    }
+}

doc-examples/example-kotlin-ksp/build.gradle.kts

@@ -13,9 +13,12 @@ micronaut {
 
 dependencies {
     ksp(projects.micronautSerdeProcessor)
+    ksp(mnValidation.micronaut.validation.processor)
 
     implementation(projects.micronautSerdeJackson)
     implementation(mn.micronaut.http.client)
+    implementation(mnValidation.micronaut.validation)
+    implementation("jakarta.validation:jakarta.validation-api")
 
     runtimeOnly(mnLogging.logback.classic)
 

doc-examples/example-kotlin-ksp/src/main/kotlin/example/FruitCommand.kt

@@ -0,0 +1,10 @@
+package example
+
+import io.micronaut.serde.annotation.Serdeable
+import jakarta.validation.constraints.NotEmpty
+
+@Serdeable // <1>
+data class FruitCommand(
+    @field:NotEmpty val name: String, // <2>
+    val description: String? = null // <3>
+)

doc-examples/example-kotlin-ksp/src/test/kotlin/example/FruitCommandTest.kt

@@ -0,0 +1,47 @@
+package example
+
+import io.micronaut.context.annotation.Property
+import io.micronaut.context.annotation.Requires
+import io.micronaut.http.HttpRequest
+import io.micronaut.http.annotation.Body
+import io.micronaut.http.annotation.Controller
+import io.micronaut.http.annotation.Post
+import io.micronaut.http.client.HttpClient
+import io.micronaut.http.client.exceptions.HttpClientResponseException
+import io.micronaut.runtime.server.EmbeddedServer
+import io.micronaut.test.extensions.junit5.annotation.MicronautTest
+import jakarta.inject.Singleton
+import org.junit.jupiter.api.Assertions
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+
+@MicronautTest
+@Property(name = "spec.name", value = "FruitCommandTest")
+class FruitCommandTest {
+
+    @Test
+    fun testCommandPost(embeddedServer: EmbeddedServer) {
+        embeddedServer.applicationContext.createBean(HttpClient::class.java, embeddedServer.url).use { client ->
+            val ex = assertThrows<HttpClientResponseException> {
+                client.toBlocking()
+                    .exchange<FruitCommand, String>(
+                        HttpRequest.POST("/fruits", FruitCommand("", ""))
+                    )
+            }
+            val embedded = ex.response.getBody(MutableMap::class.java).get().get("_embedded") as Map<String, Any>
+            val message = ((embedded["errors"] as List<*>)[0] as Map<String, Any>)["message"]
+            Assertions.assertEquals("fruitCommand.name: must not be empty", message)
+        }
+    }
+
+    @Singleton
+    @Controller("/fruits")
+    @Requires(property = "spec.name", value = "FruitCommandTest")
+    class FruitCommandController {
+
+        @Post
+        fun save(@Body fruitCommand: FruitCommand): FruitCommand {
+            return fruitCommand
+        }
+    }
+}

doc-examples/example-kotlin/build.gradle.kts

@@ -12,9 +12,12 @@ micronaut {
 
 dependencies {
     kapt(projects.micronautSerdeProcessor)
+    kapt(mnValidation.micronaut.validation.processor)
 
     implementation(projects.micronautSerdeJackson)
     implementation(mn.micronaut.http.client)
+    implementation(mnValidation.micronaut.validation)
+    implementation("jakarta.validation:jakarta.validation-api")
 
     runtimeOnly(mnLogging.logback.classic)
 

doc-examples/example-kotlin/src/main/kotlin/example/FruitCommand.kt

@@ -0,0 +1,10 @@
+package example
+
+import io.micronaut.serde.annotation.Serdeable
+import jakarta.validation.constraints.NotEmpty
+
+@Serdeable
+data class FruitCommand(
+    @field:NotEmpty val name: String,
+    val description: String? = null
+)

doc-examples/example-kotlin/src/test/kotlin/example/FruitCommandTest.kt

@@ -0,0 +1,47 @@
+package example
+
+import io.micronaut.context.annotation.Property
+import io.micronaut.context.annotation.Requires
+import io.micronaut.http.HttpRequest
+import io.micronaut.http.annotation.Body
+import io.micronaut.http.annotation.Controller
+import io.micronaut.http.annotation.Post
+import io.micronaut.http.client.HttpClient
+import io.micronaut.http.client.exceptions.HttpClientResponseException
+import io.micronaut.runtime.server.EmbeddedServer
+import io.micronaut.test.extensions.junit5.annotation.MicronautTest
+import jakarta.inject.Singleton
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+
+@MicronautTest
+@Property(name = "spec.name", value = "FruitCommandTest")
+class FruitCommandTest {
+
+    @Test
+    fun testCommandPost(embeddedServer: EmbeddedServer) {
+        embeddedServer.applicationContext.createBean(HttpClient::class.java, embeddedServer.url).use { client ->
+            val ex = assertThrows<HttpClientResponseException> {
+                client.toBlocking()
+                    .exchange<FruitCommand, String>(
+                        HttpRequest.POST("/fruits", FruitCommand("", ""))
+                    )
+            }
+            val embedded = ex.response.getBody(MutableMap::class.java).get().get("_embedded") as Map<String, Any>
+            val message = ((embedded["errors"] as List<*>)[0] as Map<String, Any>)["message"]
+            assertEquals("fruitCommand.name: must not be empty", message)
+        }
+    }
+
+    @Singleton
+    @Controller("/fruits")
+    @Requires(property = "spec.name", value = "FruitCommandTest")
+    class FruitCommandController {
+
+        @Post
+        fun save(@Body fruitCommand: FruitCommand): FruitCommand {
+            return fruitCommand
+        }
+    }
+}