test: add Kotlin verification smoke test

operator-framework-core/pom.xml

@@ -30,6 +30,11 @@
   <name>Operator SDK - Framework - Core</name>
   <description>Core framework for implementing Kubernetes operators</description>
 
+  <properties>
+    <!-- Used only for test sources, to verify that the framework works properly with Kotlin. -->
+    <kotlin.version>2.4.10</kotlin.version>
+  </properties>
+
   <dependencies>
     <dependency>
       <groupId>io.github.java-diff-utils</groupId>
@@ -101,6 +106,13 @@
       <artifactId>kube-api-test-client-inject</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <!-- Test-only, used to verify JOSDK works properly when used from Kotlin. -->
+      <groupId>org.jetbrains.kotlin</groupId>
+      <artifactId>kotlin-stdlib</artifactId>
+      <version>${kotlin.version}</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>
@@ -147,6 +159,37 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <!--
+          Compiles the Kotlin test sources under src/test/kotlin, used only to verify that JOSDK
+          works properly when used from Kotlin (see https://github.com/operator-framework/java-operator-sdk/issues/2967).
+          Bound to process-test-sources so the compiled Kotlin classes are on the classpath before
+          the regular Java test sources are compiled.
+        -->
+        <groupId>org.jetbrains.kotlin</groupId>
+        <artifactId>kotlin-maven-plugin</artifactId>
+        <version>${kotlin.version}</version>
+        <configuration>
+          <jvmTarget>${java.version}</jvmTarget>
+        </configuration>
+        <executions>
+          <execution>
+            <id>kotlin-test-compile</id>
+            <goals>
+              <goal>test-compile</goal>
+            </goals>
+            <phase>process-test-sources</phase>
+            <configuration>
+              <sourceDirs>
+                <sourceDir>${project.basedir}/src/test/kotlin</sourceDir>
+                <!-- Not compiled by Kotlin, only needed so the Kotlin sources can reference the
+                     existing Java test classes (e.g. TestCustomResource). -->
+                <sourceDir>${project.basedir}/src/test/java</sourceDir>
+              </sourceDirs>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
     </plugins>
   </build>
 </project>

operator-framework-core/src/test/kotlin/io/javaoperatorsdk/operator/processing/dependent/workflow/KotlinCheckedExceptionDependentResourceTest.kt

@@ -0,0 +1,88 @@
+/*
+ * Copyright Java Operator SDK Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.javaoperatorsdk.operator.processing.dependent.workflow
+
+import io.javaoperatorsdk.operator.AggregatedOperatorException
+import io.javaoperatorsdk.operator.api.reconciler.Context
+import io.javaoperatorsdk.operator.api.reconciler.dependent.DependentResource
+import io.javaoperatorsdk.operator.api.reconciler.dependent.ReconcileResult
+import io.javaoperatorsdk.operator.api.reconciler.dependent.managed.ManagedWorkflowAndDependentResourceContext
+import io.javaoperatorsdk.operator.processing.event.EventSourceRetriever
+import io.javaoperatorsdk.operator.sample.simple.TestCustomResource
+import java.util.concurrent.Executors
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.mockito.Mockito.mock
+import org.mockito.Mockito.`when`
+
+/**
+ * Smoke test verifying that JOSDK works properly when used from Kotlin.
+ *
+ * Unlike Java, Kotlin does not distinguish between checked and unchecked exceptions, so a Kotlin
+ * [DependentResource] can throw a plain [java.lang.Exception] from `reconcile` without declaring
+ * it, even though the Java `DependentResource.reconcile` method does not declare `throws
+ * Exception`. Before https://github.com/operator-framework/java-operator-sdk/pull/2965 such an
+ * exception was not caught by [NodeExecutor], since it only handled [RuntimeException], so it
+ * would not have been recorded as an error and retries would not have been triggered. This test
+ * makes sure such an exception is properly caught and reported, see
+ * https://github.com/operator-framework/java-operator-sdk/issues/2967.
+ */
+class KotlinCheckedExceptionDependentResourceTest {
+
+  private class CheckedException(message: String) : Exception(message)
+
+  private class ThrowingDependentResource :
+      DependentResource<String, TestCustomResource> {
+    override fun reconcile(
+        primary: TestCustomResource,
+        context: Context<TestCustomResource>
+    ): ReconcileResult<String> {
+      throw CheckedException("checked exception thrown from Kotlin")
+    }
+
+    override fun resourceType(): Class<String> = String::class.java
+  }
+
+  @Test
+  fun checkedExceptionThrownFromKotlinDependentResourceTriggersRetry() {
+    val dependentResource = ThrowingDependentResource()
+
+    val workflow =
+        WorkflowBuilder<TestCustomResource>()
+            .addDependentResource(dependentResource)
+            .withThrowExceptionFurther(false)
+            .build()
+
+    @Suppress("UNCHECKED_CAST")
+    val context = mock(Context::class.java) as Context<TestCustomResource>
+    `when`(context.managedWorkflowAndDependentResourceContext())
+        .thenReturn(mock(ManagedWorkflowAndDependentResourceContext::class.java))
+    `when`(context.workflowExecutorService).thenReturn(Executors.newCachedThreadPool())
+    @Suppress("UNCHECKED_CAST")
+    `when`(context.eventSourceRetriever())
+        .thenReturn(mock(EventSourceRetriever::class.java) as EventSourceRetriever<TestCustomResource>)
+
+    val result = workflow.reconcile(TestCustomResource(), context)
+
+    // the checked exception was caught by the workflow executor, not left uncaught, so it is
+    // reported as an error for the dependent resource, which is what allows JOSDK to retry the
+    // reconciliation.
+    assertThat(result.erroredDependents).containsOnlyKeys(dependentResource)
+    assertThat(result.erroredDependents[dependentResource]).isInstanceOf(CheckedException::class.java)
+    assertThrows<AggregatedOperatorException> { result.throwAggregateExceptionIfErrorsPresent() }
+  }
+}