From a1b4f51ac175aef1ae59c09a6a516c0c401beb27 Mon Sep 17 00:00:00 2001
From: Evgeny Mandrikov <mandrikov@gmail.com>
Date: Tue, 29 Apr 2025 15:48:00 +0200
Subject: [PATCH 1/2] (WIP) add validation test

---
 .../pom.xml                                   | 17 ++++++
 .../kotlin/KotlinSerializableTest.java        | 34 +++++++++++
 .../targets/KotlinSerializableTarget.kt       | 61 +++++++++++++++++++
 3 files changed, 112 insertions(+)
 create mode 100644 org.jacoco.core.test.validation.kotlin/src/org/jacoco/core/test/validation/kotlin/KotlinSerializableTest.java
 create mode 100644 org.jacoco.core.test.validation.kotlin/src/org/jacoco/core/test/validation/kotlin/targets/KotlinSerializableTarget.kt

diff --git a/org.jacoco.core.test.validation.kotlin/pom.xml b/org.jacoco.core.test.validation.kotlin/pom.xml
index 609325879e..0a4060c173 100644
--- a/org.jacoco.core.test.validation.kotlin/pom.xml
+++ b/org.jacoco.core.test.validation.kotlin/pom.xml
@@ -43,6 +43,11 @@
       <artifactId>kotlinx-coroutines-core</artifactId>
       <version>1.8.0</version>
     </dependency>
+    <dependency>
+      <groupId>org.jetbrains.kotlinx</groupId>
+      <artifactId>kotlinx-serialization-core-jvm</artifactId>
+      <version>1.6.3</version>
+    </dependency>
   </dependencies>
 
   <build>
@@ -60,6 +65,18 @@
             </goals>
           </execution>
         </executions>
+        <configuration>
+          <compilerPlugins>
+            <plugin>kotlinx-serialization</plugin>
+          </compilerPlugins>
+        </configuration>
+        <dependencies>
+          <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-maven-serialization</artifactId>
+            <version>${kotlin.version}</version>
+          </dependency>
+        </dependencies>
       </plugin>
     </plugins>
   </build>
diff --git a/org.jacoco.core.test.validation.kotlin/src/org/jacoco/core/test/validation/kotlin/KotlinSerializableTest.java b/org.jacoco.core.test.validation.kotlin/src/org/jacoco/core/test/validation/kotlin/KotlinSerializableTest.java
new file mode 100644
index 0000000000..1afc08cf5a
--- /dev/null
+++ b/org.jacoco.core.test.validation.kotlin/src/org/jacoco/core/test/validation/kotlin/KotlinSerializableTest.java
@@ -0,0 +1,34 @@
+/*******************************************************************************
+ * Copyright (c) 2009, 2025 Mountainminds GmbH & Co. KG and Contributors
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *    Evgeny Mandrikov - initial API and implementation
+ *
+ *******************************************************************************/
+package org.jacoco.core.test.validation.kotlin;
+
+import org.jacoco.core.test.validation.ValidationTestBase;
+import org.jacoco.core.test.validation.kotlin.targets.KotlinSerializableTarget;
+import org.junit.Test;
+
+/**
+ * Test of code coverage in {@link KotlinSerializableTarget}.
+ */
+public class KotlinSerializableTest extends ValidationTestBase {
+
+	public KotlinSerializableTest() {
+		super(KotlinSerializableTarget.class);
+	}
+
+	@Test
+	public void test_method_count() {
+		assertMethodCount(
+				/* main + 3 constructors + 3 getters + 1 method in companion */8);
+	}
+
+}
diff --git a/org.jacoco.core.test.validation.kotlin/src/org/jacoco/core/test/validation/kotlin/targets/KotlinSerializableTarget.kt b/org.jacoco.core.test.validation.kotlin/src/org/jacoco/core/test/validation/kotlin/targets/KotlinSerializableTarget.kt
new file mode 100644
index 0000000000..d6eb2a5368
--- /dev/null
+++ b/org.jacoco.core.test.validation.kotlin/src/org/jacoco/core/test/validation/kotlin/targets/KotlinSerializableTarget.kt
@@ -0,0 +1,61 @@
+/*******************************************************************************
+ * Copyright (c) 2009, 2025 Mountainminds GmbH & Co. KG and Contributors
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *    Evgeny Mandrikov - initial API and implementation
+ *
+ *******************************************************************************/
+package org.jacoco.core.test.validation.kotlin.targets
+
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.descriptors.PrimitiveKind
+import kotlinx.serialization.descriptors.PrimitiveSerialDescriptor
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+
+/**
+ * Test target with [Serializable] class.
+ */
+object KotlinSerializableTarget {
+
+    @Serializable // assertEmpty()
+    data class Example( // assertFullyCovered()
+        @SerialName("d") val data: String // assertFullyCovered()
+    ) // assertEmpty()
+
+    @Serializable(with = CustomSerializer::class) // assertEmpty()
+    data class ExampleWithCustomSerializer( // assertFullyCovered()
+        val data: String // assertFullyCovered()
+    ) // assertEmpty()
+
+    object CustomSerializer : KSerializer<ExampleWithCustomSerializer> {
+        override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("Example", PrimitiveKind.STRING)
+        override fun serialize(encoder: Encoder, value: ExampleWithCustomSerializer) = encoder.encodeString(value.data)
+        override fun deserialize(decoder: Decoder): ExampleWithCustomSerializer =
+            ExampleWithCustomSerializer(decoder.decodeString())
+    }
+
+    data class ExampleWithHandWrittenCompanion(
+        val data: String
+    ) {
+        companion object {
+            fun serializer(): KSerializer<ExampleWithCustomSerializer> = CustomSerializer // assertNotCovered()
+        }
+    }
+
+    @JvmStatic
+    fun main(args: Array<String>) {
+        Example("").data
+        ExampleWithCustomSerializer("").data
+        ExampleWithHandWrittenCompanion("")
+    }
+
+}

From 0abbc622d7cfb4ba7b168ee66c2159ab17c6b90a Mon Sep 17 00:00:00 2001
From: Evgeny Mandrikov <mandrikov@gmail.com>
Date: Wed, 30 Apr 2025 11:32:16 +0200
Subject: [PATCH 2/2] (WIP) add unit tests

---
 .../filter/KotlinSerializableFilterTest.java  | 172 ++++++++++++++++++
 .../filter/KotlinSerializableFilter.java      |  29 +++
 2 files changed, 201 insertions(+)
 create mode 100644 org.jacoco.core.test/src/org/jacoco/core/internal/analysis/filter/KotlinSerializableFilterTest.java
 create mode 100644 org.jacoco.core/src/org/jacoco/core/internal/analysis/filter/KotlinSerializableFilter.java

diff --git a/org.jacoco.core.test/src/org/jacoco/core/internal/analysis/filter/KotlinSerializableFilterTest.java b/org.jacoco.core.test/src/org/jacoco/core/internal/analysis/filter/KotlinSerializableFilterTest.java
new file mode 100644
index 0000000000..41a1901115
--- /dev/null
+++ b/org.jacoco.core.test/src/org/jacoco/core/internal/analysis/filter/KotlinSerializableFilterTest.java
@@ -0,0 +1,172 @@
+/*******************************************************************************
+ * Copyright (c) 2009, 2025 Mountainminds GmbH & Co. KG and Contributors
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *    Evgeny Mandrikov - initial API and implementation
+ *
+ *******************************************************************************/
+package org.jacoco.core.internal.analysis.filter;
+
+import org.junit.Test;
+import org.objectweb.asm.Label;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.MethodNode;
+
+/**
+ * Unit test for {@link KotlinSerializableFilter}.
+ */
+public class KotlinSerializableFilterTest extends FilterTestBase {
+
+	private final IFilter filter = new KotlinSerializableFilter();
+
+	/**
+	 * <pre>
+	 * &#064;kotlinx.serialization.Serializable
+	 * data class Example(val data: String)
+	 * </pre>
+	 */
+	@Test
+	public void should_filter_synthetic_writeSelf_method() {
+		final MethodNode m = new MethodNode(
+				Opcodes.ACC_PUBLIC | Opcodes.ACC_FINAL | Opcodes.ACC_STATIC
+						| Opcodes.ACC_SYNTHETIC,
+				"write$Self$pkg",
+				"(Lpkg$Example;Lkotlinx/serialization/encoding/CompositeEncoder;Lkotlinx/serialization/descriptors/SerialDescriptor;)V",
+				null, null);
+		m.visitInsn(Opcodes.NOP);
+
+		filter.filter(m, context, output);
+
+		assertMethodIgnored(m);
+	}
+
+	/**
+	 * <pre>
+	 * &#064;kotlinx.serialization.Serializable
+	 * data class Example(val data: String)
+	 * </pre>
+	 */
+	@Test
+	public void should_filter_synthetic_constructor() {
+		final MethodNode m = new MethodNode(
+				Opcodes.ACC_PUBLIC | Opcodes.ACC_SYNTHETIC, "<init>",
+				"(ILjava/lang/String;Lkotlinx/serialization/internal/SerializationConstructorMarker;)V",
+				null, null);
+		m.visitInsn(Opcodes.NOP);
+
+		filter.filter(m, context, output);
+
+		assertMethodIgnored(m);
+	}
+
+	/**
+	 * <pre>
+	 * &#064;kotlinx.serialization.Serializable // line 1
+	 * data class Example(val data: String)
+	 * </pre>
+	 */
+	@Test
+	public void should_filter_generated_serializer_method() {
+		context.className = "Example$Companion";
+
+		final MethodNode initMethod = new MethodNode(Opcodes.ACC_PRIVATE,
+				"<init>", "()V", null, null);
+		// no line numbers
+		filter.filter(initMethod, context, output);
+
+		final MethodNode m = new MethodNode(
+				Opcodes.ACC_PUBLIC | Opcodes.ACC_FINAL, "serializer",
+				"()Lkotlinx/serialization/KSerializer;",
+				"()Lkotlinx/serialization/KSerializer<LExample;>;", null);
+		final Label label0 = new Label();
+		m.visitLabel(label0);
+		m.visitLineNumber(1, label0);
+		m.visitFieldInsn(Opcodes.GETSTATIC, "Example$$serializer", "INSTANCE",
+				"LExample$$serializer;");
+		m.visitTypeInsn(Opcodes.CHECKCAST, "kotlinx/serialization/KSerializer");
+		m.visitInsn(Opcodes.ARETURN);
+
+		filter.filter(m, context, output);
+
+		assertMethodIgnored(m);
+	}
+
+	/**
+	 * <pre>
+	 * &#064;kotlinx.serialization.Serializable
+	 * data class Example(val data: String) {
+	 *     companion object // line 2
+	 * }
+	 * </pre>
+	 */
+	@Test
+	public void should_filter_generated_serializer_method_in_hand_written_companion() {
+		context.className = "Example$Companion";
+
+		final MethodNode initMethod = new MethodNode(Opcodes.ACC_PRIVATE,
+				"<init>", "()V", null, null);
+		final Label initMethodLineNumberLabel = new Label();
+		initMethod.visitLabel(initMethodLineNumberLabel);
+		initMethod.visitLineNumber(2, initMethodLineNumberLabel);
+		filter.filter(initMethod, context, output);
+
+		final MethodNode m = new MethodNode(
+				Opcodes.ACC_PUBLIC | Opcodes.ACC_FINAL, "serializer",
+				"()Lkotlinx/serialization/KSerializer;",
+				"()Lkotlinx/serialization/KSerializer<LExample;>;", null);
+		final Label label0 = new Label();
+		m.visitLabel(label0);
+		m.visitLineNumber(2, label0);
+		m.visitFieldInsn(Opcodes.GETSTATIC, "Example$$serializer", "INSTANCE",
+				"LExample$$serializer;");
+		m.visitTypeInsn(Opcodes.CHECKCAST, "kotlinx/serialization/KSerializer");
+		m.visitInsn(Opcodes.ARETURN);
+
+		filter.filter(m, context, output);
+
+		assertMethodIgnored(m);
+	}
+
+	/**
+	 * <pre>
+	 * data class Example(val data: String) {
+	 *     companion object { // line 2
+	 *         fun serializer(): KSerializer&lt;Example&gt; = CustomSerializer
+	 *     }
+	 * }
+	 * </pre>
+	 */
+	@Test
+	public void should_not_filter_hand_written_serializer_method() {
+		context.className = "Example$Companion";
+
+		final MethodNode initMethod = new MethodNode(Opcodes.ACC_PRIVATE,
+				"<init>", "()V", null, null);
+		final Label initMethodLineNumberLabel = new Label();
+		initMethod.visitLabel(initMethodLineNumberLabel);
+		initMethod.visitLineNumber(2, initMethodLineNumberLabel);
+		filter.filter(initMethod, context, output);
+
+		final MethodNode m = new MethodNode(
+				Opcodes.ACC_PUBLIC | Opcodes.ACC_FINAL, "serializer",
+				"()Lkotlinx/serialization/KSerializer;",
+				"()Lkotlinx/serialization/KSerializer<LExample;>;", null);
+		final Label label0 = new Label();
+		m.visitLabel(label0);
+		m.visitLineNumber(3, label0);
+		m.visitFieldInsn(Opcodes.GETSTATIC, "CustomSerializer", "INSTANCE",
+				"LCustomSerializer;");
+		m.visitTypeInsn(Opcodes.CHECKCAST, "kotlinx/serialization/KSerializer");
+		m.visitInsn(Opcodes.ARETURN);
+
+		filter.filter(m, context, output);
+
+		assertIgnored(m);
+	}
+
+}
diff --git a/org.jacoco.core/src/org/jacoco/core/internal/analysis/filter/KotlinSerializableFilter.java b/org.jacoco.core/src/org/jacoco/core/internal/analysis/filter/KotlinSerializableFilter.java
new file mode 100644
index 0000000000..57baf85a7e
--- /dev/null
+++ b/org.jacoco.core/src/org/jacoco/core/internal/analysis/filter/KotlinSerializableFilter.java
@@ -0,0 +1,29 @@
+/*******************************************************************************
+ * Copyright (c) 2009, 2025 Mountainminds GmbH & Co. KG and Contributors
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *    Evgeny Mandrikov - initial API and implementation
+ *
+ *******************************************************************************/
+package org.jacoco.core.internal.analysis.filter;
+
+import org.objectweb.asm.tree.MethodNode;
+
+/**
+ * Filters methods generated by <a href=
+ * "https://github.com/JetBrains/kotlin/tree/v2.1.20/plugins/kotlinx-serialization">Kotlin
+ * serialization compiler plugin</a>.
+ */
+final class KotlinSerializableFilter implements IFilter {
+
+	public void filter(final MethodNode methodNode,
+			final IFilterContext context, final IFilterOutput output) {
+		// TODO
+	}
+
+}