build(kotlin): Add spotless ktfmt and enable explicit api mode for li…

…brary code. (#1912)


## What does this PR do?

This PR modifies the build to:
1) add ktfmt - Since the fury java uses GOOGLE style, the fury kotlin
will also use GOOGLE style. The version of ktfmt used is the highest
compatible with the spotless maven plugin.
2) explicit api mode
3) parameterized kotlin version in pom.xml so it is easy to change in
future
4) Update README.md with build, format and testing instructions.

## Related issues

Closes #1896 

## Does this PR introduce any user-facing change?
None.

## Benchmark
N/A

kotlin/README.md

@@ -35,3 +35,22 @@ Additional support is added for the following classes in kotlin:
 Additional Notes:
 
 - wrappers classes created from `withDefault` method is currently not supported.
+
+## Building Fury Kotlin
+
+```bash
+mvn clean
+mvn -T10 compile
+```
+
+## Code Format
+
+```bash
+mvn -T10 spotless:apply
+```
+
+## Testing
+
+```bash
+mvn -T10 test
+```

kotlin/pom.xml

@@ -29,11 +29,12 @@
     <modelVersion>4.0.0</modelVersion>
 
     <properties>
-      <maven.compiler.source>1.8</maven.compiler.source>
-      <maven.compiler.target>1.8</maven.compiler.target>
-      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <kotlin.code.style>official</kotlin.code.style>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <kotlin.compiler.jvmTarget>1.8</kotlin.compiler.jvmTarget>
+        <maven-spotless-plugin.version>2.43.0</maven-spotless-plugin.version>
+        <kotlin.version>2.0.20</kotlin.version>
     </properties>
 
     <build>
@@ -136,6 +137,9 @@
                                 <sourceDir>${project.basedir}/src/main/kotlin</sourceDir>
                                 <sourceDir>${project.basedir}/src/main/java</sourceDir>
                             </sourceDirs>
+                            <args>
+                                <arg>-Xexplicit-api=strict</arg> <!-- Enable explicit api mode -->
+                            </args>
                         </configuration>
                     </execution>
                     <execution>
@@ -148,6 +152,8 @@
                             <sourceDirs>
                                 <sourceDir>${project.basedir}/src/test/kotlin</sourceDir>
                             </sourceDirs>
+                            <args>
+                            </args>
                         </configuration>
                     </execution>
                 </executions>
@@ -168,6 +174,26 @@
                     <target>8</target>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>com.diffplug.spotless</groupId>
+                <artifactId>spotless-maven-plugin</artifactId>
+                <version>${maven-spotless-plugin.version}</version>
+                <configuration>
+                    <java>
+                        <googleJavaFormat>
+                            <!-- 1.19.1 support JDK21 -->
+                            <version>1.19.1</version>
+                            <style>GOOGLE</style>
+                        </googleJavaFormat>
+                    </java>
+                    <kotlin>
+                        <ktfmt>
+                            <version>0.46</version>
+                            <style>GOOGLE</style>
+                        </ktfmt>
+                    </kotlin>
+                </configuration>
+            </plugin>
         </plugins>
     </build>
 
@@ -180,13 +206,13 @@
         <dependency>
             <groupId>org.jetbrains.kotlin</groupId>
             <artifactId>kotlin-test-testng</artifactId>
-            <version>2.0.20</version>
+            <version>${kotlin.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.jetbrains.kotlin</groupId>
             <artifactId>kotlin-stdlib</artifactId>
-            <version>2.0.20</version>
+            <version>${kotlin.version}</version>
         </dependency>
     </dependencies>
 </project>

kotlin/src/main/java/org/apache/fury/serializer/kotlin/KotlinSerializers.java

@@ -20,127 +20,128 @@
 package org.apache.fury.serializer.kotlin;
 
 import kotlin.*;
+import kotlin.UByteArray;
+import kotlin.UIntArray;
+import kotlin.ULongArray;
+import kotlin.UShortArray;
 import kotlin.text.*;
 import kotlin.time.Duration;
 import kotlin.time.DurationUnit;
-import kotlin.time.TestTimeSource;
 import kotlin.time.TimedValue;
 import kotlin.uuid.Uuid;
-import kotlin.UByteArray;
-import kotlin.UIntArray;
-import kotlin.ULongArray;
-import kotlin.UShortArray;
 import org.apache.fury.AbstractThreadSafeFury;
 import org.apache.fury.Fury;
 import org.apache.fury.ThreadSafeFury;
 import org.apache.fury.resolver.ClassResolver;
 import org.apache.fury.serializer.collection.CollectionSerializers;
 import org.apache.fury.serializer.collection.MapSerializers;
 
-/**
- * KotlinSerializers provide default serializers for kotlin.
- */
+/** KotlinSerializers provide default serializers for kotlin. */
 @SuppressWarnings({"rawtypes", "unchecked"})
 public class KotlinSerializers {
 
-    public static void registerSerializers(ThreadSafeFury fury) {
-        AbstractThreadSafeFury threadSafeFury = (AbstractThreadSafeFury) fury;
-        threadSafeFury.registerCallback(KotlinSerializers::registerSerializers);
-    }
-
-    public static void registerSerializers(Fury fury) {
-        ClassResolver resolver = fury.getClassResolver();
-
-        // UByte
-        Class ubyteClass = KotlinToJavaClass.INSTANCE.getUByteClass();
-        resolver.register(ubyteClass);
-        resolver.registerSerializer(ubyteClass, new UByteSerializer(fury));
-
-        // UShort
-        Class ushortClass = KotlinToJavaClass.INSTANCE.getUShortClass();
-        resolver.register(ushortClass);
-        resolver.registerSerializer(ushortClass, new UShortSerializer(fury));
-
-        // UInt
-        Class uintClass = KotlinToJavaClass.INSTANCE.getUIntClass();
-        resolver.register(uintClass);
-        resolver.registerSerializer(uintClass, new UIntSerializer(fury));
-
-        // ULong
-        Class ulongClass = KotlinToJavaClass.INSTANCE.getULongClass();
-        resolver.register(ulongClass);
-        resolver.registerSerializer(ulongClass, new ULongSerializer(fury));
-
-        // EmptyList
-        Class emptyListClass = KotlinToJavaClass.INSTANCE.getEmptyListClass();
-        resolver.register(emptyListClass);
-        resolver.registerSerializer(emptyListClass, new CollectionSerializers.EmptyListSerializer(fury, emptyListClass));
-
-        // EmptySet
-        Class emptySetClass = KotlinToJavaClass.INSTANCE.getEmptySetClass();
-        resolver.register(emptySetClass);
-        resolver.registerSerializer(emptySetClass, new CollectionSerializers.EmptySetSerializer(fury, emptySetClass));
-
-        // EmptyMap
-        Class emptyMapClass = KotlinToJavaClass.INSTANCE.getEmptyMapClass();
-        resolver.register(emptyMapClass);
-        resolver.registerSerializer(emptyMapClass, new MapSerializers.EmptyMapSerializer(fury, emptyMapClass));
-
-        // Non-Java collection implementation in kotlin stdlib.
-        Class arrayDequeClass = KotlinToJavaClass.INSTANCE.getArrayDequeClass();
-        resolver.register(arrayDequeClass);
-        resolver.registerSerializer(arrayDequeClass, new KotlinArrayDequeSerializer(fury, arrayDequeClass));
-
-        // Unsigned array classes: UByteArray, UShortArray, UIntArray, ULongArray.
-        resolver.register(UByteArray.class);
-        resolver.registerSerializer(UByteArray.class, new UByteArraySerializer(fury));
-        resolver.register(UShortArray.class);
-        resolver.registerSerializer(UShortArray.class, new UShortArraySerializer(fury));
-        resolver.register(UIntArray.class);
-        resolver.registerSerializer(UIntArray.class, new UIntArraySerializer(fury));
-        resolver.register(ULongArray.class);
-        resolver.registerSerializer(ULongArray.class, new ULongArraySerializer(fury));
-
-        // Ranges and Progressions.
-        resolver.register(kotlin.ranges.CharRange.class);
-        resolver.register(kotlin.ranges.CharProgression.class);
-        resolver.register(kotlin.ranges.IntRange.class);
-        resolver.register(kotlin.ranges.IntProgression.class);
-        resolver.register(kotlin.ranges.LongRange.class);
-        resolver.register(kotlin.ranges.LongProgression.class);
-        resolver.register(kotlin.ranges.UIntRange.class);
-        resolver.register(kotlin.ranges.UIntProgression.class);
-        resolver.register(kotlin.ranges.ULongRange.class);
-        resolver.register(kotlin.ranges.ULongProgression.class);
-
-        // Built-in classes.
-        resolver.register(kotlin.Pair.class);
-        resolver.register(kotlin.Triple.class);
-        resolver.register(kotlin.Result.class);
-        resolver.register(Result.Failure.class);
-
-        // kotlin.random
-        resolver.register(KotlinToJavaClass.INSTANCE.getRandomDefaultClass());
-        resolver.register(KotlinToJavaClass.INSTANCE.getRandomInternalClass());
-        resolver.register(KotlinToJavaClass.INSTANCE.getRandomSerializedClass());
-
-        // kotlin.text
-        resolver.register(Regex.class);
-        resolver.register(KotlinToJavaClass.INSTANCE.getRegexSerializedClass());
-        resolver.register(RegexOption.class);
-        resolver.register(CharCategory.class);
-        resolver.register(CharDirectionality.class);
-        resolver.register(HexFormat.class);
-        resolver.register(MatchGroup.class);
-
-        // kotlin.time
-        resolver.register(DurationUnit.class);
-        resolver.register(Duration.class);
-        resolver.registerSerializer(Duration.class, new DurationSerializer(fury));
-        resolver.register(TimedValue.class);
-
-        // kotlin.uuid
-        resolver.register(Uuid.class);
-        resolver.registerSerializer(Uuid.class, new UuidSerializer(fury));
-    }
+  public static void registerSerializers(ThreadSafeFury fury) {
+    AbstractThreadSafeFury threadSafeFury = (AbstractThreadSafeFury) fury;
+    threadSafeFury.registerCallback(KotlinSerializers::registerSerializers);
+  }
+
+  public static void registerSerializers(Fury fury) {
+    ClassResolver resolver = fury.getClassResolver();
+
+    // UByte
+    Class ubyteClass = KotlinToJavaClass.INSTANCE.getUByteClass();
+    resolver.register(ubyteClass);
+    resolver.registerSerializer(ubyteClass, new UByteSerializer(fury));
+
+    // UShort
+    Class ushortClass = KotlinToJavaClass.INSTANCE.getUShortClass();
+    resolver.register(ushortClass);
+    resolver.registerSerializer(ushortClass, new UShortSerializer(fury));
+
+    // UInt
+    Class uintClass = KotlinToJavaClass.INSTANCE.getUIntClass();
+    resolver.register(uintClass);
+    resolver.registerSerializer(uintClass, new UIntSerializer(fury));
+
+    // ULong
+    Class ulongClass = KotlinToJavaClass.INSTANCE.getULongClass();
+    resolver.register(ulongClass);
+    resolver.registerSerializer(ulongClass, new ULongSerializer(fury));
+
+    // EmptyList
+    Class emptyListClass = KotlinToJavaClass.INSTANCE.getEmptyListClass();
+    resolver.register(emptyListClass);
+    resolver.registerSerializer(
+        emptyListClass, new CollectionSerializers.EmptyListSerializer(fury, emptyListClass));
+
+    // EmptySet
+    Class emptySetClass = KotlinToJavaClass.INSTANCE.getEmptySetClass();
+    resolver.register(emptySetClass);
+    resolver.registerSerializer(
+        emptySetClass, new CollectionSerializers.EmptySetSerializer(fury, emptySetClass));
+
+    // EmptyMap
+    Class emptyMapClass = KotlinToJavaClass.INSTANCE.getEmptyMapClass();
+    resolver.register(emptyMapClass);
+    resolver.registerSerializer(
+        emptyMapClass, new MapSerializers.EmptyMapSerializer(fury, emptyMapClass));
+
+    // Non-Java collection implementation in kotlin stdlib.
+    Class arrayDequeClass = KotlinToJavaClass.INSTANCE.getArrayDequeClass();
+    resolver.register(arrayDequeClass);
+    resolver.registerSerializer(
+        arrayDequeClass, new KotlinArrayDequeSerializer(fury, arrayDequeClass));
+
+    // Unsigned array classes: UByteArray, UShortArray, UIntArray, ULongArray.
+    resolver.register(UByteArray.class);
+    resolver.registerSerializer(UByteArray.class, new UByteArraySerializer(fury));
+    resolver.register(UShortArray.class);
+    resolver.registerSerializer(UShortArray.class, new UShortArraySerializer(fury));
+    resolver.register(UIntArray.class);
+    resolver.registerSerializer(UIntArray.class, new UIntArraySerializer(fury));
+    resolver.register(ULongArray.class);
+    resolver.registerSerializer(ULongArray.class, new ULongArraySerializer(fury));
+
+    // Ranges and Progressions.
+    resolver.register(kotlin.ranges.CharRange.class);
+    resolver.register(kotlin.ranges.CharProgression.class);
+    resolver.register(kotlin.ranges.IntRange.class);
+    resolver.register(kotlin.ranges.IntProgression.class);
+    resolver.register(kotlin.ranges.LongRange.class);
+    resolver.register(kotlin.ranges.LongProgression.class);
+    resolver.register(kotlin.ranges.UIntRange.class);
+    resolver.register(kotlin.ranges.UIntProgression.class);
+    resolver.register(kotlin.ranges.ULongRange.class);
+    resolver.register(kotlin.ranges.ULongProgression.class);
+
+    // Built-in classes.
+    resolver.register(kotlin.Pair.class);
+    resolver.register(kotlin.Triple.class);
+    resolver.register(kotlin.Result.class);
+    resolver.register(Result.Failure.class);
+
+    // kotlin.random
+    resolver.register(KotlinToJavaClass.INSTANCE.getRandomDefaultClass());
+    resolver.register(KotlinToJavaClass.INSTANCE.getRandomInternalClass());
+    resolver.register(KotlinToJavaClass.INSTANCE.getRandomSerializedClass());
+
+    // kotlin.text
+    resolver.register(Regex.class);
+    resolver.register(KotlinToJavaClass.INSTANCE.getRegexSerializedClass());
+    resolver.register(RegexOption.class);
+    resolver.register(CharCategory.class);
+    resolver.register(CharDirectionality.class);
+    resolver.register(HexFormat.class);
+    resolver.register(MatchGroup.class);
+
+    // kotlin.time
+    resolver.register(DurationUnit.class);
+    resolver.register(Duration.class);
+    resolver.registerSerializer(Duration.class, new DurationSerializer(fury));
+    resolver.register(TimedValue.class);
+
+    // kotlin.uuid
+    resolver.register(Uuid.class);
+    resolver.registerSerializer(Uuid.class, new UuidSerializer(fury));
+  }
 }

kotlin/src/main/kotlin/org/apache/fury/serializer/kotlin/CollectionBuilder.kt

@@ -22,29 +22,26 @@ package org.apache.fury.serializer.kotlin
 /**
  * Collection builder interface adapts an iterable to allow incremental build by the fury protocol.
  */
-interface CollectionBuilder <E, T: Iterable<E>> {
-    fun add(element: E): Boolean
-    fun result(): T
+public interface CollectionBuilder<E, T : Iterable<E>> {
+  public fun add(element: E): Boolean
+
+  public fun result(): T
 }
 
-/**
- * Abstract builder for [kotlin.collections.List] interface.
- */
-abstract class AbstractListBuilder<E, T:List<E>>
-    : CollectionBuilder<E, T>, AdaptedCollection<E>() {
-    protected open val builder: MutableList<E> = mutableListOf()
-    override val size: Int
-        get() = builder.size
-    override fun add(element: E) =
-        builder.add(element)
-    override fun iterator(): MutableIterator<E> = builder.iterator()
+/** Abstract builder for [kotlin.collections.List] interface. */
+public abstract class AbstractListBuilder<E, T : List<E>> :
+  CollectionBuilder<E, T>, AdaptedCollection<E>() {
+  protected open val builder: MutableList<E> = mutableListOf()
+  override val size: Int
+    get() = builder.size
+
+  override fun add(element: E): Boolean = builder.add(element)
+
+  override fun iterator(): MutableIterator<E> = builder.iterator()
 }
 
-/**
- * Builder for [kotlin.collections.ArrayDeque].
- */
-class ArrayDequeBuilder<E>(
-    override val builder: ArrayDeque<E>
-): AbstractListBuilder<E, ArrayDeque<E>>() {
-    override fun result(): ArrayDeque<E> = builder
+/** Builder for [kotlin.collections.ArrayDeque]. */
+public class ArrayDequeBuilder<E>(override val builder: ArrayDeque<E>) :
+  AbstractListBuilder<E, ArrayDeque<E>>() {
+  override fun result(): ArrayDeque<E> = builder
 }