From bb4d621a32f5521d000414218a3ee7bf52e77596 Mon Sep 17 00:00:00 2001
From: Mark Paluch <mpaluch@pivotal.io>
Date: Fri, 31 Jul 2020 10:49:52 +0200
Subject: [PATCH] DATACMNS-1779 - Consider kotlin.Unit a simple type.
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kotlin.Unit is now considered a simple type to avoid PersistentEntity creation.

ReflectionUtils.isVoid(…) now encapsulates the check so that calling code doesn't need to check if Kotlin is on the class path.
---
 .../data/mapping/model/SimpleTypeHolder.java  |  2 +-
 .../support/MethodInvocationValidator.java    |  2 +-
 .../data/util/ReflectionUtils.java            | 23 ++++++++++++++++++-
 .../data/util/ReflectionUtilsUnitTests.java   | 12 ++++++++++
 4 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/src/main/java/org/springframework/data/mapping/model/SimpleTypeHolder.java b/src/main/java/org/springframework/data/mapping/model/SimpleTypeHolder.java
index effa9178c..72120967e 100644
--- a/src/main/java/org/springframework/data/mapping/model/SimpleTypeHolder.java
+++ b/src/main/java/org/springframework/data/mapping/model/SimpleTypeHolder.java
@@ -156,7 +156,7 @@ public class SimpleTypeHolder {
 
 		String typeName = type.getName();
 
-		if (typeName.startsWith("java.lang") || type.getName().startsWith("java.time")) {
+		if (typeName.startsWith("java.lang") || type.getName().startsWith("java.time") || typeName.equals("kotlin.Unit")) {
 			return true;
 		}
 
diff --git a/src/main/java/org/springframework/data/repository/core/support/MethodInvocationValidator.java b/src/main/java/org/springframework/data/repository/core/support/MethodInvocationValidator.java
index 7edd28556..b6de75bb8 100644
--- a/src/main/java/org/springframework/data/repository/core/support/MethodInvocationValidator.java
+++ b/src/main/java/org/springframework/data/repository/core/support/MethodInvocationValidator.java
@@ -160,7 +160,7 @@ public class MethodInvocationValidator implements MethodInterceptor {
 		}
 
 		private static boolean requiresNoValue(MethodParameter parameter) {
-			return parameter.getParameterType().equals(Void.class) || parameter.getParameterType().equals(Void.TYPE);
+			return ReflectionUtils.isVoid(parameter.getParameterType());
 		}
 
 		public boolean[] getNullableParameters() {
diff --git a/src/main/java/org/springframework/data/util/ReflectionUtils.java b/src/main/java/org/springframework/data/util/ReflectionUtils.java
index 63b60d16d..323ff6a66 100644
--- a/src/main/java/org/springframework/data/util/ReflectionUtils.java
+++ b/src/main/java/org/springframework/data/util/ReflectionUtils.java
@@ -70,6 +70,27 @@ public final class ReflectionUtils {
 		}
 	}
 
+	/**
+	 * Check whether the given {@code type} represents a void type such as {@code void}, {@link Void} or Kotlin
+	 * {@code Unit}.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @return whether the given the type is a void type.
+	 * @since 2.4
+	 */
+	public static boolean isVoid(Class<?> type) {
+
+		if (type == Void.class || Void.TYPE == type) {
+			return true;
+		}
+
+		if (type.getName().equals("kotlin.Unit")) {
+			return true;
+		}
+
+		return false;
+	}
+
 	/**
 	 * A {@link FieldFilter} that has a description.
 	 *
@@ -399,7 +420,7 @@ public final class ReflectionUtils {
 	 */
 	public static boolean isNullable(MethodParameter parameter) {
 
-		if (Void.class.equals(parameter.getParameterType()) || Void.TYPE.equals(parameter.getParameterType())) {
+		if (isVoid(parameter.getParameterType())) {
 			return true;
 		}
 
diff --git a/src/test/java/org/springframework/data/util/ReflectionUtilsUnitTests.java b/src/test/java/org/springframework/data/util/ReflectionUtilsUnitTests.java
index f0b0497ff..a1ee9b763 100755
--- a/src/test/java/org/springframework/data/util/ReflectionUtilsUnitTests.java
+++ b/src/test/java/org/springframework/data/util/ReflectionUtilsUnitTests.java
@@ -17,11 +17,14 @@ package org.springframework.data.util;
 
 import static org.assertj.core.api.Assertions.*;
 
+import kotlin.Unit;
+
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
 
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.core.MethodParameter;
 import org.springframework.data.mapping.model.TypeCreatingSyntheticClassKt;
@@ -163,6 +166,15 @@ public class ReflectionUtilsUnitTests {
 		assertThat(ReflectionUtils.isSupportedKotlinClass(TypeCreatingSyntheticClassKt.class)).isFalse();
 	}
 
+	@Test // DATACMNS-1779
+	public void shouldReportIsVoid() {
+
+		assertThat(ReflectionUtils.isVoid(Void.class)).isTrue();
+		assertThat(ReflectionUtils.isVoid(Void.TYPE)).isTrue();
+		assertThat(ReflectionUtils.isVoid(Unit.class)).isTrue();
+		assertThat(ReflectionUtils.isVoid(String.class)).isFalse();
+	}
+
 	static class Sample {
 
 		public String field;