Support Kotlin value class properties in SpEL

This commit adds support for inlined Kotlin value
class properties in SpEL by leveraging Kotlin
reflection instead of Java reflection broken
by the mangled method name.

Closes gh-30468

Author: sdeleuze

spring-expression/spring-expression.gradle

@@ -4,6 +4,7 @@ apply plugin: "kotlin"
 
 dependencies {
 	api(project(":spring-core"))
+	optional("org.jetbrains.kotlin:kotlin-reflect")
 	testImplementation(testFixtures(project(":spring-core")))
 	testImplementation("org.jetbrains.kotlin:kotlin-reflect")
 	testImplementation("org.jetbrains.kotlin:kotlin-stdlib")

spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectivePropertyAccessor.java

@@ -27,7 +27,15 @@
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 
+import kotlin.jvm.JvmClassMappingKt;
+import kotlin.reflect.KClass;
+import kotlin.reflect.KMutableProperty;
+import kotlin.reflect.KProperty;
+import kotlin.reflect.full.KClasses;
+import kotlin.reflect.jvm.ReflectJvmMapping;
+
 import org.springframework.asm.MethodVisitor;
+import org.springframework.core.KotlinDetector;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.convert.Property;
 import org.springframework.core.convert.TypeDescriptor;
@@ -55,6 +63,7 @@
  * @author Juergen Hoeller
  * @author Phillip Webb
  * @author Sam Brannen
+ * @author Sebastien Deleuze
  * @since 3.0
  * @see StandardEvaluationContext
  * @see SimpleEvaluationContext
@@ -401,7 +410,8 @@ private Method findMethodForProperty(String[] methodSuffixes, String prefix, Cla
 		Method[] methods = getSortedMethods(clazz);
 		for (String methodSuffix : methodSuffixes) {
 			for (Method method : methods) {
-				if (isCandidateForProperty(method, clazz) && method.getName().equals(prefix + methodSuffix) &&
+				if (isCandidateForProperty(method, clazz) &&
+						(method.getName().equals(prefix + methodSuffix) || isKotlinProperty(method, methodSuffix)) &&
 						method.getParameterCount() == numberOfParams &&
 						(!mustBeStatic || Modifier.isStatic(method.getModifiers())) &&
 						(requiredReturnTypes.isEmpty() || requiredReturnTypes.contains(method.getReturnType()))) {
@@ -557,6 +567,13 @@ public PropertyAccessor createOptimalAccessor(EvaluationContext context, @Nullab
 		return this;
 	}
 
+	private static boolean isKotlinProperty(Method method, String methodSuffix) {
+		Class<?> clazz = method.getDeclaringClass();
+		return KotlinDetector.isKotlinReflectPresent() &&
+				KotlinDetector.isKotlinType(clazz)  &&
+				KotlinDelegate.isKotlinProperty(method, methodSuffix);
+	}
+
 
 	/**
 	 * Captures the member (method/field) to call reflectively to access a property value
@@ -755,4 +772,24 @@ public void generateCode(String propertyName, MethodVisitor mv, CodeFlow cf) {
 		}
 	}
 
+	/**
+	 * Inner class to avoid a hard dependency on Kotlin at runtime.
+	 */
+	private static class KotlinDelegate {
+
+		public static boolean isKotlinProperty(Method method, String methodSuffix) {
+			KClass<?> kClass = JvmClassMappingKt.getKotlinClass(method.getDeclaringClass());
+			for (KProperty<?> property : KClasses.getMemberProperties(kClass)) {
+				if (methodSuffix.equalsIgnoreCase(property.getName()) &&
+						(method.equals(ReflectJvmMapping.getJavaGetter(property)) ||
+								property instanceof KMutableProperty<?> mutableProperty &&
+										method.equals(ReflectJvmMapping.getJavaSetter(mutableProperty)))) {
+					return true;
+				}
+			}
+			return false;
+		}
+
+	}
+
 }

spring-expression/src/test/kotlin/org/springframework/expression/spel/SpelReproKotlinTests.kt

@@ -55,6 +55,20 @@ class SpelReproKotlinTests {
 		assertThat(expr.getValue(context, Boolean::class.java)).isFalse()
 	}
 
+	@Test
+	fun `gh-30468 Unmangle Kotlin inlined class getter`() {
+		context.setVariable("something", Something(UUID(123), "name"))
+		val expr = parser.parseExpression("#something.id")
+		assertThat(expr.getValue(context, Int::class.java)).isEqualTo(123)
+	}
+
+	@Test
+	fun `gh-30468 Unmangle Kotlin inlined class setter`() {
+		context.setVariable("something", Something(UUID(123), "name"))
+		val expr = parser.parseExpression("#something.id = 456")
+		assertThat(expr.getValue(context, Int::class.java)).isEqualTo(456)
+	}
+
 	@Suppress("UNUSED_PARAMETER")
 	class Config {
 
@@ -71,4 +85,11 @@ class SpelReproKotlinTests {
 		}
 
 	}
+
+	@JvmInline value class UUID(val value: Int)
+
+	data class Something(
+		var id: UUID,
+		var name: String,
+	)
 }