Fix ClassFileMethodMetadata return type names for primitives and arrays

Return correct names for primitive and array types
Introduce resolveTypeName helper for ClassDesc handling
Add ClassFileMethodMetadataTests (java24Test)
Extend AbstractMethodMetadataTests with void return case

See gh-36577

Signed-off-by: Junseo Bae <ferrater1013@gmail.com>

spring-core/src/main/java24/org/springframework/core/type/classreading/ClassFileMethodMetadata.java

@@ -143,7 +143,7 @@ final class ClassFileMethodMetadata implements MethodMetadata {
 		AccessFlags flags = methodModel.flags();
 		String declaringClassName = methodModel.parent().map(parent -> ClassUtils.convertResourcePathToClassName(parent.thisClass().name().stringValue())).orElse(null);
 		ClassDesc returnType = methodModel.methodTypeSymbol().returnType();
-		String returnTypeName = returnType.packageName() + "." + returnType.displayName();
+		String returnTypeName = resolveTypeName(returnType);
 		Source source = new Source(declaringClassName, flags, methodName, methodModel.methodTypeSymbol());
 		MergedAnnotations annotations = methodModel.elementStream()
 				.filter(element -> element instanceof RuntimeVisibleAnnotationsAttribute)
@@ -154,6 +154,18 @@ final class ClassFileMethodMetadata implements MethodMetadata {
 	}
 
 
+	private static String resolveTypeName(ClassDesc type) {
+		if (type.isPrimitive()) {
+			return type.displayName();
+		}
+		if (type.isArray()) {
+			return resolveTypeName(type.componentType()) + "[]";
+		}
+		String packageName = type.packageName();
+    	return (packageName.isEmpty() ? type.displayName() : packageName + "." + type.displayName());
+	}
+
+
 	/**
 	 * {@link MergedAnnotation} source.
 	 * @param declaringClassName the name of the declaring class

spring-core/src/test/java/org/springframework/core/type/AbstractMethodMetadataTests.java

@@ -102,6 +102,11 @@ public abstract class AbstractMethodMetadataTests {
 				String.class.getName());
 	}
 
+	@Test
+	void getReturnTypeReturnsVoidForVoidReturnType() {
+		assertThat(getTagged(WithVoidMethod.class).getReturnTypeName()).isEqualTo("void");
+	}
+
 	@Test
 	void isAbstractWhenAbstractReturnsTrue() {
 		assertThat(getTagged(WithAbstractMethod.class).isAbstract()).isTrue();
@@ -217,6 +222,13 @@ public abstract class AbstractMethodMetadataTests {
 
 	}
 
+	public static class WithVoidMethod {
+
+		@Tag
+		public void test() {}
+
+	}
+
 	public static class WithMethodWithOneArgument {
 
 		@Tag

spring-core/src/test/java24/org/springframework/core/type/classreading/ClassFileMethodMetadataTests.java

@@ -0,0 +1,81 @@
+package org.springframework.core.type.classreading;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.core.type.MethodMetadata;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ClassFileMethodMetadataTests {
+
+	@Test
+	void getReturnTypeReturnsVoidForVoidReturnType() throws Exception {
+		MethodMetadata metadata = new ClassFileMetadataReaderFactory(getClass().getClassLoader())
+				.getMetadataReader(WithVoidMethod.class.getName())
+				.getAnnotationMetadata()
+				.getAnnotatedMethods(Tag.class.getName())
+				.iterator().next();
+
+		assertThat(metadata.getReturnTypeName()).isEqualTo("void");
+	}
+
+	@Test
+	void getReturnTypeReturnsPrimitiveForPrimitiveReturnType() throws Exception {
+		MethodMetadata metadata = new ClassFileMetadataReaderFactory(getClass().getClassLoader())
+				.getMetadataReader(WithIntMethod.class.getName())
+				.getAnnotationMetadata()
+				.getAnnotatedMethods(Tag.class.getName())
+				.iterator().next();
+
+		assertThat(metadata.getReturnTypeName()).isEqualTo("int");
+	}
+
+	@Test
+	void getReturnTypeReturnsReferenceTypeForReferenceReturnType() throws Exception {
+		MethodMetadata metadata = new ClassFileMetadataReaderFactory(getClass().getClassLoader())
+				.getMetadataReader(WithStringMethod.class.getName())
+				.getAnnotationMetadata()
+				.getAnnotatedMethods(Tag.class.getName())
+				.iterator().next();
+
+		assertThat(metadata.getReturnTypeName()).isEqualTo(String.class.getName());
+	}
+
+	@Test
+	void getReturnTypeReturnsArrayTypeForArrayReturnType() throws Exception {
+		MethodMetadata metadata = new ClassFileMetadataReaderFactory(getClass().getClassLoader())
+				.getMetadataReader(WithStringArrayMethod.class.getName())
+				.getAnnotationMetadata()
+				.getAnnotatedMethods(Tag.class.getName())
+				.iterator().next();
+
+		assertThat(metadata.getReturnTypeName()).isEqualTo("java.lang.String[]");
+	}
+
+	@Retention(RetentionPolicy.RUNTIME)
+	@interface Tag {}
+
+	public static class WithVoidMethod {
+		@Tag
+		public void test() {}
+	}
+
+	public static class WithIntMethod {
+		@Tag
+		public int test() { return 0; }
+	}
+
+	public static class WithStringMethod {
+		@Tag
+		public String test() { return ""; }
+	}
+
+	public static class WithStringArrayMethod {
+		@Tag
+		public String[] test() { return new String[0]; }
+	}
+
+}