Fix generic with WildcardType return type support in HttpServiceMethod

Signed-off-by: anaconda875 <hflbtmax@gmail.com>

Author: anaconda875

spring-core/src/main/java/org/springframework/core/GenericTypeResolver.java

@@ -154,11 +154,8 @@ public static Class<?> resolveReturnType(Method method, Class<?> clazz) {
 	public static Type resolveType(Type genericType, @Nullable Class<?> contextClass) {
 		if (contextClass != null) {
 			if (genericType instanceof TypeVariable<?> typeVariable) {
-				ResolvableType resolvedTypeVariable = resolveVariable(
+				ResolvableType resolvedTypeVariable = resolveVariableConsiderBound(
 						typeVariable, ResolvableType.forClass(contextClass));
-				if (resolvedTypeVariable == ResolvableType.NONE) {
-					resolvedTypeVariable = ResolvableType.forVariableBounds(typeVariable);
-				}
 				if (resolvedTypeVariable != ResolvableType.NONE) {
 					Type type = resolvedTypeVariable.getType();
 					if (type instanceof ParameterizedType) {
@@ -179,18 +176,16 @@ else if (genericType instanceof ParameterizedType parameterizedType) {
 					for (int i = 0; i < typeArguments.length; i++) {
 						Type typeArgument = typeArguments[i];
 						if (typeArgument instanceof TypeVariable<?> typeVariable) {
-							ResolvableType resolvedTypeArgument = resolveVariable(typeVariable, contextType);
-							if (resolvedTypeArgument == ResolvableType.NONE) {
-								resolvedTypeArgument = ResolvableType.forVariableBounds(typeVariable);
-							}
+							ResolvableType resolvedTypeArgument = resolveVariableConsiderBound(
+									typeVariable, contextType);
 							if (resolvedTypeArgument != ResolvableType.NONE) {
 								generics[i] = resolvedTypeArgument;
 							}
 							else {
 								generics[i] = ResolvableType.forType(typeArgument);
 							}
 						}
-						else if (typeArgument instanceof ParameterizedType) {
+						else if (typeArgument instanceof ParameterizedType || typeArgument instanceof WildcardType) {
 							generics[i] = ResolvableType.forType(resolveType(typeArgument, contextClass));
 						}
 						else {
@@ -203,10 +198,39 @@ else if (typeArgument instanceof ParameterizedType) {
 					}
 				}
 			}
+			else if (genericType instanceof WildcardType wildcardType) {
+				Type[] originalLowerBound = wildcardType.getLowerBounds();
+				Type[] originalUpperBound = wildcardType.getUpperBounds();
+
+				if (originalLowerBound.length == 1) {
+					Type lowerBound = resolveType(originalLowerBound[0], contextClass);
+					if (lowerBound != originalLowerBound[0]) {
+						return ResolvableType.forWildCardTypeWithLowerBound(
+								wildcardType, ResolvableType.forType(lowerBound))
+								.getType();
+					}
+				} else if (originalUpperBound.length == 1) {
+					Type upperBound = resolveType(originalUpperBound[0], contextClass);
+					if (upperBound != originalUpperBound[0]) {
+						return ResolvableType.forWildCardTypeWithUpperBound(
+								wildcardType, ResolvableType.forType(upperBound))
+								.getType();
+					}
+				}
+				return wildcardType;
+			}
 		}
 		return genericType;
 	}
 
+	private static ResolvableType resolveVariableConsiderBound(TypeVariable<?> typeVariable, ResolvableType contextType) {
+		ResolvableType resolvedTypeArgument = resolveVariable(typeVariable, contextType);
+		if (resolvedTypeArgument == ResolvableType.NONE) {
+			resolvedTypeArgument = ResolvableType.forVariableBounds(typeVariable);
+		}
+		return resolvedTypeArgument;
+	}
+
 	private static ResolvableType resolveVariable(TypeVariable<?> typeVariable, ResolvableType contextType) {
 		ResolvableType resolvedType;
 		if (contextType.hasGenerics()) {

spring-core/src/main/java/org/springframework/core/ResolvableType.java

@@ -98,6 +98,8 @@ public class ResolvableType implements Serializable {
 	private static final ConcurrentReferenceHashMap<ResolvableType, ResolvableType> cache =
 			new ConcurrentReferenceHashMap<>(256);
 
+	private static final Type[] EMPTY_TYPE_ARRAY = new Type[0];
+
 
 	/**
 	 * The underlying Java type being managed.
@@ -616,7 +618,8 @@ private boolean determineUnresolvableGenerics(@Nullable Set<Type> alreadySeen) {
 
 		ResolvableType[] generics = getGenerics();
 		for (ResolvableType generic : generics) {
-			if (generic.isUnresolvableTypeVariable() || generic.isWildcardWithoutBounds() ||
+			if (generic.isUnresolvableTypeVariable() ||
+					generic.isUnresolvableWildcard(currentTypeSeen(alreadySeen)) ||
 					generic.hasUnresolvableGenerics(currentTypeSeen(alreadySeen))) {
 				return true;
 			}
@@ -676,14 +679,32 @@ private boolean isWildcardWithoutBounds() {
 		if (this.type instanceof WildcardType wildcardType) {
 			if (wildcardType.getLowerBounds().length == 0) {
 				Type[] upperBounds = wildcardType.getUpperBounds();
-				if (upperBounds.length == 0 || (upperBounds.length == 1 && Object.class == upperBounds[0])) {
-					return true;
-				}
+				return upperBounds.length == 0 || (upperBounds.length == 1 && (Object.class == upperBounds[0]));
 			}
 		}
 		return false;
 	}
 
+	/**
+	 * Determine whether the underlying type represents a wildcard
+	 * has unresolvable upper bound or lower bound, or simply without bound
+	 */
+	private boolean isUnresolvableWildcard(Set<Type> alreadySeen) {
+		if (this.type instanceof WildcardType wildcardType) {
+			Type[] lowerBounds = wildcardType.getLowerBounds();
+			if (lowerBounds.length == 1) {
+				ResolvableType lowerResolvable = ResolvableType.forType(lowerBounds[0], this.variableResolver);
+				return lowerResolvable.isUnresolvableTypeVariable() || lowerResolvable.determineUnresolvableGenerics(alreadySeen);
+			}
+			Type[] upperBounds = wildcardType.getUpperBounds();
+			if (upperBounds.length == 1 && upperBounds[0] != Object.class) {
+				ResolvableType upperResolvable = ResolvableType.forType(upperBounds[0], this.variableResolver);
+				return upperResolvable.isUnresolvableTypeVariable() || upperResolvable.determineUnresolvableGenerics(alreadySeen);
+			}
+		}
+		return isWildcardWithoutBounds();
+	}
+
 	/**
 	 * Return a {@code ResolvableType} for the specified nesting level.
 	 * <p>See {@link #getNested(int, Map)} for details.
@@ -1185,6 +1206,51 @@ public static ResolvableType forClassWithGenerics(Class<?> clazz, @Nullable Reso
 				(generics != null ? new TypeVariablesVariableResolver(variables, generics) : null));
 	}
 
+	/**
+	 * Return a {@code ResolvableType} for the specified {@link WildcardType} with pre-declared upper bound.
+	 * @param wildcardType the WildcardType to introspect
+	 * @param upperBound the upper bound of the wildcardType
+	 * @return a {@code ResolvableType} for the specific wildcardType and upperBound
+	 */
+	public static ResolvableType forWildCardTypeWithUpperBound(WildcardType wildcardType, ResolvableType upperBound) {
+		Assert.notNull(wildcardType, "WildcardType must not be null");
+		Assert.notNull(upperBound, "UpperBound must not be null");
+		Type[] originalLowerBound = wildcardType.getLowerBounds();
+		Assert.isTrue(originalLowerBound.length == 0,
+				() -> "The WildcardType has lower bound while upper bound provided " + wildcardType);
+
+		Type upperBoundType = upperBound.getType();
+		VariableResolver variableResolver = upperBoundType instanceof TypeVariable<?> typeVariable
+				? new TypeVariablesVariableResolver(
+						new TypeVariable<?>[]{typeVariable}, new ResolvableType[]{upperBound})
+				: null;
+
+		return forType(new WildcardTypeImpl(new Type[]{upperBoundType}, EMPTY_TYPE_ARRAY), variableResolver);
+	}
+
+	/**
+	 * Return a {@code ResolvableType} for the specified {@link WildcardType} with pre-declared lower bound.
+	 * @param wildcardType the WildcardType to introspect
+	 * @param lowerBound the lower bound of the wildcardType
+	 * @return a {@code ResolvableType} for the specific wildcardType and lowerBound
+	 */
+	public static ResolvableType forWildCardTypeWithLowerBound(WildcardType wildcardType, ResolvableType lowerBound) {
+		Assert.notNull(wildcardType, "WildcardType must not be null");
+		Assert.notNull(lowerBound, "LowerBound must not be null");
+		Type[] originalUpperBound = wildcardType.getUpperBounds();
+		Assert.isTrue(originalUpperBound.length == 0 || originalUpperBound[0] == Object.class,
+				() -> "The WildcardType has upper bound %s while lower bound provided %s"
+						.formatted(originalUpperBound[0], wildcardType));
+
+		Type lowerBoundType = lowerBound.getType();
+		VariableResolver variableResolver = lowerBoundType instanceof TypeVariable<?> typeVariable
+				? new TypeVariablesVariableResolver(
+						new TypeVariable<?>[]{typeVariable}, new ResolvableType[]{lowerBound})
+				: null;
+
+		return forType(new WildcardTypeImpl(new Type[]{Object.class}, new Type[]{lowerBoundType}), variableResolver);
+	}
+
 	/**
 	 * Return a {@code ResolvableType} for the specified instance. The instance does not
 	 * convey generic information but if it implements {@link ResolvableTypeProvider} a
@@ -1628,6 +1694,56 @@ public Object getSource() {
 	}
 
 
+	private static final class WildcardTypeImpl	implements WildcardType, Serializable {
+
+		private final Type[] upperBound;
+		private final Type[] lowerBound;
+
+		private WildcardTypeImpl(Type[] upperBound, Type[] lowerBound) {
+			this.upperBound = upperBound;
+			this.lowerBound = lowerBound;
+		}
+
+		@Override
+		public Type[] getUpperBounds() {
+			return upperBound.clone();
+		}
+
+		@Override
+		public Type[] getLowerBounds() {
+			return lowerBound.clone();
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (!(o instanceof WildcardType that)) {
+				return false;
+			}
+			return Arrays.equals(upperBound, that.getUpperBounds()) && Arrays.equals(lowerBound, that.getLowerBounds());
+		}
+
+		@Override
+		public int hashCode() {
+			return Arrays.hashCode(getLowerBounds()) ^ Arrays.hashCode(getUpperBounds());
+		}
+
+		@Override
+		public String toString() {
+			if (getLowerBounds().length == 1) {
+				return "? super " + typeToString(getLowerBounds()[0]);
+			}
+			if (getUpperBounds().length == 0 || getUpperBounds()[0] == Object.class) {
+				return "?";
+			}
+			return "? extends " + typeToString(getUpperBounds()[0]);
+		}
+
+		private static String typeToString(Type type) {
+			return type instanceof Class<?> cls ? cls.getName() : type.toString();
+		}
+	}
+
+
 	private static final class SyntheticParameterizedType implements ParameterizedType, Serializable {
 
 		private final Type rawType;

spring-core/src/test/java/org/springframework/core/GenericTypeResolverTests.java

@@ -22,13 +22,16 @@
 import java.lang.reflect.Type;
 import java.lang.reflect.TypeVariable;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.function.Supplier;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.core.GenericTypeResolver.getTypeVariableMap;
@@ -251,6 +254,14 @@ void resolveTypeFromGenericDefaultMethod() {
 		assertThat(resolvedType).isEqualTo(InheritsDefaultMethod.ConcreteType.class);
 	}
 
+	@ParameterizedTest
+	@ValueSource(strings = {"getUpperBound", "getLowerBound"})
+	void resolveTypeFromWildcardType(String methodName) {
+		Type type = method(MyInterfaceType.class, methodName).getGenericReturnType();
+		Type resolvedType = resolveType(type, MySimpleInterfaceType.class);
+		assertThat(resolvedType).isEqualTo(method(MySimpleInterfaceType.class, methodName).getGenericReturnType());
+	}
+
 	@Test
 	void resolveTypeFromNestedParameterizedType() {
 		Type resolvedType = resolveType(method(MyInterfaceType.class, "get").getGenericReturnType(), MyCollectionInterfaceType.class);
@@ -268,12 +279,29 @@ private static Method method(Class<?> target, String methodName, Class<?>... par
 
 
 	public interface MyInterfaceType<T> {
+		default Optional<? extends T> getUpperBound() {
+			return Optional.empty();
+		}
+
+		default List<? super T> getLowerBound() {
+			return Collections.emptyList();
+		}
+
 		default T get() {
 			return null;
 		}
 	}
 
 	public class MySimpleInterfaceType implements MyInterfaceType<String> {
+		@Override
+		public Optional<? extends String> getUpperBound() {
+			return MyInterfaceType.super.getUpperBound();
+		}
+
+		@Override
+		public List<? super String> getLowerBound() {
+			return MyInterfaceType.super.getLowerBound();
+		}
 	}
 
 	public class MyParameterizedInterfaceType<P> implements MyInterfaceType<Collection<P>> {

spring-core/src/test/java/org/springframework/core/ResolvableTypeTests.java

@@ -41,10 +41,13 @@
 import java.util.SortedSet;
 import java.util.TreeSet;
 import java.util.concurrent.Callable;
+import java.util.stream.Stream;
 
 import org.assertj.core.api.AbstractAssert;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
 import org.mockito.ArgumentCaptor;
 import org.mockito.Captor;
 import org.mockito.junit.jupiter.MockitoExtension;
@@ -1549,6 +1552,31 @@ void gh34541() throws Exception {
 		assertThat(typeWithGenerics.isAssignableFrom(PaymentCreator.class)).isTrue();
 	}
 
+	@ParameterizedTest
+	@MethodSource("wildcardInfo")
+	void gh36474(ResolvableType typeVariable, Class<?> resolved) {
+		assertThat(typeVariable.resolve()).isEqualTo(resolved);
+	}
+
+
+	static Stream<Object[]> wildcardInfo() throws Exception {
+		WildcardType listxs = getWildcardType(AssignmentBase.class, "listxs");
+		WildcardType listsc = getWildcardType(AssignmentBase.class, "listsc");
+		ResolvableType owner = ResolvableType.forType(Assignment.class).as(AssignmentBase.class);
+
+		ResolvableType lbWildcard = ResolvableType.forWildCardTypeWithUpperBound(
+				listxs, ResolvableType.forType(listxs.getUpperBounds()[0], owner));
+		ResolvableType ubWildcard = ResolvableType.forWildCardTypeWithLowerBound(
+				listsc, ResolvableType.forType(listsc.getLowerBounds()[0], owner));
+		return Stream.of(new Object[] {lbWildcard, String.class}, new Object[] {ubWildcard, CharSequence.class});
+	}
+
+
+	static WildcardType getWildcardType(Class<?> cls, String field) throws Exception {
+		ResolvableType type = ResolvableType.forField(cls.getField(field));
+		return (WildcardType) type.getGeneric(0).getType();
+	}
+
 
 	private ResolvableType testSerialization(ResolvableType type) throws Exception {
 		ByteArrayOutputStream bos = new ByteArrayOutputStream();
@@ -1579,13 +1607,13 @@ private static ResolvableTypeAssert assertThatResolvableType(ResolvableType type
 	@SuppressWarnings("unused")
 	private HashMap<Integer, List<String>> myMap;
 
-
 	@SuppressWarnings("serial")
 	static class ExtendsList extends ArrayList<CharSequence> {
-	}
 
+	}
 	@SuppressWarnings("serial")
 	static class ExtendsMap extends HashMap<String, Integer> {
+
 	}