Consistently handle generics in TypeDescriptor.equals

Properly processes recursive types through always comparing generics via the top-level ResolvableType (rather than through nested TypeDescriptors with custom ResolvableType instances).

Closes gh-33932

Author: jhoeller

Diff for: spring-core/src/main/java/org/springframework/core/convert/TypeDescriptor.java

@@ -34,7 +34,6 @@
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
-import org.springframework.util.ObjectUtils;
 
 /**
  * Contextual descriptor about a type to convert from or to.
@@ -501,16 +500,7 @@ public boolean equals(@Nullable Object other) {
 		if (!annotationsMatch(otherDesc)) {
 			return false;
 		}
-		if (isCollection() || isArray()) {
-			return ObjectUtils.nullSafeEquals(getElementTypeDescriptor(), otherDesc.getElementTypeDescriptor());
-		}
-		else if (isMap()) {
-			return (ObjectUtils.nullSafeEquals(getMapKeyTypeDescriptor(), otherDesc.getMapKeyTypeDescriptor()) &&
-					ObjectUtils.nullSafeEquals(getMapValueTypeDescriptor(), otherDesc.getMapValueTypeDescriptor()));
-		}
-		else {
-			return Arrays.equals(getResolvableType().getGenerics(), otherDesc.getResolvableType().getGenerics());
-		}
+		return Arrays.equals(getResolvableType().getGenerics(), otherDesc.getResolvableType().getGenerics());
 	}
 
 	private boolean annotationsMatch(TypeDescriptor otherDesc) {

Diff for: spring-core/src/test/java/org/springframework/core/ResolvableTypeTests.java

@@ -1387,6 +1387,30 @@ void hasUnresolvableGenericsWithEnum() {
 		assertThat(type.hasUnresolvableGenerics()).isFalse();
 	}
 
+	@Test  // gh-33932
+	void recursiveType() {
+		assertThat(ResolvableType.forClass(RecursiveMap.class)).isEqualTo(
+				ResolvableType.forClass(RecursiveMap.class));
+
+		ResolvableType resolvableType1 = ResolvableType.forClassWithGenerics(Map.class,
+				String.class, RecursiveMap.class);
+		ResolvableType resolvableType2 = ResolvableType.forClassWithGenerics(Map.class,
+				String.class, RecursiveMap.class);
+		assertThat(resolvableType1).isEqualTo(resolvableType2);
+	}
+
+	@Test  // gh-33932
+	void recursiveTypeWithInterface() {
+		assertThat(ResolvableType.forClass(RecursiveMapWithInterface.class)).isEqualTo(
+				ResolvableType.forClass(RecursiveMapWithInterface.class));
+
+		ResolvableType resolvableType1 = ResolvableType.forClassWithGenerics(Map.class,
+				String.class, RecursiveMapWithInterface.class);
+		ResolvableType resolvableType2 = ResolvableType.forClassWithGenerics(Map.class,
+				String.class, RecursiveMapWithInterface.class);
+		assertThat(resolvableType1).isEqualTo(resolvableType2);
+	}
+
 	@Test
 	void spr11219() throws Exception {
 		ResolvableType type = ResolvableType.forField(BaseProvider.class.getField("stuff"), BaseProvider.class);
@@ -1836,6 +1860,16 @@ public void doA() {
 	}
 
 
+	@SuppressWarnings("serial")
+	static class RecursiveMap extends HashMap<String, RecursiveMap> {
+	}
+
+	@SuppressWarnings("serial")
+	static class RecursiveMapWithInterface extends HashMap<String, RecursiveMapWithInterface>
+			implements Map<String, RecursiveMapWithInterface> {
+	}
+
+
 	private static class ResolvableTypeAssert extends AbstractAssert<ResolvableTypeAssert, ResolvableType>{
 
 		public ResolvableTypeAssert(ResolvableType actual) {

Diff for: spring-core/src/test/java/org/springframework/core/convert/TypeDescriptorTests.java

@@ -770,6 +770,30 @@ void equalityWithGenerics() {
 		assertThat(td1).isNotEqualTo(td2);
 	}
 
+	@Test  // gh-33932
+	void recursiveType() {
+		assertThat(TypeDescriptor.valueOf(RecursiveMap.class)).isEqualTo(
+				TypeDescriptor.valueOf(RecursiveMap.class));
+
+		TypeDescriptor typeDescriptor1 = TypeDescriptor.map(Map.class,
+				TypeDescriptor.valueOf(String.class), TypeDescriptor.valueOf(RecursiveMap.class));
+		TypeDescriptor typeDescriptor2 = TypeDescriptor.map(Map.class,
+				TypeDescriptor.valueOf(String.class), TypeDescriptor.valueOf(RecursiveMap.class));
+		assertThat(typeDescriptor1).isEqualTo(typeDescriptor2);
+	}
+
+	@Test  // gh-33932
+	void recursiveTypeWithInterface() {
+		assertThat(TypeDescriptor.valueOf(RecursiveMapWithInterface.class)).isEqualTo(
+				TypeDescriptor.valueOf(RecursiveMapWithInterface.class));
+
+		TypeDescriptor typeDescriptor1 = TypeDescriptor.map(Map.class,
+				TypeDescriptor.valueOf(String.class), TypeDescriptor.valueOf(RecursiveMapWithInterface.class));
+		TypeDescriptor typeDescriptor2 = TypeDescriptor.map(Map.class,
+				TypeDescriptor.valueOf(String.class), TypeDescriptor.valueOf(RecursiveMapWithInterface.class));
+		assertThat(typeDescriptor1).isEqualTo(typeDescriptor2);
+	}
+
 
 	// Methods designed for test introspection
 
@@ -987,6 +1011,16 @@ public void setListProperty(List<Number> t) {
 	}
 
 
+	@SuppressWarnings("serial")
+	static class RecursiveMap extends HashMap<String, RecursiveMap> {
+	}
+
+	@SuppressWarnings("serial")
+	static class RecursiveMapWithInterface extends HashMap<String, RecursiveMapWithInterface>
+			implements Map<String, RecursiveMapWithInterface> {
+	}
+
+
 	// Annotations used on tested elements
 
 	@Target({ElementType.PARAMETER})