Allow Enum type to be a source in controllers.

spring-graphql/src/main/java/org/springframework/graphql/data/method/annotation/support/SourceMethodArgumentResolver.java

@@ -55,7 +55,6 @@ private static boolean isExcludedSimpleValueType(Class<?> type) {
 		// Same as BeanUtils.isSimpleValueType except for CharSequence and Number
 		return (Void.class != type && void.class != type &&
 				(ClassUtils.isPrimitiveOrWrapper(type) ||
-						Enum.class.isAssignableFrom(type) ||
 						Date.class.isAssignableFrom(type) ||
 						Temporal.class.isAssignableFrom(type) ||
 						URI.class == type ||

spring-graphql/src/test/java/org/springframework/graphql/execution/EnumSchemaMappingTests.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.graphql.execution;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.graphql.GraphQlSetup;
+import org.springframework.graphql.ResponseHelper;
+import org.springframework.graphql.TestExecutionGraphQlService;
+import org.springframework.graphql.data.method.annotation.SchemaMapping;
+import org.springframework.stereotype.Controller;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EnumSchemaMappingTests {
+
+    private static final String schema = """
+            type Query {
+            	animals: [Animal!]!
+            }
+            type Animal {
+            	id: ID!
+            	name: String!
+            	classification: Classification!
+            }
+            type Classification {
+            	id: ID!
+            	name: String!
+            }
+            """;
+
+    private static final List<Animal> animalList = new ArrayList<>();
+
+
+    static {
+        animalList.add(new Animal("1", "Penguin", Classification.Bird));
+        animalList.add(new Animal("2", "Dog", Classification.Mammal));
+        animalList.add(new Animal("3", "Shark", Classification.Fish));
+    }
+
+	private final ClassificationController classificationController = new ClassificationController();
+
+
+    @Test
+    void resolveFromInterfaceHierarchyWithClassNames() {
+
+        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+        context.registerBean(ClassificationController.class, () -> classificationController);
+        context.refresh();
+
+        GraphQlSetup graphQlSetup =
+                GraphQlSetup.schemaContent(schema).runtimeWiringForAnnotatedControllers(context);
+
+
+        String document = """
+                query Animals {
+                	animals {
+                		__typename
+                		name
+                		classification {
+                			id
+                		}
+                	}
+                }
+                """;
+
+
+
+        TestExecutionGraphQlService service =
+                graphQlSetup.queryFetcher("animals", env -> animalList).toGraphQlService();
+
+        ResponseHelper response = ResponseHelper.forResponse(service.execute(document));
+        assertThat(response.errorCount()).isEqualTo(0);
+
+
+        String classificationIdBird = response.rawValue("animals[0].classification.id");
+        assertThat(classificationIdBird).isEqualTo(Classification.Bird.ordinal() + "-" + Classification.Bird.name());
+
+        String classificationIdMammal = response.rawValue("animals[1].classification.id");
+        assertThat(classificationIdMammal).isEqualTo(Classification.Mammal.ordinal() + "-" + Classification.Mammal.name());
+
+        String classificationIdFish = response.rawValue("animals[2].classification.id");
+        assertThat(classificationIdFish).isEqualTo(Classification.Fish.ordinal() + "-" + Classification.Fish.name());
+
+    }
+
+
+
+    record Animal(String id, String name, Classification classification) {}
+
+    enum Classification {
+        Bird,
+        Fish,
+        Mammal
+    }
+
+    @Controller
+    @SchemaMapping(typeName = "Classification")
+    static class ClassificationController {
+
+        @SchemaMapping
+        public String id(Classification classification) {
+            return classification.ordinal() + "-" + classification.name();
+        }
+
+    }
+
+
+}