Allow test classes to provide runtime hints via declarative mechanisms

Prior to this commit, it was possible to register hints for individual
test classes programmatically via the
org.springframework.test.context.aot.TestRuntimeHintsRegistrar SPI;
however, that requires that a custom TestRuntimeHintsRegistrar be
registered via "META-INF/spring/aot.factories". In addition,
implementing a TestRuntimeHintsRegistrar is more cumbersome than using
the core mechanisms such as @Reflective, @ImportRuntimeHints, and
@RegisterReflectionForBinding.

This commit address this by introducing support for @Reflective and
@ImportRuntimeHints on test classes. @RegisterReflectionForBinding
support is available automatically since it is an extension of the
@Reflective mechanism.

Closes gh-29455

spring-test/src/main/java/org/springframework/test/context/aot/TestContextAotGenerator.java

@@ -16,7 +16,10 @@
 
 package org.springframework.test.context.aot;
 
+import java.util.Arrays;
+import java.util.LinkedHashSet;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Stream;
 
@@ -30,12 +33,19 @@ import org.springframework.aot.generate.GeneratedClasses;
 import org.springframework.aot.generate.GeneratedFiles;
 import org.springframework.aot.generate.GenerationContext;
 import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
 import org.springframework.aot.hint.TypeReference;
+import org.springframework.aot.hint.annotation.ReflectiveRuntimeHintsRegistrar;
+import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.aot.AotServices;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.annotation.ImportRuntimeHints;
 import org.springframework.context.aot.ApplicationContextAotGenerator;
 import org.springframework.context.support.GenericApplicationContext;
+import org.springframework.core.annotation.MergedAnnotation;
+import org.springframework.core.annotation.MergedAnnotations;
+import org.springframework.core.annotation.MergedAnnotations.SearchStrategy;
 import org.springframework.core.log.LogMessage;
 import org.springframework.javapoet.ClassName;
 import org.springframework.test.context.BootstrapUtils;
@@ -117,16 +127,31 @@ public class TestContextAotGenerator {
 		try {
 			resetAotFactories();
 
+			Set<Class<? extends RuntimeHintsRegistrar>> coreRuntimeHintsRegistrarClasses = new LinkedHashSet<>();
+			ReflectiveRuntimeHintsRegistrar reflectiveRuntimeHintsRegistrar = new ReflectiveRuntimeHintsRegistrar();
+
 			MultiValueMap<MergedContextConfiguration, Class<?>> mergedConfigMappings = new LinkedMultiValueMap<>();
 			ClassLoader classLoader = getClass().getClassLoader();
 			testClasses.forEach(testClass -> {
 				MergedContextConfiguration mergedConfig = buildMergedContextConfiguration(testClass);
 				mergedConfigMappings.add(mergedConfig, testClass);
+				collectRuntimeHintsRegistrarClasses(testClass, coreRuntimeHintsRegistrarClasses);
+				reflectiveRuntimeHintsRegistrar.registerRuntimeHints(this.runtimeHints, testClass);
 				this.testRuntimeHintsRegistrars.forEach(registrar ->
 						registrar.registerHints(this.runtimeHints, testClass, classLoader));
 			});
-			MultiValueMap<ClassName, Class<?>> initializerClassMappings = processAheadOfTime(mergedConfigMappings);
 
+			coreRuntimeHintsRegistrarClasses.stream()
+					.map(BeanUtils::instantiateClass)
+					.forEach(registrar -> {
+						if (logger.isTraceEnabled()) {
+							logger.trace("Processing RuntimeHints contribution from test class [%s]"
+									.formatted(registrar.getClass().getCanonicalName()));
+						}
+						registrar.registerHints(this.runtimeHints, classLoader);
+					});
+
+			MultiValueMap<ClassName, Class<?>> initializerClassMappings = processAheadOfTime(mergedConfigMappings);
 			generateAotTestContextInitializerMappings(initializerClassMappings);
 			generateAotTestAttributeMappings();
 		}
@@ -135,6 +160,25 @@ public class TestContextAotGenerator {
 		}
 	}
 
+	/**
+	 * Collect all {@link RuntimeHintsRegistrar} classes declared via
+	 * {@link ImportRuntimeHints @ImportRuntimeHints} on the supplied test class
+	 * and add them to the supplied {@link Set}.
+	 * @param testClass the test class on which to search for {@code @ImportRuntimeHints}
+	 * @param coreRuntimeHintsRegistrarClasses the set of registrar classes
+	 */
+	private void collectRuntimeHintsRegistrarClasses(
+			Class<?> testClass, Set<Class<? extends RuntimeHintsRegistrar>> coreRuntimeHintsRegistrarClasses) {
+
+		MergedAnnotations.from(testClass, SearchStrategy.TYPE_HIERARCHY)
+				.stream(ImportRuntimeHints.class)
+				.filter(MergedAnnotation::isPresent)
+				.map(MergedAnnotation::synthesize)
+				.map(ImportRuntimeHints::value)
+				.flatMap(Arrays::stream)
+				.forEach(coreRuntimeHintsRegistrarClasses::add);
+	}
+
 	private void resetAotFactories() {
 		AotTestAttributesFactory.reset();
 		AotTestContextInitializersFactory.reset();