RequestFactory tests fails under java 21 due to changes in the List API

[Ahmad K. Bawaneh]

GWT version: 2.11
Browser (with version):
Operating System:Ubuntu

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Description

While building GWT using java 21 RequestFactorySuite tests failed with 58 errors

Testcase: testFetchEntityWithRelation took 0.007 sec
	Caused an ERROR
Exception caught: Cannot invoke "com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverse(com.google.web.bindery.autobean.shared.AutoBeanVisitor, com.google.web.bindery.autobean.shared.impl.AbstractAutoBean$OneShotContext)" because "bean" is null
com.google.web.bindery.event.shared.UmbrellaException: Exception caught: Cannot invoke "com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverse(com.google.web.bindery.autobean.shared.AutoBeanVisitor, com.google.web.bindery.autobean.shared.impl.AbstractAutoBean$OneShotContext)" because "bean" is null
	at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$StandardPayloadDialect.processPayload(AbstractRequestContext.java:413)
	at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$5.onTransportSuccess(AbstractRequestContext.java:1160)
	at com.google.web.bindery.requestfactory.server.testing.InProcessRequestTransport.send(InProcessRequestTransport.java:64)
	at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext.doFire(AbstractRequestContext.java:1154)
	at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext.fire(AbstractRequestContext.java:595)
	at com.google.web.bindery.requestfactory.shared.impl.AbstractRequest.fire(AbstractRequest.java:56)
	at com.google.web.bindery.requestfactory.shared.impl.AbstractRequest.fire(AbstractRequest.java:61)
	at com.google.web.bindery.requestfactory.gwt.client.RequestFactoryTest.testFetchEntityWithRelation(RequestFactoryTest.java:856)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
	at com.google.gwt.junit.client.GWTTestCase.runTest(GWTTestCase.java:419)
	at com.google.gwt.junit.client.GWTTestCase.run(GWTTestCase.java:247)
Caused by: java.lang.NullPointerException: Cannot invoke "com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverse(com.google.web.bindery.autobean.shared.AutoBeanVisitor, com.google.web.bindery.autobean.shared.impl.AbstractAutoBean$OneShotContext)" because "bean" is null
	at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverseProperties(ProxyAutoBean.java:382)
	at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.traverse(AbstractAutoBean.java:166)
	at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverseProperties(ProxyAutoBean.java:358)
	at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.traverse(AbstractAutoBean.java:166)
	at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.accept(AbstractAutoBean.java:101)
	at com.google.web.bindery.requestfactory.shared.impl.ProxySerializerImpl.serialize(ProxySerializerImpl.java:118)
	at com.google.web.bindery.requestfactory.gwt.client.RequestFactoryTestBase.checkSerialization(RequestFactoryTestBase.java:181)
	at com.google.web.bindery.requestfactory.gwt.client.RequestFactoryTest$23.onSuccess(RequestFactoryTest.java:860)
	at com.google.web.bindery.requestfactory.gwt.client.RequestFactoryTest$23.onSuccess(RequestFactoryTest.java:857)
	at com.google.web.bindery.requestfactory.shared.impl.AbstractRequest.onSuccess(AbstractRequest.java:131)
	at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$StandardPayloadDialect.processPayload(AbstractRequestContext.java:380)
	

tracing the issue alongside @niloc132 we found the reason of the failure is that in java 21 a new methods are added to the list class getFirst, getLast, isEmpty, and in the ProxyAutoBean when tries to build the propertData for a list field is collect those methods as getters, this result in the field to be recognized as a nested entity that need to be traversed for its internal properties and is being processed as a reference instead of a value causing the above exception.

full logs are attached
logs.txt

Steps to reproduce

cd into gwt user folder and run the command

ant test.nongwt -Dgwt.nongwt.testcase.includes='**/RequestFactoryJreSuite.class'

Known workarounds

adding a simple check to skip Collection classes from the propertyData will make this pass.

private static Map<String, Data> calculateData(Class<?> beanType) {
    Map<String, Data> toReturn;
    synchronized (cache) {
      toReturn = cache.get(beanType);
      if (toReturn == null) {
        Map<String, Data> getters = new HashMap<String, Data>();
        List<Method> setters = new ArrayList<Method>();
        if (!Collection.class.isAssignableFrom(beanType)) { // <------ here
          for (Method method : beanType.getMethods()) {
            if (BeanMethod.GET.matches(method)) {
              // match methods on their name for now, to find the most specific
              // override
              String name = method.getName();

            Type genericReturnType = TypeUtils.resolveGenerics(beanType, method.getGenericReturnType());
              Class<?> returnType = TypeUtils.ensureBaseType(genericReturnType);

              Data data = getters.get(name);
              
...