Generic field type issue (composition)

[seregamorph]

In addition to #440 there is one more issue related to generic type support.
Consider the test:

import static org.assertj.core.api.Assertions.assertThat;

import java.io.Serializable;
import org.junit.jupiter.api.Test;

public class Generic2Test {

    @Test
    void genericComposedShouldBeCorrectlyPopulated() {
        // given
        EasyRandom easyRandom = new EasyRandom();

        // when
        CompositeResource composite = easyRandom.nextObject(CompositeResource.class);

        // then
        assertThat(composite.longResource.getId())
                .isInstanceOf(Long.class);
    }

    static abstract class IdResource<K extends Serializable, T extends IdResource<K, ?>> {

        private K id;

        @SuppressWarnings("unchecked")
        public T setId(K id) {
            this.id = id;
            return (T) this;
        }

        public K getId() {
            return id;
        }
    }

    static class LongResource extends IdResource<Long, LongResource> {
    }

    static class CompositeResource {
        private LongResource longResource;
    }
}

Instead of generating correct beans it fails with NPE:

org.jeasy.random.ObjectCreationException: Unable to create a random instance of type class org.jeasy.random.Generic2Test$CompositeResource

	at org.jeasy.random.EasyRandom.doPopulateBean(EasyRandom.java:172)
	at org.jeasy.random.EasyRandom.nextObject(EasyRandom.java:100)
	at org.jeasy.random.Generic2Test.genericInheritedShouldBeCorrectlyPopulated(Generic2Test.java:16)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
	at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
	at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
	at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75)
	at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)
Caused by: org.jeasy.random.ObjectCreationException: Unable to create type: org.jeasy.random.Generic2Test$LongResource for field: longResource of class: org.jeasy.random.Generic2Test$CompositeResource
	at org.jeasy.random.FieldPopulator.populateField(FieldPopulator.java:98)
	at org.jeasy.random.EasyRandom.populateField(EasyRandom.java:209)
	at org.jeasy.random.EasyRandom.populateFields(EasyRandom.java:198)
	at org.jeasy.random.EasyRandom.doPopulateBean(EasyRandom.java:165)
	... 67 more
Caused by: org.jeasy.random.ObjectCreationException: Unable to create a random instance of type class org.jeasy.random.Generic2Test$LongResource
	at org.jeasy.random.EasyRandom.doPopulateBean(EasyRandom.java:172)
	at org.jeasy.random.FieldPopulator.generateRandomValue(FieldPopulator.java:160)
	at org.jeasy.random.FieldPopulator.populateField(FieldPopulator.java:93)
	... 70 more
Caused by: java.lang.NullPointerException
	at org.jeasy.random.FieldPopulator.getParametrizedType(FieldPopulator.java:170)
	at org.jeasy.random.FieldPopulator.getRandomizer(FieldPopulator.java:123)
	at org.jeasy.random.FieldPopulator.populateField(FieldPopulator.java:79)
	at org.jeasy.random.EasyRandom.populateField(EasyRandom.java:209)
	at org.jeasy.random.EasyRandom.populateFields(EasyRandom.java:198)
	at org.jeasy.random.EasyRandom.doPopulateBean(EasyRandom.java:165)
	... 72 more

[fmbenhassine]

Every new feature comes with new bugs 😄 ER should clearly not fail with a NPE. Thank you for reporting this.

[reitzmichnicht]

I have spottet the same and added a simple test here:
#450
But did not found a solution yet

[seregamorph]

@reitzmichnicht you can find a raw solutions here:
master...seregamorph:generic-base-class-classmate - uses com.fasterxml.classmate (jackson also has this dependency) to resolve generic type
Alternative impl:
master...seregamorph:generic-base-class-spring-core-no-spring - it is based on the spring-core code, the spring code copied and cleaned up (all unused lines), alternatively spring-core dependency can be used.

These branches were rejected in this project, but you still can find a solution here.

[fmbenhassine]

@reitzmichnicht I'm adding your failing test here since #450 was closed.

@Test
void testGenericFieldRandomization() {
    // given
    class Base<T> {
        T t;
    }
    class Concrete {
        Base<String> f;
    }

    // when
    Concrete concrete = easyRandom.nextObject(Concrete.class);

    // then
    assertThat(concrete.f).isInstanceOf(Base.class);
}

This fails with the same stacktrace as above.

[fmbenhassine]

@seregamorph

These branches were rejected in this project, but you still can find a solution here.

Thank you for pointing out these solutions. I just wanted to give a bit of context here about the reasons of rejecting those options.

master...seregamorph:generic-base-class-classmate - uses com.fasterxml.classmate (jackson also has this dependency) to resolve generic type

My concern with those changes is that they are based on #426, which was rejected for the reasons explained in details here: #426 (comment). While your changes are different from those in #426, the new GenericType is what concerning me the most, because java-classmate already defines its own GenericType. That said, I'm not against adding java-classmate as a dependency if it makes our lives easier regarding generic types introspection, and I'm open for contributions to fix this issue in a way that is not based on #426 and which remains relatively easy in order to control complexity.

master...seregamorph:generic-base-class-spring-core-no-spring - it is based on the spring-core code, the spring code copied and cleaned up (all unused lines), alternatively spring-core dependency can be used.

The reasons why this has been rejected were detailed here: #425 (comment).

[mjureczko]

I submitted a fix for this issue: #466.

There are a number of challenges around this issue (e.g. issue #440) that my fix does not address and the project is in maintenance mode. Thus, @beans can I ask you to look at it ahead and give me a shout if it has a chance for being accepted and if so, when it can be released?

[struberg]

Did hit the same issue today while upgrading a project.
Afaiu the problem is that the RandomizationContext is constructed with the CompositeResource. And from there all the parameterized information is taken. But this is completely wrong if a field/member has nothing to do with the parameterization hierarchy of that class but has it's own one like with LongResource.

The ParameterizedType of LongResource is defined as IdResource<Long, LongResource> and is completely independent of whatever generic information is in CompositeResource or if it doesn't have any at all, isn't?

I locally have a working hack (needs further polishing) where I create a fresh independent 'sub-RandomizationContext' in case I hit a field which has nothing to do with the generic hierarchy of the current class. Not quite sure though if this is the right way to approach it.