ClassNotFoundException when using `void` as return type on `@Action` method

[tobHai]

I created a simple agent in Java:

import com.embabel.agent.api.annotation.AchievesGoal;
import com.embabel.agent.api.annotation.Action;
import com.embabel.agent.api.annotation.Agent;
import com.embabel.agent.api.common.Ai;

@Agent(description = "Course")
public class CourseAgent {

   private final CourseRepository courseRepository;

   public CourseAgent(CourseRepository courseRepository) {this.courseRepository = courseRepository;}

   @Action
   public MarketingText generateText(Course course, Ai ai) {
      var prompt = """
                Create a catching marketing text for the following sport course:
                Type: %s, Level: %s, Duration: %s, Location: %s
                """.formatted(
            course.sport(), course.level(), course.durationInHours(), course.location());
      return ai
            .withDefaultLlm()
            .createObject(prompt, MarketingText.class);
   }

   @AchievesGoal(description = "Generate a marketing text for a sport course")
   @Action
   public void updateCourseMarketingText(Course course, MarketingText marketingText) {
      courseRepository.updateMarketingText(course.id(), marketingText.text());
   }

}

It looks to me like the void combined with @AchievesGoal results in a class not found exception:

java.lang.ClassNotFoundException: void
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:580)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:490)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:467)
	at java.base/java.lang.Class.forName(Class.java:458)
	at com.embabel.agent.core.JvmType.clazz_delegate$lambda$1(JvmType.kt:57)
	at kotlin.SynchronizedLazyImpl.getValue(LazyJVM.kt:74)
	at com.embabel.agent.core.JvmType.getClazz(JvmType.kt:56)
	at com.embabel.agent.core.JvmType.infoString(JvmType.kt:205)
	at com.embabel.agent.core.AgentScope.infoString$lambda$8(AgentScope.kt:68)
	at kotlin.text.StringsKt__AppendableKt.appendElement(Appendable.kt:85)
	at kotlin.collections.CollectionsKt___CollectionsKt.joinTo(_Collections.kt:3490)
	at kotlin.collections.CollectionsKt___CollectionsKt.joinToString(_Collections.kt:3507)
	at kotlin.collections.CollectionsKt___CollectionsKt.joinToString$default(_Collections.kt:3506)
	at com.embabel.agent.core.AgentScope.infoString(AgentScope.kt:68)
	at com.embabel.agent.core.Agent.infoString(Agent.kt:112)
	at com.embabel.common.core.types.HasInfoString.infoString$default(HasInfoString.kt:28)
	at com.embabel.agent.core.Agent.getPlanningSystem(Agent.kt:101)
	at com.embabel.agent.core.support.BlackboardWorldStateDeterminer.<init>(BlackboardWorldStateDeterminer.kt:38)
	at com.embabel.agent.core.support.SimpleAgentProcess.<init>(SimpleAgentProcess.kt:54)
	at com.embabel.agent.core.support.SimpleAgentProcess.<init>(SimpleAgentProcess.kt:30)
	at com.embabel.agent.core.support.DefaultAgentPlatform.createAgentProcess(DefaultAgentPlatform.kt:173)

It is not a big deal since it can be prevented by using Void as a return type, but that feels a bit clunky.
Maybe the user experience can be improved a bit here?

[johnsonr]

Thank you for the report. Will look into it.

[johnsonr]

The AchievesGoal annotation works by looking at the return type of the goal action method. Otherwise it would be impossible to determine which was the goal type if there were >1 parameters to the goal action.

This would not be an issue for the new utility planning style, but might be problematic for GOAP usage where you expect a particular type from the agent.

Will investigate. The answer may be to flag this as an error if it's in a configuration that doesn't make sense.