Description of the bug

Default methods that are annotated with @ClientCallable are not published, because AbstractServerHandlers recurses the declared methods upon the class hierarchy (thus failing to detect any default method declared in an interface).

Expected behavior

methodFromInterface should be published to $server because it's a public method in TestViewWithCallables and such method is annotated with @ClientCallable. The method is not overriden in the class, thus the annotation from the interface remains.

Indeed TestViewWithCallables.class.getMethod("callFromInterface").isAnnotationPresent(ClientCallable.class) returns true.

Minimal reproducible example

1. Run the following example
2. Click "Call from parent class", observe that the method declared in a superclass is called.
3. Click "Call from interface", observe that the method declared in an interface is not called.

abstract class AbstractViewWithCallable extends Div {
  @ClientCallable
  private void methodFromParentClass() {
    System.out.println("Called from parent class");
  }
}


interface InterfaceWithCallable {
  @ClientCallable
  default void methodFromInterface() {
    System.out.println("Called from interface");
  }
}

@Route
public class TestViewWithCallables extends AbstractViewWithCallable implements InterfaceWithCallable {

  public TestViewWithCallables() {
    add(new Button("Call from parent class", ev -> {
      getElement().executeJs("this.$server.methodFromParentClass()");
    }));

    add(new Button("Call from interface", ev -> {
      getElement().executeJs("this.$server.methodFromInterface()");
    }));
  }
}

As a workaround, override the default method in the view class, and annotate it again with @ClientCallable

  @Override
  @ClientCallable
  public void methodFromInterface() {
    InterfaceWithCallable.super.methodFromInterface();
  }

Versions

• Vaadin / Flow version: 24.1.1