Push not enabled despite annotation `@Push` added to `AppShell` in Vaadin 16

To reproduce:

• Download and unzip this project
• Go to project folder / import project into IDE
• Run the Maven goal jetty:run
• Browse to http://localhost:8080

AppShell class contents:

@PWA(name = "Project Base for Vaadin", shortName = "Project Base", enableInstallPrompt = false)
@Push
public class AppShell implements AppShellConfigurator {
}

The MainView class contains only this code:

@Route("")
public class MainView extends VerticalLayout {

    @Override
    protected void onAttach(AttachEvent attachEvent) {
        add(new Span("pushed"));
        getUI().get().push();
    }
}

Erroneous behavior: The explicit UI::push in call fails with the following:

java.lang.IllegalStateException: Push not enabled
	at com.vaadin.flow.component.UI.push(UI.java:654)
	at org.vaadin.example.MainView.onAttach(MainView.java:21)
	at com.vaadin.flow.component.ComponentUtil.onComponentAttach(ComponentUtil.java:230)
...

Expected behavior: The explicit UI::push call does not fail. This works in Vaadin 15 series versions, e.g., 15.0.4.

Versions:

• Vaadin 16.0.0.beta1
• Java 8

[nicoulaj]

@manolo It’s a regression between 15 and 16. I believe it is more related to AppShellConfigurator not used correctly to initialize UI.pushConfiguration. Push works correctly after I enable it using the property.

[manolo]

As reference, the workaround is to use the server side bootstrap by enabling the appropriate flag