AppShellSettings.getUi returns null

[Artur-]

Description of the bug

When I implement AppShellConfigurator and override the configurePage method I expect to be able to use the provided getUi() method on AppShellSettings to get the target UI instance, like the javadoc says. However, calling getUi() returns an Optional which has a null value.

Expected behavior

getUi should return the UI instance so I for instance can configure push parameters.

Minimal reproducible example

@SpringBootApplication
public class Application extends SpringBootServletInitializer implements AppShellConfigurator {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Override
    public void configurePage(AppShellSettings settings) {
        System.out.println("UI is " + settings.getUi().get());
    }
}

Versions

Vaadin: 22.0.2
Flow: 9.0.2
Java: Homebrew 11.0.12
OS: aarch64 Mac OS X 12.0.1
Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.93 Safari/537.36

[caalador]

Without deeper knowledge on the AppShellSettings feature I noted that there is in use the error message:

    private static final String MSG_UNSUPPORTED_NO_UI = "It only works when "
            + "useDeprecatedV14Bootstrapping is enabled. "
            + "Use a UIInitListener instead if there are server-side views.";

for many methods which would sound like getUI will not return a UI in a early state if not using the v14 bootstrapping.

Fusion/Hilla team should perhaps have a look at this though.

[platosha]

True, this is by design, getUi cannot return UI there in the default mode, because it has not been created yet. In fact it was wrapped in Optional intentionally to indicates that it may return null.

As mentioned, works differently when useDeprecatedV14Bootstrapping is enabled. Also enabling eagerServerLoad flag makes UI available there, if I remember correctly.

As the message suggests, using UIInitiListener is preferred.

See #6939

[Artur-]

Can we remove it then if it does not work by default?

[Legioth]

We would still need something for the non-default cases that need it. Maybe just deprecating?