[login] Unable to show a login overlay defined in a LitTemplate

[Artur-]

Description

A <vaadin-login-overlay> added in a LitTemplate cannot be shown.

No matter if you define it as <vaadin-login-overlay opened> or show it using Java as

public class MyTemplate extends LitTemplate {

@Id
private LoginOverlay login;

  public MyTemplate() {
    login.setOpened(true);
  }
}

Expected outcome

The login overlay is shown

Actual outcome

The login overlay is not shown

Minimal reproducible example

Steps to reproduce

git clone https://github.com/Artur-/test-login-overlay.git
cd test-login-overlay
mvn

Open http://localhost:8080/login-v1 or http://localhost:8080/login-v2

If you open http://localhost:8080/ and click on the link for login-v1 or login-v2, then it renders as expected

Environment

• Vaadin 20.0.3
• mac

[Artur-]

Note that this works fine with Vaadin 14.x

[Artur-]

One of the reasons seems to be that whenever a <vaadin-login-overlay> is moved in the DOM, it is closed

[vlukashov]

Possibly related: vaadin/flow-components#841