Dynamic loading of a web component fails with 'Error Application ROOT-2521314 already initialized'

Description of the bug

I’ve implemented dynamic loading of a Vaadin exported web component inside a Vaadin 23.2 view, the respective commit is here: https://gitlab.com/mrts/vaadin-embedding-example-guestbook/-/commit/b091d08c1038264f25b6f2c725652297852494ce.

The custom element is loaded and registered successfully, but rendering fails with the error Application ROOT-2521314 already initialized:

Loading custom element guest-book   dynamic-webcomponent-loader.ts:37:16
registering <guest-book> using id GuestBook-0   guest-book.js:112:13
Processing time was 2ms   FlowClient.js:205:19
Uncaught Error: Application ROOT-2521314 already initialized
    initApplication   FlowBootstrap.js:93

Expected behavior

When I open http://localhost:8080/dynamic-loader and click the Load web component button, then the web component is loaded and displayed on the page, the same way as in http://localhost:8080/basic.html.

Minimal reproducible example

See https://gitlab.com/mrts/vaadin-embedding-example-guestbook.

Run the project using mvn jetty:run and open http://localhost:8080/dynamic-loader in the browser to test.

Versions

• Vaadin / Flow version: 23.2.9
• Java version: 11
• OS version: Ubuntu 22.04
• Browser version (if applicable): Firefox 107
• Application Server (if applicable): Jetty

[Artur-]

With #15315 the embedding seems to work fine

[mcollovati]

The fix seems to work well. However, I see continuous web socket disconnections, but I don’t have yet understood if it is an issue with jetty version in use or if it is somehow related to the test project code