Vaadin Framework version: 8, all versions

There is a major error in the class com.vaadin.server.VaadinSession (and possibly other classes too, if this is some kind of cargo cult programming in the Vaadin team)

Most public methods in the class use assertions to "check" if the session has the lock. This is fundamentally wrong. Assertions are the wrong tool to check preconditions in public meth

Vaadin 17.

RouterLink assumes you want to navigate to a java component. If I want to navigate to a client-side view, I need to create an Anchor and set the router-link attribute manually. It would be handy to have a new RouterLink(String href, String text) option.

Describe the bug
Running a simple, valid program in the JS.do example website may lead to a valid script terminating.

Error message is:
`Operation """": no method found, argument in overloaded package WebPerl::JSObject.
exit(255) called, but NO_EXIT_RUNTIME is set, so halting execution but not exiting the runtime or preventing further async execution (build with NO_EXIT_RUNTIME=0, if you