Hi,
As you’ve correctly deduced, the error messages means you need to do a widgetset compile.
I’m afraid
every
add-on with a client-side implementation (and that includes CSSInject) requires that you compile the widgetset. Completely unavoidable, I’m afraid, and I can’t imagine that will change in the short-to-medium term[1]
If you search the forums, there are examples of ant scripts that do just that (compile all the addons)
Sorry to be the bearer of bad news,
Cheers,
Charles.
[1]
All of Vaadin’s client-side components are built on top of GWT. GWT requires compilation. At least with Vaadin you only have to do a GWT compile every time you add a new add-on : GWT Compiles are long and heavy compared to java compiles.