With the current version of the plugin, only Jetty 6 is supported. If the user is building an app with Jetty embedded then they can use whatever version they want. If they are building a war then there are other options such as the cargo plugin (to test against many container types) and the gretty plugin (which allows running and testing against various Jetty and Tomcat versions). We generally steer people towards these at the moment - the Jetty plugin is more or less in maintenance mode right now. That's why it wouldn't necessarily be the end of the world to just disable it and issue an error message rather than port to Jetty 9 - users should probably be using Gretty instead anyway.

It could go either way though - in the past I have used the jetty plugin on a couple of personal projects just to do some basic end-to-end testing in a servlet container, and it's useful to have that built in.

If there are projects that Fedora packages that need it, I think adding the Gretty plugin to the build would probably do the trick - it even uses the same task names "jettyRunWar", "jettyStop" etc. Authors would probably appreciate having the fix upstreamed :)

We may end up modernising the Jetty plugin at some point, but the general trend over time has been to add functionality like that via external plugins.

Cheers

Tom